用金属型浇注铸铁件时,金属型材料应选用()。 ["灰铸铁","碳钢","铜合金","铝合金"]
研究表明,侧流烟气中的有()含量较主流烟气低。 ["许多成分","少量成分","大量成分","全部成分"]
已知对称三相电源中B相的电动势瞬时时值函数式为νB=311sin(wt-30°)V,则其它两相的相电压瞬时值函数式为()。 ["νA=311sin(wt-120°),νC=311sin(wt+120°)","νA=311sinwt,νC=311sin(wt+120°)","νA=311sin(wt+90°),νC=311sin(wt-90°)","νA=311sin(wt+90°),νC=311sin(wt-+20°)"]
烟气中自由基() ["不存在于气相与粒相中","存在于气相与粒相中","存在于气相中","存在于粒相中"]
电炉炼钢时,还原渣有三种--白渣、电石渣和弱电石渣,()适于冶炼含碳量较高的钢种。 ["白渣","电石渣","混合渣","弱电石渣"]
新古典主义美术起源、特征及代表画家起源