Perhaps you should try some spelling variations:
double helixes » double helices, double helix, double helical
double eyelid » double helix, double eged, double eye
double felix » double helix, double fed, double field
double folio » double folding, double fusion, double folded

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: the ((((((double felix) OR (double helixes))) OR (double eyelid))) OR (double folio)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "the ((((((double felix) OR (double helixes))) or (double eyelid))) or (double folio))".
• Adding a wildcard symbol may retrieve word variants: the ((((((double felix) OR (double helixes))) or (double eyelid))) or (double folio))*.