From the National Library of Medicine:
The List of Serials Indexed for Online Users (LSIOU) provides bibliographic information for all journals whose articles were ever indexed over time with the MeSH vocabulary and cited in MEDLINE, the backbone of the NLM PubMed database. It includes titles that ceased publication, changed titles, or are no longer indexed. More detailed bibliographic data and information about indexing coverage for serials cited in MEDLINE/PubMed can be found in LocatorPlus, the NLM online catalog, and the NLM Catalog, an Entrez database.
The 2015 edition of the LSIOU contains 14,856 serial titles, including 5,623 titles currently indexed for MEDLINE as well as titles indexed over time which have ceased or changed titles, listed alphabetically by the journal title abbreviation.
The LSIOU is produced in XML. Use of the data is permitted after reading Terms and Conditions (includes the links to the DTD and the data).
Tailored lists of indexed journals may be generated from the NLM Catalog.
While the XML version of the LSIOU is a snapshot in time, the results of a search in the NLM Catalog will provide a “real time” list for the LSIOU. Enter reportedmedline in the search box and click “Search”.