Perhaps you should try some spelling variations:
des prasidenten » des patienten
prasidenten der » prasident des
tumor factors » major factors
der tumor » der humor, der amor, der tur
yang jin » yang jie, yang jun, ying jin
wan yan » wang yan, nan yan, wai yan

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

• Performing a fuzzy search may retrieve terms with similar spellings: wan yan ((yang jin) or (zhang fan)) des prasidenten der tumor factors ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: wan yan ((yang jin) OR (zhang fan)) des prasidenten der tumor factors ;*.