现在完成时
1. 结构：
肯定句：主语+助动词have（has）+动词过去分词-ed
否定句：主语+助动词have（has）+not(haven’t,hasn’t)+动词过去分词-ed
一般疑问句：Have(Has)+ 主语+动词过去分词-ed+？
特殊疑问句：疑问词+have(has)+ 主语+动词过去分词-ed+？
2.用法
含义：现在完成时用来表示现在之前已发生或完成的动作或状态，但其结果却和现在有联系, 也就是说, 动作或状态发生在过去但它的影响现在还存在。
1）现在完成时往往同表示不确定的过去时间状语连用, 如already, yet, just, before, recently, lately等
Mr. Wang has just come back from America. 王先生刚从美国回来。
I haven’t seen much of him recently (lately).
We have seen that film before.
Have they found the missing child yet?
现在完成时中的时间状语：
already通常用于肯定句中，意为―已经，位于行为动词之前, be动词、助动词之后。有时可放在疑问句句尾，表示惊讶。
例如：We have already cleaned the classroom.
Have you finished it already？
yet用于疑问句中表示―已经；用于否定句中，表示还(没)。
例如：—Has he found his watch yet？他还没找到他的表吗？
—No, not yet. 是, 还没有。
ever意为曾经，常用于疑问句或否定句中，位于助动词和过去分词之间，表示从过去到目前为止的时间。
例如： Have you ever been there？你曾经去过那里吗？
Nothing has ever happened here. 这里未曾发生过什么事。
never意为（曾经）从未、没有, 是否定副词，在句中位于助动词和过去分词之间。ever与否定词not连用相当于never。例如：
I haven’t ever spoken to her. = I have never spoken to her. 我从未跟她讲过话。
just意为―刚刚, 用于现在完成时, 表示行为刚刚过去, 位于助动词与过去分词之间。
e.g. He has just come back from school.他刚从学校回来。
just now意为―刚才, 表示过去某时, 用于一般过去时, 位于句首或句尾均可。
e.g. He came from school just now.他刚才从学校回来。
for 和since的用法及区别。for 与一段时间连用，since 与时间点连用。注意：since 后接过去时的时间状语或过去时的句子。
e.g. I have been to Shanghai twice since 1970.
I haven’t seen her since she left Shanghai.
I saw Ping Ping six years ago. Since I havenever seen her.
have/has gone to、have/has been to 和have/has been in的区别。
have/ has gone to 去了,在去某地的路上或在某地, 人还未回来
have/ has been to 曾经去过, 人已经回来了
have/ has been in 已经在, 常与一段时间连用
e.g. She has been to Shanghai before. 她以前曾去过上海。
She has been in Shanghai for ten years. 她在上海10年了。
Has he gone to Qingdao? 他去青岛了吗？但不能说 Have you gone to Qingdao?
2）、现在完成时还可用来表示过去发生的动作一直延续到现在，常带有for或since 等表示一段时间的状语。
如：Mr Wang has lived here since 1983.
I haven’t seen much of him recently (lately).
We have seen that film before.
Have they found the missing child yet?
3）、现在完成时瞬间动词即终止性动词不能与表示一段时间的状语连用。
常见终止性动词与延续性动词 (或状态动词) 的对应关系如下:
come / go / arrive / get / reach / move--- be in/at
open --- be open die --- be dead
close --- be closed become ---be
borrow --- keep put on --- wear
buy --- have leave ----- be away (from)
begin / start ----- be on fall asleep ---- be asleep
end/finish ----- be over catch a cold ----- have a cold
join the army ---- be in the army, be a soldier
join the Party---- be in the Party , be a Party member
例：吉姆买这支已有两年了。
Jim bought this pen two years ago.
Jim has had this pen for two years.
Jim has had this pen since two years ago.
Jim has had this pen since 2007
It is two years since Jim bought this pen.
4）.在表示“最近几世纪/ 年/ 月以来……”时间状语中，谓语动词用现在完成时。
in the past few years/months/weeks/days；over the past few years; during the last three months; for the last few centuries, through centuries; throughout history 等
5）.表示“第几次做某事，”或在 “It is the best (worst, most interesting ) +名词 ＋that” 后面跟现在完成时。
例：This is my first time that I have visited China.
This is the most interesting film I have ever seen.
That is the only book that he has written.
6）have / has been to + 地点 意为“曾去过某地”，暗含目前已不在该地仅表示当事人的一种经历而已。
have / has gone to + 地点 “到了某地去了”，暗含“已离开原地去了某地”之意，但是否到达了某地尚不确定。
如：He has gone to Shanghai. 他去了上海。
He has been to Shanghai. 他去过了上海。
