Prescription optimization of vinblastine hydrophilic group-modified cationic liposomes by central composite design-response surface method Optimization for preparation technology of baicalin-phospholipid complex in situ nasal gel by central composite design-response surface method Preparation and characterization of Sanguisorbae Radix/nano-silver composites Preparation and characterization of Indigo Naturalis-Alumen composite particles based on particle design principle Optimization of bi-layer osmotic pump controlled release tablets of total flavonoids from Ginkgo Folium by central composite design-response surface methodology