单词:direct vacuum tube current
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This is Scientific American 60-Second Science. I'm Cynthia Graber. This will just take a minute. The fridge is one of your home's biggest energy hogs. Better insulation can make refrigerators much more efficient. And a panel encasing a vacuum is one
No Housework Day is one of those days you see on calendars on the Internet but dont know where it came from. It is always on April 7th. It is one day of the year when it is OK to do nothing in the house. Everybody has the day off from doing the house
Section C Great Ideas Some of the most important inventions of the past 2,000 years may surprise you. Want to get rich? Become famous? You don't have to be a film star or a basketball player or a musi
BBC Learning English London Life Friendliness on the tube Yvonne:I'm Yvonne Archer and this is London Life from bbclearningenglish.com. Hello! In today's programme, we're talking about friendliness on London's tubes. Is there any? As you probably kn
物理学 statics 静力学 motion 运动 inertia 惯性 gravitation 引力 relativity 相对 gravity 地心引力 vibration 震动 medium (media) 媒质 frequency 频率 wavelength 波长 pitch 音高 intensity 强度 echo 回声 resonance 回声,洪