① 求英语从句语法资料！
在句子中起名词作用的句子叫名词从句(NounClauses） 名词从句的功能相当于名词词组,它在复合句版中能担任主语、宾权语、表语、同位语等，因此根据它在句中不同的语法功能，名词从句又可分别称为主语从句、宾语从句、表语从句和同位语从句。 给你分享一份“英语语法大全”:，更多资料到Vickey新概念英语上学习！
② 求高中英语语法中的从句部分，尽量讲得详细些的。
这个 三言两语讲不清
①【定语从句】
表特指：This“s the school that you visit
***********such和不定代词版all，much，little，few都可以做先行词
***********reason后面的连接词用权why还是that/which【注意】
***********time后面的连接词用when还是that【注意】
***********定语从句中缺状语（情况）/reason后面跟why还是that
②非限制性定语从句
非限制性定语从句通常不能用that引导
非限制性定语从句不能用why引导
非限制性定语从句置于句首时，不能用which引导
非限制性定语从句由“介词+关系代词”引导时，其中的关系代词不能用as
在非限制性定语从句中，指人的关系代词作宾语时，只能用宾格whom; 不能用who替换，也不能省略
【注意积累思考感悟~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~顺祝学习进步】
③ 谁能讲一下英语中从句和各种语法
这个很多的，不好说呀，不过推荐给你一本不错的书呦，书名是高中英语语法，黑皮的，里面讲得很详细，很易懂的，很不错，对你会有帮助的。
④ 几个英语从句中的语法求人指点下。
To sell such a suit as that （is） to a millionaire！
这个句子中as是介词，意思是像那样。和它引导的定语从句一样的意思。就是结构不同。如后面加上is那就是它引导了定语从句。因先行词被such修饰所以用as来引导。如下面的例子
I have never heard such things as you told us. （as引导的正是定语从句和它也是因为先行词被such修饰）
I have never heard such things as that.(这句中的as是介词和你给的句子一样，这样后面就不是从句但从意思上看也相当于上面那样的定语从句。)
在宾语从句中的时态要看主句。分两种情况。 当主句为一般现在时，从句根据时间状语可用各种时态。如 I want to know where you went yesterday.
当主句为一般过去时，从句也用过去时的一种，除客观真理用一般现在时。如
He told me that he would go to Beijing next month.
He told me that he had met Tom the day before.
The teacher told us that the earth goes around the sun.(客观真理用一般现在时)
⑤ 英语语法中的从句
大致有下面几种（以下是我个人总结的，仅供参考）：
一、名词性从句
其中又包括主语从句、同位语从句、宾语从句、表语从句
What I have is only a piece of bread.(What引导的主语从句)
News spread in the village that he came back.(that引导的同位语从句)
I think that you are right.(that引导的宾语从句)
What I appreciate is that you are brave.(that引导的标语从句)
二、形容词性从句
也就是定语从句
The mountain is beautiful from the top of which we can see our school.(which 引导的定语从句)
三、状语从句
主要有时间状语从句、地点状语从句、原因状语从句、条件状语从句、目的状语从句、让步状语从句、比较状语从句、程度状语从句、方式状语从句、结果状语从句
I will call you as soon as I arrive in Beijing. （as soon as引导的时间状语从句）
You should have put the book where you found it.(where引导的地点状语从句)
I hate you because you hurt me.(because 引导的原因状语从句)
If it is convenient,I will help you.(if引导的条件状语从句)
You must speak louder so that you can be heard.（so that 引导的目的状语从句）
She passed the examination though she had not studied very hard.(though引导的让步状语从句)
She finds it easier to read than to write．（than引导的比较状语从句）
⑥ 求英语所有语法
1、小学英语介词at，in与on在时间方面的用法
at表示时间的一点；in表示一个时期；表示特殊日子。如：
He goes to school at seven o’clock in the morning. 他早晨七点上学。
Can you finish the work in two days. 你能在两天内完成这个工作吗？
Linda was born on the second of May. 琳达五月二日出生。
1>. at后常接几点几分，天明，中午，日出，日落，开始等。如：
at five o’clock （五点），at down （黎明），at daybreak （天亮），at sunrise （日出），at noon （中午），at sunset （日落），at midnight （半夜），at the beginning of the month （月初）， at that time （那时），at that moment （那会儿），at this time of day （在一天的这个时候）。
2>. in后常接年，月，日期，上午，下午，晚上，白天，季节，世纪等。如：
in 2006（2006年），in May，2004 （2004年五月），in the morning （早晨/上午），in the afternoon （下午），in the evening （晚上），in the night （夜晚），in the daytime （白天），in the 21st century （21世纪），in three days （weeks/month）三天（周/个月），in a week （一周），in spring （春季）。
3>. on后常接某日，星期几，某日或某周日的朝夕，节日等。如：
on Sunday （星期日），on a warm morning in April （四月的一个温暖的上午），on a December night （12月的一个夜晚），on that afternoon （那天下午），on the following night （下一个晚上），on Christmas afternoon （圣诞节下午），on October 1，1949 （1949年10月1日），on New Year’s Day （新年），on New Year’s Eve （除夕），on the morning of the 15th （15日的早上）等。
2、 巧记形容词的排列顺序
当两个以上形容词修饰一个名词，形容词该如何排 列?为什么不能说a black new pen，而是说成a new black pen? 这里面有无规则可循? 如果你记住opshacom这个为帮助记忆而杜撰的词， 就能掌握英语中形容词排列的顺序。 opshacom中p代表opinion，指表示人们观点的形容 词，如beautiful，horrible，lovely，nice等； sh代表shape，指表示形状的形容词，如long，short，round, narrow等； a代表age，指表示年龄、时代的形容词，如old，new，young等； c代表colour，指表示颜色的形容词，如red,black, orange等； o代表origin，指表示国籍、地区的形容词，如british，canadian，german等； m代表material，指表示材料的形容词，如plastic，metal，aluminium等。 英语中这六类形容词连用时就按上述先后顺序排列， 如a nice long new black british plastic pen 当然，实际语言使用中不可能出现这么多形容词连 用的情况。
请根据形容词排列规则完成以下练习：
1>.she has a ___ jacket.(leather，brown，beautiful)
2>.he has a ___ car. (american，long，red)
3>.they live in a ___ house. (old，beautiful)
4>.we have a ___ table. (antique,small，wooden)
5>.he has a ___ jumper. (woollen, lovely, red)
6>.she has a ___ ring. (diamond，new，fabulous)
7>.it was a ___ song.(french，old, lovely)
8>.he owns a ___ dog.(black，horrible，big)
9>.she bought a ___ scarf.(gorgeous，silk，pink)
一、一般现在时主要用于：
1 、表示经常性或习惯性动作。
e.g. It seldom snows here.
2 、表示现在的特征或状态。
e.g. He is always ready to help others.
3 、普遍真理。
e.g. Action speaks louder than words.
4 、剧情图片介绍，背景说明，动作解说。
e.g. (Tom enters the room_and_sits at the table)
Doctor ： What`s your trouble, young man?
Tom ： I`ve caught a cold, doctor.
5 、时间、条件、让步、方式状语从句表将要发生的动作时。
e.g. Tomorrow we shall go for an outing unless it rains.
与这种时态连用的时间状语常有：
always, often, never, seldom, usually, once, a week, now 等。
二、一般过去时主要用于：
1 、表示过去某个时间发生的动作或情况（包括习惯性的动作或状态）
e.g. When did you read the novel?
She often came to help us in those days.
2 、谈到过去的情况时
e.g. I didn`t know you were so busy.
3 、谈到已死人的情况时
e.g. Lei Feng was a great communist fighter.
与这个时态连用的时间状语常有：
yesterday, last night, the other day, two months ago, in 1985, then, just now,
when, after, as soon as 引导的时间状语从句，表示主句动作开始的时间。
三、现在完成时主要用于：
1 、表示到现在为止这一时期中发生的动作或情况，即多次动作的总和。
e.g. We have learnt four English songs this month.
How many times have you read the novel?
For many days we haven`t seen each other.
2 、表示对现在有影响的某一已发生的动作。
e.g. The delegation has left 代表团已经走了（说明现在不在这里）
Look, what you have done. 看你干的事。
与这一时态连用的时间状语有：
already, yet, just, ever, never, by now, so far, recently, by the end of this month, since, for 短语，连词 since 引导的时间状语从句。
一般过去时与现在完成时的区别：
一般过去时：重在说明动作在过去发生时的具体情况（时间、地点、方式、对象、细节等）。
现在完成时：只提起已发生的动作（事实）及其影响，不说明动作发生时的具体情况。
cf. Have you had your lunch?
What did you have for lunch?
I have ever been to the Great Wall,_and_I went there last summer with my father.
注：现在完成时表达的动作常具有反复性，故下面一句是错的：
Have you seen the six thirty`s news program?
应改为：
Did you see the six thirty`s news program?
四、现在完成进行时主要用于：表示过去开始的某一动作一直持续到现在，以至延伸到将来，它强调动作延续时间之长久。
e.g. I`ve been writing an article. 我一直在写一篇文章。（还在写）
cf. I`ve written an article. 我写了一篇文章。（已写完）
It has been raining these days. 这些天一直在下雨。
五、过去完成时
1 、过去完成时是一个相对时态，表示过去的过去，只有在两个过去发生的动作相比较时才可显示出来。
e.g. As soon as we got to the station, the train had left.
注：主从句表达的动作紧接时，即两动作发生的时间没有明显时间上的悬殊或空档时，主从句都可用一般过去时。
e.g. Where did your brother study before he joined the army?
2 、过去完成时可表示截止过去某一时间动作的总或动作的结束。
e.g. By the end of last month. We had reviewed four books
By eight o`clock, he had finished his homework.
与这个时态连用的时间状语常有：
by 1985, by eight o`clock, by then, by the end of last month, by the time when, when, as soon as, before 等连词引导的时间状语从句，表示主句动作结束的时间。
六、现在进行时主要用于：
1 、表示现在或现阶段正在进行的动作。
e.g. Listen, someone is crying.
What are you doing these days?
2 、代替一般现在时，表示经常性动作或状态，而含有某种感情色彩。
e.g. How are you feeling today?
你今天感觉怎样？（显得亲切）
He is doing well in his lessons.
他的功课很好。（赞扬）
You are always boasting.
你老爱吹牛。（厌烦）
3 、动词 go, come, leave, arrive 等表将要发生的动作时。
e.g. They are leaving for Shanghai.
与这种时态连用的时间状语常有：
now, these days, recently, this week 等。
七、过去进行时主要用于：
表示过去某个时刻或阶段正在进行的动作。
e.g. At that time she was working in a PLA unit.
那时她在解放军某部工作。
What were you doing this time yesterday?
与这个时态连用的时间状语常用：
at nine o`clock, this time last night, these days, at that time 等。
用 when 引导的时间状语从句表示主句的动作正在进行的时间。
e.g. When he came in, I was reading a newspaper.
注：
1 、 while 引导时间状语从句叙述过去的动作时，从句常用过去进行时。
e.g. I read a magazine while I was waiting for the bus.
2 、 when 用作并列连词，意为“这时”，连接两分句时，第一句多用过去进行时。
e.g. I was reading a newspaper when he came in.
一般过去时与过去进行时的区别：
一般过去时：强调过去某一时间开始或完成的动作。
过去进行时：强调过去某一时间正在进行的动作。
试区别下面两句： We were building a reservoir last winter.
去年冬天我们在修建一座水库。（可能尚未建成） We built a reservoir last winter.
去年冬天我们修建了一座水库。（已经建成）
八、一般将来时主要用于：
表示将要发生的动作或情况
e.g. Tom will have a bike of his own.
与这个时态连用的时间状语常用：
tonight, tomorrow, the day after tomorrow, next week, in three hours, two days later 等。
一般将来时态与其它结构表将来情况的区别：
一般将来时态 ：主要从时间的角度表将要发生的动作或情况。
be going to 结构 ：①表（主观上）打算或准备做某事时。 ②表有发生某事的预兆时。
e.g. They are going to have a competition with us in studies. It is going to rain.
据以上区别，故下面一句是错的：
I am going to be eighteen years old next year.
应改为： I shall be eighteen years old next year.
be about to do sth 结构 ：意为“刚要做某事”、“马上要做某事”强调时间之紧迫性。
e.g. We are about to discuss this problem.
我们将马上讨论这个问题。
be to do sth 结构： 表示按计划、安排、规定将实施某事或表示注定会发生某事。
e.g. When is the train to leave.
回答者： 凌心骊歌 - 试用期 一级 2009-6-3 21:39
1.I went home （at six）.(就划线部分提问）你给他讲，问时间用What time/When代替，放在句首，这是一般过去时，变成一般疑问句时“did+主语+动词原形”，划线的部分去掉，就变成了：What/When did you go home?
2.He can sing English songs.(变成否定句），这是含有情态动词的句子，变否定句时，在can的后面加not就行了。就是：He can not/can't sing English songs.
3.She will wash her clothes tomorrow.你给他们讲：这是一般将来时，变成一般疑问句时，把will提到句首，和主语调换位置，其它的落下来，句末加问号。就变成了：Will she wash her clothes tomorrow?
4.Tom is in.(同意句）in的意思是在家，爱他at home也是在家的意思，所以，in与at home意思相同，故Tom is in.的同意句就是：Tom is at home.
5.There is a sheep on the hill.(山上有一只羊）（变成复数句）
讲，is的复数是are,a的复数是some，sheep的单数与复数相同，所以应变成：
There are some sheep on the hill.
这种方法对你很有帮助的，坚持下去！
⑦ 求英语从句及其分析
什麼是定语从句
在句中起定语作用,修饰某一名词或代词,或修饰整个主句的从句,叫做定语从句(The Attributive Clause).被定语从句所修饰的词叫做先行词(Antecedent).定语从句通常跟在先行词之后,由关系词(Relatives)引出.因此,定语从句又可称为关系分句.
关系词
关系词可分为：
(1)关系代词 e.g.:that,which,who,whom,whose etc.
(2)关系副词 e.g.:when,where,why etc.
关系词既起著联系从句与主句的作用,又代替先行词在从句中担任一定的语法成分.如主句,宾语,定语,状语等.
e.g.:
The woman who is standing by the classroom is our Chinese teacher.
在此句中,the woman是先行词;关系代词who引导定语从句,同时代替先行词在从句中担任主语.
This is the room where Bin Ladin once lived.
在此句中,the room是先行词;关系副词where引导定语从句并在从句中担任地点状语.
关系代词引导定语从句
Who:代替人.
做主语:
The girl who plays the piano very well is his girlfriend.
做表语:
She is no longer the woman who she used to be.
做宾语:
I can't remember the man who I gave the key to.
Whom:代替人.
做动词宾语:
Where is the student whom Professor Nirth praised at the meeting.
做介词宾语:
The girl with whom he was traveling is his girlfriend.
注：在「介词提前」即「介词+关系代词」结构出现时，关系代词只能用 whom 和 which 。
Whose(=of whom/Which):
代替人(做从句中某名词的定语):
She is looking after the little child whose parents have gone to Singapore.
代替物(做从句中某名词的定语):
He lived in the room whose windows face south.
That:
代替人:
做主语:
The man that is speaking at the meeting is a famous scientist.
做宾语:
Is this the teacher that you talked about yesterday.
做表语:
She is no longer the girl that she was in her childhood.
代替物:
做主语:
The train that has just left is for Beijing.
做宾语:
Is this the photo that you took last summer?
做表语:
I wish my home town was not a polluted place that you think it to be.
Which:代替物.
做主语:
The building which stands near the train station is a company.
做宾语:
The computer which she wanted to buy was sold out.
做表语:
She was fond of dancing,which her husband never was.
关系副词引导宾语从句
关系副词在意义上常常相当与一个"prep.+which"的结构.
When(=at,on,in,ring + which):代替时间名词.做时间状语:
I shall never forget the day when(on which) we moved into our new flat.
Where(=in,at + which):代替地点名词.做时间状语:
This is the place where(at which) John parks his car.
Why(=for which):代替指代原因.做原因状语:
She didn't know the reason why(for which) she was dismissed.
⑧ 英语从句语法知识求教
英语中六大从句用法总结
1.主语从句
1）主语从句可直接位于主语的位置，如果从句较长，谓语又较短，可用it作形式主语，而将从句放在句末。常见的句型有：
*It is a fact\a pity\a question\good news that...
*It seems\appears\happened\has turned out that...
*It is clear\important\likely\possible that...
*It is said\reported\estimated\has been proved that...
It is said that comic books create a connection between people of the same generation.
It seems that the performance is very useful.
2)what引导的主语从句表示“...的东西时”，一般不用it作形式主语。
What we lack is experience.
3)what,who,when,why,whether等词含有各自的疑问意义，但它们引导的主语从句，都用陈述语序。
How the plan is to be carried out should be discussed again.
I did know why I felt like crying.
2.宾语从句
1）宾语从句可位于及物动词、介词和某些形容词后。连词that常可省略。介词后一般接疑问词引导的宾语从句。in that(因为),except that(除了),but that(只是）已构成固定搭配，其他介词后一般不接that引导的宾语从句。
*I promised that I would change the situation.
*All this is different from what American young people would say about friendship.
*He is certain that watching so much television is not good for children.
*This article is well-written except that it is a bit too long.
2)宾语从句后如有宾补，要用形式宾语it来代替，而把宾语从句移至宾补之后。
He has made it clear that he would not change his mind.
3)在think,believe,suppose,expect等动词后的宾语从句中，如果谓语是否定的，一般将否定词移至主句谓语上，宾语从句则变成肯定形式。
He didn't think that the money was well spent.
3.表语从句
表语从句出现在结构为“主语+系动词+表语从句”的句子中。表语从句除可用that,what,when,why,whether,how等引导外，还可由because,as if(though)等引导。that常可省略。如主句主语为reason,只能用that引导表语从句，不可用because.
Perhaps the most important thing to remember is that there is no one common type of life in America.
The reason why so many people died there is that there were not enough food supplies.
It looks as if successful international cultural communication will make the world smaller.
4.同位语从句
同位语从句用于对前面出现的名词作进一步说明，一般用连词that引导，由于先行名词的意义不同，也可用whether,who,when,where,what,why,how等引导。常见的先行名词有fact,idea,belief,news,hope,conclusion,evidence,suggestion,order,problem,report,decision.有时由于谓语较短，将同位语从句位于谓语之后。
She finally made the decision that she would join the fashion show.
I had no idea how many books I could borrow at a time.
The news came that their team had won the championship.
5.定语从句
定语从句所修饰的先行词可以是名词或代词，也可以是一个句子。定语从句通常位于先行词之后，由关系代词或关系副词引导。
*限制性定语从句
限制性定语从句修饰先行词，对先行词起修饰作用，紧接先行词之后，无逗号，若省去，原句意思不完整。引导定语从句的关系代词有who,whom,whose,which,that等。who,whom,whose用于指人，whose有时也可指物，相当于of which；which用于指物；that既可指人也可指物，但只用于限制性定语从句中。关系代词除了引导定语从句，替代先行词外，还在从句中担任主语、宾语、定语等。
The computers and cables which make up the Internet are owned by people and organizations.
Those
⑨ 英语语法英语从句
主要是宾语从句和状语从句，如果说考的稍微难一些的话就是定语从句以及名词性从句，一般考的话后两者的难度不会很大。
宾语从句在句中作及物动词或介词的宾语，从句放在主句之后，前后不用逗号分开。
宾语从句：
引导宾语从句的词有：
连词that(在口语中that常可省略)，if, whether,如：
He knows that Jim will work hard.
连接代词who, whom, which等，如：
Do you know who (whom) they are waiting for?
连接副词when, where, how, why等，如：Could you tell me how we can get to the station?
3.whether和if都有“是否”的意思，一般情况下两者可以换用，但在介词之后，
不定式之前，与or not连用，在句首或在引导表语从句，同位语从句时，只能用whether,如：I want to know if/whether the news is true. He doesn't know whether to stay or not?
4.宾语从句要用陈述句语序。
5.宾语从句一定要注意时态呼应，即：当主句谓语动词是过去式时，从句中谓语动
词也要用过去范畴的时态，但若从句陈述的是真理或客观规律，其谓语的时态仍用一般现在时，如：
He asked who could answer the question.
My father told me that the earth goes around the sun.
6.一个宾语从句只能用一个连词。
7.当主句谓语动词是think, believe等动词时，宾语从句的否定意义要放到主句中。另外，当主句主语为第一人称时，后面若接附加疑问句，那么附加疑问句的主语、谓语应与从句中的主谓语保持一致。如：
I don't think he looks like his father, does he?
8.直接引语和间接引语也是宾语从句，直接引语是引述别人的原话，放在引号内，
不用连词联接；间接引语是用自己的话转述别人的话，通常用连接词与主句联接。
(1)陈述句变为以that引导的宾语从句，如：
He said,“I'm happy.”[FY()[FY]]He said that he was happy.
(2)一般疑问句变为if(whether)引导的宾语从句，如：
He asked me,“Does his father know Mr Green?”
---He asked me if his father knew Mr Green.
(3)特殊疑问句变为由who, what, where, how等疑问词(连接代词或连接副词)引导的宾语从句，如：
He asked me,“Where is Mr Wang?”
---He asked me where Mr Wang was.
注意上述例句中连词、时态、语序等变化
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高中英语各种复合句精品课程讲解
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什么叫名词性从句？
在句子中起名词作用的句子叫名词从句 (Noun Clauses）
名词从句的功能相当于名词词组, 它在复合句中能担任主语、宾语、表语、同位语等，因此根据它在句中不同的语法功能，名词从句又可分别称为主语从句、宾语从句、表语从句和同位语从句
【一】主语从句 【二】表语从句 【三】宾语从句
【四】定语从句 【五】同位语从句 【六】状语从句
【一】主语从句：在主句种充当主语成分的从句叫主语从句，
引导主语从句的连词有：从属连词；连接代词；连接副词
A 从属连词：that，whether。
从属连词；that，whether引导的主语从句在主语从句中不充当任何成分,只起连接词的作用，通常不可以省略。分句置于句首时，that绝对不可以省略。如果是由It作形式主语，后面that可以省略.
1,有that 引导的主语从句如下：
1. That the driver could not control his war was obvious.
=It was obvious（that）the driver could not control his car.
2. That she was chosen made us very happy.
=it made us very happy that she was chosen
3. That he is still alive is sheer luck. 他还活着全靠运气。
=It is sheer luck that she is still alive
4. That the whole project is doomed to failure is quite clear
=It is quite clear that the whole project is doomed to failure.
很清楚，整个计划注定要失败。
5. That you should have to leave is a pity
=It's a pity that you should have to leave.
你非走不可真是件憾事。
6. That he will refuse this piece of advice is impossible.
=It is impossible that he will refuse this piece of advice
7. That they should like each other is natural
=It is natural that they should like each other
8. That he will not come to the meeting this evening is true
=It is true that he will not come to the meeting this evening
9. That he will help others is a fact
10. That the earth turns around the sun is known to all.
=It is known to all that the earth turns around the sun.
11. That we can win is certain
=It is certain that we can win.
12. That you have made a mistake is a fact.
=It is a fact that you have made a mistake
13. It is ordered that we should leave at once.
14. That you don’t like him is none of my business.
用it作形式主语的that-从句有以下四种不同的搭配关系：
a. It + be +形容词+ that-从句
It is necessary that…有必要……
It is important that…重要的是……
It is obvious that… 很明显……
It’s certain that… 肯定…
It is possible that... 很可能……
It is unlikely that... 不可能……
It is necessary \important \natural\... that…
It is possible that she will come back tomorrow.
It is obvious that this measure is effective.
b. It + be +V ed 分词+ that-从句
It is known to all that…从所周知……
It has been decided that… 已决定……
It is said that... 据说……
It is known to all that... 众所周知……
It is reported that... 据报道……
It is believed that...据信……;人们相信……
It is suggested that + (should）do... 建议……
It must be admitted that…必须承认……
It cannot be denied that… 不可否认……
It must be pointed out that…需指出的是……
It was reported that 20 people were killed in the accident.
It was suggested that we should eat more vegetable and do more exercise
c. It + be +名词+ that-从句
It is a pity/shame that... 遗憾的是……
It is a surprise that…令人惊奇的是…
It is common knowledge that… …是常识
It is common knowledge that…是常识
It is a fact that…事实是……
It was a pity that we lost the match.
It was a fact that he cheated in the exam.
d. It +不及物动词+ that-分句
It appears that…似乎……
It happens that…碰巧……
It occurred to me that…我突然想起……
It occurred to me that I forgot to send this letter
It happened that I came into the office at that time.
It is important(necessary / advisable / desirable / imperative / true / strange / possible ...)that ...需要注意的是,这类主语从句中,谓语动词很多为"(should)＋动词原形",即要用虚拟语气。例如:
It is necessary that several nurses (should) stay.
几个护士留在这儿是很有必要的。
It is imperative that everyone (should) learn from practice.
每个人都应该从实践中学习。
It is reported (well-known / hoped / thought / expected / said / believed / decided / suggested / ordered ...)that ...例如:
It is said that many people was killed in the earthquake.
据说很多人在这次地震中丧生了。
it seems(appears / doesn’t matter / makes no difference / ...)that ...
例如:
It makes no difference whether he will attend the meeting or not.
他是否会参加会议都无关紧要。
当用it作形式主语,而将主语从句放在句尾时,主语从句中的否定词常要前移至主句中。例如:
It doesn’t seem that they are from the same university.
It doesn’t appear that we’ll have a sunny day tomorrow.
if 不能用在主语从句中，而是用whether，如果主语从句放在句首，不能用if引导，但是如果用it 做形式主语，而把主语从句放在句末时，也可以用if引导.或把if 改为whether
If Mary really heard him is really doubtful.
正：It was doubtful if Mary really heard him.
正: Whether Mary really heard him is really doubtful.
Whether he left (or not) is unknown
Whether he will come is not clear.
Whether it will rain or not) is not clear
Whether he’ll come here isn’t clear. 他是否会来这里还不清楚。
Whether we will go tomorrow )hasn’t been decided yet
Whether the meeting will be put off has not been decided yet.
Whether the policeman will come is not certain.
Whether the 2000 Olympic Games will be held in Beijingis not known yet.
Whether we’ll go camping tomorrow depends on the weather.
whether he likes the job is not clear.
.注意区分it 作形式主语的主语从句与强调句
强调句句型It is/was+被强调部分+that, 去掉It is/was, that，句子仍然成立。
It is natural that they should have different views. 主语从句
It is only lately that he had had a family himself. 强调句
What was it that he wanted? I don’t know what it was that he wanted.
It was in the hotel where he stayed that we discussed the serious problem
8.注意it 作形式主语的主语从句和as引导非限制性定语从句引导的不同
It is known to all that the earth is round.
As is known to all. the earth is round.
B连接代词who ，what ，which, whatever, whichever, whoever (Who, whom, which, what可以和ever构成合成词，和what一样引导从句，ever起到强调作用。此类主语从句不能用形式主语it引导，它们在句子中担任成分，不能省略，语序为陈述语序)
What many scientists believe is that the earth is round …
Who will take part in the meeting has not been decided.
Whoever breaks the law will be punished.
Which student will win is uncertain.
Whatever was said here must be kept secret.
这里说的话都应当保密。
Whoever makes mistakes must correct them.
凡犯了错误的人都必须改正。
What is needed for success) is your hard work.
Who can join in the sport meet) is decided by the teacher
What he needs is that book.
What he needs are some books.
What he needs are some books.
Who he is and where he is from are important.
What he saw are the stars in the sky
What he said at the meeting astonished everybody present
Whoever leaves the room last ought to turn off the lights.
C连接副词when，where， how， why等。
Why they suddenly disappeared still remains a mystery.
When they will leave is not decided.
Where she is from is unknown.
How we will paint the house has not been decided.
When they will arrive has been told to the teacher
Where we will go tomorrow hasn’t been decided yet
When he will come is not known
When he will come is a puzzle
Where we shall spend the holiday isn’t decided.
Where he comes from is a mystery.
Conclusion:主语从句作 主语时，谓语动词一般用单数形式
主语从句的规律
规律一、主语从句一律用陈述语序，即主语在前，谓语在后。
规律二、连词that 在从句中无实际意义，但不能省略。
规律三、whether 可以引导主语从句， 放在句首，但if不能
规律四、主语从句中的连词不能重叠使用
规律五、含主语从句的主句谓语动词多用单数第三人称形式。
规律六、what 引导的主语从句，可根据表语决定主句动词的单复数形式
规律七、主语从句为了避免头重脚轻现象，用 it 做形式主语，把从句放在后面。