law of migration

• 人口迁移规律

law of migration的用法和样例：

例句

1. Based on the characteristics of biomass fuel, this article summarizes the sources of alkali metals in biomass and the elutriation and migration.
   摘要在明确了生物质燃料特点的基础上，对生物质中碱金属元素的来源和析出迁移规律进行了概述。