The volume of published material in biomedicine is so large databases are needed to make the material accessible. There are 32 million records in PubMed alone. Finding the small number you need within such a large pool is challenging.
Databases make it easier to find material by adding structure or metadata:
Which should you use?
They contain largely the same material. PubMed has some material that is not in Medline - this includes some historic material and articles loaded into PubMed by publishers which has not yet been indexed for Medline.
It is largely a matter of preference which you use, so consider the following:
But like any application, the free and the paid version work differently:
At The Health Sciences Library we recommend using Medline, but the choice is yours.
Embase is a private database run by the publisher Elsevier. It is larger than Pubmed, claiming to contain over 30 million records. Differences include:
Although most of the material is also in Medline/PubMed, for comprehensive searches we recommend searching Embase as well as Medline.
For drug and device related topics Embase should be considered as first choice.
PsycInfo is a database run by the American Psychological Association. It specialises in psychological, social and behavioural health. If your topic is related to mental health or psychiatry then you are recommended to search PsycInfo.
Cochrane is best known for it's systematic reviews (Cochrane Database of Systematic Reviews). You may not find a systematic review exactly on your topic, but you should examine the reference list of any reviews of closely related topics.
The Cochrane Central Register of Controlled Trials (CENTRAL) is a highly concentrated source of reports of randomised and quasi-randomised controlled trials. The majority of CENTRAL records are taken from bibliographic databases (mainly MEDLINE and Embase), but records are also derived from other published and unpublished sources. CENTRAL can be used to identify trials on your topic.
The International Clinical Trials Registry Platform is run by the World Health Organisation. it provides access to a central database containing the trial registration data sets provided by the registries listed on the webpage. It also provides links to the full original records.
The Australia New Zealand Clinical Trials Registry is an online registry of clinical trials being undertaken in Australia, New Zealand and elsewhere.
Google Scholar is a search engine, not a database. As it is not possible to build a structured search in Scholar it is should be a supplement to database searching, not a replacement for it.
However, Scholar is one of the few methods of searching the full text of articles. If your topic is relating to a tool or procedure (or similar concept) and you are finding it is not being mentioned in the title or abstract of articles, then Scholar may be useful.
More information - Google for research guide
Scholar also be used for citation tracking, ie to identify articles that cite important or relevant papers on the grounds that they may be on the same topic, though Web of Science or Scopus probably do this better.