Perhaps you should try some spelling variations:
"rana chensinensis ovum" » "rank chensinensis ovum", "rand chensinensis ovum", "ran chensinensis ovum", "rana chinensis ovum", "rana chensinensis novum"
"rana chensinensis oviduct" » "rank chensinensis oviduct", "rand chensinensis oviduct", "ran chensinensis oviduct", "rana chinensis oviduct"
"rna chensinensis oviduct" » "rna chinensis oviduct"

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: (("rana chensinensis ovum") OR ((("rana chensinensis oviduct") OR ("rna chensinensis oviduct")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"rana chensinensis ovum\") or (((\"rana chensinensis oviduct\") OR (\"rna chensinensis oviduct\"))))".
• Removing quotes may allow a broader search: (( rana chensinensis ovum ) or ((( rana chensinensis oviduct ) OR ( rna chensinensis oviduct )))).
• Adding a wildcard symbol may retrieve word variants: (("rana chensinensis ovum") or ((("rana chensinensis oviduct") OR ("rna chensinensis oviduct"))))*.