Research Gate (scroll down to the search)
Science.gov
PLANTS database
Plants in Motion Videos
Biodiversity Heritage Library
Biodiversity Heritage Images
National Institute of Health
National Library of Medicine
PubMed Database
National Academy of Science
How Stuff Works
Moon Phase Calendar
EarthSky
National Geographic
Encyclopedia of Life
Everyday Mysteries
LOC Science Reference Services
Dr. Dendro Virginia Tech
Cornell Labs
National Audubon Society
National Wildlife Federation
Virginia Native Plant Society
Animal Diversity Web
Sea and Sky
Wildscreen Arkive
USDA Agricultural Library
AGRICOLA
Wildfinder Database
Notes from Nature
CalBug
Weather Underground Historical Weather