名词
中文翻译：时期
同义词：
['duration', 'interval', 'span', 'time period']
例句：
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1.The scientist studied the earth's climate over a 20-year period.
这位科学家研究了地球气候的20年。
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2.During the 19th century, there were many significant technological advancements.
在19世纪，发生了许多重要的技术革新。
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3. The company has been in operation for several decades now.
这家公司已经运营了几十年。