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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
美国英语听力80篇
Grammar Girl here. Today's topic is words that can get you into trouble. Guest-writer Bonnie Trenga writes: Once upon a time, some mistaken citizens stood up for American principals, p-r-i-n-c-i-p-a-l-s. Across the Atlantic, a nutty queen sat on her
英语语法 Grammar Girl
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
Scientific American(八)月
Ethiopia will accomplish the construction at any cost whether donors continue funds or not. The giant Gibe III dam, now being built on the Omo River in southwestern Ethiopia is a boon for some, a problem for others. Supporters say it will provide ele
VOA标准英语2010年(九)月
Every winter some twenty million tons of salt are dumped on America's road.That sodium chloride melts the ice, so it prevents its formatin, helping to prevent accidents. But road salt has its downside. This is not very economical because salt is main
2016年Scientific American(一)月
This week on Why Tell Me Why, we are finding out why the oceans are so salty. So the oceans are salty because the oceans have been around, lets say, for over five hundred million years. And over the course of time what we found out is that weve alway
自然百科2009年