General:
* Learned
* Erudite
* Academic
* Intellectual
* Knowledgeable
* Studious
* Brilliant
* Wise
* Astute
More specific:
* Distinguished (for a highly respected scholar)
* Renowned (for a famous scholar)
* Prolific (for a scholar who produces a lot of work)
* Innovative (for a scholar who comes up with new ideas)
* Pioneering (for a scholar who breaks new ground in their field)
* Critical (for a scholar who is known for their incisive analysis)
* Analytical (for a scholar who is skilled at breaking down complex information)
* Theoretical (for a scholar who focuses on abstract ideas)
* Empirical (for a scholar who relies on observation and data)
The best adjective to use will depend on the specific context and the qualities you want to emphasize.