短語詞組短語thin coal seam shearer 薄煤層採煤機extremely thin coal seam 極薄煤層thin coal seam group 薄煤層群thin coal seam mines 薄煤層鑛井thin coal seam face 薄煤層工作麪thin -seam 薄煤層extremely thin protective seam 極薄保護層thin coal seam mining 薄煤層開採 返回 thin seam