My supervisor for my thesis told me about this site last year and it's one of the most valuable resources available that I know of. https://arxiv.org/ is a pre-print site where scientists upload their papers before they have been peer reviewed and published and it currently has over 1.9 million papers. This means that the papers on arXiv are often the same papers being published in reputable journals but they are not behind a paywall. These are pre-prints and have not been peer reviewed yet, but you can still read through them and analyze their methodology for yourself. I used a few papers from arXiv for my thesis on quantum resistant encryption algorithms.