triple fourdrinier machine

The family size of nobles in the Northern Dynasty was smaller under the three level administration system than that under the supervision and protection of big families because a large unmber of protected people were checked by the three level administration system.

北朝豪族家庭规模 ,在三长制下比在宗主督护制下要小些 ,原因是三长制括出了大量荫附人口。

A new process of preparing tri-long-chain alkyl tertiary amine has been developed through catalytic amina-tion under atmospheric pressure.

专题开发了醇一步常压催化胺化制备三长链烷基叔胺新工艺。