LibGuides: Alternatives to United States NLM Resources: Databases which use PubMed

Databases which use PubMed

Material from PubMed/Medline forms a substantial part of a number of well-used databases. These include (but are not limited to):

Europe PMC
Embase
CENTRAL (Cochrane Register of Controlled Trials)
Epistemonikos
TRIP
OpenAlex

For some of these databases, it is possible to make a rough estimate of the percentage of material that comes from PubMed. Embase have provided a detailed breakdown (listed in adjacent tab), while CENTRAL and Europe PMC allow filtering of results by source, enabling the percentages to be worked out manually. In others, this is not possible.

Below is a graphic illustrating the percentages of material taken from PubMed in some databases. It is a rough estimate for visualisation purposes only.

The Cochrane Register of Controlled Trials pulls information from a variety of sources, including Pubmed, Embase, ClinicalTrials.gov, ICTRP, CINAHL, and other unnamed sources. Further information about this is here.

It is possible to restrict search results in CENTRAL to specific sources either by using the filters on the left-hand side of the results page, or by using specific search syntax (eg. embase:an).

Using this method, a rough estimate of percentages of material from each source has been calculated as below

CENTRAL	Total number	Percentage
PubMed, Embase and CINAHL	402434	18.09%
PubMed Only	543535	24.43%
Embase only	373233	16.78%
CINAHL only	33941	1.53%
ICTRP	281440	12.65%
CT.gov	275939	12.40%
Other	314066	14.12%
ALL	2224588

Embase is a large biomedical and pharmacological database, produced by Elsevier. Embase also has a Medline supplement.

Elsevier have provided the following information about how Embase is indexed and sourced, and the effect on the database of any changes to Medline.

"As of January 1, 2025, Embase includes 8,386 journals:

39% (3,257 journals): Embase unique – sourced directly from publishers and indexed with Emtree.
40% (3,359 journals): Embase/MEDLINE – covered in both Embase and Medline, but Elsevier sources the journal content directly from the publisher and indexes it using Emtree.
21% (1,770 journals): MEDLINE unique – sourced via NIH, with MeSH terms mapped to Emtree.

Embase also covers preprints from BioRxiv, MedRxiv and SSRN, as well as conference abstracts, which are unaffected by NIH.

If MEDLINE production stops:

Embase/MEDLINE content: MeSH terms will no longer be available, but journals will remain indexed with Emtree.
MEDLINE unique content: We will no longer receive this content but are working to source it directly from publishers and remove the dependency on NIH.

All existing content in Embase, including MEDLINE unique content, will persist unless legally required to be removed.

In summary: Embase users continue to have access to the majority of up-to-date content regardless of any potential disruptions at NIH. We are also actively reducing remaining dependencies to maintain Embase as the most trusted resource for biomedical insights."

Europe PMC is not a direct mirror of PubMed, but it sources approximately 86% of its total material from it. The rest comprises mostly of biological patents and preprints. Find out more about where EuropePMC sources its content on its help pages, here.

Source	Percentage
PubMed/Medline NLM	84.23%
Biological Patents	9.23%
Preprints	2.02%
Agricola	2.01%
PubMed Central	1.80%
EthOs Theses	0.39%
Chinese Biological Abstracts	0.31%
NHS Evidence	0.01%
CiteXplore	0.01%
Europe PMC Book metadata	0.00%

*worked out by searching for each source individually, eg. SRC:"MED". The total number of entries can be found with SRC:*