Think! The sciences are interdisciplinary.
If your topic is in microbiology or biochemistry, perhaps the chemistry databases will have information for you. If your topic is in environmental science, check the geoscience or earth science databases. If your topic is health related, check the health databases. If you're investigating the life sciences industry, check the business databases, too.
Recommended databases are chosen because they may be standards in their field, may be larger, or may contain better quality information on average than the other database choices. This does not guarantee that they are the best choice for YOUR research topic.
These databases were selected because they contain a significant amount of science content. Additional databases such as the general or multidisciplinary databases may contain good science journals, too. It is just that science is not a significant portion of their content.