研究发现背向的电子发射产额不满足余弦关系，这是由于H2 +上的价电子所引起的。
The results show that backward electron emission yield deviates from inverse cosine law, due to the role of the valence electrons of H2 +.
我们的房子背向河流。
最独特和艺术的拍摄，是让你的拍摄对象背向阳光，调成手动模式，对着拍摄对象曝光过度这样可以使你的拍摄者平均受光。
For a most unique and artistic shot, place your subject with thier back to the setting sun. On Manual mode, overexpose the portrait so your subject is evenly lit.
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