牙底

指出了现场使用的标准API钻具螺纹所存在的缺点，并针对这些缺点提出了相应的改进措施，即改进螺纹牙底形状和改变螺纹锥度配合。

The author explores the weak points of the API standard threads on drilling tools used in the field , and presents accordingly some measures for improvement that is , to modify the root form and the taper fit of the threads .

螺纹牙底圆弧半径的测量方法

Methods for Measuring the Circular Radius of the Bottom of Thread

螺纹联接外螺纹牙底表面裂纹应力强度因子的实验研究

Experimental research on stress intensity factor for surface crack at external thread root of threaded connection

疲劳裂纹的形成是由于螺纹牙底存在脱碳和折叠裂纹等缺陷，这些缺陷的存在使该材料产生了较大的应力集中，从而导致螺栓开裂失效。

The fatigue fracture occurred in the root of the screw where defects such as decarburization and cracks existed , and these defects made the zone to be a stress concentration area and caused the bolts to break finally .

高压氧对动物牙周袋底菌斑和厌氧菌的影响

Effect of Hyperbaric Oxygen on Subgingival Plaque of Experimental Periodontitis in Animals

下颌前牙牙槽窝底距下颌骨下缘高度的观测

Observation on the vertical distance between alveoli fossa of mandible anterior teeth and lower margin of mandible

目的观测国人的下颌前牙牙槽窝底到下颌骨下缘垂直距离的数据。

Objective To study the vertical distance between alveoli fossa of mandible anterior teeth and lower margin of mandible in Chinese people .

大径指过外螺纹牙顶或内螺纹牙底的圆柱面直径。

The root of the external thread or the crest of the inner thread .