1. Redd cloud nigrescence cloud, there is rain on.
红云变黑云，必有大雨淋。
来自互联网
2. This paper work out a better applied technique of steel normal-temperature quick nigrescence via discussing various factors' influence on the speed of nigrescence and the capability of plating.
本文讨论了诸多因素对黑化速度及黑化膜性能的影响，确定较好的常温快速化学发黑实用技术。
来自互联网
3. This paper work out a better applied technique of steel normal-temperature quick nigrescence via discussing various factors' influence on the speed of nigrescence and the capability of plating.
