as只能引导非限制性定语从句吗?

你首先要搞清楚限制性定语从句和非限制性定语从句的区别,然后再把as的用法搞清楚,这样才能知道他们的可比性.s……as
AS +adj(原级)+AS
AS +adv(原级)+AS
as soon as 一……就
as soon as possible 尽可能快地
as early as possible 尽可能早的
as carefully as you can 尽可能认真地
as careful as you can 尽可能认真的
1.as是连词,表示“随着”的意义.lives是life的复数,意义是“生活”.

2.as是连词,表示“因为,由于”的意义.wanting是现在分词,表示主动意义,wanting to buy cars=who want to buy cars.
As的用法小结
as可以作连词、介词及关系代词和副词.现将其用法小结如下:
（一）、 as作连词的用法:
1.作“在-------期间,当----的时候”引导时间状语从句.注意与when、 while的用法区别.
①下列情形时,只用as, 而不用when或while.
1)用于表示同一个人的两种动作交替进行,指一边----一边. 如:
The girl sings as she goes to school.
He looked behind occasionally as he went forward in the forest.
2)表示两个同步发生的动作或行?意思是随着-----的发展.如:
As time went on / by, she became more and more beautiful .
As children get older, they become more and more interested in everything.
3)表示两个短暂行为或事情几乎同时发生.如:I watched her as she read the book.
I thought of it just as you opened your mouth.
Just as the flying worm hit her face, she gave a loud cry.
4)接在名词后面表示某一个年龄段时.如:
As a young man, he was active in sports.
②when作"当……的时候"解,可以指较短的(一点)时间,也可指一段时间.如:When I was at college, I could speak several foreign languages. When the clock struck twelve, I had slept for 2hours.
③ while常表示一段较长的时间或一个过程,强调主句谓语动词与从句谓语动词同时发生.如:Work while you work. Play while you play.
2. As =Since 作"既然"、"由于"解,引导原因状语从句,常用来表示已为人们所知或显而易见的原因或理由.如: As he’s been ill for ages, I will help him.
As / Since you're not feeling well, you may stay at home.
As he wasn't ready , we went without him.
3. As =in the way that作"像"、"按照……的方式"解,引导方式状语从句.如:
Do as I told you.
Remember, you must do everything as I do.
4. 用于as--- as或not / so/ as ---- as中,前一个as是副词,后一个as是连词,引导比较状语从句.如:They helped the old as much as possible.
I don't speak English so/ as well as she does.
5. 表示虽然,尽管 等,引导让步状语从句,常用倒装语序,模式为:
adj. /adv. / n.+as +主语+谓语+主句.如: Young as he is, he knows much.
Tired as they were, they walked on.
6. 表示也------一样. She is a doctor, as was her husband.
（二）、 as作关系代词,引导定语从句,表示正如,这一点.如:
He is very careful, as we all know.
As is well-known, * belongs to China.
另外,当先行词被the same, such等词修饰时,常用as来引导定语从句.如:
Such a clever girl as she can learn anything quickly.
I was reading the same book as he bought yesterday.
（三）、as作介词的用法.
1.表示好像.如:He dressed as a policeman.
2. 表示作为当作.如：I found a job as a guide.
3. 当某人是某身份时.如：As a child , she was sent to abroad.
4. as引导的介词短语大多用作状语,as译为"作为";少数情况可引起宾语补足语.如:
As a Party member, I'll take the lead in everything. (状语)
She works as a model. (状语)
She has me as one of her best friends.(引起宾语补足语)
（四）、作副词的用法 1 表示与------等同.如：This dress is twice as expensive as that one. 2 像,如等.如：As before, he remained unmoved.
总之,通过以上的分析,我们对as的词性和用法有了比较全面的理解和把握,才能在实际的运用中做到心中有数,应付自如.限制性定语从句限制所修饰名词或代词的意义,一般说来如把从句去掉句子意思就不清楚,甚至失去意义.而非限制性定语从句主句(句子的其他部分)关系不太紧密,对所修饰名词或代词的意思没有太大影响,把它们拿掉,句子依然很完整,它们可以说是附加上去的东西,而且通常都有逗号把它们和句子的其他部分分开.具体说来,限制性定语从句与非限制性定语从句有以下几个方面的区别：

1. 形式不同限定性定语从句主句和从句之间不用逗号隔开,口语中使用时也不停顿；而非限定性定语从句与主句之间通常2. 作用不同限定性定语从句用于对先行词的意义进行修饰、限制和识别,如果去掉,就会造成句意不完整或概念不清；而非限定性定语从句用于对先行词起补充说明作用,如果省略,句意仍然清楚、完整： People who take physical exercise live longer.
进行体育锻炼的人活得长些.(若把从句去掉句子就失去意义)
His daughter, who is in Boston now, is coming home next week. 他女儿现在波士顿,下星期回来.(若把从句去句子意义仍然完整)
3. 翻译不同在翻译定语从句时,一般把限定性定语从句翻译在它所修饰的先行词之前,而把非限定性定语从句与主句分开：He is the man whose car was stolen. 他就是汽车被窃的那个人.
I’ve invited Jim, who lives in the next flat. 我请了吉姆,他就住在隔壁.
我请了吉姆,他就住在隔壁.
4. 含义不同比较：I have a sister who is a doctor. 我有一个当医生的姐姐.(姐姐不止一个)
I have a sister ,who is a doctor. 我有一个姐姐,她是当医生的.(只有一个姐姐)
5. 先行词不同限定性定语从句的先行词只能是名词或代词,而非限定性定语从句的先行词则可以是名词或代词,也可以是短语或句子；另外,当先行词为专有名词或其他具有独一无二性的nt: 2.0">Peter drove too fast, which was dangerous. 彼得开车很快,这是很危险的.(which指drive too fast)He changed his mind, which made me very angry. 他改变了主意,这使我很生气.(which指整个主句)Mr. Smith, who is our boss, will leave for Japan LINE-HEIGHT: 18pt; mso-char-indent-count: 2.0">我们的老板史密斯先生下周要去日本.(先行词为专有名词,要用非限制性定语从句修饰)
Her father, who has a lot of money, wishes her to study abroad. 她父亲很有钱,希望她出国学习.(先行词为表独一无二意义的普通名词,要用非限制性定语从句修饰)
6. 关系词不同关系词that和why可用于限制性定语从句中,通常不用于非限制性定语从句；另外,在限制性定语从句中,关系词有时可以省略,而在非限制性定语从句中关系词一律不省略.