there are three main types synthetic soil conditioner available, derived from petroleum chemicals, the tertiary period minerals and organic materials.
人工合成土壤结构改良剂可分为石油化工产品、第三纪矿物产品以及无机物与有机物相结合产品共三类。
the tertiary period is an important coal-accumulating period of northeast china, lignite is main coal species.
第三纪是东北地区重要的一个聚煤期,煤种主要以褐煤为主;
weak cemented fine quicksand layer deposited at the tertiary period and jurassic period is widely distributed in china's northeast and southwest regions.
第三纪和晚侏罗纪时期沉积的弱胶结粉细砂层在我国东北、南地区有广泛的分布。