现在完成时怎么用
答案如下：
1.现在完成时常用的时间状语有lately，recently，just，already，yet，up to now，till now，so far，to this day，in the past few years/months/weeks/days，over the past few years，during the last three months，
for the last few centuries，through centuries，throughout history等。
2.在时间状语从句中，谓语动词可以用现在完成时代替将来完成时。例如：
Mother won’t let her watch TV until she has finished her homework.母亲要到她做完作业才让她看电视。
The dinner party will begin after all the guests arrive/have arrived.所有的客人到了以后，聚餐就开始了。
3.has/have been to与has/have gone to的区别。has/have been to表示“曾去过”，说明有某种经历；has/have gone to表示“已去某地(在途中或已经到达目的地)。例如：
They have been to Sweden many times.他们去过瑞典许多次了。
Jack isn’t in. He has gone to the supermarket.杰克不在，他去超市了。
4.现在完成时特别强调瞬间动词和持续性动词。瞬间动词表示短暂、不能持续一段时间的动作，如come，go，leave，start，begin，become，receive，die，而持续性动词表示能持续一段时间的动作，如work，stay，live，learn等。
下面列举一些常用的瞬间动词和对应的持续性动词：leave，be away；die，be dead；put on，wear；fall ill，be ill；borrow，keep；catch cold，have a cold；buy，have；join the army，be in the army。例如：
My brother has been in the army for some time.我兄弟参军有一段时间了。
My brother joined the army some time ago.我兄弟是一段时间以前参的军。
He has been up for an hour.他起床有一小时了。
He got up an hour ago.他一小时前起的床。
Jack has been a soldier for some time.杰克当兵有段时间了。
Jack became a soldier some time ago.杰克是在一段时间前当的兵。
但是，瞬间动词的肯定结构可以用不与“for+时间段”连用的现在完成时，说明某个动作已经发生；瞬间动词的否定结构可以与“for+时间段”连用，说明某动作不发生的状态可以持续一段时间。
