现在完成时和一般过去式 since yet 用法
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1.现在完成时现在完成时用来表示之前已发生或完成的动作或状态,其结果的确和现在有联系。
动作或状态发生在过去, 但它的影响现在还存在;也可表示持续到现在的动作或状态。
其构成:have (has) +过去分词。
2.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.3. 比较since和forSince 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.4. 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+ agoI 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 student5.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 metB. have metC. metD. 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 beenB. had beenC. wasD. will be答案A. 等待的动作由过去开始,持续到现在,应用现在完成时关于since;since的用法主要有两点:一是表示“自从……以来”,二是表示“既然”之意。
但如果只了解词的含义,而不了解其用法,在使用时就会造成错误。
例如:I have not heard from him since I lived in Shanghai.不少人会望文生义,将该句译为:“自从我住在上海以来,就再也没有收到他的信了。
”而实际上这个句子的译文并非如此,那么正确的含义是什么呢?下面谈谈since作连词引导时间状语从句的用法。
一、若since引导的状语从句的谓语动词是终止性的过去时,则从句表示的时间是“从动作开始的那一时刻起”。
如:He has studied very hard since he came to our school.自从他来到我们学校,他学习就非常努力。
We have been missing them since they left here自从他们离开这里,我们就一直很想念他们。
这是最常见的一种用法,此处不再多述。
二、若since引导的状语从句的谓语动词是持续性动词或表示状态的动词的过去时时,则从句表示的时间是“从那持续动作或状态结束时算起”。
如:I haven’t heard any noise since I slept. Sleep 为持续性动词,sleep的动作结束时,即“醒来”时,这句应译为“我醒后还未听到任何声音”。
John is now with his parents in New York, it is already three years since he was a teacher约翰现在和父母一起住在纽约,他不当教师已经三年了。
本文开始出现的那个句子就可以译为“自从我离开上海,就再也没有收到他的信。
”这种译法常被人们误用,我们不妨再多举几个例子看看:How long is it since you lived in Shanghai?你离开(没住在)上海多久了?It is half a month since he was a League member.他退团(不当团员)半个月了。
It’s been quite some time since I was last in London我离开伦敦已很长时间了。
比较:He has written to me frequently since I was ill.自从我病愈以来,他屡次给我写信。
(从句谓语为状态动词)He has written to me frequently since I fell ill.自从我生病以来,他就屡次给我写信。
(从句谓语为终止性动词)三、若since引导的状语从句的谓语为持续性动词的现在完成时,则表示动作和状态延续到现在(说话时刻),其表示的时间的起点应从动作发生之时算起。
如:I haven’t heard from him since he has lived there。