natural son私生子naturaladj.自然的；天然的；私生的natural resoturce depletion自然资源耗减natural regionalization map自然区划图natural gas calorific value天然气热值natural antibacterial agent水提液natural moisturizing factor天然保湿因子natural disaster perception自然灾害知觉natural language dictionary自然语言词典natural freezing/thawing自然冷融Natural bacterial inhibitor天然防腐剂natural self-purification天然自净化作用