Prela普雷拉PREabbr.Petroleum Refining Engineer炼油工程师prednisolone tebutate强的松龙叔丁乙酯precondition operator预条件算子precheliceral segment螯前节precoated metal sheet预涂金属板pre-paid phone card储值卡pre - understanding前理解pre-mixing concrete预拌混凝土precondition analysis先决条件分析prerotation mechanism预旋机理pre-harvest tillage收割前耕作