Trace Nb微量铌tracen.痕迹；微量；踪迹v.追踪；描绘；找出根源trace-element fertilizer[化] 微量元素肥料trace of aircraft and ship飞机和飞船轨迹trace sth. to its source究其根源trace of electron scanning电子扫描trace fragrance components微量香味成分trace arsenic and selenium痕量砷和硒Trace lead contained water含微量铅水体Trace elements in the blood血液微量元素trace examination appraisal痕迹检验trace of a compact operator紧算子的迹