現在完成時的結構課件
由“have/has+過去分詞”構成，主要有兩個含義： ①表示動作發生在過去，但與現在的情況有聯系，有時無時間狀語，有時和一些表示不確定的過去時間狀語連用，如：many times，just，yet，ever，never，already，before，so far, by now等連用。 ②表示從過去某一時間開始一直延續到現在并還可能繼續延續下去的動作，用于延續性動詞，且句中常帶有表示一段時間的時間狀語，如：for two months, so far等。
時態結構
現在完成時由“have/has+過去分詞”構成，主要有兩個含義：
①表示動作發生在過去，對現在有影響，有時無時間狀語，有時和一些表示不確定的過去時間狀語連用，如：many times，just，yet，ever，never，already，before，so far, by now等連用。
②表示從過去某一時間開始一直延續到現在并還可能繼續延續下去的動作，用于延續性動詞，且句中常帶有表示一段時間的時間狀語，如：since + 時間點/從句，for two months, so far等。[1]
在“it is the first/second...time that...。”或在“it/this/that is the +最高級+名詞+that...。”結構中，that從句中的動詞常用現在完成時；表示到說話時為止動作發生過幾次。在“it + be...+since從句”這一結構中，be可用一般現在時或現在完成時，since從句一般用過去時。have/has/had +been +動詞的現在進行時。
1）現在完成時和一般過去時都能表示過去發生過的動作，但現在完成時表示過去動作對現在的影響，并且表示這一動作已完成或還可能繼續下去；
2）而一般過去時與現在的情況沒有聯系，僅表示過去的動作，且這一動作到說話時已終止。因此現在完成時不能與表示明確的過去時間如：in1949，yesterday，last week等的狀語連用，并且用when或where對這些時間和地點狀語提問時，一般只用一般過去時。
比較過去時與現在完成時
1）過去時表示過去某時發生的動作或單純敘述過去的事情，強調動作；現在完成時為過去發生的，強調過去的事情對現在的影響，強調的是result (結果）。
2）過去時常與具體的時間狀語連用，而現在完成時通常與模糊的時間狀語連用，或無時間狀語。一般過去時的時間狀語:
yesterday, last week，…ago, in1980, just now, 具體的時間狀語
共同的時間狀語:
this morning, tonight, this April, now, once，before, already, recently，lately
現在完成時的時間狀語
for, since, so far, ever, never, just, yet, till / until, up to now, in past years, always,
不確定的時間狀語
3）現在完成時可表示持續到現在的動作或狀態，動詞一般是延續性，如live, teach, learn, work, study, know.
過去時常用的非持續性動詞有come, go, leave, start, die, finish, become, get married等。
舉例：
I saw this film yesterday.
（強調看的動作發生過了。）
I have seen this film.
（強調對現在的'影響，電影的內容已經知道了。）
Why did you get up so early?
（強調起床的動作已發生過了。）
Who hasn't handed in his paper?
（強調有卷子，可能為不公平競爭。）
She has returned from Paris.
她已從巴黎回來了。
She returned yesterday.
她是昨天回來了。
He has been in the League for three years.
(在團內的狀態可延續)
He has been a League member for three years.
(是團員的狀態可持續)
He joined the League three years ago.
( 三年前入團，joined為短暫行為。)
I have finished my homework now.
---Will somebody go and get Dr. White?
---He's already been sent for.
句子中如有過去時的時間副詞（如 yesterday, last, week, in 1960）時，不能使用現在完成時，要用過去時。
（錯）Tom has written a letter to his parents last night.
（對）Tom wrote a letter to his parents last night.
用于現在完成時的句型
1）It is the first / second time…. that…結構中的從句部分，用現在完成時。
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…結構，that從句要用現在完成時.
This is the best film that I've (ever) seen.
這是我看過的最好的電影。
This is the first time (that) I've heard him sing.這是我第一次聽他唱歌。
典型例題
---No, this is the first time I ___ here.
was B. have been C. came D. am coming
答案B. This is the first time 后面所加從句應為現在完成時，故選B。
---No, it's the first time I ___ here.
even, come B. even, have come C. ever, come D. ever, have come
答案D. ever意為曾經或無論何時，反意詞為never，此兩詞常用于完成時。 This is the largest fish I have ever seen. It is / was the first time +that-clause 的句型中，從句要用完成時。
注意：非延續性動詞的否定形式可以與表示延續時間的狀語連用。即動作不發生的狀態是可以持續的。
（錯）I have received his letter for a month.
（對）I haven't received his letter for almost a month.
比較since和for
Since 用來說明動作起始時間，for用來說明動作延續時間長度。
I have lived here for more than twenty years.
I have lived here since I was born..
My aunt has worked in a clinic since 1949.
Some new oilfields have been opened up since 1976.
I have known Xiao Li since she was a little girl.
My brother has been in the Youth League for two years.
I have not heard from my uncle for a long time.
注意：并非有for 作為時間狀語的句子都用現在完成時。
I worked here for more than twenty years.
(我現在已不在這里工作。)
I have worked here for many years.
(現在我仍在這里工作。)
小竅門：當現在完成時+一段時間，這一結構中，我們用下面的公式轉化，很容易就能排除非延續動詞在完成時中的誤使。
(對) Tom has studied Russian for three years.
= Tom began to study Russian three years ago, and is still studying it now.
(錯) Harry has got married for six years.
= Harry began to get married six years ago, and is still getting married now.
顯然，第二句不對，它應改為 Harry got married six years ago.或 Harry has been married for six years.
