When searching databases, take time to design your search strategy thoroughly.
Focus on one concept at a time; list your main idea for concept #1 along with synonyms, abbreviations, and alternate spellings. Everything in Concept 1 should use the OR boolean.
Do the same thing for your other concepts.
Use the AND boolean to combine your concepts together.
Using a Venn Diagram can be useful in your search strategy design:
Additional searching tips:
* (asterisk) - Most databases recognize this as a truncation tool. Use it to truncate your word and search a variation of the words. For example: neoplas* will search for neoplasm, neoplasms, neoplastic, non-neoplastic, neoplasia, etc.
" " (quotations) - Most databases will search your words as a phrase when they are placed in quotation marks. For example, a database will search for the words molecular and biomarker together when they are placed in quotations, like this "molecular biomarker". If you search for molecular biomarker without the quotation marks, the database will search for the words molecular and biomarker, but they won't be next to each other. In other words, the resource you find may discuss the term biomarkers (e.g., blood biomarkers, nanosized biomarkers, cancer biomarkers, etc.) in one paragraph and the term molecular (molecular weights, molecular effects, molecular mechanisms, molecular phenotypes, etc.) in another paragraph.
Here's a video from B.D. Owens Library (Northwest Missouri State University) to help explain Boolean operators, asterisks, and quotation marks: