Before you can really start searching, you need to consider which search engines you want to use for your topic. For example, there are broad, multidisciplinary databases such as Scopus or Google Scholar, but also databases that specialize in a particular field, such as PsycInfo (psychology) or MLA (modern languages). Other databases focus primarily on a particular type of source, such as gray literature.
The differences in search results between search engines can be significant. That is why it is important to choose the right search engine for your search query.
To compare search engines, you can consider the following points:
- the coverage: what material is included?
- is it subject specific or multidisciplinary?
- what years (publication years/ historical periods)?
- what languages (most databases focus on English)?
- what kind of publications? (journal(article)s, books, websites)?
- Every element of those publications (for instance also the book reviews in journals or the chapters in books)?
- which of a certain kind of publication (which journals precisely)?
- the indexing depth: are you searching by:
- words from the title and the author's name?
- keywords, added by the author?
- the summaries/abstracts?
- the full text?
- extra keywords added by the makers of the database (like a thesaurus)?
- the choice of search fields: most search engines let you decide what fields to search, but sometimes differ in the choices they offer. Search engines for journal articles often offer the default option: title/abstract/keywords. Under advanced search you will find more options.
- (relevance) ranking: in what order are the results shown?
- by year of publication (most recent first or the oldest first)?
- based on relevancy (the publications that best answer your question are shown on top)
- based on frequency of the terms (the more often a term occurs, the higher the ranking in the list of results)?
- based on the number of citations?
- based on popularity (the more often a source is viewed, the higher the ranking)?
- by the position of the terms in the source (for instance words from the title are more important than words from the text)?
- in a mixture of the items above?
- the default treatment of your search terms
- must all search terms occur or is it also fine if only 3 of the 4 search terms occur?
- are related terms automatically included?
- are terms strongly resembling your search terms automatically included?
- are terms that are related automatically included ?
- are terms strongly resembling your search terms automatically included?
- are terms with slightly different endings (singular/plural, verbs) automatically included?
- how does the search engine interpret search terms put between inverted commas? ("exact phrase")
- Is there deduplication of (strongly resembling) search results?
Some of the questions above can be answered rather easily, for other you need to get to know the database a little better.
