then与since then的区别?直接引语变成间接引语时,now要变成then,改成since then就不对吗?

then与since then的区别?直接引语变成间接引语时,now要变成then,改成since then就不对吗?
then与since then的区别?
直接引语变成间接引语时,now要变成then,改成since then就不对吗?

then与since then的区别?直接引语变成间接引语时,now要变成then,改成since then就不对吗?
then 意思是：在那时
用于过去时.
since then 意思是：从那以后直到现在
用于现在完成时
直接引语变成间接引语使用的时态一般都是和过去相关的,例如：过去时,过去进行时,过去完成时,过去将来时等等
现在完成时就不对了,所以 then不能改成since then, 而且两者意思也不一样.

then那时=at that time当时，一般用于一般过去时；
而since then自从那时起，一般用于现在完成时。
如：
He said that he was in the classroom then.他说他当时在教室里。
He has lived in Shanghai since then.从那里起，他一直住在上海。

简单点说吧，then中文为“那时”，指的是过去的一个时间点。since then中文是“从那时起”到现在为止，是一个时间段。

then =at that time （多用过去时态）

副词 adv.

1.当时, 那时 

I was travelling in Europe then.

那时我正在欧洲旅行。

2.接着, 于是, 然后，其后，后来 

We had dinner together, and then went to the concert.

我们一起进晚餐, 然后去参加音乐会。

Then came the day of his examination.

接着到了他考试的日子。

3.还有, 而且，另外，再者 

Then there is Mr. Smith.

还有史密斯先生。

4.那么; 因此；既然如此 

You say you don't want to call a doctor.Then what do you want to do?

你说你不想请医生, 那么你想怎么办?

5.（指将来）到那时，届时；总之；（表示交谈、陈述等的开始或结束）那么 

形容词 adj.

1. 当时（任职等）的

since then (多用完成时态）

从那时起，从那时以来

Since then he has been drawing a pension.

从那时起他一直领退休金。

He has never been able to rekindle her love since then.

从那时起他再也不能激发起她的爱情。

Since then, we've lived far apart and never seen each other again.

从那以后， 我们山南海北再也没有见过面。

I have visited almost every year since then.

从那时起，我几乎每年都来此访问。

And I no longer like skating since then.

从那时起我就不再喜欢滑冰了。

Every Saturday since then, I have taken one marble out and thrown it away.

自从那之后，每个星期六，我都拿出一个弹珠，把它扔掉。

How have we evolved since then?

从那时起我们的发展状况如何呢？

And since then, the markets have not bounced back.

而自从那时起，市场就再没恢复过来。

Since then we have added some language explaining it.

从那以后我们又添加了一些说明 的文字。

Since then I have avoided secret meetings of any kind," he said.

“从那以后，我就尽量避免各种形式的秘密聚会，”他说。

Since then, there have been another 12 outbreaks, all in South Asia.

自那时以来，又发生过另外12次疫情，均在南亚。

Since then, 28 people have transmitted the virus to their partners.

从那时以来，有28人将病毒传给了其伴侣。

Yes, monsieur, one and twenty years ago; and since then we have not seen the poor marquis three times.

是的，先生，那是二十一年以前的事了，从那以后，我们见到可怜的侯爵总共不过三次。

Since then, there have been another ten outbreaks, all in Australia, and three involving human cases.

自那时以来，又发生过十次疫情，全部在澳大利亚，其中三次有人类病例。

But since then, scientists have been stumped about how they got there.

但是自从那时以来，科学家们一直无法解释它的成因。

Since then, we have seen the development of molecular biology, work on gene expression and studies on the enzymatic properties of proteins.

自那时以来，我们发展了分子生物学，致力于基因表达，并开展了蛋白质酶学性质的研究。

Since then profits of most power-generation companies have declined due to the recession.

自那时以来，由于经济衰退的缘故，大多数电力公司的利润下降。

Five years have passed since then.

自从那时以来，五年已经过去了。

Since then, it had participated in all the Summer Olympics.

自那以后，它参加了所有的夏季奥运会。

Every three months since then, I have deposited pocket money for them in their savings accounts and, as they have grown older, their clothing allowance as well.

从那时起每三个月，我会在他们的帐户里存入他们的零花钱。 在他们长大后，这笔存款里也包括了他们的服装津贴。

Since then, robots have joined the fight.

从那时起，机器人加入了战斗。

Since then, I’ve managed to trim my library by more than half.

从那时起，我就把我的图书馆精简到了原来数量的一半还多。

But since then it has been starved of resources and isolated from the rest of the world.

但是从那以后，它的资源开始变得匮乏，而且与世界的其它地方隔绝。

then:然后。
since then：从那以后。