单词：cesium perchlorate
单词：cesium perchlorate 相关文章
[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
If we are looking for Martian bugs, we should search for life forms at least as tough and alien as this. Im looking at Mars in a point of view of a microbe. And as a microbe, I really need very, very tiny amount of water. I could probably live my ent
自然百科2012年
As July 4th approaches, Americans look to the skies. Throughout the country, fireworks will be launched in celebration of the nation's independence. But what goes up must come down. Reporter Eric Libby looks at the environmental issues surrounding f
VOA标准英语2008年（七月）