问题
问答题 简答题
电镜为何要求一定的真空度？
答案
参考答案：
如果含有很多的其他分子，会与电子发生碰撞，使电子散射，引起眩光，影响成像质量；碰撞也会使电子束不稳定，产生闪烁现象；灼热的灯丝遇气体也易腐蚀和断裂。
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电镜为何要求一定的真空度？
参考答案：
如果含有很多的其他分子，会与电子发生碰撞，使电子散射，引起眩光，影响成像质量；碰撞也会使电子束不稳定，产生闪烁现象；灼热的灯丝遇气体也易腐蚀和断裂。
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| There is a wonderful fable about a young orphan girl who had no family and no one to love her. One day, feeling particularly 1 , she was walking through a meadow 2 she noticed a small butterfly 3 in a thorn bush. The more the butterfly 4 to free itself, the 5 the thorns cut into its body. The young orphan girl carefully 6 the butterfly from its captivity (围困). 7 flying away, the little butterfly changed into a beautiful fairy. The young girl rubbed her eyes in 8 . "For your 9 kindness," the good fairy said to the girl, "I will grant (给予) you any 10 you would like." The little girl thought for a moment and then replied, "I want to be 11 !" The fairy said, "Very well," and leaned toward her, 12 in her ear. Then the good fairy disappeared. 13 the little girl grew up, there was no one in the land as happy as she. Everyone asked her the 14 of her happiness. She would only answer, "It is that I 15 a good fairy when I was a little girl." When she was very old and on her deathbed, the neighbors all gathered around her, 16 that her fabulous secret of happiness would die with her. "Tell us, please," they 17 , "Tell us what the good fairy said." The lovely old woman 18 and said, "She told me that everyone, no matter how 19 they seemed, no matter how old or young, how rich or poor, had 20 of me. If I would be loved, love and be lovable." | ||||
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