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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
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
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
Tony: Who did you invite over for dinner Saturday? Carmela: I invited Keith, Sung, Stephanie, and Luis. Tony: You didnt! Carmela: I did. Why? Tony: Youre going to have a hard time cooking for them. Keith is a vegan and only eats food thats organic. S
地道美语播客
First off, I'll mention that at the bottom of the sea there exist veins of zinc, iron, silver, and gold whose mining would quite certainly be feasible. 首先，我对您说，海底有锌、铁、银、金等矿藏，开发并不是不可能的事。
《海底两万里》中英双语有声读物