Basel winger Mohamed Salah has followed Bertrand Traore and Nemanja Matic in at Stamford Bridge, while Kevin de Bruyne has left for Wolfsburg and Juan Mata is finalising his departure to Manchester United.
"Hopefully we are done," Mourinho said. "We are not bringing in a striker in this window.
"We are trying to keep the level and improve, to improve the team, to improve the squad, to change the style of play.
"And we're still trying to get results and still trying to win matches.
"We need that mixture of young players growing up and experienced players giving stability to the team.
"We are doing that. You can see what we're trying to do. Nemanja is 26, Salah 21, so we are trying to build a team for the future."
Mourinho plans to field a strong team in Sunday's FA Cup clash against Stoke as Chelsea bid to continue their fine recent record in the FA Cup.
The Blues have won the trophy in four of the last seven years but their boss is wary of a side that got the better of his team in October.
"We lost against this team and it was not a long time ago," Mourinho added.
"Everybody knows who Stoke is: very physical, very direct, very strong on set-pieces, they come here to compete.
"I expect a very difficult match. That's why I'm going to play with a strong team.
"I'm not going to make big changes in the team, because we are going to try to go as far as possible in the competition. We have to play with a very strong team."