Perhaps you should try some spelling variations:
using dna » using dea, using data, using drag
hua gene » human gene, a gene, hua ren
gene yan » gene bank, ren yan, see yan
hong shu » cong shu, tong shui, wong shiu
wong yue » wang yue, hong yu
using a » using _
yan tan » tan tan, yan clan, yan guan

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: done ((using dna) OR (using a)) hua gene yan tan ((hong shu) OR (wong yue)) ;~.
• Adding a wildcard symbol may retrieve word variants: done ((using dna) or (using a)) hua gene yan tan ((hong shu) or (wong yue)) ;*.