瞬间动词可以用于现在完成时，但不能和表 示一段时间的状语连用。如可说“He has left.”但 不能说“He has left for three years.” 如果要表达 “他已走了三年了”可用以下几种表达法：
一.换时态：用ago,使用一般过去时。
He left here three years ago.
7. 结尾的字母d变t。如： lend → lent → lent; build → built → built; send → sent → sent 8. 变为以-ought或-aught结尾。如： buy → bought → bought; bring → brought → brought; catch → caught → caught; teach → taught → taught
过去分词的构成： 一、规则变化： 1. 一般在动词词尾直接加ed。如： pick → picked → picked; wish → wished → wished; stay → stayed → stayed 2. 以不发音的e结尾的动词后面加d。如： like → liked → liked; hope → hoped → hoped; phone → phoned → phoned
have a cold be
keep
2.转换成be+名词/介词短语
join the army
join the Party go to school
be a soldier/be in the army be a Party member be a student/ be in school
3转换成be+形容词或副词 die leave close be dead finish be over begin
3. 以“辅音字母 + y”结尾的动词，变y为i， 再加-ed。如： study → studied → studied; hurry → hurried → hurried; reply → replied → replied 4. 词尾只有一个辅音字母的重读闭音节动 词，要双写辅音字母，再加-ed。如： stop → stopped → stopped; clap学：关志艳
现在完成时 Present perfect tense 用法一： 表示过去开始的动作或状态已经结束，但是 对现在有影响（强调结果现在还存在）

构成:
助动词have/has + 过去分词
1.肯定句 主语+have +过去分词+其他. 主语（三单)+has +动词过去分词+其他.
2.疑问句:Have/Has+主语+过去分词+…. 回答用Yes，---have/has． “No，---haven’t/hasn’t．
二、不规则变化： （见课本136页） 5. 以不变应万变。如： let → let → let; put → put → put; read → read → read 6. 若中间有双写e，则去掉一个e，单词 末尾再加t。如： feel → felt → felt; keep → kept → kept; sleep → slept → slept
用法二：表示过去已经开始，持续到现在的动 作或状态，也可以表示一直持续到现在并可能 还将持续下去。 A 动词使用延续性动词。 B 和表时间段的时间状语连用。常与for或since 引导的时间连用so far, up to/till now, in the last/past+一段时间，all one’s life, by now, these days,for+时间段，since+时间点/从句(从句时态 为一般过去时) She has learnt English for 3 years.她学英语有 三年了 I have lived here since 1990.自从1990年以来 我一直住在这儿
3.否定句： 现在完成时的否定句式是 “主语+have/has+not+过去分词+……”. 4.特殊疑问句句型 特殊疑问词+have/has+主语+过去分词+…….
How many times have you been to the Great Wall?
How long have you known each other? 与表示时间副词 just （刚刚）,already（已经(肯定句) before, （一般疑问(句末） ： yet已经；否定句：还） never, ever (疑问句) twice recently(近来）等状语连用
以上三种表示方法适用于所有瞬间动词。
另外，还可用其它表示方法，但只适用于部分瞬间动 词。具体办法是将瞬间动词转化为表延续的动词或者表状 态的be+名词／形容词或副词／介词短语等。
换动词
1.直接转化成延续性动词 buy borrow
have
catch (get) a cold come/go/become
For example:
1 He has become a doctor.他已经成为一名医生 He has been a doctor for five years.他当医生已 经五年了。
2 His grandfather has died.他爷爷已去世了。 His grandfather has been dead for ten years.他 爷爷已经去世10年了。 3 The film has begun.电影已经开始了。 The film has been on for five minutes.电影已经 开始5分钟了。
二.换结构：1.用“It is +一段时间＋since ＋一般过去时从句
It is three years since he left here.
Three years has passed since he left here.
2.“ 一段时间＋has passed + since + 一般过去时从句”