natural gum天然胶树胶naturaladj.自然的；天然的；私生的Natural forest communities自然森林群落natural circular frequence自然圆频率, 自然周频natural botanical extracts天然植物精华Natural constitutive plant天然植物natural language retrieval自然查询natural gas transportation天然气输送natural vibrating property自振特性natural winter-green oil天然冬青油natural circular frequency自然周频率,自然圆弧频率natural polymeric material天然聚合物材料