Slips of bamboo and wood are the most commonly used material for writing.
竹、木简牍是纸发明前最主要的书写材料。
The role, working principle, structure and commonly used material of steel aluminum composite conductor rail in the three-rail system are introduced.
介绍钢铝复合导电轨在三轨系统中的作用、工作原理、结构和常用材料。
The role, working principle, structure and commonly used material of steel aluminum composite conductor rail in the three-rail system are introduced.
介绍钢铝复合导电轨在三轨系统中的作用、工作原理、结构和常用材料。
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