protective gap保护放电器,保险隙protectiveadj.保护的；防卫的protective countermeasures保护对策protective lung vetilation肺保护性通气策略protective tillage machine保护性耕作技术Protective electric device保护性电器protective circuit breaker保护断路器protective action of liver保肝作用protective faceplate cover面板保护盖板Protective enzyme in plant植物保护酶protective layer thickness保护层厚度protective service workers防卫服务人员