一、现在完成时的构成
（一）肯定式
主语＋助动词have ／has ＋过去分词＋其它
说明：这里的have ／has是助动词，没有什么具体意义。当主语是第三人称单数时助动词用has，其余人称一律用have。 has，have的缩略式分别为's或've。规则动词过去分词的构成与过去式的构成方式一样，不规则动词可参看不规则动词表。实例：
1）I've just copied all the new words ．我刚抄写了所有的生词。 (表示不要再抄了)
2）She has lost her books ．她丢失了她的书。 （表示到目前为止还没有找到）
(如果用过去时：She lost her books . 则强调书是过去丢的这一动作，而不知现在有没有找到)
3）We've just cleaned the classroom ．我们刚好打扫了教室。（表明现在教室是干净的）
（二）否定式
主语＋助动词have ／has＋not＋过去分词＋其它
说明：现在完成时构成否定句时，只需在助动词have ／has后面加not就行。have not，has not的缩略式分别为haven't ，hasn't。另外，肯定句中有some，already时，改为否定时要分别改成any，yet。实例：
1）I haven't finished my homework yet．我还没有完成我的作业。
2）She hasn't travelled on a train ．她没有坐火车旅行过。
3）We have never spoken to a foreigner．我们从来没有和外国人说过话。
注：有时not可以用never代替，表示“从来没有”的意思。又如：
4）I have never seen him before．以前我从来没有见过他。
（三）一般疑问式
助动词Have ／Has ＋主语＋过去分词＋其它 ？
说明：把陈述句中的have或has放到句首，句末打问号，同时把句中的some ，already改为any ，ye t就构成了一般疑问句。肯定回答用“Yes ，主语＋have／has．否定回答用“No，主语＋haven't／hasn't．”有时也可以用“No，not yet．／No ，never．／No，not even once．”等。实例：
1）—Have you ever made dumplings ？你曾经做过饺子吗？
—Yes ，I have ．是的，我做过。
2）—Has she ever been abroad ？她曾经出过国吗？
—No，never．不，从来没有。
3）—Have they found the lost books yet ？他们已经找到了丢失的书吗？
—Yes ，they have．是的，他们找到了。
注意：当句中有否定词not ，hardly（几乎不），never的时候，在改为反意疑问句时，附加部分用肯定形式。例如：You have never come to our school ，have you ？你以前从来没有来过我们学校，是吗？
二、现在完成时的用法
（一）现在完成时的用法1：表示过去发生或已经完成的某一动作对现在造成的影响或结果。此时，常与时间副词already（已经） ，yet（还、已经） ，just(刚刚、仅仅) ，ever（曾经） ，never（从不） ，before（以前）等连用。这几个副词的用法如下：
1．already意为“已经”，通常用于肯定句中，可放在助动词之后，过去分词之前，也可以放在句末。实例：
1）I've already read this book. 我已经读过这本书了。
（“读”这一动作发生在过去，对现在造成的影响是“知道书中的内容”。）
2）I've washed my clothes already．我已经洗了衣服。
（洗衣服的动作已完成，其结果是“衣服冼干净了”。）
注意：在表示吃惊或明知故问等感情色彩时，already也可用于（口语）疑问句中。实例：
3）Have you met him already ？你（真的）已经见过他了？
2．yet用在疑问句中意为“已经”，用在否定句中意为“还”，常放在句末。实例：
1）—Has he found his watch yet ？他已经找到他的手表了吗？
—No，not yet．不，还没有。
2）The woman hasn't found her dog yet ．
那位妇女还没有找到她的狗。（没找到狗，心里着急，这就是对现在的影响）
3．just意为“刚刚”，表示行为刚刚过去，常放在助动词与过去分词之间。实例：
He has just come back from school ．他刚从学校回来。
4．ever意为“曾经”，用于疑问句或否定句中，放在助动词与过去分词之间。实例：
1）Have you ever been to Hong Kong ？你曾去过香港吗？
2）I haven't ever spoken to her．我未曾和她说过话。
5．never意为“从来没有”常与before连用（before要放在句尾，而never多放在助动词与过去分词之间。实例：
I have never travelled by plane before．我以前从来没有乘飞机旅行过。
6．before意为“以前”，指过去不确定的某个时间，总是放在句末，不受句型的限制。实例：
1）Have you been to Hainan before ？你以前去过海南吗？
2）I haven't eaten Guangdong food before．我以前没吃过广东菜。
（二）现在完成时用法二2——持续性用法（肯定句，疑问句中谓语动词必须是延续性动词）：表示过去已经开始，持续到现在的动作或状态。此时常与“for ＋一段时间或“since＋过去的点时间或从句（从句用一般过去时）以及so far（到目前为止）等时间状语连用。
for + 段时间
since +点时间
实例：
1）I've lived here since 1990．自从1990年以来我就住在这里。
= I've lived here since 13 years ago.
= I've lived here for 13 years.
= It is 13 years since I began to live here.
2）I haven't seen him for three years ．我三年没有看见他了。
= I haven't seen him since three years ago
= I haven't seen him since 2000.
= It is 3 years since I saw him last time.
3）Mr Wang has worked in the factory since he came to the city ．
自从到这个城市以来，王先生一直在这家工厂工作。
4）She's been at this school since five years ago．
自从五年前以来她就在这个学校。
注意：①在这类句子的肯定句和疑问句中谓语动词必须用延续性动词。短暂性动词由于动作不能持续，故不能与for(达到；累计)或since（自从。。。到现在）引出的时间状语连用。
②对for和since引导的时间状语提问要用How long
1） 他入团两年了。
误：He has joined the League for two years．
正：He has been a League member for two years．
2）我买这辆自行车三年了。
误：I have bought this bike for three years．
正：I have had this bike for three years．
2） ▲部分短暂性动词与之对应的延续性动词：
短暂性动词 延续性动词
die → be dead
borrow → keep
buy/catch → have
get up → be up
come → be in
finish → be over
leaver → be away
open → be open
close → be closed
begin → be on
become interested in → be interested in
有人可能会问：一般过去时和现在完成时所表示的动作都发生在过去，那么这两种时态有什么区别呢？
☆答：①一般过去时与具体的表示过去时间状语如：yesterday连用；强调动作在过去发生，与现在无关。
②现在完成时与自已的特征词连用，强调过去发生的动作对现在的影响或过去开始发生一直持续到现在的动作。
例： He saw the film last night. (过去时，表示他昨晚看过那部电影了，现在不知还要不要再看一次)
He has (ever) seen the film before.（现在\完成时，表时他已看过那部电影，现在不想再看了）
巩固练习：
I．按要求转换下列各句，每空一词。
1、He has already finished his homework．（改为否定句）
He _______ finished his homework ________．
2．They have found the lost books already．（改为一般疑问句，并作否定回答）
______ they _______ the lost books _______？No，they________．
3．Julia has not got home from school yet．（改为肯定句）
Julia ______ _______ ________ home from school ．
4．You have never been to Shanghai before，_________ _________ ？（改为反意疑问句）
5. He’s gone to Beijing, ______ ______?（改为反意疑问句）
6．Mr Wang began to teach English in this school in 1999．（改为同义句）
Mr Wang _________ _________ English in this school since 1999．
7. He hasn’t left home for 3 days.(同义句)
He _____ ______ ______ home for 3 days.
8. They have lived here since 3 years ago. (对划线提问)
II．选择正确答案。
( )1．—Who is Mary ？
—____？I saw you talking with her at the meeting ．
A．Don't you meet her yet B．Didn't you met her yet
C．Haven't you met her yet D．Hadn't you met her yet
( )2．—How do you like Beijing ，Mr Black？
—Oh ，I ____ such a beautiful city ．
A．don't visit B．didn't visit
C．haven't visited D．hadn't visited
( )3．The old people ____ lonely at all since we began to visit them once a week．
A．don't feel B．hasn't felt
C．haven't felt D.didn’t feel
( ) 4．We have lived here ____ five years ago．
A．when B．since C．before D．after
11.11 用于现在完成时的句型
1）It is the first / second time…. that…结构中的从句部分，用现在完成时。
It is the first time that I have visited the city.
It was the third time that the boy had been late.
2）This is the… that…结构，that 从句要用现在完成时.
This is the best film that I've (ever) seen.
这是我看过的最好的电影。
This is the first time (that) I've heard him sing. 这是我第一次听他唱歌。
典型例题
(1) ---Do you know our town at all?
---No, this is the first time I ___ here.
A. was B. have been C. came D. am coming
答案B. This is the first time 后面所加从句应为现在完成时，故选B。
(2) ---Have you ____ been to our town before?
---No, it's the first time I ___ here.
A. even, come B. even, have come C. ever, come D. ever, have come
答案D. ever意为曾经或无论何时，反意词为never，此两词常用于完成时。 This is the largest fish I have ever seen. It is / was the first time +that-clause 的句型中，从句要用完成时。
注意：非延续性动词的否定形式可以与表示延续时间的状语连用。即动作不发生的状态是可以持续的。
（错）I have received his letter for a month.
（对）I haven't received his letter for almost a month.
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