Yes you can, but it depends on the version of Project Server you are using.
Project Server 2007
This version introduced the reporting database. It is populated whenever a project is published. (You can query unpublished data by using the drafts database.)
Microsoft have provided a report pack which may already contain the report you need. It also contains many examples on how to use the reporting database.
The complete database schema is available for download in the Project 2007 SDK (look for pj12ReportingDB.chm).
Project Server 2003
As this is an older version there is less information available, however there are example queries from EPM Central that show how to query resources.
The complete database schema is also available from Microsoft.