natural fur天然毛皮naturaladj.自然的；天然的；私生的natural productive forces自然生产力natural draft transformer自然风冷变压器natural acquired immunity天然后天免疫natural stone base course天然石基础层Natural lexical frequency自然词频natural tourist resources自然旅游资源natural pollution sources天然污染源natural red yolk duck egg天然红心鸭蛋natural and human ecology自然与人文生态Natural eco-environment自然生态环境