周期性地

The geyser erupts periodically.

间歇泉地喷发。

Economic crises recur periodically.

经济危机地发生。

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

在中国东部早第三纪沉积演化程中曾地发生海侵,从而形成了具有海相特征的岩石类型、古生物组合。