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1、八年级英语下册现在完成时知识精讲一、定义现在完成时主要用来表示过去发生的动作对现在造成的影响或结果。如：I have already seen the film.She has just had a bath.第一句说明看电影是过去发生的，用了现在完成时是要表示说话者可能不想再看了，或者对该电影的内容已经很熟悉了，等等。第二句说明她洗澡是过去发生的，用了现在完成时是要表示她不需要再洗澡了等。二、基本结构现在完成时的句子结构一般为：肯定句主语+have/has+过去分词+其他成分We have already had lunch.He has been away for a week.肯定句：主
2、语+have/has+动词的过去分词+其他否定句：主语+have/has+not+动词的过去分词+其他一般疑问句：Have/Has+主语+动词的过去分词+其他特殊疑问句：特殊疑问词+一般疑问句（have/has+主语+过去分词+其他）三、主要用法1、表示过去发生并且已经完成的动作对现在造成的影响或结果。此时，常和谓语动词一起使用的副词有already、just、never、ever、yet等。如：They have already come back from the museum.She has already finished her homework.2、表示一个动作或状态从过去开始，一
3、直延续到现在，还可能继续下去。此时常与：for +时间段、since+过去时间点、since+一般过去时态的从句、since+一段时间+ago、 in the past/last +时间段 连用。谓语动词用延续性动词，可以用how long提问。 for + 一段时间 I have learned English for 8 years since + 过去的一个时间点 I have learned English since 2001since + 时态为一般过去时的时间状语从句 I have learned English since I was 5 years old注意：现在完成时中，
4、 与一段时间连用时应注意句中的谓语动词须是延续性动词，非延续性动词不可和一段时间连用。其它非延续性动词与时间段连用时的变形2buyhave borrow keep,fall asleepbe asleep leave be awaybegin be on die be dead,join be in或be a member of return be backcome/arrive be in marry be marriedI have lived here for ten years.He has kept the clavichord since thirty years ago.3、表示
5、从过去某一时间到说话时这段时间中反复发生的动作。此时，常和谓语动词一起使用的主要是表频度的副词often、always、seldom、never等，以及表次数的单词或短语（如once、twice、three times）。如：You have never listened to me like this before.She has ever been to France.They have visited the Summer Palace many times.四、动词的过去分词1、规则变化其变化规则与动词的一般过去时基本相同，主要是在词尾加-ed或-d。具体的有：1）直接加-ed。如：w
6、orked、played。2）以不发音的e结尾的动词后加-d。如：lived、danced。3）以辅音字母加y结尾的动词后改y为i，再加-ed。如：studied、cried。4）以重读闭音节结尾的动词后，双写最后一个辅音字母再加-ed。如：stopped、shopped。2、不规则变化如果结合动词的过去式，动词的过去分词的不规则变化中，又有一些相对的规则现象。如：1）AAA型。如：put put put；read read read。其中，read的过去式和过去分词虽然拼写时一样的，但其发音与原形不同，ea不再读作i，而是e。2）ABB型。如：keep kept kept；sit sat s
7、at3）ABA型。如：run ran run；come came come4）ABC型。如：lie lay lain；drink drank drunk5）AAB型。如：beat beat beaten五、标志性词语1、副词already、just、never、ever、yet等。如：She hasnt arrived in Scotland yet.They have just left for Shanghai.2、for和since。for+一段时间，since+具体时间。如：He has learned Italian for five months.He has learned It
8、alian since five months ago.3、so far和up to/till now。表示“迄今为止”。如：So far, no one has heard any news about her.She has read fifty books up to now.4、recently、lately等表示“最近；最新”的副词和形容词。如：Ive met her on several occasions recently.He hasnt had enough sleep lately.5、in the past/last+一段时间，表示“在过去的.时间里”。如：In the
9、past few years, new buildings have sprung up all over Beijing.He had aged rapidly in the last few months.6、次数。如：Ive tried many times, but theres no way.He has been there at least twice.六、have been to/have gone to/have been in1、have been to表示“去过，已回”。句子主语就在现场。如：They have been to Rome many times.She has been to Shanghai more than once.2、have gone to表示“去了，未回”。句子主语不在现场。如：Jerry has gone to Hangzhou. Mary has gone to Finland.3、have been in表示“一直待在某地”。如：We have been in Beijing for five weeks.They have been in China since 2012.