北京地区旧石器文化遗物丰富，自1990年开始在北京城区和郊区县开展旧石器调查和试掘以来，发现旧石器时代文化遗址或地点38处。

There are plenty of Paleolithic culture sites in Beijing area. Some archaeological researches have been done since 1990 and 38 sites have been discovered in the area up to now.

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纯掘工种与纯采工种各工龄段的 工龄别尘肺患病率之间，自1970年入矿年代以后差异无显著性（P>0.05）。

There was no obvious difference in the cumulative incidence of pneumoconiosis by exposure time between pure digging and pure mining workers with the year of mine-entrance after 1970(P>0.05).

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纯掘工种与纯采工种各工龄段的 工龄别尘肺患病率之间，自1970年入矿年代以后差异无显著性（P>0.05）。

There was no obvious difference in the cumulative incidence of pneumoconiosis by exposure time between pure digging and pure mining workers with the year of mine-entrance after 1970(P>0.05).

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