梯姆肯法
参考答案:
借助梯姆肯极压试验机测定极压齿轮润滑剂承压能力、抗摩擦和抗磨损性能的试验方法。
根据首字母或汉语提示完成各句所缺单词。
1. What t______ do you usually get up?
2. T______ for your letter.
3. School s______ at nine o'clock.
4. My mother gets up at _______(大约)7 o'clock.
5. My dad usually takes a ______(洗澡) in the morning.
传声器的指向性有什么特点?按指向性的不同传声器分为哪几种?