at weekly/20-minute etc intervalsREGULARevery week, 20 minutes etc 每周/每20分钟等 The trains run at half-hourly intervals. 火车每半小时开出一班。
at weekly/20-minute etc intervals• After ingestion of sucrose, breath hydrogen was measured at 20 minute intervals for 160 minutes.
→ at weekly/20-minute etc intervals at interval(2)