You will see a message on the searching screen of PubMed that ” Due to the lapse in government funding, PubMed is being maintained with minimal staffing. Information will be updated to the extent possible, and the agency will attempt to respond to urgent operational inquiries.
Updates regarding government operating status and resumption of normal operations can be found at http://www.usa.gov. ”
That means the effect from USA shutdown
crisis. Some free full-text articles are still available.