Perhaps you should try some spelling variations:
"classical mechanical" » "chemical mechanical", "physical mechanical", "statistical mechanical"
"physical mechanisms" » "physiological mechanisms"
"causal mechanisms" » "neural mechanisms", "central mechanisms"

Try widening your search to All Fields.

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: (((("causal mechanisms") OR ("physical mechanisms"))) OR ((("classical mechanics") OR ("classical mechanical")))).
• Removing quotes may allow a broader search: (((( causal mechanisms ) or ( physical mechanisms ))) or ((( classical mechanics ) or ( classical mechanical )))).
• Adding a wildcard symbol may retrieve word variants: (((("causal mechanisms") or ("physical mechanisms"))) or ((("classical mechanics") or ("classical mechanical"))))*.