When historians talk about "primary sources", they mean a letter or a diary entry.  A telegram,  a newspaper report from the day of an event like 9/11 - - something that was written by someone who was present at an event, or is describing their own experiences.  

When scientists talk about "primary sources" we mean something completely different.  A primary scientific source is essentially a formal research report or lab report.  It describes in careful detail  - - described so carefully, in fact, that it can be reproduced by others - -  the exact steps and procedures that the scientists followed to get the research results they are writing about.