Do not look for a topic on economics in a biology database. Keep in mind how many years the database covers. Keep in mind that most only go back perhaps ten years time. Use bound indexes to try to locate older articles. Many topics may be best covered using bound, not computer, indexes.
Some resources cover many disciplines.
Do not use these for advanced research. Instead, choose a subject-specific resource. Search using broader terms if you get little or no results. Search using a narrower term if you get too many results. In searching for journal articles you may be able to be very specific.