yet放在句首和句中句尾的区别
yet是什么时态的时间状语标志？
yet是什么时态的时间状语标志？
yet多用于现在完成时的否定句中。但也可以用于一般现在时等时态。
句尾出现yet要用过去分词嘛？
句尾出现yet，那么这个句子一般来说是现在完成时，动词就应该用过去分词。
but 和yet 的区别？
1、 but是并列连词,而yet则可作并列连词或副词,不可说and but,但可说and yet,but不可放在句尾,而yet可放在句尾；
2、but表示对照或对立时,一般都比较轻松自然,而yet在表示对照或对立时,则往往比较强烈,时常出人意料；
3、but在某些习惯说法中不可用yet替代.；
but是并列连词,yet属于副词
but一般是在句子的开始部分,而yet是用于句尾的
but是用语肯定句中,yet用语否定句或疑问句中
一、副词 yet 作“还”,“仍然”讲
yet remains to be done.尚有许多事情待做.
molecules are always moving,some perhaps as fast as a mile per second.
分子仍然总在运动,其中有些分子的运动速度达每秒一英里.
experiment is not yet over.这项试验尚未结束.
one has yet seen an electron.还没人见过电子.
has not yet learned to store the suns heat.人类尚未学会贮藏太阳热.
二、副词 yet 和比较级连用,作“还要”,“更”讲,常可用 even 代替
is a yet ( 或 even) more difficult task.这是一项更为艰巨的任务.
2.We must study yet ( 或 even) harder.我们必须更加努力学习.
三、副词 yet 用于现在完成时作“已经”讲,只用于否定句和疑问句中
1.Have you seen such a space shuttle yet你（已）见过这样的航天飞机吗
2.Has the bell rung yet铃已打过了吗
bell has not been repaired yet.铃尚未修好.
注：在肯定句中表示“已经”要用 already,不能用 yet.若在疑问句中用 already 代替 yet,则表示惊异的语气.
eg:Has the bell rung already铃真的打过了吗
四、连词 yet 和 and yet,but yet 用法举例
is very good,yet ( 或 but) it can be better.这很好,但还能精益求精.
is strange,and yet it is true.( It is strange yet ( 或 but) true.) 真奇怪,却是真的.
has weight,and yet it is very light.空气有重量,虽然很轻.
this matter sounds strange,yet it is true.此事听起来虽然奇怪,但却是事实.
wheel is the simplest yet ( 或 but) perhaps the most remarkable of all inventions.
轮子是所有发明中最简单却也许是最非凡的一种.
6.Everyone thinks that this is a simple method,(but) yet he cannot believe it.
大家都认为只是个简单方法,但他不信.
五、词组 as yet （到目前为止）和 just yet （就在此刻）常用于否定句中
have not made such an advanced computer as yet.
他们目前尚未制造出这样一种先进的计算机.
one has as yet been able to produce the absolute zero of temperature.
还没有人能产生绝对零度.
will not happen just yet.此事一时尚不至于发生.