第1个回答 2006-08-01
1. 一般过去时表示过去某个时间发生的事、存在的状态或经常发生的动作。说话的侧重点只在于陈述一件过去的事情,不强调对"现在"产生的影响。如:
He visited Guilin in 1998.他1998年参观过桂林。(只说明去桂林的时间)
2. 现在完成时表示动作发生在过去,对现在造成了影响或产生了结果。不与确定的过去时间状语连用。如:
Jill has bought a new computer.吉尔买了一台新电脑。(着重点是现在有了一台新电脑)
3. 两种时态的区分
(1)一般过去时的谓语动词用过去式,而现在完成时的谓语基本构成是"助动词have /has +过去分词"。如:
(2)一般过去时通常与表示过去的时间状语连用。如:yesterday, last week, two years ago, just now, in 2002等;而现在完成时则常与just, already, ever, never等副词和these days, this week, since..., for...等表示一段时间的状语连用。
看看以下的几组句子,有什么区别?
① Have you seen the film?(A)
Did you see the film?(B)
[说明] 你看过这部电影吗?(A)句强调的是被问者对剧情是否了解;(B)句强调的是看这部电影的动作是否发生过,并不强调是否知道其内容。
② How has he done it?(A)
How did he do it?(B)
[说明]他是怎么做的这件事?(A)句强调的是他做这件事的方式对现在产生了某种影响;(B)句单纯的
询问做这件事的方式。
③ He has lived in Beijing for 8 years.(A)
He lived in Beijing for 8 years.(B)
[说明]他在北京住了8年。(A)句讲的是到目前为止他在北京住了8年,可能还会继续在北京住下去。(B)句讲的是他在北京住过8年,现在不在北京了。
第2个回答 2006-08-01
现在完成时
1. 动词的构成:现在完成时由“助动词have(第三人称单数用has)+动词过去分词”构成。规则动词的过去分词与过去式是一样的, 不规则动词的过去分词需逐个记忆。 e.g. Have you seen Peter recently?
2. 用法
A. 表示发生在过去并已完成但对现在仍有影响或产生结果的动作。常用的状语有already, ever, never, just, up to now, not…yet , so far, by now, recently, lately等。
e.g. He has already heard the bad news, so you don’t have to tell him about it again. I have just finished my work.
B. 表示过去持续到现在或可能继续下去的动作或状态。
常与表示一段时间的状语连用,如how long, for ten years, since 1980 (以及since引导的时间状语从句), by that time等 .
e.g. I have waited for him for two hours, but he hasn’t been here yet.
特别提醒
A. 现在完成时不能与表示具体过去时间的状语连用,象yesterday, last week, ago, when , just now (刚才)等。例如:
不能说:I have seen the film a week ago .
应该说:I have seen the film before./I saw the film a week ago.
B.某些短暂性动作概念的动词,不能与表示一段时间的时间状语(for ten years , since 1980 等)连用
不能说:I have left my hometown for ten years.
应该说:I have been away from my hometown for ten years ./ I left my hometown ten years ago.
不能说: I have left my hometown since 1980.
应该说: I have been away from my hometown since 1980./ I left my hometown twenty years ago.
C. 这些短暂性动作概念的动词的否定式,一般是可以与表示一段时间的时间状语连用的。
e.g. I haven’t gone to see my uncle for two years.
D. have/has been to与have/has gone to 的区别:这两个结构都可表示“去”, 但含义不同,have/has been to表示“曾去过某地”,强调过去的经历,常与状语ever, never等连用, 而have/has gone to表示“已经去某地了”,说话时不在此地。
e.g. I have been to the bank today. --have you ever been to the Great Wall? —No , I have never been there.
Some of the boys have gone to the reading-room.
E. have gone to的肯定式一般只能用语第三人称, 不能用于第一,第二人称,因为 have gone to 的含义是:主语不在说话的地方。
可以说:She has gone to the reading-room. 不能说:I have gone to the reading-room./You have gone to the reading-room.
F. 在“It is + 一段时间+since”结构中,It is也可改用It has been. e.g. It is (has been) a year since I came to this school.
G. 在“It is the first time (that) …”中, that从句中用现在完成时。
e.g. It is the first time that I have visited Guangzhou.
比较过去时与现在完成时
1)过去时表示过去某时发生的动作或单纯叙述过去的事情,强调动作;现在完成时为过去发生的,强调过去的事情对现在的影响,强调的是影响。
2)过去时常与具体的时间状语连用,而现在完成时通常与模糊的时间状语连用,或无时间状语。
一般过去时的时间状语:yesterday, last week,…ago, in1980, in October, just now, 具体的时间状语
共同的时间状语: this morning, tonight,this April, now, once,before, already, recently,lately
现在完成时的时间状语for, since, so far, ever, never, just, yet, till / until, up to now, in past years, always,
不确定的时间状语
3)现在完成时可表示持续到现在的动作或状态,动词一般是延续性的,如live, teach, learn, work, study, know.
过去时常用的非持续性动词有come, go, leave, start, die, finish, become, get married等。
举例:I saw this film yesterday.(强调看的动作发生过了。)
I have seen this film. (强调对现在的影响,电影的内容已经知道了。)
Why did you get up so early?(强调起床的动作已发生过了。)
Who hasn't handed in his paper? (强调有卷子,可能为不公平竞争。)
She has returned from Paris. 她已从巴黎回来了。
She returned yesterday. 她是昨天回来了。
He has been in the League for three years. (在团内的状态可延续)
He has been a League member for three years. (是团员的状态可持续)
He joined the League three years ago. ( 三年前入团,joined为短暂行为。)
I have finished my homework now.
---Will somebody go and get Dr. White? ---He's already been sent for.
句子中如有过去时的时间副词(如 yesterday, last, week, in 1960)时,不能使用现在完成时,要用过去时。
(错)Tom has written a letter to his parents last night.
(对)Tom wrote a letter to his parents last night.
11.11 用于现在完成时的句型
1)It is the first / second time…that…结构中的从句部分,用现在完成时。It is the first time that I have visited the city. It was the third time that the boy had been late.
2)This is the… that…结构,that 从句要用现在完成时.This is the best film that I've (ever) seen. 这是我看过的最好的电影。 This is the first time (that) I've heard him sing. 这是我第一次听他唱歌。
典型例题
(1) ---Do you know our town at all? ---No, this is the first time I ___ here.
A. was B. have been C. came D. am coming
答案B. This is the first time 后面所加从句应为现在完成时,故选B。
(2) ---Have you ____ been to our town before? ---No, it's the first time I ___ here.
A. even, come B. even, have come C. ever, come D. ever, have come
答案D. ever意为曾经或无论何时,反意词为never,此两词常用于完成时。 This is the largest fish I have ever seen. It is / was the first time +that-clause 的句型中,从句要用完成时。
注意:非延续性动词的否定形式可以与表示延续时间的状语连用。即动作不发生的状态是可以持续的。
(错)I have received his letter for a month. (对)I haven't received his letter for almost a month.
11.12 比较since和for Since 用来说明动作起始时间,for用来说明动作延续时间长度。
I have lived here for more than twenty years. I have lived here since I was born..
My aunt has worked in a clinic since 1949. Some new oilfields have been opened up since 1976.
I have known Xiao Li since she was a little girl. My brother has been in the Youth League for two years.
I have not heard from my uncle for a long time.
注意:并非有for 作为时间状语的句子都用现在完成时。
I worked here for more than twenty years. (我现在已不在这里工作。)
I have worked here for many years. (现在我仍在这里工作。)
小窍门: 当现在完成时+一段时间,这一结构中,我们用下面的公式转化,很容易就能排除非延续动词在完成时中的误使。
1)(对) Tom has studied Russian for three years.
= Tom began to study Russian three years ago, and is still studying it now.
2)(错) Harry has got married for six years.=Harry began to get married six years ago, and is still getting married now.
显然,第二句不对,它应改为 Harry got married six years ago. 或 Harry has been married for six years.
11.13 since的四种用法
1) since+过去一个时间点(如具体的年、月、日期、钟点、1980, last month, half past six) I have been here since 1989.
2) since +一段时间+ ago I have been here since five months ago.
3) since +从句 Great changes have taken place since you left.
Considerable time has elapsed since we have been here.
4) It is +一段时间+ since从句 It is two years since I became a postgraduate student.
11.14 延续动词与瞬间动词
1) 用于完成时的区别
延续动词表示经验、经历; 瞬间动词表示行为的结 果,不能与表示段的时间状语连用。
He has completed the work. 他已完成了那项工作。 (表结果)
I've known him since then. 我从那时起就认识他了。(表经历)
2) 用于till / until从句的差异
延续动词用于肯定句,表示"做……直到……" 瞬间动词用于否定句,表示"到……,才……"
He didn't come back until ten o'clock. 他到10 点才回来。
He slept until ten o'clock. 他一直睡到10点。
典型例题
1. You don't need to describe her. I ___ her several times. A. had met B. have met C. met D. meet
答案B. 首先本题后句强调对现在的影响,我知道她的模样,你不用描述。再次,several times告知为反复发生的动作,因此用现在完成时。
2.---I'm sorry to keep you waiting. ---Oh, not at all. I ___ here only a few minutes.
A. have been B. had been C. was D. will be
答案A. 等待的动作由过去开始,持续到现在,应用现在完成时。