现在完成时的用法和过去式的主要区别：
1.概念上的区别：
现在完成时，①表示过去发生并且已经完成的动作对现在造成影响或后果；
②过去某一时间开始并一直持续到现在并且有可能还会持续的动作或状态。
He visited Guilin in 1998.他1998年参观过桂林。(只是简单表明在过去某个时间[in 1998]去过桂林这一事实，除此以外别无其他)
Jill has bought a new computer.吉尔买了一台新电脑。（造成的结果是，Jill现在有了一台新电脑）
The plane has already arrived. 飞机已经抵达了。（说明现在的情况：飞机在这儿。）
The plane arrived a quarter of an hour ago. 飞机是一刻钟以前抵达的。（强调动作发生的时间
在过去。）
第一种：对目前造成的影响；过去发生并且已经完成的动作对现在造成影响或后果；
Have you seen the film? （A）
Did you see the film? （B）
[说明] 你看过这部电影吗？
（A）句强调的是被问者对剧情是否了解；
（B）句强调的是看这部电影的动作是否发生过，并不强调是否知道其内容。
第二种：过去某一时间开始并一直持续到现在并且有可能还会持续的动作或状态。
He has lived in Beijing for 8 years.（A）
He lived in Beijing for 8 years. （B）
[说明]他在北京住了8年。
（A）句讲的是到目前为止他在北京住了8年，可能还会继续在北京住下去。
(B)句讲的是他在北京住过8年，现在不在北京了。
2. 结构上的区别
现在完成时：
基本结构：主语+have/has+动词的过去分词(p.p)（V-ed）
①肯定句：主语+have/has+动词的过去分词(p.p)（V-ed）+宾语.
He has finished it. They have worked it out.
②否定句：主语+have/has+not+动词的过去分词(p.p)（V-ed）+宾语.
He hasn’t finished it. They have worked it out.
③一般疑问句：Have/Has+主语+动词的过去分词(p.p)（V-ed）+宾语.
Has he finished it? Yes, he has; No he hasn’t
Have they have worked it out? Yes, I have; No I haven’t
study的过去分词
④特殊疑问句：特殊疑问词或词组+have/has+主语+过去分词（v-ed）+其他）Where have they been? They have been to Yunnan.
一般过去式：
主语＋动词的过去式（肯定式）
He did it. We hoped to go there.
主语＋did ＋not ＋动词原形（否定式）
He didn’t do it. They weren’t there yesterday.
Did＋主语＋动词的原形（疑问式）
Did he do it? Yes, he did. No, he didn’t
※过去分词的概念：
①规则动词的过去分词的构成：v+ed, 如work-worked；study-studied；finish-finished
②不规则动词的过去分词构成：如be-been；have-had；hear-heard；do-done
③动词的过去分词
．．．不是一个概念
．．．．和动词的过去式
注意：不规则的动词
．．．．．．过去分词和过去式有时候一样，有时候不一样；
have-had-had; do-did-done; see-saw-seen; be-was/were-been
※过去分词的变化规则：规则动词的过去分词的构成规则与规则动词的过去式的构成规则相同。四点变化规则：
(1)一般动词，在词尾直接加“ ed ”：
work---worked---worked ,visit---visited---visited
(2)以“ e ”结尾的动词，只在词尾加“ d ”：
live---lived---lived ,
(3)、以“辅音字母+ y ”结尾的动词，将"y" 变为"i" ，再加“ ed ”：
study---studied---studied ,cry---cried---cried
(4)、重读闭音节结尾，末尾只有一个辅音字母，先双写该辅音字母，再加“ ed ”：
stop---stopped---stopped , drop---dropped—dropped.
3.句子中所用时间词语的区别
一般过去时：通常与表示过去的时间状语连用，如：
yesterday, yesterday morning (afternoon, evening…)；last night (week, m onth, year…)；
一段时间+ago(several days ago)、two days ago、a week ago,…；in 2002，(in 1990, in 1997，in July…)等；just now, at that time/moment, then , long long ago
例子：
He was here yesterday.
I got up at seven yesterday morning.
My mother didn’t work yesterday afternoon.
Did you have a good time last summer?
My mother often went to work by taxi last year.
When I was a student, I often listened to music.
Three months ago, they were still students.
现在完成时：
现在完成时往往同表示不确定的过去时间状语连用，如already（已经）, yet（已经）, just（刚）, before（之前）, recently（最近）, lately（近来），ever（曾经）等副词；
其中already，just多用于肯定句中，ever，yet，never多用于疑问句和否定句中）
He has already obtained（获得）a scholarship.他已经获得了奖学金。
He has just had his meal．他刚吃过饭。
Have you ever been to Beijing？你曾经去过北京吗？
I haven’t seen much of him recently (lately).我最近没太看到他。
We have seen that film before. 我们之前看过那部电影。
Have they found the missing child yet？他们已经到了那个丢失的孩子了吗？
for + 时间段如: for ten years
时间点如: since nine o’clock
since 时间段+ ago 如: since ten years ago
一般过去时态从句(主句是现在完成时)
如: since you came
since you got home
例如：We have lived in this city for more than 40 years. 我们在这个城市里已经生活了40 多年。
We have lived in this city since 1958. 我们从1958 年起就住在这个城市里。
Have you seen her parents these days? 这些天你看见她的父母了吗？
Mary has been ill for three days.
I have lived here since 1998.
非延续性动词即瞬间动词不能用于“现在完成时＋表示一段时间的状语”的句型中。这类动词有：come，go，start，leave，die，buy，finish，borrow等。例如：
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