at [above, below] eye level
目の高さ［より上，より下］に
at fifteen hundred hours
午後３時に
at first [last]
最初に［最後に］
at first glance
一見（して）
At first I had difficulty (in) telling one student from another.
初めは学生の顔を見分けるのに苦労した
At first sight this plan looks promising.
一見したところ，この計画はうまくいくかに見える
at frequent intervals
頻繁に
at frequent intervals
ひんぱんに
at full [half] cock
打ち金をいっぱいに［半分］起こして；用意が十分［不十分］で
at full [a great] lick
ものすごい速さで
