yi过去进行时过去进行时表示过去某一时刻或某段时间正在进行的动作.构成过去进行时常由"助动词be的过去时was/were+现在分词"构成.用法如下：1、表示过去某一时刻正在或过去某段时间正在进行的动作.动作发生的特定时间常用一个短语或时间状语从句来表明.注意：在含有时间状语从句的复合句中,延续时间较长的动作用过去进行时,另一个动作用一般过去时.如果表示两个延续动作在过去某一时刻同时进行,而不考虑动作的先后长短,则主句和从句的谓语动词都用过去进行时.When I entered the room, she was sitting at her desk.我进屋的时候,她正坐在书桌前面.The students were reading while the teacher was grading their homework.学生们在看书,而老师在批改他们的家庭作业.2、用来描写故事发生的背景在口语或记叙文中,可以用过去进行时表示的持续动作作为背景,以此引出由一般过去时表示的新动作.It was a dark night. The wind was blowing hard and the rain was falling heavily. A young woman suddenly appeared on the river bank.一个漆黑的夜晚,狂风大作,大雨倾盆,一位年轻的妇女突然出现在河岸上.3、代替过去将来时用于come, go ,leave, start, stay, arrive等表位置转移的动词,以表示过去将要发生的动作.She asked me whether he was starting the next day.她问我他是否第二天就走4、表达褒贬等感情色彩过去进行时也可以和always,constantly,continually,forever等连用,表示说话人的主观感情,如赞扬、不满、厌烦等.He was always trying out new ideas.他总是试验一些新的设想He was forever complaining about something.他老是怨这怨那5、wonder, hope, think,want 等表示心理的动词用于进行时可以表示婉转的语气---Excuse me, sir. Would you do me a favor? --打扰了,先生.你能帮我个忙吗?---Of course. What is it? --当然.什么事?---I was wondering if you could tell me how to fill out this form. --我一直在想你是否能告诉我怎样填这张表（六）现在完成时现在完成时由"助动词have/has+过去分词"构成.现在完成时的用法如下：1、表示发生在过去的动作或存在的状态到说话时刚刚完成或结束,通常使用不具有延续意义的动词,arrive, become, begin, break等.这种用法可带有迄今意义的时间状语,如up to now, so far, already, not...yet等.也可带有包括现在时间在内的时间状语,如now, recently, in the past few years, just等.I have already posted the photos.我已经把照片寄出了2、表示从过去某时开始一直延续到现在的动作或状态,也许还将继续下去.这种用法通常用于具有延续意义的动词,如live, stay, work等,并带有表示时间段的状语或迄今意义的时间的状语,如for, since等They have lived in Beijing since 2002.他们自从2002年以来就住在北京.注意：表示短暂的动作动词或状态动词不能用于这种用法,如arrive, come, go, leave等.如,不能说：She has come to our school for 2 years.3、表示到现在为止的一段时间内重复发生的动作.常与often, always 等连用He has been late for class every morning this week.这个星期他每天早晨都迟到.My father has always gone to work by bike.我爸爸一向骑车上班4、用于时间、条件状语从句中,表示将来要完成的动作或一个动作先于另一个动作.He will be back before I have finished my work.我完成工作之前他会回来的.5、用在"It(This) is(will be ) the first/second/third...time+ that从句"中在这种从句中,当主句动词为is/will be时,that-从句的动词用现在完成时,that 可以省略.主句中的主语还可用this, this evening等; 这种结构中的first也可用其他序数词；time也可由其他名词替代This is the first time I have been here.这是我第一次来这里.It'll be the first time I've spoken in public.这将是我第一次当众讲话.6、 "It (This)is the best( worst, most interesting等) + 名词+从句"结构中的从句要求用现在完成时This is the best film I've ever seen.这是我所看过得最好的一部电影This is the most interesting novel he has ever written.这是他写得最好的一部小说.7、现在完成时可以表示反问的语气（与when连用）或感情色彩- Who is Jerry Cooper? 杰利?库珀是谁呀?- Haven't you met him yet? I saw you shaking hands with him at the meeting. 你还没见过他?我看见你和他在开会时握手了.Now you've done it.你这下可闯祸了.When have I been treated like this?我什么时候吃这一套?8、现在完成时与一般过去时的区别现在完成时与一般过去时都表示完成的动作,但现在完成时强调这一动作对现在造成的影响或结果,强调的是现在的情况,所以它不能和表示过去的时间状语连用,如yesterday, last night, three weeks ago, in1990等.而一般过去时则表示过去的动作或状态,和现在不发生关系,它可以和表示过去的时间状语连用.I have seen the film.我看过这部电影.（我了解这部电影的内容）I saw the film last week.我上星期看了这个电影.（只说明上星期看了这个电影,不涉及现在的情况）He has lived here since 1972.1972年以来他一直住在这里.（他现在还住在这里）He lived here in 1972.1972年他们住在这里.（不涉及到现在是否还住在这里）9、使用现在完成时应注意的几点（1）现在完成时不能和明确表示过去的时间状语(如yesterday, last week, in 1976, two days ago, just now等)连用,但可以和下列不确定的时间状语连用,如never, ever, always, yet, already, before, just, lately, so far, recently等She has already come.她已经来了.I have met him before.我以前曾见过他.（2）现在完成时还可以和表示从过去某时刻延续到现在 (包括现在在内)的时间状语连用.如today,this year,these days,this morning等It has been hot this summer. 今年夏天一直很热.(说话时仍是夏天)I have written two letters this morning. 今天上午我写了两封信.(说话时仍是上午)（3）表示短暂意义的动词,如open,go,come,die,leave,arrive,begin, return,stop等,不能与表示一段时间的状语连用.如要表达"他离开这儿已经3年了"这一意思时,不能说" He has left here for three years. "而要把其中的动词换为延续性动词或用其他表达法.如上句可用下列方式表达:He has been away from here for three years.He left here three years ago. It is three years since he left here.（4）have/has been to表示到过某个地方,而have/has gone to表示已经去了某处.He has been to the Great Wall.他到过长城.(现在他已不在长城)He has gone to the Great Wall.他去长城了.(现在他不在此地)