知识贝壳
知识贝壳
所属栏目：建筑施工英语
Manbuiltrailroadslongbeforehebuiltsteamenginesandbeforehehadevenmasteredthebasictechnologyofengineeringwithironandothermetals.Theearliesttrainswereconstructedoftimberandwereinoperationnotlaterthanthefourteenthcentury.Theywerebuilttoovercometheseverelimita ......（本文共 5610 字 ） [阅读本文] >>