Retrograde ventilation is used for Wangjiazhai coal mine, both air leakage and ventilation resistance of the main shaft are largish.是什么意思_Retrograde ventilation is used for Wangjiazhai coal mine, both air leakage and ventilation resistance of the main shaft are largish.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句