很多學(xué)生都有偏科的情況,，而英語(yǔ)又是大多數(shù)學(xué)生偏科的科目。不僅有單詞記不住的煩惱,，還有語(yǔ)法用不對(duì)的情況,，如此下來(lái)就導(dǎo)致英語(yǔ)成績(jī)一直不理想。對(duì)于單詞的記憶我之前有分享相關(guān)的方法,，今天主要將一些語(yǔ)法方面的知識(shí)點(diǎn),。
1. Since從句為非延續(xù)性動(dòng)詞的過(guò)去時(shí)或現(xiàn)在完成時(shí)，時(shí)間的起點(diǎn)應(yīng)該從從句動(dòng)作完成時(shí)刻算起,。
例如：
Things have changed a lot since I wrote to you last time.
自我上次給你寫信之后,，情況已發(fā)生了很大的變化。
She has lived with us since she has come here.
自從她來(lái)到這里,，就一直和我們住在一起,。
2. Since從句為延續(xù)性動(dòng)詞的一般過(guò)去時(shí)，表示動(dòng)作或狀態(tài)的結(jié)束,。其含義與動(dòng)詞的詞義恰好相反,，具有否定意味。
例如：
All has changed since he was at home.
自從他離開(kāi)家以后,，這里的一切都變了,。
I haven’t written to her since she lived in London.
自從離開(kāi)倫敦以來(lái)，我還沒(méi)有給她寫過(guò)信,。
但如果since從句是延續(xù)性動(dòng)詞的現(xiàn)在完成時(shí),，則表示動(dòng)作由開(kāi)始延續(xù)至說(shuō)話的時(shí)候,，具有肯定意味。
例如：
He has never been to see me since I have been ill.
自從我生病以來(lái),，他一直沒(méi)有來(lái)看我,。
She has talked little since she has stayed at home.
自從她呆在家里以后,，就很少講話。
3. 在現(xiàn)代英語(yǔ)中,，since從句是延續(xù)性動(dòng)詞的一般過(guò)去時(shí),，有時(shí)候也可以表示肯定意味。此時(shí),，多半用ever來(lái)加強(qiáng)since的語(yǔ)義,。
例如：
She has known me ever since she was a child.
她從小就認(rèn)識(shí)我了。
I have live here ever since I was born.
我生下來(lái)就住在這里,。
4. 在it is+時(shí)間+since從句結(jié)構(gòu)中,，since從句是非延續(xù)性動(dòng)詞的一般過(guò)去時(shí)，含有肯定意味,。
例如：
It is three years since her husband left her.
她丈夫離開(kāi)她已經(jīng)3年了,。
It is over sixty years since the People’s Republic of China was established.
中華人民共和國(guó)已經(jīng)成立60多年了。
5. 在it is+時(shí)間+since從句結(jié)構(gòu)中，since從句是延續(xù)性動(dòng)詞的一般過(guò)去時(shí),，含有否定的意味,。
例如：
It is three years since she stayed here.
她離開(kāi)這里已經(jīng)3年了。
How long is it since you were a league member?
你退團(tuán)有多久了?
6. 在it is+時(shí)間+since從句結(jié)構(gòu)中,，since從句是現(xiàn)在完成時(shí)或過(guò)去完成時(shí),，均含有否定意味。
例如：
It is five years since we have seen her.
我們已經(jīng)5年沒(méi)有見(jiàn)她了,。
It was years since I had seen her.
在那之前,，我已經(jīng)有好久沒(méi)有見(jiàn)到她了。
另外,，①根據(jù)英語(yǔ)慣用法,，since從句不可以否定形式出現(xiàn)。
例如：
It is four years since I have smoked a cigarette. 我已經(jīng)4年不抽煙了,。
不可說(shuō)：It is four years since I haven’t smoked a cigarette.
但由于下句中的since不作“自從”解,，所以從句可以用否定形式。
例如：
I haven’t been out anywhere since I don’t know how long.
也不知多久了,，我哪兒也沒(méi)去過(guò),。
②Since從句通常不與非延續(xù)性動(dòng)詞的現(xiàn)在完成時(shí)的肯定式連用,。
例如：
Her mother died when she was a child.
她小時(shí)候母親就去世了。
不可說(shuō)：Her mother has died since she was a child.
③Since前不可加表示時(shí)間的詞語(yǔ),，但可以與ago連用,。
例如：
She has lived with us since her mother died three years ago.
自從她母親3年前去世,，她就一直和我們住在一起。
不可說(shuō)：She has lived with us three years since her mother died.
④在It was five years ago since his father died. 一句中的since用錯(cuò)了,，因?yàn)樵诤衋go的時(shí)間范疇里,，已經(jīng)有了從過(guò)去的一個(gè)時(shí)間點(diǎn)以來(lái)的時(shí)間，即已有了since的時(shí)間范疇,，所以再用since是多余的,。
改為：
It was five years ago that his father died.
他父親5年前去世了。
It is five years since his father died.
他父親去世已經(jīng)5年了,。
