很少有美白牙膏经过任何形式的临床试验，有些美白牙膏摩擦剂含量过多，会伤害你的牙齿或让你的牙齿变得过分敏感。
Very few whitening toothpastes have undergone any type of clinical trial, and ones that are too abrasive can damage teeth or make them very sensitive.
本文抓住刚体无滑滚动的运动学特征，通过分析主动力和静摩擦力各自的贡献，提出一种形象、直观的求解方法。
This paper grasps its kinematic traits and gives a specific and intuitionistic solution through analysing each contribution of main motivity and static friction.
应用推荐