庞永生 2021-03-28 03:38 开发者_运维知识库回转式钻机指的是依靠钻具的回转运动破碎岩层而成孔。主要有大、小锅锥钻机，正、反循环转盘式钻机，液压动力头式钻机，潜孔振动回转式钻机等。简单的回转式钻机只有
This has gotten me completely frustrated I have a few webcombo boxes that are hierachial: Continent Country
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