He gave me a hearty slap on the back.

他热情地在我背上拍了一下。

He gave the child a slap on the back.

他在孩子的背上打了一巴掌。

I was nearly knocked down by a slap on the back.

我被背后突然的一击差点打倒。

We got a slap on the back for staying late at work.

我们因工作到很晚而受到了表扬。

Now if someone could only explain the science of that thing guys do when they kind of hug but slap each other on the back too.

不过我们好像也需要一个人来解释下男人在几近拥抱时在对方背上互拍这一细节中有何科学。