For general research in the literature on public health topics, these resources should cover most of your needs:
PubMed contains more than 35 million citations and abstracts of biomedical literature. Look for to get PDFs from the library's online collections or for openly available articles.
CINAHL (Cumulative Index of Nursing and Allied Health Literature) indexes 3,024 journals from the fields of nursing and allied health. Look for Full Text via LibKey or Full-Text Finder links to download PDFs.
Scopus includes peer-reviewed literature in the scientific, technical, medical, and social sciences. Look for the or buttons to download PDFs.