Adverb:

1. in a sporadic manner;

   "he only works sporadically"
   

sometimesadv.有时；间或

sporadicallyadv.偶发地；零星地

every so often时常； 不时

occasionallyadv.偶尔地

at times有时；偶尔

once in a while偶尔； 有时

from time to time有时； 不时

intermittentlyadv.间歇地

at regular intervalsadv.每隔一定时间

regularlyadv.有规律地；定期地

like clockwork规律而准确地； 顺利地

cyclicallyadj.循环的；周期性的；环形的

seasonallyadv.季节性地

continuallyadv.不断地；频繁地

1. New strains of viruses appear periodically.
   新菌系的细菌周期性地产生。
2. The state of knowledge in this field has been surveyed periodically in review papers.
   在一些评论文中对这一领域的动态周期性地进行了评述。
3. Periodically, someone comes by with a truck to fill them.
   有些人定期地用卡车运输食品，装进机器。
4. Drones must return periodically to recharge their weapons and propulsion systems.
   雄蜂一定定期地回复再休整他们的武器和推进系统。