拖拉机是农业机械的动力源和基础产品,是技术含量较高的生产力要素,其发展水平很大程度上影响和制约着其他农业机械的发展。因此,拖拉机的年产销量、保有量和质量 Tractor is the power source and basic product of agricultural machinery. It is a productive factor with high technological content. Its development level greatly influences and restricts the development of other agricultural machinery. Therefore, the annual sales of tractors, possession and quality