琉璃于战国时已经出现。

Glass has already appeared in the Warring States Period.

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因而论文选定成书于战国时期的《礼记》作为研究对象。

So the writer select Li Ji compiled in the Warring States Period as the study subject.

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该文认为，就目前所知，中国古代“物理”一词最早出现于战国时期。

This paper points out that the Chinese word Wuli was first used in the Warring States period.

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