as引导的非限制性定语从句：
1： as引导限定性定语从句，常用于以下句式，其中关系代词在从句中担当主，宾，表语：
①so/as/such+名词+as…像……一样的，像……之类 :
We have found such materials as are used in their factory.
These houses are sold at such a low price as people expected.
This book is not such as I expect.
Such things as you described are rare now.
He isn’t such a man as you described.
He is such a lazy man as nobody wants to work with
=he is such a lazy man that nobody wants to work with him. I want to have such a dictionary as he has.
I have bought such a watch as was advertised on TV.
Mount Wuyi is such an attractive place of interest as everyone likes to visit.
Such money as he earned was spent on spirits and tobacco. He was not half such a coward as we took him for.
②the same +名词+as 和…同样的
He is not the same man as he was /used to be.
The west is not the same as it was 20 years ago.
I like the same book as you do .
I shall do it in the same way as you did.
This is the same pen as I lost yesterday.
Is this the same mosquito as bit you just now?
2: as引导的非限定性定语从句，指代整个主句的内容，但不同于which的是，它引导的定语从句既可以位于主句的前面，也可以位于主句的后面。

它的意思是“正如”，在这些从句中as作主语或宾语。

经常使用的短语又：
as(it) seems likely, as (it) often happens, as (it) was printed out, as (it) was said earlier, as I remember (it), as I unde rstand (it), as (it) appears, as is known, as is said, as is reported, as announced, as we had expected, as everybody c an see, as is mentioned above. 如：
As we all know, china is a developing country.. (在句首只能使
as) As is known to all, he is the best student in our class.
As was expected, he failed in the exam.
As anybody can see, they were telling a lie.
The girl married a rich man, as is natural.
As is often the case, my mother has the final say in the argument.
______ I explained on the phone, your request will be considered at the next meeting. (2005年浙江卷)
A. When
B. After
C. As
D. Since
______ is reported in the newspapers, talks between the countries are making progress. (2004年北京卷)
A. It
B. As
C. That
D. What
______ is often the case, we have worked out the production plan.
A. Which
B. When
C. What
D. As
As is known to us all, the 2008 Olympic Games will take place in Beijing.
As is known to everybody, Taiwan is a part of china. We must unify it.
The weather turned out to be very good, which was more than we could expect.
As is known to everybody, the moon travels round the earth once everyone
=the moon travels round the earth once every month, as/which is known to everyone.
=it is known to everybody that the moon travels round the earth once every month.
=what is known to everybody is that the moon travels round the earth once every month.
She has been absent again, as is expected. Jack has won the first prize, as it often happens.
She has read widely in Romantic literature, as it appears from her essay.
As is reported in the newspapers , talks between the two countries are making progress.
As is often the case, we have worked out the production plan.
（which, when, what, as） As is mentioned above, the number of the students in senior high schools is increasing.
A war is so cruel that is always causes great losses, as has happened in Iraq and other countries. (江西联考) Meeting my uncle after all these years was an unforgettable moment, one (that) I will always treasure.
=meeting my uncle after all these years was an unforgettable moment, which I will treasure.
As I explained on the phone, your request will be considered at the next meeting.
So as you can imagine, if your skin gets burnt It can be very serious.
as 引导的限制性定语从句与其他从句的比较
This is the same book as I lost.这本书和我丢的那本一模一样。

(定语从句) This is the same book that I lost.这本书就是我丢的那本。

(定语从句)
This is such an interesting book as we all like./ This is so interesting a book as we all like. 这是大家都喜欢的如此有趣的一本书。

(定语从句)
This is such an interesting book that we all like it. / This is so interesting a book that we all like it. 这本书如此有趣，大家都喜欢。

(结果状语从句)。