permagn.清洁金属用粉permn.电烫发v.电烫（头发）permanganate oxidation高锰酸盐氧化permselective property渗透选择性permafrost environment冻土环境permuted-title index循环置换标题索引,置换题名索引permeation tube method渗透管法permafrost sub-grade冻土路基permeating deformation渗透变形permeability synthesis渗透率合成方法permutite precipitator砂滤沉淀器permeating coefficient渗透系数