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Item eight. Vocabulary. fossil, molecule, hydrogen, carbon, sulfur. Petroleum has been important since ancient times. In Latin, the name means rock oil. Petroleum is a fossil fuel. The liquid comes from the remains of plants and animals that died mil
step by step 3000 第一册
For something that could revolutionize the world, its come along very slowly. The fuel cell was invented in 1839, but there was little development until the 1950s when NASA started to use them in space where they are still used today. Now, after yea
国家地理2008年
Ecological balance - astable balance in the numbers of each species in an ecosystem. In the ecosystem of the mouth this balance is brought about by competition and cooperation between the different or
医务英语
Why Teflon Is Slippery Teflon is the trademark name for PTFE, a type of plastic. If you own any non stick cookware, then you probably use PTFE on a daily basis. You might not realize, as you fry your morning eggs, that PTFE is one of the most slipper
英语时差8，16
Because chemists for so long worked in isolation, conventions were slow to emerge. Until well into the second half of the century, the formula H2O2 might mean water to one chemist but hydrogen peroxide to another. C2H4 could signify ethylene or marsh
万物简史
We are rediscovering the enigmas(谜团) of the Moon and they're really in our own backyard Dr Jim Garvin, Nasa Goddard Space Flight Center Moon water has world in a twitter A surprising amount of water has been found to exist in the Moon's soil. Data
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