不过，这些技术实现难度很高，因此并不常用。

However, these techniques are difficult to implement and aren't commonly used.

youdao

内核支持许多的调用，但其中有很多并不常用。

The kernel supports a large number of calls, many of which are infrequently used.

youdao

我选择了棕色作为公司的主色调，尽管这种颜色并不常用。

I chose brown as my company's color, even though that's not common at all.

youdao

One miscellaneous result, which we don't use very much now, but which I should mention to you is the following.

这是一个很复杂的结果,现在并不常用,但是我要提醒你们注意下面的

耶鲁公开课 - 基础物理课程节选