宋，元时期出现了圆镜，长方镜，菱镜，八棱镜和带柄手镜等。
During the Song and Yuan Dynasties the bronze mirrors appeared in all shapes: round, rectangular, rhomboidal, octagonal, and those with a handle.
他们用轨道X射线望远镜Chandra来研究银河星系的生长方式。
They used an orbiting X-ray telescope called Chandra to study the way that clusters of galaxies grow.
他们用轨道X射线望远镜Chandra来研究银河星系的生长方式。
They used an orbiting X-ray telescope called Chandra to study the way that clusters of galaxies grow.
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