【简答题】什么是异方差性?举例说明经济现象中的异方差性。检验异方差性的方法思路是什么?
【简答题】什么是异方差性?举例说明经济现象中的异方差性。检验异方差性的方法思路是什么?
【简答题】在普通车床上用两顶尖装夹车长轴外圆,若机床刚度较低,则工件产生()的形状误差;若工件刚度较低,则工件产生()的误差。
【单选题】 Joe was caught in a traffic jam and when he got to the theatre, the play ________ for half an hour.
D.
had already been put on
【单选题】China is famous ____ the Great Wall. [ ]
【单选题】China is famous ______its food in the world.
【单选题】在普通车床上用两顶尖装夹加工细长轴外圆,若机床刚度较低,则工件产生( )的形状误差。