1.現(xiàn)在完成時(shí)
現(xiàn)在完成時(shí)用來表示之前已發(fā)生或完成的動(dòng)作或狀 態(tài),其結(jié)果的確和現(xiàn)在有聯(lián)系.動(dòng)作或狀態(tài)發(fā)生在過去 但它的影響現(xiàn)在還存在；也可表示持續(xù)到現(xiàn)在的動(dòng)作或 狀態(tài).其構(gòu)成： have (has) +過去分詞.
2.比較過去時(shí)與現(xiàn)在完成時(shí)
1）過去時(shí)表示過去某時(shí)發(fā)生的動(dòng)作或單純敘述過去的事情,強(qiáng)調(diào)動(dòng)作；現(xiàn)在完成時(shí)為過去發(fā)生的,強(qiáng)調(diào)過去的事情對(duì)現(xiàn)在的影響,強(qiáng)調(diào)的是影響.
2）過去時(shí)常與具體的時(shí)間狀語(yǔ)連用,而現(xiàn)在完成時(shí)通常與模糊的時(shí)間狀語(yǔ)連用,或無時(shí)間狀語(yǔ).
一般過去時(shí)的時(shí)間狀語(yǔ):
yesterday, last week,…ago, in1980, in October, just now, 具體的時(shí)間狀語(yǔ)
共同的時(shí)間狀語(yǔ):
this morning, tonight,this April, now, once,before, already, recently,lately
現(xiàn)在完成時(shí)的時(shí)間狀語(yǔ)
for, since, so far, ever, never, just, yet, till / until, up to now, in past years, always,
不確定的時(shí)間狀語(yǔ)
3）現(xiàn)在完成時(shí)可表示持續(xù)到現(xiàn)在的動(dòng)作或狀態(tài),動(dòng)詞一般是延續(xù)性的,如live, teach, learn, work, study, know.
過去時(shí)常用的非持續(xù)性動(dòng)詞有come, go, leave, start, die, finish, become, get married等.
舉例：
I saw this film yesterday.
（強(qiáng)調(diào)看的動(dòng)作發(fā)生過了.）
I have seen this film.
（強(qiáng)調(diào)對(duì)現(xiàn)在的影響,電影的內(nèi)容已經(jīng)知道了.）
Why did you get up so early?
（強(qiáng)調(diào)起床的動(dòng)作已發(fā)生過了.）
Who hasn't handed in his paper?
（強(qiáng)調(diào)有卷子,可能為不公平競(jìng)爭(zhēng).）
She has returned from Paris.
她已從巴黎回來了.
She returned yesterday.
她是昨天回來了.
He has been in the League for three years.
(在團(tuán)內(nèi)的狀態(tài)可延續(xù))
He has been a League member for three years.
(是團(tuán)員的狀態(tài)可持續(xù))
He joined the League three years ago.
( 三年前入團(tuán),joined為短暫行為.)
I have finished my homework now.
---Will somebody go and get Dr. White?
---He's already been sent for.
句子中如有過去時(shí)的時(shí)間副詞（如 yesterday, last, week, in 1960）時(shí),不能使用現(xiàn)在完成時(shí),要用過去時(shí).
（錯(cuò)）Tom has written a letter to his parents last night.
（對(duì)）Tom wrote a letter to his parents last night.
3. 比較since和for
Since 用來說明動(dòng)作起始時(shí)間,for用來說明動(dòng)作延續(xù)時(shí)間長(zhǎng)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 作為時(shí)間狀語(yǔ)的句子都用現(xiàn)在完成時(shí).
I worked here for more than twenty years.
(我現(xiàn)在已不在這里工作.)
I have worked here for many years.
(現(xiàn)在我仍在這里工作.)
小竅門： 當(dāng)現(xiàn)在完成時(shí)+一段時(shí)間,這一結(jié)構(gòu)中,我們用下面的公式轉(zhuǎn)化,很容易就能排除非延續(xù)動(dòng)詞在完成時(shí)中的誤使.
1) (對(duì)) Tom has studied Russian for three years.
= Tom began to study Russian three years ago, and is still studying it now.
2) (錯(cuò)) Harry has got married for six years.
= Harry began to get married six years ago, and is still getting married now.
顯然,第二句不對(duì),它應(yīng)改為 Harry got married six years ago. 或 Harry has been married for six years.
4. since的四種用法
1) since +過去一個(gè)時(shí)間點(diǎn) (如具體的年、月、日期、鐘點(diǎn)、1980, last month, half past six).
I have been here since 1989.
2) since +一段時(shí)間+ ago
I have been here since five months ago.
3) since +從句
Great changes have taken place since you left.
Considerable time has elapsed since we have been here.
4) It is +一段時(shí)間+ since從句
It is two years since I became a postgraduate student
5.延續(xù)動(dòng)詞與瞬間動(dòng)詞
1) 用于完成時(shí)的區(qū)別
延續(xù)動(dòng)詞表示經(jīng)驗(yàn)、經(jīng)歷； 瞬間動(dòng)詞表示行為的結(jié) 果,不能與表示段的時(shí)間狀語(yǔ)連用.
He has completed the work. 他已完成了那項(xiàng)工作. (表結(jié)果)
I've known him since then. 我從那時(shí)起就認(rèn)識(shí)他了.(表經(jīng)歷)
2) 用于till / until從句的差異
延續(xù)動(dòng)詞用于肯定句,表示"做……直到……" 瞬間動(dòng)詞用于否定句,表示"到……,才……"
He didn't come back until ten o'clock.
他到10 點(diǎn)才回來.
He slept until ten o'clock.
他一直睡到10點(diǎn).
典型例題
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. 首先本題后句強(qiáng)調(diào)對(duì)現(xiàn)在的影響,我知道她的模樣,你不用描述.再次,several times告知為反復(fù)發(fā)生的動(dòng)作,因此用現(xiàn)在完成時(shí).
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. 等待的動(dòng)作由過去開始,持續(xù)到現(xiàn)在,應(yīng)用現(xiàn)在完成時(shí)
關(guān)于since;
since的用法主要有兩點(diǎn)：一是表示“自從……以來”,二是表示“既然”之意.但如果只了解詞的含義,而不了解其用法,在使用時(shí)就會(huì)造成錯(cuò)誤.例如：I have not heard from him since I lived in Shanghai.
不少人會(huì)望文生義,將該句譯為：“自從我住在上海以來,就再也沒有收到他的信了.”而實(shí)際上這個(gè)句子的譯文并非如此,那么正確的含義是什么呢?
下面談?wù)剆ince作連詞引導(dǎo)時(shí)間狀語(yǔ)從句的用法.
一、若since引導(dǎo)的狀語(yǔ)從句的謂語(yǔ)動(dòng)詞是終止性的過去時(shí),則從句表示的時(shí)間是“從動(dòng)作開始的那一時(shí)刻起”.如：
He has studied very hard since he came to our school.自從他來到我們學(xué)校,他學(xué)習(xí)就非常努力.
We have been missing them since they left here自從他們離開這里,我們就一直很想念他們.
這是最常見的一種用法,此處不再多述.
二、若since引導(dǎo)的狀語(yǔ)從句的謂語(yǔ)動(dòng)詞是持續(xù)性動(dòng)詞或表示狀態(tài)的動(dòng)詞的過去時(shí)時(shí),則從句表示的時(shí)間是“從那持續(xù)動(dòng)作或狀態(tài)結(jié)束時(shí)算起”.如：
I haven’t heard any noise since I slept. Sleep 為持續(xù)性動(dòng)詞,sleep的動(dòng)作結(jié)束時(shí),即“醒來”時(shí),這句應(yīng)譯為“我醒后還未聽到任何聲音”.
John is now with his parents in New York, it is already three years since he was a teacher約翰現(xiàn)在和父母一起住在紐約,他不當(dāng)教師已經(jīng)三年了.
本文開始出現(xiàn)的那個(gè)句子就可以譯為“自從我離開上海,就再也沒有收到他的信.”這種譯法常被人們誤用,我們不妨再多舉幾個(gè)例子看看：
How long is it since you lived in Shanghai?你離開（沒住在）上海多久了?
It is half a month since he was a League member.他退團(tuán)（不當(dāng)團(tuán)員）半個(gè)月了.
It’s been quite some time since I was last in London我離開倫敦已很長(zhǎng)時(shí)間了.
比較：He has written to me frequently since I was ill.自從我病愈以來,他屢次給我寫信.（從句謂語(yǔ)為狀態(tài)動(dòng)詞）
He has written to me frequently since I fell ill.自從我生病以來,他就屢次給我寫信.（從句謂語(yǔ)為終止性動(dòng)詞）
三、若since引導(dǎo)的狀語(yǔ)從句的謂語(yǔ)為持續(xù)性動(dòng)詞的現(xiàn)在完成時(shí),則表示動(dòng)作和狀態(tài)延續(xù)到現(xiàn)在（說話時(shí)刻）,其表示的時(shí)間的起點(diǎn)應(yīng)從動(dòng)作發(fā)生之時(shí)算起.如：
I haven’t heard from him since he has lived there.
這里has lived表示動(dòng)作的持續(xù)性,時(shí)間的起點(diǎn)應(yīng)從：“開始居住”時(shí)算起.因此此句可理解為“自從他（開始）住在那兒起,我就一直沒收到他的來信”.
Since we have owned a car, we have gone camping every year.自從我們自己有了汽車,我們每年都去野營(yíng).
試比較：1. Since I’ve been at this school, we have had three headmasters.自從我到這所學(xué)校,我們已換了三個(gè)校長(zhǎng)了.
Since I was at this school, they have had three headmasters.自從我離開這所學(xué)校,他們已換了三個(gè)校長(zhǎng)了.
2.He has never been to see me since I have been ill. 自從我生病以來,他從未來看過我.
He has never been to see me since I was ill. 自從我病愈以來,他從未來看過我.
由此可見,since引導(dǎo)的從句持續(xù)動(dòng)詞的一般過去時(shí)和現(xiàn)在完成時(shí)所表示的意思恰好相反.換言之,前者以肯定的語(yǔ)法形式反映著否定的邏輯內(nèi)容,而后者的形式與內(nèi)容是一致的.
至于It is +一段時(shí)間+since…的句型與It has been +一段時(shí)間+since…意思相同.前者是規(guī)范說法,后者是口語(yǔ)說法.
應(yīng)注意的是,在這種結(jié)構(gòu)中,since引導(dǎo)的從句絕對(duì)不能用否定式的謂語(yǔ)動(dòng)詞來表示否定意義,下面兩句都錯(cuò)了：
It is a long time since he didn’t study English.
It’s two months since you didn’t come to see me.
正確的說法為：
It’s a long time since he studied English 他好久沒學(xué)英語(yǔ)了.
You haven’t come to see me for two months. 你有兩個(gè)月沒來看我了.
解析：6B 詞義辨析語(yǔ)句連貫盡（as long as）作者所能記憶的.Remember是持續(xù)性動(dòng)詞,與表示持續(xù)意義的as long as（象……一樣長(zhǎng)；只要……）連用,引導(dǎo)條件狀語(yǔ)從句.as soon as,when,since三項(xiàng)均表示短暫意義,通常與短暫性動(dòng)詞連用.