人教版八年级英语上册第九课学要掌握的重点是什么?

现在完成时用法解析1。构成现在完成时是由助动词 have(has)+动词的过去分词构成。助动词说明该谓语是属于现在时范围。它和主语的人称、数要保持一致。过去分词是主要的谓语动词,说明句子的意义。2。用法(1)表示动作发生在过去某个不确定的时间,但对现在留下了某种影响和结果。常被just、already、yet 等副词修饰。如：-Have you had lunch yet?-Yes,I have。I've just had it。你(已经)吃午饭了吗?我刚刚吃过。(现在我不饿了)(2)表示从过去某一时刻开始一直持续到现在的动作或状态。这个动作可能刚停止,可能仍然在进行。常带有for和since等表示一段时间的状语。如：He has taught here since 1981他自1981年就在这儿教书。(可能还要继续教)I have't seen her for four years。我有四年没见到她了。(3)表示说话前发生过一次或多次的动作,现在成为一种经验,一般译为汉语“过”,常带有twice,ever,never,three times等时间状语。如：I have been to Beijing twice。我去过北京二次。3。现在完成时的时间状语(1)现在完成时属于现在时范围,故不能和过去的时间状语连用。如：yesterday,last Sunday,in1990,three years ago等。但是,在强调动作产生的后果和影响时,可以和一些表示不确定的时间状语连用。a。用副词already和yet。already一般用于肯定句中,yet一般用于否定句和 疑问句中。如：We have already finished our homework。我们已完成作业了。They haven't finished their homework yet。他们还没有完成作业。b。用ever 和never。多用于否定或疑问句中,表示“曾经”或“从未“等。如：-Have you ever been to the Great Wall?你曾经去过长城吗?-I have never been to the Great Wall。我从未去过长城。c。用表示到说话为止的过去时间状语,如just,before,up to now,the past few years等。例如：I have seen her before,but I can not remember where。我以前见过她,但记不起在哪里见过。He has been there three times the last few days。近几年他去过那里三次了。d。用包括“现在”在内的时间状语,如：now,today,this morning(month,year,term)等。例如：-Have you met him today?-No,I haven't。今天你见过他吗?我 没有。How many times have you been there this year?今年你去过那里多少次?(2)现在完成时可以和带有since或for等表示“一段时间”的状语连用,表示动作或状态从某一时刻开始,一直持续到现在。如：I haven't seen him for two years。但是,像come,arrive,buy等终止性动词不能与表示“一段时间”的状语连用。要用,必须改为“be(在)”等延续性动词来表述。现归纳总结一下由非延续性动词到延续性动词的转换：arrive→be here begin(start)→be on die →be dead come back→be backleave →be away fall ill(sick,asleep)→be ill(sick,asleep)get up→be up go out →be outfinish →be over put on →wear 或be onopen →be open join →be in或 be a member of…close →be closed go to school→be a studentborrow →keep buy →have catch(a cold)→ have(a cold) get to know →knowbegin to study→study come to work→work等如：He has been a soldier for three years。他参军三年了。His father has been dead for two years。他父亲去世二年了。The film has been on for ten minutes。电影已开始十分钟了。We have studied English for three years。我们(开始)学英语已三年了。4。现在完成时和一般过去时的区别现在完成时和一般过去时都表示在过去完成的动作。但现在完成时强调的是这一动作与现在的关系。如对现在产生的结果或影响等,而一般过去时只表示动作在过去某一时刻发生,不表示和现在的关系。试比较：I have lost my new book。我把新书丢了。(现在还未找到)I lost my new book yesterday。我昨天把新书丢了。(昨天丢的,现在找到与否没说明)5。几点注意事项(1)have been(to)与have gone( to)的区别：have been(to)表示“去过某地(现在已经回来了)”,可用于各人称；have gone(to)表示“去某地了(说话时某人不在当地)”,常用于第三人称,前者可与once ,never,several times等连用,后者则不能。如：They have been to Beijing twice。他们去过北京两次。He has gone to Beijing 。他去北京了。(2)如单纯表示一段时间,或强调一段时间,虽有since一词,也不必用完成时。如：It is two years since his father died。=His father has been dead for two years。他父亲去世已有三年了。(3)终止性动词现在完成时的否定式,已变成一种可以延续的状态,因此可以和表示一段时间的状语连用。如：I haven't left here since 1997。自从1997年以来,我一直没有离开过这儿。