加料后氮排空气时间为()
参考答案:4分钟
Which one of the following may appear on a periapical radiograph of the upper third molar area
A.external oblique ridge
B.mylohyoid ridge
C.coronoid process
D.condyle
对于不稳定的系统研究稳态误差是没有意义的,因此求稳态误差时要先判别系统的稳定性。