Perhaps you should try some spelling variations:
"particle acceleration" » "particle accelerators"
"partially accelerated" » "partially correlated", "partially integrated", "partially degenerate"
"particle accelerator" » "particle accelerators"
"naturally accelerate" » "naturally regenerated"

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: (("particle accelerator") OR ((("particle acceleration") OR ((("partially accelerated") OR ("naturally accelerate")))))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"particle accelerator\") or (((\"particle acceleration\") or (((\"partially accelerated\") OR (\"naturally accelerate\"))))))".
• Removing quotes may allow a broader search: (( particle accelerator ) or ((( particle acceleration ) or ((( partially accelerated ) OR ( naturally accelerate )))))).
• Adding a wildcard symbol may retrieve word variants: (("particle accelerator") or ((("particle acceleration") or ((("partially accelerated") OR ("naturally accelerate"))))))*.