Ⅳ. 关系代词 as 代替整个主句, 并在从句中作主语、宾语、表语之用。as 引出的从句为非限制性定语从句。
As (is) announced in today's papers, they have succeeded in solving many problems in accordance with the new theory. 据今天报纸发表, 他们已根据新的理论成功地解决了许多问题。（as 在从句中作主语。）
As is often the case, we have overfulfilled the production plan. 像往常情况一样, 我们又超额完成了生产计划。（as 在从句中作主语。)
As we know, materials expand and contract with the increase and decrease of temperature. 我们都知道, 材料随温度升降而胀缩。（as 在从句中作宾语。）
This machine, as might be expected, has stopped operating. 正如所料, 这台机器已停止运转。 （as 在从句中作主语。)
She rises early and takes a walk every morning, as is usual with her. 她每天早晨早起散步, 这对她已习以为常了。（同上, 但 as 表示整个主句意思。）
As is very natural, man can't live without air and water. 人没有空气和水就不能生存, 这是当然之事。（全部同上。）
The size of the audience, as we had expected, was well over one thousand. 听众人数, 正不出我们预料, 大大超过一千人。（as 代表主句意思, 在从句中作宾语。）
If he comes late, as is usual, for another time, we’ll not receive him. 如果他再次像往常那样迟到, 我们就不予以接待。（as 表示条件从句内的 he comes late。）
Are these two totally different things, having no interconnection, as is often implied？这些是否是通常所指的没有内在联系的两个完全不同的东西？（as 在从句中作主语。现在分词短语 having no interconnection 作非限制性定语, 说明前面的 things。）
代替整个主句的关系代词 as, 常见于下列从句：
as has been said before 如上所述
as may be imagined 如可想像出来的那样
as is well known 众所周知
as we all can see 正如我们大家都能看到的那样
as often happens 正如经常发生的那样
as will be shown in Fig. 5 将如图 5 所示
as has been explained in the preceding paragraph 如在上段里已解释了的那样
as has been already pointed out 正如已指出的那样
注：上述句子按语法分析为非限制性定语从句, 但翻译时一般可译为“如…”、“像…”、“正如…”等.
Ⅴ. as 有时代替主句里的表语意思, 并在从句中作表语
Internet access is very simple, as indeed it is. 网上访问很简单, 它实际上的确是这样. (as代替 simple。)
Gasoline is combustible, as are all of the liquids listed in the following section. 汽油是易燃的, 下一节里所列举的那些液体也都是易燃。（as 代替 combustible。)
He is a brave man, as are all other members of his family. 像他家庭其他成员一样, 他也很勇敢。
An atom is not a solid spherical particle, as it was once thought to be. 原子并不像人们曾经认为的那样是刚性球粒。（as 代替 a solid spherical particle, 在从句中作 to be 后的表语, 并和 to be 一起作主语补语。）
Dr. Ouyang is a large-hearted man, as the large-minded men are apt to be. 欧阳博士是个慷慨的人, 而心胸开阔的人往往都是这样。
She thinks my answer incorrect, as it probably is. 她认为我的答案不对, 也许我的答案就是不对。（as 相当于 incorrect。)
Now many young people wish to be scientists, as it is quite possible for them to be on condition that they work hard. 目前许多青年都想当科学家。只要他们刻苦努力, 这大有可能如愿以偿的。
二、as 作关系副词, 引出定语从句
He answered with the same simplicity as he asked. 他回答和提问, 都是同样的直率简洁。
We repaired the air conditioner (in) the same way as he did. 我们采取和他同样的方法去修理那台空调器。
We go the same way as they do. 我们和他们走同样一条路。
A magnetic field maybe represented in the same manner as an electric field. 磁场可采用和电场同样的办法表示出来。(定语从句内谓语省略。）
以上例句里的 with the same simplicity, the same way, in the same manner 等词组在主句里都是状语, 而 as 所代替的也就是这些词组, 所以 as 是关系副词。
三、such as, as such 和 as that 的用法
I. “名词, such as…”这里 such as 是复合连接词, 引出同位语, 以对前面的名词起列举作用。可译为“例如”。
There are different forms of energy, such as heat energy, sound energy, electric energy, and chemical energy. 有各种不同的能, 例如热能、声能、电能和化学能。
Soft materials, such as cloth, do not carry sounds so well as wood, iron and other solids. 像布那样柔软的材料, 不如木材、铁和其它固体东西传导声音那样好。
II. “… such as”这里 such 是代词, 作“这样的人、事、物”讲, as 是关系代词, 引出定语从句。
This book is not such as I expect. 这不是一本像我所希望的书。（such 是代词作表语用, 是 as 的先行词。） 比较：This is not such a book as I expect. (句义同上, 但 such 作定语用。)
I will explain this phenomenon to such as would like to know it. 我要对那些愿意了解这种现象的人解释。(such 是代词, 作“这样的人”讲。)
上句中 to such 表示“给这样的人”，作状语，但表示间接宾语的含义，而 as 引出的定语从句说明 such, as 是从句主语。
The new type of space shuttle was made last week, such as none of us had seen before. 这种新型的航天飞机上周制成, 像这样的飞机过去我们中间谁也没有见过。
III. as such 作“像这样的人、事、物”、“作为这样的人、事、物”、“以 … 资格、名义、身份“、“因而”讲。
We agree to the plan as such. 我们同意像这样的计划。
He is an old worker, and is respected as such. 他是一位老工人, 因而受到尊敬。（或译为：受到老工人应该受到的尊敬。）
四、用连词 as 等引出状语从句
Ⅰ. 时间状语从句连词 as 正当…的时候, 随着…
He came up as I was speaking. 我正在说话的时候，他来了。
As the piston moves down, the pressure in the cylinder decreases. 当活塞下移时, 汽缸里的压力减小。
We cannot see sound waves as they travel through air. 声波在空气申传播时, 我们是看不见的。
As a little girl she began to operate a computer. 她还是个小女孩时就开始操作计算机。（ as 后省略了 she was。)
The volume varies as the temperature rises. 体积随温度升高而变。
注 1：由 as long as 或 as long as 引出的时间状语从句可参阅第 015 节 24~34, 而由 as soon as引出的时间状语从句可参阅第 015 节 34~49。
注 2：还可用 as and when 表示“当…时”, 主要用来指一件不肯定的将来的事或一个行动。例如：They will decide on their team as and when they qualify for the competition. 当他们有资格参加比赛时将决定其球队的组成。
II. 原因状语从句连词 as 或 in as much as 由于, 因为
As this problem is of great interest, we will discuss it once again. 因为这个问题很有意义, 所以我们再讨论一次。
As they had forgotten your address, they did not know how to get in touch with you. 由于忘记了你的地址, 他们（当时）不知如何跟你取得联系.
In as much as it is raining hard, I won't go for a walk. 由于正下大雨, 我就不去散步了。
III. 让步状语从句连词 as 虽然, 尽管, 无论
Busy as he is, he studies English very hard. 尽管他忙, 他还是努力学习英语。
Small as atoms are, electrons are still（或 even）smaller. 原子虽然很小, 但电子更小。
Much as I should like to see you, I am afraid you could not have any free time. 虽然我特别愿意看见你, 但恐怕你不可能有空余时间。
Child as he is, he knows something of electricity. 他虽然还是个小孩, 但他懂得一些电学知识。（注意在本句型中, 作表语用的可数名词单数前不能加冠词 a。）
Try as you may, you will not succeed. 虽然你可以试试, 但不会成功。
Study as he may, he won't get good marks, because his method of studying is not scientific. 虽然可以学习, 但他得不了好分数, 因为他的学习方法不科学。
这种让步状语从句的特点：把从句里的表语（第一、二、四句）、状语（第三句中的 much）或实义动词（第六句中的 study）提前, 紧跟着就是 as, 然后再跟随其它成分。
必须注意, 本句型偶尔可用于表示原因状语从句。只能根据上下文来判别。如果主句和从句之间在意义上有转折, 则从句为让步状语从句；如果主句和从句有因果关系, 则从句为原因状语从句。例如：
a. Old as he is, he dares the dangers of icy north。虽然他老了, 但仍敢于冒北方冰寒的危险。
b. Old as he is, he has to go to bed early. 因为他老了, 他不得不早去睡觉。
Ⅳ. 比较状语从句
A. 一般比较（从句内常省略与主语相同的成分）
(a) as … as 和……一样（或同样）的…[注意：这里第一个 as 是副词, 作“一样”讲；第二个 as 是连词, 作“如同”、“像”讲。]
This line is as long as that one (is). 这条线和那条线同样长。
本句也可写成：This line is no less long than that one. 但是注意 as long as 还可用于条件状语从句。
Dying is as natural as living. 死和生一样, 都是自然现象。（意译）
He works as hard as we. 他工作和我们同样努力。
Wheel A revolves as fast as wheel B. A 轮和 B 轮旋转得同样快。
This is just as important an experiment as that. 这个实验和那个实验正好同样重要。
The speed of sound in water is about four times as great as in air. 声音在水中的速度比在空气中大三倍左右。（直译：…… 速度是在空气中的四倍左右。）
The temperature in the tower is as high as 500°C. 塔内温度高达500℃。
The art of paper-making was discovered as early as 1800 years ago. 远在一千八百年前就发明了造纸法。
He is as diligent as (he is) honest. 他又诚实又勤奋。
The garden is as still as still (can be). 这座花园再寂静不过了。
Her answer is as plain as plain can be. 她的答复再明白也没有了。
Einstein was as great a scientist as any（或 anybody）(else). 爱因斯坦是一位少有的伟大科学家
(b)not so as 不如（或没有）……那样……
Line AB is not so long as line CD. AB 线不如 CD 线（那样）长。
Wheel A does not revolve so fast as wheel B. A 轮没有 B 轮旋转那样快。
Man uses some non-metals not so widely as metals. 人类使用某些非金属，不如金属那样广泛。
Nothing is so precious as time. 时间最可贵。（原意为：没有东西象时间那样可贵了。）
The work did not go so smoothly as we hoped. 工作进行得没有我们希望的那样顺利。
None of the pure metals is so valuable to the industry as the alloys. 对工业来说, 没有一个纯金属像合金那样有价值。
(c) not as … as 和……不一样…（强调两者间的不同）
Line AB is not as long as line CD, but a little longer（或 shorter）. AB 线和 CD 线的长度不一样，AB 线比较长一些（或短一些）。
Wheel A does not revolve as fast as wheel B, but much faster. A 轮和 B 轮的旋转速度不同，A 轮的旋转快得多。
注：上述两句中若没有接上 "but…", 则 not as … as 通常和 not so … as 同义, 都表示“前者不如后者…”含义。
