单词：organocesium
单词：organocesium 相关文章
This is the VOA Special English Health Report. A.D.H.D. is attention deficit hyperactivity disorder. Government estimates say three to seven percent of school-age children in the United States have it. Adults can also have it. People with A.D.H.D. ha
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[00:06.37]The United States has a new official clock. [00:10.95]The clock began operating late last year in the American city of Boulder,Colorado. [00:18.39]Experts say the new clock is so exact that it will neither gain nor lose so much as one secon
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Youve given some thought to oxygen, carbon, uranium. But youve probably never mused about the element ytterbium, symbol Yb. A new study by scientists at the National Institute of Standards and Technology, or NIST, says that ytterbium could find a rol
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