我敲了两次门。

I have knocked twice.

youdao

他敲了3次门。

He struck three times on the door.

《新英汉大辞典》

我敲了两次门你都没有来开。

I knocked twice, but you didn't answer your door.

youdao

And as I'm going to do many times in 3.091, I'm going to start a unit like this with a history lesson.

在3。091这门课上我会重复很多次，我会像现在一样以一个历史的故事,来开始新的一单元。

麻省理工公开课 - 固态化学导论课程节选

And I hope, as you are reading, you notice that chapter opening where once again Dean appears at the door when Sal shows up, and he's totally naked.I hope you noticed that. It's the third time that we see that so there is an eroticism between them.

我也希望，你们在阅读时注意到那一章,就是曾经萨尔去找迪安时，迪安又一次是光着身子，开的门，我希望你们注意到这一点，这是第三次,我们看到这一幕，所以他们对彼此有着性欲。

耶鲁公开课 - 1945年后的美国小说课程节选

You've got a couple of tests here.

这门课得有几次测试

耶鲁公开课 - 聆听音乐课程节选