Use * for alternate word endings
e.g., sustainab* retrieves sustainable, sustainability etc.
Use the different search lines to enter key words (not sentences) describing the different components of your search topic
Redo your search adding new keywords you find in article abstracts and subject terms given to the articles by the database
Use or between synonyms or alternate concepts
e.g., greenhouse gases* or ghg* or carbon dioxide
Use fewer search terms. Each time you put in another search term (unless they are synonyms combined with or) you will get fewer results. Start with a small number of keywords and then add more terms or try different terms based on your results.
Use quotation marks around words you want searched as a phrase
e.g., "greenhouse gases"
Databases usually offer ways to Limit or Refine your search results, such as:
To Scholarly/Peer-reviewed journals
By publication date range
To journal articles only (or books, dissertations, etc)
Some databases also have specific limits, such as:
Methodology
Age Groups
Gender
Add more search terms:
Each time you put in another search term, you will retrieve fewer results.
Start with a small number of keywords and then add more terms or try different terms based on your results.
Use the different search lines to enter more key words (not sentences) describing the different components of your topic
In the articles that are good, look for other for terms used in title, abstract, and subjects in that seem to focus on your interest