Perhaps you should try some spelling variations:
"partial differential equation" » "partial difference equations"
"partial differential equations" » "partial difference equationss"
"partial differences equations" » "partial difference equations", "partial difference equation", "partial differentes situations", "spatial differences equations", "particles differences equations"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("partial differential equation") OR ((((("partial differential equations") OR ("partial differences equations"))) OR ("partial differences equations")))).
• Removing quotes may allow a broader search: (( partial differential equation ) or ((((( partial differential equations ) or ( partial differences equations ))) or ( partial differences equations )))).
• Adding a wildcard symbol may retrieve word variants: (("partial differential equation") or ((((("partial differential equations") or ("partial differences equations"))) or ("partial differences equations"))))*.