at once

立即，马上

at ease, at first, at first sight, at full speed, at full tilt, at hand, at heart, at home, at intervals, 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 one time, at one's best, at other times, at peace, at present, at random, at regular intervals, at sb's disposal, at sb.'s heels, at sea, at sight of, at stake, at table, at that, at that rate, at the back of, at the beginning of, at the best, at the cost of, at the expense of,