trace tov.上溯；追溯到tracen.痕迹；微量；踪迹v.追踪；描绘；找出根源Trace element and REE微量元素和稀土元素Trace element content微量元素含量trace organic matters痕量有机物trace a stream upward溯流而上trace rotation system径向扫描旋转系统trace addition carbon微量碳Trace mean diffusivity迹,平均弥散系数trace metal impurities痕量金属杂质trace-level activity微量放射性trace element solution微量元素溶液