Yes. When individual articles from publications that usually require a subscription are freely available on your site, these articles can be marked as "free" in PubMed. This might be used in situations where articles are made freely available due to a special agreement with the authors, for example. Items that are temporarily free, such as sample issues, should not be marked as freely available in PubMed.
To create free links to individual citations, a separate <Link element> should be added, either in a new file or in an existing resource file. The articles should be identified by PMID, using the ObjId tag in the ObjectList or by ISSN, volume, issue, and start page number, using the <Query> tag in the <ObjectList>. <Attribute>preference</Attribute> must be used in the <ObjectUrl>.
The <Link> for free citations might look like this: