LinkOut - Linking from PubMed and Other Entrez Databases

Last Updated: December 1, 2003

• Introduction
• Resources Description
• Publishers
• Libraries
• Non-bibliographic Resources
• Frequently Asked Questions
• Cubby
• Document Delivery Service
• Outside Tool

Introduction
LinkOut is a feature of Entrez that is designed to provide users with links from PubMed and other Entrez databases to a wide variety of relevant web-accessible online resources, including full-text publications, biological databases, consumer health information, research tools, and more.   The goal is to facilitate access to relevant online resources beyond the Entrez system in order to extend, clarify, or supplement information found in the Entrez databases.

Participating LinkOut providers, including publishers, aggregators, libraries, and other web resources, can display links to their sites on records from the Entrez databases.  A current list of LinkOut providers is available.

Resources Description
LinkOut requires two types of files, Identity and Holdings files, to describe the online resources.  These files are specified in the LinkOut.DTD, and are provided by a participating provider.   These files include the necessary elements for the Entrez system to construct an appropriate URL to access specific resources. To participate in LinkOut see the appropriate document below:

Publishers
Publishers or full-text providers can use LinkOut to provide links from PubMed citations to their web-accessible full-text journals.  Publishers who supply their data to PubMed electronically may include an icon link to a site providing the full-text.   This icon is displayed on the Abstract and Citation formats by default. Other providers may consult the Cubby Help for information about promoting their icon to the Abstract and Citation display formats.

Additional information is available from LinkOut and Publisher Holdings.

Libraries
LinkOut provides a library the advantage of linking its patrons from a PubMed citation directly to the full-text of an article after a library submits its electronic holdings data to NCBI. Libraries should use the LinkOut Files Submission Utility to generate their LinkOut files. The holdings data should include those electronic journals that the library has a subscription to under a prior agreement. When a library submits their holdings data to NCBI, the providers of the holdings (publishers or aggregators) must be LinkOut participants, i.e. the providers have already submitted their electronic journal links to NCBI.

Additional information is available from LinkOut and Library Holdings.

Non-bibliographic Resources
LinkOut can also be used to provide links from Entrez databases to non-bibliographic Web resources, such as factual databases (i.e., organism-specific, taxonomy, structure and other databases), catalogs of research materials (clones, strains, probes, etc.), funding opportunities, clinical resources, research groups, and others.

Additional information is available from LinkOut and Non-Bibliographic Resources.

Cubby
Cubby may be used to store LinkOut preferences and search strategies. In Cubby you may customize your LinkOut display.  You can add icons to be displayed on the Abstract and Citation formats. You can also remove links from the LinkOut display.

Document Delivery Service
NLM's document delivery system, Loansome Doc, is available in PubMed to order full text of articles.

Other document delivery service providers must use the Document Delivery Service provided by NCBI to provide additional document delivery services to PubMed users.

Outside Tool
To supplement LinkOut, Outside Tool allows an external institution to register a tool with NCBI to provide a link from all PubMed citations back to resources offered by the institution.