From the National Library of Medicine (NLM) Technical Bulletin:
An updated version of PubMed is now available at https://pubmed.ncbi.nlm.nih.gov. The new PubMed will become the default in spring 2020 and will ultimately replace the legacy version.
The NLM article also highlights some of the new features including improved search and responsive design. It also includes links to learn more.
Direct to “New” PubMed
Direct to Legacy PubMed
See Also: From October 2019: Video/Webinar Recording: “A New PubMed: Highlights for Information Professionals”