at a distance: 离一段距离

The painting can be only admired at a distance.

这幅画要在远处欣赏.

At a distance of six miles you can't see much.

距离六英里以外的东西很难看清.

from a distance: 从远处,隔开一段距离(或时间)

In summoning the boy from a distance, the father was obliged to lift up his voice.

为了把儿子从远处叫回来,父亲不得不提高嗓子喊.

Don't get within range of their big guns; surround the camp from a distance.

不要进入他们大炮的射程以内,要隔一段距离包围住敌营.

in the distance  在远处

I could see the faint gleam of light in the distance.

我能看见远处微弱的灯光.

The thunder growled in the distance.

雷在远处隆隆地响.