Perhaps you should try some spelling variations:
"particle concentrations" » "particle concentration", "particle correlations", "particle penetration"
"particle acceleration" » "particle accelerators"
"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 concentrations") OR ("particle acceleration")))).
• Removing quotes may allow a broader search: (( particle accelerator ) or ((( particle concentrations ) or ( particle acceleration )))).
• Adding a wildcard symbol may retrieve word variants: (("particle accelerator") or ((("particle concentrations") or ("particle acceleration"))))*.