While male contraception has been studied before, no method met the stringent safety and effectiveness criteria that female methods do. It was also unclear whether men would use them.

关于男性避孕术已经早有研究，但还没发现一种比女性避孕术更安全有效的方法。而且，尚不能确定男性是否愿意使用这些方法。

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Based on a numerical model cesium atomic clock designed before, the influence of atomic velocity distribution consisting of two peaks and three peaks has been studied respectively.

基于已建立的小型铯原子钟计算机模型系统，研究了铯束原子速度为双峰分布和三峰分布对原子钟微波频谱的影响。

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The hydrogeology condition of coalfield has been studied deeply according to the research findings done before and field works, as well as the analysis and rearrangement for the collected data.

在已有的研究成果基础上，借助野外的现场调研及室内资料的分析、整理，深入了解了煤田区的水文地质条什。

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It's a phenomenon that has been studied and described before, he said.

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In just over a decade, ISARM has mapped 400 transboundary aquifers, including five in Africa that had never been accurately studied before.

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