Perhaps you should try some spelling variations:
database quality » data quality (Expand search), database query (Expand search)
quality problems » quality programs (Expand search), quality program (Expand search), quality protein (Expand search)
decrease their » decrease the (Expand search), increase their (Expand search), decreases the (Expand search)
their database » thesis database (Expand search), the database (Expand search), theses database (Expand search)
in decrease » in decreased (Expand search), on decrease (Expand search), pain decrease (Expand search)

You may be able to get more results by adjusting your search query.

• Removing quotes may allow a broader search: (( decrease their database quality problems ) OR ( decrease _ decrease in decrease ))~.