铸件表面的缩孔是怎样形成的?
具有调理作用的主要Ig是() ["A．IgG，IgA","B．IgM，IgD","C．IgE，IgG","D．IgE，IgD","E．IgD，IgG"]
惟一能通过胎盘的Ig是() ["A．IgG","B．IgA","C．IgM","D．IgD","E．IgE"]
在个体发育中合成和分泌最早的Ig是() ["A．IgG","B．IgA","C．IgM","D．IgD","E．IgE"]
病原体感染后，血清中出现最早的特异性Ig是() ["A．IgG","B．IgA","C．IgM","D．IgD","E．IgE"]
为了避免铸件表面粗糙应采取哪些措施?
