名词
中文翻译：时期
同义词：
['duration', 'interval', 'span例句：1. The scientist has been studying the periodic table for years.（这位科学家多年来一直在研究元素周期表。）']
例句：
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1. The scientist has been studying the periodic table for years.
这位科学家多年来一直在研究元素周期表。
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2.The company's performance has shown a cyclical pattern of improvement and decline.
该公司的业绩表现出周期性的改善和下降。
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3. The economy is experiencing a period of growth.
经济正在经历一个增长期。