natural end自然目的naturaladj.自然的；天然的；私生的natural scenic spot自然景区natural surfactants天然表面活性剂natural short fiber天然短纤维Natural grass field天然草场Natural grass mulch自然生草natural equivalence自然等价naturalized subject归化的臣民natural involvement自然融入natural immigration天然迁移natural pH gradient自然pH梯度