Access to primary care doctors in Massachusetts improved slightly in 2012, although about half still say they aren't accepting new patients, according to a Massachusetts Medical Society survey released Wednesday. The survey found 51 percent of internists and 50 percent of family doctors say they are taking new patients. That's a small improvement from last year when 49 percent of internists and 47 percent of family doctors were accepting new patients. Average times for new patients seeking appointments with primary care doctors remained long, according to the survey. In the 2012 survey, it took an average of about 45 days for new patients to see a family doctor. That's up from 36 days last year and 29 days in 2010.