at intervals

不时，时时

at a stretch, at a time, at a...price, at all, at all costs, at all events, at all risks, at all times, at any cost, at any rate, at any time, at best, at ease, at first, at first sight, at full speed, at full tilt, at hand, at heart, at home, at large, at last, at least, at leisure, at length, at longest, at lowest, at most, at night, at no time, at odds with, at once, at one time, at one's best, at other times, at peace, at present, at random, at regular intervals, at sb's disposal,