而环氧粉末涂料的固化反应只有环氧树脂与固化剂 - 双氰胺的交联反应.The cross - linkedstructure of epoxy and phenolic resins increased because of the crosslinking between the two resins.研究了酸度对苯胺与双氰胺加成反应生成苯基双胍的影响.The effect of acidity on synthesis of phen...
两百多万年的化石fossils over two million years old这些化石可能有100万年了.The fossils may be a million years old.恐龙绝种已有几百万年了.Dinosaurs have been extinct for millions of years....