as引导的定语从句的用法
定语从句（也称关系从句、形容词性从句），是指一类由关系词（英语：relative word）引导的从句,因为这类从句的句法功能多是做定语，所以曾被称为定语从句（英语：attributive clause），这类从句除了可以做定语之外，还可以充当状语等其他成分，所以现代语言学多使用“关系从句”这一术语。以下是小编帮大家整理的as引导的定语从句的用法，欢迎大家借鉴与参考，希望对大家有所帮助。
ove, as is often the case, as/indeed it is
例:As is well known，great changes have taken place in China. 或Great changes, as is well known, have taken place in China.众所周知，中国发生了巨大的变化。（ as在定语从句中作主语。）
This experiment is very simple，as indeed it is.实验非常简单，事实上也确实如此。（as在定语从句中作表语。）
注意：
① which在引导非限制性定语从句时，也有和as一样的功能，可以代替整个句子，但which只能用在主句之后。
②在as所引导的非限制性定语从句中，如果运用的是被动语态结构，be动词可以省略；但which没有此用法，be动词不可省。例如:She married him，which was unexpected.＝She married him as（was） unexpected.她嫁给了她，这一点大家都没有料到。（作主语，代替前面的句子；用which时was不可省。）
二 as除了代替整个句子，也可以代替主句中一个特定的词。as在它引导的定语从句（限制性或非限制性）中可以充当主语，宾语和表语；在这种用法中它经常和such, so, the same等词搭配使用；且当先行词中有such, so, the same等词修饰时，关系代词通常必须用as。
例如:1. They were satisfied with this decision，as was agreed beforehand.他们对这个决定都满意，这事先已经经过他们同意了。（ as在定语从句中作主语，其先行词是this decision）
2. I never heard such stories as he tells.我从未听过他讲的这类故事。（ as在定语从句中作宾语，先行词是such stories.）
3.The place doesn't look the same as it was before liberation.这个地方看上一去和解放前大不一样了。（ as在定语从句中作表语，先行词是same）
4.Have you bought the same book as I referred to yesterday?你有没有买我昨天说的那本书啊？（ as在定语从句中作宾语，先行词是book）
注意:先行词中有the same修饰时，定语从句也可用that引导，但意思上有区别，as表示与此同类； that表示就是那一个，同物。
例如:Have you brought the same book that I gave you yesterday?
你有没有把我昨天给你的那本书带来啊？（ that在定语从句中作宾语，先行词是book。体会：本句中所指的书是同一本，上句中指的是同一类书，而并不就是那一本。）
介词+关系词怎么用？介词加关系词分别等于什么？
答：一、“介词＋关系代词”的用法
当关系代词在定语从句中作介词宾语时，我们通常用“介词＋关系代词”引导定语从句。如果指“人”，用“介词＋whom”；如果指“物”，用“介词＋which”。例如：
Do you know the lady with whom our manager is talking in the office? Where is the supermarket in which you bought the laptop last week?
●使用“介词＋关系代词”要注意以下几点：
（一）选用介词的依据：
（1） 根据定语从句中谓语动词的搭配习惯（即固定短语）。例如：
Yesterday we visited the West Lake for which Hangzhou is famous.
（2） 根据先行词的搭配习惯（约定俗成，不一定是短语）。例如：
The old woman with whom you talked just now is a famous artist.
（3） 根据句子的意思来选择。例如：
The naughty boy made a hole in the wall through which he could see what is happening outside.
（4） 表示“所有”关系或“整体中的一部分”时，通常用介词of。例如： I have about 20 books, half of which were written by Bing Xin, the famous writer.
（二）在定语从句中，含介词的短语动词不可拆开使用（短语拆开后含义发生变化），如look after, look for等。例如：
The babies whom the nurses are looking after are very healthy.（正） The babies after whom the nurses are looking are very healthy.（误）
（三）“of which / whom”有时可以用“whose＋名词”结构来改写。例如： The building whose roof was damaged in the earthquake has been
repaired.
＝The building of which the roof was damaged in the earthquake has been repaired.
（四）当先行词为way并且定语从句中缺少状语时，通常用in which或that引导定语从句（in which或that可省略）；如果定语从句中不缺少状语，则用关系代词引导（that 或which 可省略）。例如：
All of us disliked the way（in which / that）Tom settled the maths problem.
I don’t understand the way（that/which）the teacher explained to me.
（五）in that不可以引导定语从句，但可以引导原因状语从句。例如：
She didn’t attend the meeting in that / because she was seriously ill.
二、“介词＋关系代词”与关系副词的转化
（1）当先行词表示地点，定语从句中缺少地点状语时，通常用关系副词where引导，此时也可选用表示地点的介词＋which来代替关系副词where。例如：
I visited the village where many children couldn’t go to school because of poverty.
＝I visited the village in which many children couldn’t go to school because of poverty.
（2） 当先行词表示时间，定语从句中缺少时间状语时，通常用关系副词when引导，此时也可选用表示时间的介词＋which来代替关系副词when。例如：
We’d better fix a date when we will practice speaking English next week.
＝We’d better fix a date on which we will practice speaking English next week.
（3） 当先行词为reason，定语从句中缺少表示原因状语时，通常用关系副词why引导，此时也可以用for which来代替关系副词why。例如：
Can you tell me the reason why you were late for school?
＝Can you tell me the reason for which you were late for school? 介词+关系代词”引导的定语从句
由“介词+关系代词”引导的定语从句主要用于正式文体中，这儿的关系代词主要是which和whom，介词的选用要根据句意或一些固定搭配来确定。
“介词+关系代词”（关系代词一般指的是which/whom）引导的定语从句，有以下几种情况:
1.“介词+which”在定语从句中作时间地点原因状语，相当于关系副词。如:
（1）This is the reason for which（=why） he left the company. 这就是他离开公司的原因。
（2）He will never forget the day on which （=when） he went there. 他永远忘不了去那儿的那一天。
（3）Is this company the one in which （=where） you worked half a year ago?这就是半年前你在那儿工作的公司吗?
2.“介词+which/whom”在定语从句中作目的方式状语。如:
（1）Can you tell me for whom you are working?
你能告诉我你现在为谁工作吗?
（2）There is a big hole on the wall through which he can see what’s happening inside.
墙上有一个大洞，通过这个洞他能看到里面所发生的一切。
（3）The train by which he is travelling is arriving.
他乘坐的那辆火车就要到了。
（4）In the dark street， there wasn’t a single person to whom she could turn for help.在漆黑的街上，没有一个人她可以求助。
3.“不定代词数词或名词+of which/whom”在定语从句中充当主语。如:
（1）There are sixty students in our class， all of whom are working hard.
班上有60 名学生，他们都在努力学习。
（2）He paid the boy ten yuan for cleaning the windows， most of which hadn’t been cleaned for at least a year.
他给了那个男孩十元钱擦那些至少一年未擦的窗户。
4.“形容词最高级+介词+关系代词”在定语从句中充当主语。如:
（1）There are sixty students in the class， the tallest of whom is Li Ming. 班上有六十名学生，其中最高的是李明。
（2）There are seven continents in the world， the largest of which is Asia. 全球有七大洲，最大的是亚洲。
5.“the+n.+of+which”引导的定语从句，相当于whose引导的定语从句。如:
（1）We took a photo of a rocket， the length of which was about 30 meters.=We took a photo of a rocket， whose length was about 30 meters. 我们给火箭拍了照，火箭大约长30米。
（2）Recently I bought an ancient Chinese vase， the price of which was very reasonable.=Recently I bought an ancient Chinese vase， whose price was very reasonable.
最近我买了一个中国古代花瓶，价格非常合理。
6.“介词+whose”修饰后面的名词。如:
He is the very man in whose pocket I found my lost money.
他就是那个我在他的口袋里找出我丢掉的钱的人。
7.“介词+which+不定式”此结构相当于一个简化了的定语从句。如:
（1）He found something about which to write（=he could write）. 他发现有些事是可以写的。
（2）The poor man has no house in which to live.=The poor man has no house in which he can live. 这个穷人没有房子住。
8.介词的选用要根据句意或一些固定搭配决定。其中的介词可以是in， on， about， from， for， with， at， of， without， to。如:
（1）Galilia built a telescope through which he could study the sky. 伽利略建起了望远镜，通过望远镜他可以研究天空。
（2）The cloth of which this coat is made is produced in Shanghai. 这件外套的`布料是由上海制造的。
（3）He wrote many articles in which he expressed his love for
his motherland.
他写了许多文章，在文章中他表达了对祖国的热爱。
但有些含介词的短语动词一般不能拆开，介词仍放在动词的后面。
如:listen to， depend on， take care of， pay attention to， look at等。
This is the boy whom she has taken care of.
这就是那个她照顾的非常好的男孩。
That is a problem we should pay close attention to.
这是一个我们应该密切关注的问题。
强调句与定语从句的区别是：在定语从句中一般使用关系代词that, which，who, whom或关系副词when, where，why等,先行词（中心词）一般是名词或名词短语，而在强调句中，可以用副词、介词短语或从句来作被强调的内容。；而在强调句中则主要使用that，who；
有时强调句在形式上和定语从句、状语从句很相似。我们除了从意思上进行区分外，还能根据强调句的结构特点来进行判断，如能去掉It was...that...后，句子仍然通顺，就是强调句。这一点很重要.
试比较：
①It is a question that needs careful consideration.
②It is novels that Miss Williams enjoys reading.
简析：句①是含有定语从句的句子，在此It是指示代词，It is a question是个"主语+系动词+表语"结构，如果去掉It is...that,句子结构就不完整了。句②是强调句，在此It是个引导词，没有具体含义，如果去掉It is...that，把语序稍加调整，句子结构仍然是完整的。
区分定语从句与强调句 区分定语从句和强调句可用还原法，因为强调句的基本句式为 It is （was）+被强调部分+that+句子的其余部分，因此只需将it is（was） 后面的部分还原到原来的句子中，如果成份完整，则为强调句，如果成份不完整则为定语从句。
1） It is this street _______I happened to meet him.
It is in this street _______I happened to meet him.
A．that
B．where
C．which
D．from which 首先，我们看到主句部分为 it is结构，可能是定语从句可能是强调句，利用还原法，将两部分分别还原，得出1．I happened to meet him this street. 2．I happened to meet him in this street. 1句子成份不完整，为定语从句，用where；2句子成份完整为强调句，选that。
2） Where did you meet him?
It is in the cinema_______ I met him.
It is in the cinema_______ door faces west.
A．that
B．where
C．whose
D．which 仍然采取还原法，得出1．I met him in the cinema. 2．Door faces west in the cinema. 1句子成份完整，确定为强调句，用that选A；2明显不是一个意思表达清楚的句子，其实本句是一个省略句，全句为：It is in the cinema _______door faces west that I met him. 强调句部分已经省略，而句中door faces west 是一个定语从句，表示门朝西开的电影院，因此选C，whose 在做题中我们经常可以看见带有定语从句的强调句，这时仍可用还原法加以辨别：
（1） Was it in the cinema _______Smith met you _______you saw the film?
A．that, that B．whom, then C．where, that D．which, where （C）
（2） Where did you found XingMing? It was in the office _______he worked. A．this B．which
在定语从句中one of 后的先行词若是可数名词的复数，谓语动词就用复数形式，the only one of 后的谓语动词用的是单数形式。
e.g. Tom is one of the boy students in our class who are often late. Tom is the only one of the boy students in our class who is often late.
5. 代词/名词＋ 定语从句，从句谓语动词的单复数与所修饰的词一致。 I , who am wrong, should apologize to him. 我错了，应该向他道歉。
She came across a former classmate who is very wealthy.
注意：在“ one of +复数名词＋定语从句”，定语从句一般看作修饰复数名
词，从句中的谓语动词用复数；在“the only one of＋复数名词＋定语
从句”结构中，定语从句应视为修饰单数名词，从句谓语动词用单数。 This is one of those cars that were damaged in the accident.
这是事故中被损坏的车中之一。
She is the only one of the girls who is interested in literature.
她是这些人中唯一喜欢文学的女孩。
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