The two systems are, at bottom, conceptual models.

这两个系统实际上是概念模型。

The rotor is at bottom of the picture.

图片底部是转子。

But what was June, 1848, at bottom?

但是，究其实，1848年六月到底是怎么回事？

But whose heart is at bottom unchanging.

可它的心在深深的海底，却始终如一。

Place non-essential links at bottom of page.

将不重要的链接放置在页面底部。