by all means 一定;务必

by any means 无论如何

by no means 绝不

By all means, I must visit my sick friend.

我一定要探望我生病的朋友。

You must get there by all means before dark.

你们一定在天黑之前到达那里。

A:Could I borrow your pen, please?

我可以借用你的钢笔吗?

B:By all means.

当然可以。