There are a number of possibilities. Here are some I can think of.
"At this time" - right now / at this moment:
"At this time I would like all of the tourists to return to the bus."
"I would like to pay you back your money, but at this time I simply don't have it."
"This time" - this instance
"I'm going to win the tennis match this time. He beat me (the) last time (we played)."
"In this time"- during this period of time - it sounds a little wrong to my ears unless you add "of + Noun Phrase":
"In this time of economic problems, everyone is watching their spending carefully."