The relevance sort option was first announced “as coming soon” about 5 weeks ago. It went live today.
From the NLM Technical Bulletin:
The “Relevance” sort option [is] available from the “Display Settings” menu under the “Sort by” selections.
The relevance sort order for search results is based on an algorithm that analyzes each PubMed citation that includes the search terms. For each search query, “weight” is calculated for citations depending on how many search terms are found and in which fields they are found. In addition, recently-published articles are given a somewhat higher weight for sorting.
Easy access to the relevance sort will also initially be provided under a “New feature” discovery tool
Users may either choose “Relevance” from the “Display Settings Sort by” menu or click the “Sort by Relevance” link in the New Feature discovery tool.
Results for My NCBI users that are signed in with a modified default sort order will continue to display in the modified order until a different sort order is selected. A Relevance default sort selection in My NCBI PubMed Preferences will be added after the initial implementation of this new feature.