Perhaps you should try some spelling variations:
"particle concentrations" » "particle concentration", "particle correlations", "particle penetration"
"particle accelerations" » "particle accelerators", "particles acceleration", "particelle acceleratori", "particle acceleratorss"
"particle acceleration" » "particle accelerators"
"parallel acceleration" » "parallel generation", "parallel application", "parallel operation"
"particle accelerator" » "particle accelerators"

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