[Studies on morphology, buoyant density of virus-like particles in duck sera and disease background of duck liver].
D000818:Animals; D004372:Ducks / Q000382:microbiology*; D006520:Hepatitis, Animal / Q000382:microbiology; D008107:Liver Diseases / Q000382:microbiology / Q000662:veterinary*; D011201:Poultry Diseases / Q000382:microbiology*; D014766:Viremia / Q000382:microbiology / Q000662:veterinary; D014780:Viruses / Q000302:isolation & purification*