Migration and transformation of agricultural non-point source pollutants in drainage ditches .

农业非点源污染物在排水沟渠中的迁移转化研究进展。

All the cylinders can be blocked when the vehicle overcomes ditches that are up to 4 m wide .

当车辆需要通过宽4米以上的水沟时，这些气缸可以都被塞住。

He made ditches in the fields to draw off the water .

他在田里挖了沟以便排水。

They were kept busy digging ditches .

他们一刻不停地忙于挖沟。

These are proving very useful because of their portability and also their downward attack trajectory , which enables them to be effective against enemy personnel hiding behind cover or in ditches .

这些火炮因易移动和其向下攻击的弹道轨道而被证明非常有用，这让它们能有效对付躲在掩蔽物后面或壕沟里的地方人员。