Viscous crude oils and oil sands are important energy resources, but it is difficult to exploit them due to the dominated heavy constituents such as asphaltenes.是什么意思_Viscous crude oils and oil sands are important energy resources, but it is difficult to exploit them due to the dominated heavy constituents such as asphaltenes.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句