现在完成时讲解一、构成:肯定式：主语 + 助动词have/has + 动词的过去分词. 疑问式：助动词Have/Has + 主语 + 动词的过去分词?否定式: 主语 + 助动词have/has + not + 动词的过去分词.过去分词规则变化：a)一般情况下，直接加ed, （work-worked，water-watered, finish-finished等;）b)以“辅音字母+ y”结尾的动词, 把y 变成i 再加ed, （carry-carried study-studied等;）c)以辅+元+辅结尾且中读的动词，要双写最后一个辅音字母，再加ed。 （stop-stopped，shop-shopped）d)以不发音的e结尾的动词，只加d （ 过去分词不规则变化表：二、用法：用法一：表示过去（已经、曾经或从未）发生的某一动作对现在造成的影响或结果。 标志词： already, never, ever, just, yet, before, once/twice/数字+ times 例： I have cleaned my room. 我已打扫了房间(房间现在是干净的，不需要打扫了)They have left. -他们已经离开了,也就是说现在他们人不在这里I have never had a car (我从未有过汽车。)I have been there twice.a）already 往往用于肯定句，用在疑问句时表示强 调或加强语气；yet 用于否定句和疑问句。He has already left here. 他已经离开这里了。Has he already left here? 他（真的）已经离开这里了吗？（表示加强语气）My teachers havent had breakfast yet. 我的老师们还没有吃早饭。Have you written to your parents yet? 你已经给你父母写过信了吗？b） never 是否定词，表示“从来没有”，而ever 表示“曾经”We have never been to the Great Wall. 我们从来没有去过长城。Have you ever been to Canada? 你们曾经去过加拿大吗？ c） just用于句中, 表示“刚刚”Ive just had breakfast. 我刚吃完早饭。What have they just done? 他们刚刚做了什么？d） before用于句末, 表示“以前”Ive seen it before. 我以前见过它。 练习：用never，ever，already，before, just或yet填空。1. I have _seen him before, so I have no idea about him.2. Jack has _finished his homework. 3. -Have you _seen the film? -No, I have _seen it.4. -Has the bus left _? -Yes, it has _ left.5. Would you like to go to the zoo with me? Yes, but I have been there _. has gone to, has been to, has been in 的区别：1. have/has gone to 去了某地（还在某地没回来） -Where is your father? 你爸爸在哪里？-He has gone to Shanghai. 他去上海了。2. have/has been to 曾经去过（已回，已不在去过的地方） +次数（once/twice/ 数字+times）My father has been to Shanghai 3 times. 我爸爸去过上海3次。画线提问：_ has your father been to Shanghai?3. have/has been in 待了多久（去了，现在仍在所待的地方）+ for + 时间段/ + since + 时间点 My father has been in Shanghai for two months/ since two months ago. 我爸已经在上海待了两个月了。画线提问：_has your father been in Shanghai?注意：注意遇到四个地点副词要去掉to/in， 这四个地点副词是：here ,there ,home ,abroad练习：用have gone to / have been to / have been in / went to 填空。1. _ you ever _ Disneyland?2. How many times _ you _ Disneyland ?3. I _ Nanjing since two years ago4. Mr. Li _ Hong Kong. And hell come back in two days.5. How long _ you _ Disneyland ? For three days. I _ the theme park last Sunday.6. My father _ Hong Kong two weeks ago. 7. My father _ Hong Kong in 2005.8. My father _ Hong Kong since 2005.9. My father _ Hong Kong twice.10. My father _ Hong Kong and he hasnt come back yet.11. Wheres Lucy? She has_ to a restaurant for lunch.12. Have you _ to this park before.13. I have_ there only once this year.14. She has _ to the shop to buy a notebook.15. Youre late, Lao Wang has _ to Guangzhou.用法二：表示过去已经开始, 并一直持续到现在的动作或状态。 标志词：up to now, so far, for +时间段 since+时间点 I have learnt English for more than ten years.我已经学了10多年的英语。She has swum since half an hour ago.我已经游泳了半个小时a) for +一段时间Eg. I have been here for 5 weeks. 我在这里5周了。 Hes studied English for 3 years. 他学习英语3年了。b) since +(表示过去某一时间的)时间点/单词/词组/ 从句(一般过去时)Eg. I have been here since 2000. 我自从2000年开始在这里。 I have been here since 5 years ago. 我自从5年前就在这里。 I have been here since I graduated in 2000. 我自从2000年毕业就在这里。注：1) 对for或since引导的时间状语提问 必须用how long, 决不能用when.Eg. I have lived here for 10 years. 画线提问： _ _ have you lived here?注2): 短暂性动词不能和for或since引导的时间状语连用, 当然也不能用于how long引导的问句中 Eg. (误)I have left there for 5 years.(正)I have been away there for 5 years. 为了表述这种意思,我们常用相应的延续性动词 来代替短暂性动词。 become be, begin have , borrow keep, buy have, go out be out come (go, arrive, get) be in die be dead, finish be over, join be in （be a member of ） leave be away ( from), open be open close be closed 练习： 选用 for和 since填空:1.We havent seen each other _ a long time.2.His father has been in the Party _ 10 years ago.3.The film has been on _ 20 minutes.4.Mr Green has worked here _ he came to China.5.His grandparents have been dead _ several years.6. Its five years _ we met last time.三、与一般过去时的用法比较1现在完成时和一般过去时都是说过去的事情，但现在完成时注意的不是事情本身，而是强调事情与现在保持的某种密切联系（如现在的结果，影响,一直延续到现在等），不与表示过去的时间连用; 而一般过去时，则只讲述发生在过去的动作和事情与现在没有关系，常与表示过去的时间连用。 eg：He has bought an English-Chinese dictionary. 他已经买了一本英汉字典。 He bought an English-Chinese dictionary. 他曾买过一本英汉字典。第一句用现在完成时时态，想表达意为：“He bought an English-Chinese dictionary.