所有这些变化都是在一段时间内发生的。

All these changes happened over a period of time.

她有一段时间曾帮助垂危的癌症患者。

She spent a period of time working with people dying of cancer

她过了一段时间才适应独自生活。

It took her a while to adjust to living alone.

有一段时间，他们好像大有获胜的希望。

At one stage it looked as though they would win.

我们有很长一段时间没有见到他们了。

It's been an age since we've seen them.

她病了很长一段时间之后回去工作了。

She returned to work after a long period of incapacity.

他在海外工作了一段时间，却没有变得老练。

A period spent working abroad had done nothing to mellow him.

数字电视已经面市一段时间了。

Digital television has been around for some time now.

这些变化经过了很长一段时间才形成。

These changes have occurred over a long time span.