Perhaps you should try some spelling variations:
"particle acceleration" » "particle accelerators"
"particles accelerated" » "particles acceleration", "particle accelerator", "partially accelerated"
"particle acceleraton" » "particle accelerator", "particles acceleration", "particle accelerations"
"practice accelerate" » "practice accelerated", "practices accelerate", "practices accelerating"

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 acceleration") OR ((((("practice accelerate") OR ("particles accelerated"))) OR ("particle acceleraton")))).
• Removing quotes may allow a broader search: (( particle acceleration ) or ((((( practice accelerate ) or ( particles accelerated ))) or ( particle acceleraton )))).
• Adding a wildcard symbol may retrieve word variants: (("particle acceleration") or ((((("practice accelerate") or ("particles accelerated"))) or ("particle acceleraton"))))*.