Because it was in the 1950's or so, maybe the late 1940's, that people started to discover lithium, even though it had no natural function, it did do something in our bodies.

因为在二十世纪五十年代左右，可能是四十年代末期，人们开始发现锂，尽管不参与人体的正常生理活动，但是它确实会对我们的身体产生影响。

麻省理工公开课 - 化学原理课程节选

And so it went, through the years from the 1950s through the 1970s.

就这样不停地做下去,从二十世纪五十年代到了七十年代

耶鲁公开课 - 生物医学工程探索课程节选

The first is this era, of the 1820s, '30s, '40s and '50s, Antebellum America, exemplified most obviously by the anti-slavery movement, which is where we're going to get to as we leave today.

第一个时期,是十九世纪二十年代,三十年代,四十年代和五十年代,内战前的美国,废奴运动就是其典型,这是我们今天下课前要弄明白的

耶鲁公开课 - 美国内战与重建课程节选