名词
中文翻译：时期
同义词：
['era', 'interval', 'span', 'phase', 'cycle']
例句：
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1.The scientist has been studying the periodic table for decades.
这位科学家已经研究元素周期表几十年了。
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2.The company's performance has been in a period of decline.
该公司的业绩一直处于下滑期。
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3. The new policy will have a period of effect until next year.
这项新政策将在接下来的一年里产生效果。