two major systems

• 两大体系

two major systems的用法和样例：

例句

1. Safety certification is also classed into American and Europe standard two series.
   安全认证也分美规和欧规两大体系。
2. A new density functional approach for calculations of large systems is presented.
   提出一种新的对大体系进行分区密度泛函计算的方法。