haihongyuan.com
海量文库 文档专家
全站搜索:
您现在的位置:首页 > 初中教育 > 初中英语初中英语

for和since

发布时间:2014-01-10 12:50:50  

由since和for构成的句子或短语是现在完成时的常用状语。现就它们的用法作以下归纳。

一、现在完成时既可以与since引导的时间状语从句连用,又可以与since构成的短语连用。

1. since作连词,后跟句子,它所表示的时间是“从某一点开始”。若从句谓语为终止性动词,主句的时间则从句谓语为终止性动词,主句的时间则从这一“时刻”算起。如:He has lived here since he lefts Shanghai.

若从为延续性或状态性动词,则从其动作结束“那点”算起。例如:(1) It is six years since he was a teacher. (2) I haven't heard from her since she lived there .

2. since作介词,后跟表示时间的名词,必须是表示“时间的一点”,不能表示时间的一段。例如:

He has taught at this school since 1965.

二、现在完成时与介词for构成的短语连用。

1. 介词for构成的短语,表示时间的长度,后跟一段时间,不能跟时间的一点。例如:

(1) We have studied English for two years.

(2) They have known each other for five years.

2. 终止性动词不能与表示一段时间的介词for连用,但它的否定式可与介词for连用。例如:

3. I have not received his letter for two months.

for He has had the dictionary for two weeks(buy 用 have代替) My father has been in the Party for ten years (join 用 be in) 1 现在完成时的用法

现在完成时可以用来表示过去已经开始,持续到现在的动作或状态。可以和表示从过去某一时刻延续到现在(包括“现在”在内) 的一段时间的状语连用。常与for或since等引导的时间状语连用。

例:①We’ve lived in Beijing for ten years.

我们在北京已住了十年了。

②She has been a doctor since 1990.

她自1990年以来就是医生。

2 延续性动词

英语中的动词可分为延续性动词与非延续性动词。延续性动词本身在概念或意义上是可以延续的。如:live,be,work,sleep,study,learn,walk,teach,draw,know,wait,have等。现在完成时与for或since等引出表持续时间的时间状语连用时,须用延续性动词,不能用非延续性动词。

例:①I have taught here for over five years.

我在这里任教已五年了。

②They have known her since she was a child.

在她还是个孩子的时候,他们就认识她了。

2 语法句型

1 主语+keep+宾语+形容词

本句型中,动词keep须接复合宾语结构,形容词说明宾语的情况,是宾语意义上不可缺少的补足语,与句型中宾语一起构成复合宾语。

例:①You should keep the classroom clean.

你们应使教室保持清洁。

②The glasses keep their eyes safe.

眼镜保护他们的眼睛。

类似keep可以带宾语补足语的动词还有think,find,make等。

例:①He found the story quite interesting.

他发现这个故事很有趣。

②Do you think the picture beautiful?

你认为这幅画美吗?

2 It’s one’s turn to do sth.

这个句型中it是形式主语,代替由动词不定式(to do th.)表示的真正主语。句型中的turn为名词,意为“顺序”、“次序”。表示“轮到某人做某事”时常用本句型。

例: ①It was Class 3’s turn to visit the factory.

轮到三班去参观这家工厂。

②It’s their turn to do the cleaning today.

今天轮到他们做清洁了。

3 学习中应注意的问题

1 for和since的用法区别

介词for后面所跟的时间不能是一点时间,而只能是一段时间;since后面所跟的时间不能是一段时间,而只能是一点时间。如:since four o’clock, since January,since 1976,since last Friday,since then,since he came here;for an hour,for five minutes, for two weeks,for several years, for a long time. for表示的段时间不能与ago连用;而since表示的点时间则可与ago连用。

例:① He has learned English for two years.(正)他已学了两年英语。 He has learned English for two years ago.(误)

② Lin has waited there since half an hour ago.(正)

琳自半小时前就已经在那里等候。

Lin has waited there since half an hour.(误)

2 注意“非延续性”动词的用法

有些动词的意义决定它们所表示的动作不能延续,只是一瞬间就结束的动词。这类动词叫做“非延续性”动词或“瞬间”动词,也称“终止性”动词。常见的有:come,go,arrive,reach,leave,begin,start,buy,join,die,borrow,get up等。这类动词也可以用于完成时态,说明某个动作的结果还存在,但不能和for 表示的一段时间的状语连用。

例:①Jim has come back from England.(正)

吉姆已从英国回来了。(他现在在这里。)

②Jim has come back for a month.(误)

吉姆已回来一个月了。

例②错是因为come back 的动作不可能延续一个月,要表达“回来已一个月”这个概念,可用be back代替come back,以表示“回来”这一状态持续了多久。

例:Jim has been back for a month.

这句话可转换为:

① Jim came back a month ago.

② It is a month since Jim came back.(句中的it指时间,主句的时态常为一般现在时或现在完成时,since为从属连词,引导一个从句。 从句中的动词用一般过去时。)由此可见,要解决非延续性动词与段时间的状语连用的问题,可将终止性动词改为相应的表示延续性的动词或短语,相对应的有:leave—be away, borrow—keep, die—be dead, buy—have等。也可用“It is+一段时间+since+从句(动词用一般过去时)”的句型,还可按例①中的方法用一般过去时表示。

3 在否定句中,非延续性动词也可用表示一段时间的状语来修饰

例:①We haven’t seen her for a year.

我们已有一年未看到她。

②She hasn’t borrowed any books from the library since last spring. 自去年春季以来她就没有在图书馆借过书。 现在完成时for 与since

英语教学 2008-10-03 06:45:36 阅读196 评论0 字号:大中小 订阅

今天让我们来讲讲有关since的用法,特别是it+be+一段时间+since从句的用法和since和for的区别。

since这个词很多词典和资料书解释的很繁琐,很不容易理解,我们总结了一个简便的方法,拿出来给大家共享,如有不对的地方,还请大家批评指正。

1. since的意思是“自从??时候起”,一般后面有一个状语从句。那么这里就有一个时间上的起始点的问题,这个时间的起始点应该是和谓语动词有关。在英语中,谓语动词被分为短暂性动词和延续性动词(也可称之为状态动词)。那么这个时候我们就要注意了,since 表示的是“自从该动作或者该状态结束时起”,只要谨记这一点,很多句子就可以轻易理解了!大家可以尝试用这样的方式来理解下面的两个句子:

It's three years since he joined the army.

It's three years since lie was a soldier.

上面的两个句子很多学生都觉得意思应该是一样的,就是因为他们对于since这个词的用法不熟悉造成的,或者他们查过词典,但是对词典上的那种锣嗦的解释给弄糊涂了。如果你能用我刚才的方法就很容易找出来他们意思不同之处了。第一个例句的意思是:他参军已经三年了,而第二个例句的意思是他已经退伍三年了,或表示他不是一个战士已经三年了。大家可以再看一个句子。

We haven't seen each other since we were children.

自从我们长大以后我们就再也没有见过对方了。 It + be +一段时间十since从句在这一句型中,主句中的be动词常用is或has been,since引导的从句中的谓语动词常用一般过去时。如果主句中的be动词为was,since从句中的谓语动词则用过去完成时。注意:从

句中的谓语动词如果为短暂性动词,应为肯定意“某人做某事已经有多长时间了”;如果从句中的谓语动词为延续性动词,则为否定意“某人已经有多长时间没做某事了”。又如:It is/has been three years since he left his village.“他离开村子已经有五年了”。It was six years

since she had lived in this city.“那时他不住在这个城市已有三年了”。有时考查该句型中的谓语动词。

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.

2. since和for用法比较:

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。)

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。

I)(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 year-, 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.

网站首页网站地图 站长统计
All rights reserved Powered by 海文库
copyright ©right 2010-2011。
文档资料库内容来自网络,如有侵犯请联系客服。zhit326@126.com