1) difficulty
难关
2) technical difficulties
技术难关
1.
This paper analyzes the structure of the fuel cell vehicle elaborates that proton exchange membrane fuel cell(PEMFC) is the first choice of the vehicle power supply;summarizes the technical difficulties at present and the developmental situation of the fuel cell vehicle.
阐述了燃料电池汽车的结构及质子交换膜燃料电池(PEMFC)是燃料电池汽车动力源的首选;对燃料电池汽车目前存在的技术难关及发展形势进行了综述。
3) the five difficult passes of human being's life
五大难关
4) engineering roadblock
工程难关
5) degree of beating
浆度难关
6) bottleneck in production
生产中的难关
补充资料：难关
1.难以通过的关口。比喻不易克服的困难。
说明：补充资料仅用于学习参考，请勿用于其它任何用途。