一般完成时主要用于表达过去发生的动作对现在的影响或结果，也可以表示过去某一时间段内发生的动作或状态一直持续到现在。其构成是主语 + have/has + 过去分词。以下是一些一般完成时的例句：
表示已完成的动作对现在的影响
I have studied English for 10 years.
They have been dating for 3 months.
I have finished my homework.
表示一段时间内发生的动作
She has been to 10 different countries in the past year.
We have looked all over for the lost wallet.
表示刚刚完成的动作
I have just finished my dinner.
Help, I'm stuck!
强调持续的状态
I was stuck with him for the whole journey.
You may be stuck with a miserable existence for the rest of your life.
与时间状语连用
I have not heard from her so far.
We have learned five hundred words up to the present.
这些例句展示了一般完成时在表达不同时间背景下的动作和状态时的应用。希望这些例子能帮助你更好地理解和运用一般完成时。