This is the 731st most frequent Chinese word.
此时
"At this time" or "at this moment."
此时 is used to indicate the specific moment when the described event is occurring.
此时，阳光刚刚洒满大地。
At this moment, the sunlight just bathed the land.
此时 here emphasizes the time immediately following a preceding action or event.
刚刚紧急应对完出故障的机器，此时又来了另一项任务。
Just after handling the malfunctioning machine, another task came at this moment.
In this case, 此时 marks a pivotal moment of realization and emotional reaction.