periodically 考研雅思

The streets are periodically scavenged.

定期街道清

Sea mammals must emerge periodically to breathe.

哺乳动物必须不断地浮现出面呼吸

The results show that the impeller flows periodically under large negative prewhirl angle.

结果表明，在较的负预旋角度下，叶轮流动呈现出周期性；

In eastern China, transgression occured periodically during Eogene, and formed specially paleobio-cenosis,mineral association and rock type.

在中国东部纪沉积演化过程中曾周期性地发过侵,从而形成了具有相特征的岩石类型、古物组合。

The time-varying and incommutable character of the coefficient matrix of periodically time-varying linear systems are the bottleneck of the design for high precision direct integration methods.

周期时变线性系统系数矩阵的时变性与不可交换性是其精细积分算法设计中的瓶颈。

As part of the program, Lown Scholars may also return to Harvard periodically for short-term stays of one week to several months to continue collaborations.

作为该项目的一部分，获得奖学金的学者或需定期返回哈佛进行一周至数月不等的短期访问，以继续与学院的合作。

Halosere A plant community in a succession that starts on land periodically inundated by the sea. Haloseres include salt-and flooding-tolerant pioneer communities on mudflats and saltmarshes.

盐演替系列：是一种在周期性被水淹没的陆地上进行演替的植物群落。它包括那些在泥滩和盐沼上活的耐盐耐淹的先锋群落。