Quills were the chief writing implement from the 6 th century AD until the advent of steel pens in the mid 19 th century.从公元6世纪到19世纪中期钢笔出现以前,羽毛笔是主要的书写工具.Defensive quills dot the backs of these troublesome creatures.防御性的刺...
Double - wall steel cofferdam is the important facility of bridges deepwater foundation.双壁钢围堰是桥梁深水基础施工的重要设施.The other part is temporary cofferdam and the rear land - based connection project.二是临时围堰及后方陆域连接工程.Temporary pro...