Lead in
一般过去时导入：一般过去时的概念
一般过去时表示过去某个时间发生的动作或存在的状态。
I lost my pen.(过去时)
I have lost my pen.（现在完成时）
过去时一般表示过去所发生的动作或存在的状态。“我把笔丢了”，说话人只是想告诉对方在过去的某一个时间里他的笔丢了，仅此而已。（仅仅是在陈诉过去的一个事实，与现在没有关系）
New lesson
一．现在完成时的构成：
助动词have/has(not) +动词过去分词
She has turned on the lights.
肯定式：have/ has+过去分词
否定式：haven’t/hasn’t+过去分词
疑问式：把have/has 提到主语前面
肯定回答：Yes,…have/has
否定回答：No,…..haven’t/hasn’t
二．用法
1.表示过去发生的动作对现在造成的影响或结果.
例如:She has gone. 她走了. She went in the past.(She is not here
now.)
I have just cleaned my hands.
我刚洗过手。（“洗手”是发生在过去的动作，对现在造成的结果是“手干净了”）
I have closed the door. (The door is close now.)
She has turned on the lights. (The lights are on now.)
He has written his name on the blackboard. (The name is on the blackboard now.)
Mother has cooked the dinner. (We can have dinner now.)
You have seen the film. （You know what the film is about.)
We have cleaned the classroom. (The classroom is clean now.)
2. 表示动作发生在过去，并且一直延续到现在，甚至还可能继续延续下去。这时常和since所引导的短语或从句或for引导的短语连用(for有时可以省去)。以及so far, by now, these days, in the last/past … years/days…等连用。
I have lived here for over ten years. （表示他现在还在这里居住，并且还有可能继续住下去）比较：I lived here ten years ago.(仅仅说明了他十年前在这里记住过的事实,不代表现在他还住在这里)
He has studied here since 2006.
都用How long 提问，例：
We have learned English for three years.
We have learned English since three years ago.
-How long have you learned English?
They have written 15 songs so far.
Mr. Green has been in China these years.
附:have been 与have gone 的用法比较
1:“have been +in+地点名词”或“have been + 位置副词”的意思是“在某地呆过（多久）”.
如：Mr. Green has been in China for many years. 格林先生在中国呆过好多年。
I have been here since I began to work. 我工作以来一直呆在这儿。2:“have been + to +地点名词”或“have been+ 位置副词”意思是“曾经到过某地（多少次）,已经到了某地”。
如：Miss Brown has been to Japan twice. 布朗小姐到日本去过两次。
Have you ever been here before? 你以前到过这吗？
I have been to Xiamen.(我曾经去过厦门)
3: “have gone to + 地点名词”或“have gone + 副词”意思是“在去某地的路上,还没有到”
I have gone to Xiamen.(我已经在去厦门的路上了.)
三.现在完成时句中常见的时间状语
(一). just, already, yet, ever, never，before ，recently有此类副词时, 常强调动作完成, 不强调动作的持续.
She has never /just/ already /ever eaten a Mango.
He has ___just/ already______ come.
I have finished your homework already.
Have you milked the cow yet?
He has not come yet.
We have seen the movie before，我们以前看过这个电影
其中just用于肯定句, 意为“刚刚”，already用于肯定句, 意为“已经”，yet用在疑问句中也意为“已经”，ever用于一般疑问句，意为“曾今”。
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？
