as作定语从句

　　as和which都能引导定语从句,并都可以在定语从句中做主语或宾语,代表前面整个句子.以下是小编为大家整理分享的as作定语从句，欢迎阅读参考。

　　as作定语从句

　　透析which与as在定语从句中的运用

　　定语从句是高中英语的主要语法项目之一,也是高考英语的常考知识点,尤其是as和which引导的定语从句,更是历年高考试题中的重点和热点.as和which在引导定语从句时既有相同点又存在着很大的区别.

　　一、相同点

　　1. as和which都能引导定语从句,并都可以在定语从句中做主语或宾语,代表前面整个句子.

　　例 1 He married her, as / which was natural. 他跟她结婚了,这是很自然的事.

　　例 2 He is honest, as we can see. 他很诚实, 这一点我们看得出来.(表示人们从日常主观常识, 经验对某一事情的看法、评价,用as为妥.)

　　2. 当非限定性定语从句置于句末时,as和which都可用来引导这个定语从句.

　　例 3 The number of senior high school students is increasing, as is mentioned above. （as引导非限定性定语从句,意思是“正如”.此时也可以换用which引导,但意思有别,意思是：“这一点上面提到了”.）

　　二、不同点

　　（一）语义上的区别

　　as作为关系代词仍多少保留 “理由”“比较” “方式” “等同”等意义,而which没有这些意义.因此,由as引导的定语从句通常在意义上不可与主句相悖,而且一般是肯定的,对主句意义起相辅作用,表示 “正如”等意义；而which引导从句则不受此限制.

　　例 4 Mother treats me just like a baby,which I can’t bear．妈妈对我就像小孩,我真受不了.

　　例 5 She has married again,which was unexpected．她又结婚了,这是大家没有预料到的.

　　上面两句中的which都不宜用as.

　　但当否定的定语从句作正面理解,对主句起相辅作用而不是与其相悖时,仍可用as.

　　例 6 He turned his eyes on Philip’s face,as he had not done for ten years．他转过身来看着菲利普的脸,他十年来没有这样看过他的脸了.

　　例 7 He really can’t lend you the money,as you might not realize．他的确不能把那些钱借给你,这一点你可能意识不到.

　　（二）用法上的区别

　　1. which与as引导非限制性定语从句的区别：

　　（1）which只能放在主句后面,而as引导的从句位置相对比较灵活,可以放在前,也可以放在后,甚至还可以分割主句.另外,as 常常有“正如、正像”的含义.

　　例 8 As he realized, I was very useful to him.（在前）

　　例 9 Air, as we know, is a gas. （在中）

　　例 10 He was a foreigner, as I know from his accent. (在后)

　　例 11 He came late again, which made his boss angry.（在后）

　　例 12 As is known to all, China is a developing country. 众所周知,中国是发展中国家.

　　（2）在which引导的.定语从句中,谓语动词若是am, is, are,则这些系动词不能省略,而as后面若是这种情况,则可以省略.

　　例 13 He is a teacher, as (is) clear from his manner. (is可以省略)

　　例 14 He said he had never seen her before, which was not true. （was 不可省略）

　　（3）当which引导的从句在意义上近乎并列关系时,可以用and this, and that代替,意思是“这件事”.

　　例 15 He changed his mind, which(and this, and that) made me very angry. 他改变了主意,这使我很生气.

　　而as主要起与上下文连接的作用,表达说话人的看法、观点,并指出主句内容的出处或根据等.

　　例 16 Einstein, as we know, is a famous scientist.爱因斯坦,众所周知,是一位伟大的科学家.

　　例 17 As is announced in today’s newspaper, we must improve our style of work. 今天的报纸上说,我们必须改进工作作风.

　　（4）做主语时,which既可以作系动词be的主语,也可以作实义动词的主语,而这时as 只可以做系动词be的主语.

　　例 18 He married her, which was natural. （可用as代替which）他和她结婚,这是很自然的事.

　　例 19 He won a /the Nobel Prize in chemistry, which made him illustrious. (不可用as代替which)他获得了诺贝尔化学奖,这使他名扬天下.

　　（5）当定语从句位于主句之后,纯粹表示主句所述的内容,不带有“如……那样”的意思时,往往用which, 而不用as.

　　例 20 They were invited to the state banquet, which(as) was a great honor to them. 他们被邀请参加国宴,这对他们来说是莫大的荣幸.

　　例 21 We had to sleep in our wet clothes, which was most uncomfortable. 我们不得不穿着湿衣服睡觉,这简直太不舒服了.

　　（6）当定语从句有“如同……那样”的含义时,用as比用which更常见,而这些从句几乎成为固定说法.

　　例 22 Things will turn out contrary to one’s wishes, as is often the case. 事与愿违,这是常有的事.

　　例 23 As was natural, this inordinate hope was followed by an excessive depression.这种过分希望之后,接着是极度的沮丧,是很自然的事.

　　例 24 The material is elastic, as is show in the figure. 这种材料有弹性,如图所示.

　　例 25 As we know. 众所周知.

　　例 26 As has been said above/ before. 正如前文所述 .

　　（7）当定语从句的关系代词指的是先行词本身时,只能用which.

　　例 27 These apple trees, which I planted tree years ago, have not borne any fruit.这些苹果树是我三年前种下的,没结出任何果实.

　　例 28 The Thames, which is now clean enough to swim in, was polluted for over a hundred years.泰晤士河,现在已经很干净,可以在里面游泳,它曾被污染了一百多年.

　　（8）带介词的典型的定语从句,必须用which,不能用as.

　　例 29 There is a great deal of oxygen around us, without which we could not live. 我们周围有许多氧气,没有它我们就无法生存.

　　例 30 The shed in our garden, in which we often played, has lasted for a long time. 我们经常玩耍的花园里的那个棚子,已经有很长时间了.

　　（9）as常与从句中的know,see, hear,expect等动词连用,也常用于as often happens,as is often the case（常有的事）等句子中；而which一般不用于以上情况.

　　例 31 As is well known,Shanghai is a big city．

　　（10）当后置的非限制性定语从句是否定结构时,只能用which引导.

　　例 32 The result of the experiment was very good, which we hadn’t expected.

　　2. 引导限制性定语从句时which与as的区别：

　　(1)先行词如果是表示物的名词或代词,在从句中又做介词的宾语时,只能用which.

　　例 33 This is the pan in which I boiled the milk. 这就是我煮牛奶的锅.

　　（2）前面有as时,引导定语从句的关系代词用as, 不用which.

　　例 34 There are as many dictionaries as are needed.所需要的字典都有了.

　　（3）前面有such时,引导的定语从句的关系代词用as, 不用which.

　　例 35 Such women as know Tom thought he was charming. 认识汤姆的女人都认为他很迷人.

　　例 36 I have never heard such stories as he tells. 他讲的那些故事我从没听过.

　　（4）前面有the same时,引导定语从句的关系代词用as而不用which.

　　例 37 We are facing the same problems as we did years ago.我们正面临着和多年以前同样的困难.

　　例 38 This is the same wallet as I lost. 这只钱包与我丢失的那只相同.

　　（5）单个词引导限制性定语从句时,一般不用as而用which和that.由于关系词在从句中作宾语,which和that都可以省略.

　　例 39 The project which/that a British businessman has invested in is under construction at present.

　　（6）“介词+关系代词”引导定语从句时,只能用which.

　　例 40 Recently I bought an ancient Chinese vase, the price of which was very reasonable.

　　注：此时的which不能用as来代替.另外还应注意：引导定语从句时,which不能单独作定语,此时不管先行词是人还是物,都只能用whose引导,但指物时,可以用of which替换.

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