2016.2.22
1、since的用法：
(1)接时间点：（延续性动词）
例： I have stayed in that country since 1995.
(2)接一段时间 + ago：（延续性动词）
例：They have lived in that house since two years ago.
(3)接时间状语从句：
例： I have loved her since I met her last time. / Lily has stayed at home since she left school.
要求：主句的谓v.用现在完成时，而且须是延续性动词；从句的谓v.用一般过去时，而且须是终止性动词。
(4)用于句型“It’s / It has been + 一段时间 + since + 时间状语从句”中：
例：It’s / has been three months since he moved to this city.
要求：主句的谓v.用一般现在时或现在完成时;从句的谓v.用一般过去时，而且须是终止性动词。
(5)用于句型“一段时间 + has passed since + 时间状语从句”中：
例： Three months has passed since he moved to this city.
要求：主句的谓v.用现在完成时，而且动词必须是has passed；从句的谓v.用一般过去时，而且须是终止性动词。
（注：当since用于否定句时，主句的谓v.可以是终止性动词。例： He hasn’t seen the film since last month. ）
(7)相关词组：“从那时起”:ever since、since then、from then on ：
（注：ever since作为一个词组，放句尾可单独使用。例：I have given up smoking ever since. ）另外，还可在since后接句子。since前加ever，加重语气。例： I have given up smoking ever since I caught a bad cough.
(8) since还可引导原因状语从句，相当于because ：
例：Since he was lazy, he didn’t finish his homework.
2016.2.23
2、现在完成时
(1) 现在完成时的句型结构
①肯定句：主语+ have/has+ 过去分词
②否定句：主语+ have/has+ not+过去分词
③疑问句：Have/Has +主语+过去分词
(2) 现在完成时的用法
①现在完成时用来描述截至目前，已经重复完成过几次的动作。常和never, ever, several times等连用。
如：I’ve never been to Africa.
②. 现在完成时用来描述与现在有联系，对现在有影响的已经完成的动作。常与just, already, yet, so far等词语连用。
如：He has just finished his new book.
注意：just now用于过去时。
③. 现在完成时用来描述从过去开始发生，并一直持续到现在的动作。常与for或since连用。
如：I have lived in Qingdao for 6 years. /since 6 years ago/since 2003/since I came to this city.
(It is/has been …+ since….)
It’s been seven years since we last saw each other.
注意:for+一段时间，since后接一个过去的时间点或一般过去时的句子。
④ 在表将来的时间状语和条件状语从句中代替将来完成时.
如：You can go home when you have finished your work.
比较：You can go home when you finish your work.
因篇幅问题不能全部显示，请点此查看更多更全内容