As 专题

1. As +名词

as是介词

a:作状语，一般会和主句分开

例如：As a logical consequence of this development，separate journals have now appeared aimed mainly towards either professional or readership

b：放在名词后作定语

例如：As a result, the support for ambition as a healthy impulse， a quality to be admired and fixed in the mind of the young， is probably lower than it has ever been in the U.S.
As a result:状语
as a healthy impulse定语

2. 动词+名词+as

as是介词

例如：regard 。。。as。。。；define。。。as。。。；view。。。。as。。。
例如：I shall view him as a genius

3. As 引导定语从句

As引导定语从句，可放在句子前面，也可后面

a.限制性定语从句，主要再such....as.....；the same.....as/that....；as......as.....；so......as......等

As 引导的限制性定语从句一般做主语或者宾语
例如：It is the same person as we wanted to find（宾语）
Such girls as he knows are good at English （宾语）
There are as many books as are needed （主语）

b非限制性定语从句：as 引导非限制性定语从句，指代整个句子，可位于句首，句中，句尾。

例如：
As everyone knows，China is a beautiful country（宾语）
The earth，as we know，moves round the sun（宾语）
Tome works hard and is willing to help others，as we all know。（宾语）
She fight aginst it，like a bravely man as she is （表语）
As 引导非限制性定语从句谓语动词被动时候，As做主语
例如
As is known to all，Taiwan is part of China
As is illustrated in the picture。。。。
As is known/announced/reported to all。。。。

综上所述，as 引导定语从句，必须做成分，否则就是下面的状语从句，做从属连词

例如：

1.as 表示当。。。时候引导时间状语从句

As I waited at the stop，I saw you
Shed rose up as he entered

2. As 表示因为由于，引导原因状语从句

As she was not well， went there alone
As he is a tailor，he knows what to do with this cloth

3. As 表示虽然 ；但是 引导让步状语从句，从句常用倒装，可用though代替

Child as he is，he knows a lot=Though he is a child， he knows a lot

4.as 表示按照，依照，像引导方式状语从句，从句位于主句之后

You should do as the teacher tell you

5. As。。。as 比较状语从句，

She does not work as hard as I （do）

参考《不就是语法和长难句吗》