To Compare Effects of Two Method on Coal Quality and Economic Results between the Fully-mechanized Mining with Roof Caving and the method of One-time Cutting Whole Height是什么意思_To Compare Effects of Two Method on Coal Quality and Economic Results between the Fully-mechanized Mining with Roof Caving and the method of One-time Cutting Whole Height在线翻译_英语_读音_用法_例句