Furthermore, highway network mostly is the trouble of technical grade and service low.
中小城市的道路网普遍存在着公路网技术等级低、服务水平差等问题。
Phosphoric acid technical grade can be used to produce variety of phosphate, refractory clay and rust –proof coating;
工业级磷酸用作生产各种磷酸盐， 磷酸耐火泥， 涂料工业用作 金属防锈漆；
Phosphoric acid is grouped as four kinds by its production method, that is agricultural grade, technical grade, food grade and semiconductor grade.
磷酸按生产方法可分为热法磷酸和湿法磷酸，按用途可分为农业级、工业级、食品级和半导体级磷酸。
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