as引导的定语从句用法解析如下：

一、as引导的限制性定语从句

as可引导限制性定语从句，用于指代与先行词同类型的人或物，在从句中作主语、宾语或表语。常与such, same等连用。

1.as与such连用： such…..as……. 像….那样的

We have found such ingredient as is used by them. 我们已经找到了像他们采用的那种原料。

as指代与他们使用的同类型的ingredient，在从句中作主语。

He asked such questions as were natural for an innocent man to ask. 他问了（像）清白的人自然而然地会问的那些问题。

as指代与清白的人问的类似的questions，在从句中作主语。

There is no such book as you refer to. 这里没有你提到的那种书。

as指代与你提到的同类型的book，在从句中作宾语。

I don’t know whether he is such a great man as people say.

I am just such a little girl as you are. 我只是一个和你一样如此小的女孩子。

as指代与你一样小的little girl，在从句中作表语。

2. as与same连用：the same….as…. 和….一样的

She started giving the same answers as were given by the others. 她开始给出和其他人给的一样的答案。

as指代与其他人给的一样的answers，在从句中作主语。

She bought the same bike as you did. 她买了和你买的一样的自行车。

as指代与你买的一样的bike，在从句中作宾语。从句中的谓语动词与主句的谓语动词一致，用did代替

They are facing the problem as we did ten years ago.

This is not the same job as it was 10 years ago. 这工作和10年前的工作不一样。

as指代十年前的job，在从句中作表语。

She is much the same as (she was) 10 years ago.

3.As many…as / as many as和as much…as / as much as

You can take as many books as you need.

There are a lot of books here. You can take as many as you want.

You can drink as much wine as you want.

You can drink as much as you want.

We can learn as much from success as from failure.

二、as引导的非限定性定语从句

as可引导非限制性定语从句，含有“正如/像”之意。

1.常用于指代整个主句，对主句内容进行评述或加以说明，有点像插入语。在从句中作主语、宾语或表语。

He is a boy, as we all know from his voice. 他是个男孩，听他的声音就知道了。

as指代句子（He is a boy），在从句中作宾语。

As has been said before, we must solve the problem as soon as possible.

正如之前所述，我们应当尽快解决问题。

He is an honest man, as indeed he is.

as引导的非限制性定语从句，可在主句前或后，常与 know, say, explain, mention, expect, see等搭配，常见句型搭配：

As is often the case 通常如此

As is well known to all 众所周知

As has been said/stated above/before 如上所述

As was expected 正如预料的那样

As has been pointed out 业已指出

As explained before 如前所释

As has been proved 业已证明

As might be expected 正如所料

As mentioned above 如上所述

As often happens 正如经常发生的那样

As is shown in the picture 如图中所示

As has been announced 正如被宣布的那样

As often happens 正如经常发生的那样

As appears 正如呈现的那样

As we all know 正如我们所知

As we can see 正如我们所见

As we had expected 正如我们所料

2.as有时可指代主句中的名词，作主语补语。

The Chief Officer, as he is often called, is actually the boss of the company.

常被成为主管的他实际上是公司的老板。