Knock on 和Knock at 有什么区别啊?

Knock on:
敲（门、窗等）
例句与用法:
1.He accidentally knocked on (the pass from Jones).
他非故意犯规,用手向前击了（从琼斯传来的）球.
2.Jim sat up when he heard the knock on his bedroom door.
吉姆听到敲寝室门的声音时便坐了起来.
3.Please do not enter before knocking on the door.
进来前请先敲门.
Knock at:
vt.敲
例句与用法:
1.There was a furious knock at the door.
有人在猛烈地敲门.
2.Did I hear a knock at the door?
是有人敲门吗?
3.Did you hear the knocks at the door?
你听到敲门声了吗?
没什么大区别

用at表明敲的对象是硬的,而on是软的.

当knock作为名词的时候,介词用at,如a knock at the door
敲门声
动词是介词用on,如knock on the door 敲门

两者做"敲"解释是无区别

当knock作为名词的时候,介词用at,如a knock at the door
敲门声
动词是介词用on,如knock on the door 敲门