菊科植物的萼片,通常变态为()、()和()三种类型。
下列牌号中为铁素体不锈钢() ["A.1Cr17","B.1Cr13","C.1Cr18Ni9Ti","D.4Cr13"]
下列牌号中为马氏体不锈钢() ["A.1Cr17","B.0Cr13","C.1Cr18Ni9Ti","D.4Cr13"]
拆卸下来的零部件考虑到(),应做好记号、分别存放。 ["A、维修质量","B、维修场地有序","C、维修场地有限","D、回装正确"]
当不锈钢中加入铬时可使钢获得单相基体组织。当含铬量大于()、含碳量较低时,可获单相铁素体不锈钢。 ["A.12.7%","B.13%","C.17%","D.27%"]
十字花科植物的花瓣()片,呈()形排列,()雄蕊,子房()位,()果。