Perhaps you should try some spelling variations:
"particle concentrations" » "particle concentration", "particle correlations", "particle penetration"
"particle accelerations" » "particles acceleration", "particelle acceleratori", "particle correlations"
"particle accelerators" » "particle accelerated", "particle accelerate", "particle 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 accelerator") OR ((((("particle accelerators") OR ("particle acceleration"))) OR ((("particle accelerations") OR ("particle concentrations")))))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"particle accelerator\") or (((((\"particle accelerators\") OR (\"particle acceleration\"))) or (((\"particle accelerations\") or (\"particle concentrations\"))))))".
• Removing quotes may allow a broader search: (( particle accelerator ) or ((((( particle accelerators ) OR ( particle acceleration ))) or ((( particle accelerations ) or ( particle concentrations )))))).
• Adding a wildcard symbol may retrieve word variants: (("particle accelerator") or ((((("particle accelerators") OR ("particle acceleration"))) or ((("particle accelerations") or ("particle concentrations"))))))*.