fractions形态fractionn.小部分；少许；分数；片段Fraction of Rated Power部分额定动力fraction distance point分距点fraction of outdoor air新风比fractionated swallowing分次性吞咽[一种钡剂造影法]fractionation mechanism分馏机理fractionation technique分级分离技术Fractionized Regularity细分规则fraction representation分数表示fractionate contraction不全收缩fractions of heavy metal重金属形态