仙后婧婧(谭思婧) 2015/03/24
[img=,498,383]http://ng1.17img.cn/bbsfiles/images/2015/03/201503241751_539449_2989334_3.png[/img][img=,635,447]http://ng1.17img.cn/bbsfiles/images/2015/03/201503241752_539451_2989334_3.png[/img][img=,695,347]http://ng1.17img.cn/bbsfiles/images/2015/03/201503241752_539450_2989334_3.png[/img] 材料对x光的衰减系数与其原子序数有关