The Library Catalog can searched by keyword and Refine Results by Format, setting it to "Score" and "E-Score" on the left side column.
Most of the hard copy scores are located at the Schneider Music Library, not at Alkek.
As far as databases, try:
Classical Scores Library: Volumes 1-4
International Music Score Library Project (IMSLP)
Recent Researches in Music Online (RRIMO)
UCLA's Sheet Music Consortium offers a "digitized sheetmusic" option under the search box. It will bring up results for freely-viewable scanned pieces.