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 analysis痕量元素分析,微量元素分析trace of precipitation微量降水trace impurity element微量元素trace element mobility微量元素活动性trace mineralized salt微量元素traceability mechanism可追溯机制trace elements and PGR微量元素与激素trace matter detection微量物质检测trace analysis program踪迹分析程序trace between the lines可从字里行间看出