现在完成时 - 例句分析

1.

I have just received a letter from my brother,Tim.

Tim此处是“同位语”，它是来解释说明前面名词的，既然是解释人家，所以说的是同一件事，因此叫“同位语”。
同位语可以有一个词充当，还可以有一个词组充当，甚至还可以是一个句子。

have just received现在完成时，表示“现在的之前”。
just这个词表示“刚刚”，它经常夹在完成时中间使用。
其实想”强调之前”还有几个个词already(已经)，ever(曾经)，never(从来都不)。

have just done
have already done
have ever done
have never done

2.

He has been there for six months.

for一词有很多种用法，常用的有2种：
for+时间，表示持续了一段时间；
还可以表示“目的/为了什么什么”，比如“….for you”

3.

He is working for a big firm and he has already visited a great number of different places in Australia.

has already visited是谓语
a great number of表示“许多，大量”

4.

He has just bought an Australian car and has gone to Alice Springs, a small town in the
centre of Australia

谓语动词是has just bought和has gone to
a small town in the centre of Australia是“同位语”，解释前面的名词Alice Springs。

have gone to 
#表示“去了”，还没有回来，单程。
have been to
#表示“去过”，已经回来了，是往返的过程。

5.

My brother has never been abroad before, so he is finding this trip very exciting.

has never been现在完成时。
he is finding this trip very exciting词句是“主谓宾补”的句型。

go / travel / study / live + abroad

abroad是副词，是用来修饰动作的，紧挨着动词。

have been to abroad  #错误用法
have been abroad    #正确用法