The calculated results show that the aza Wittig reaction is a two step reaction, having one four membered ring intermediate on its reaction surface.
计算结果表明该反应是一个二步反应，在反应途径上存在一个四元环中间体。
The skin's protective reaction of constricting surface blood vessels is slower with age, and the cold-induced rise in metabolic rate is also weakened in older people, but the mechanism is unknown.
随着年龄的增长，皮肤的保护性反应——表层血管的收缩减慢，对低温的反应可以增加代谢率，可老年人的代谢率却在不断减弱，哪一代谢机体的下降却不明。
After two decades, 95 percent of the elemental mercury on the surface of a filling had gone through a chemical reaction. It became beta-mercury sulfide, a black-colored solid.
经过了20年的光阴，旧填充物表面有95%的汞元素已经发生了化学反应，它变成了黑辰砂(beta - mercury sulfide)，一种黑色的固体。
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