Since this is such a large database, it's easy to be overwhelmed by the sheer number of articles returned by a search. Here are a few tips to make sure you get the best results.
1) Be specific! Use scientific names and terminology.
2) Limit your search to "Subscribed publications" and "Open Access articles" (under Refine your search)
3) You can also limit your search to a subset of journals that focus on a discipline or subject. Scroll through the list under "All Sciences" to see the choices.
4) Limit by publication date.