短語詞組短語bed d silt 底粉砂bed -silt 河底淤泥silt bed 粉砂層;巖屑牀silt bed load 推移質(zhì)泥沙relative silt bed depth 相對(duì)促牀厚度movable silt bed 動(dòng)牀fine silt bed 粉細(xì)砂層 返回 bed silt