These website are useful to search and manage especially science papers in biology, medical area.
For example, the paper "The hallmarks of aging" in 2013 is one of the most cited one in aging biology. Here is the PubMed page . You can see the number of citation (4031, at 16th March, 2022). You can also see links to Full text access. The DOI (Digital Object Identifier) https://doi.org/10.1016/j.cell.2013.05.039 on the page is used for the reference of the paper.
PubMed Central (PMC)
The PubMed Central (PMC) is the site to mange free full text papers. You can also bookmark the PMC site, and manage both PubMed and PMC pages in the same bookmark collection. But personally I am only bookmarking the PubMed pages.
If you want to access to the paid science paper network, one possible way is to register in a national library near you. See my past article https://junaruga.hatenablog.com/entry/2022/03/07/040404.
The site arXiv.org is used to see the papers of early version. Because it takes time (1 year?) to be published by peer-reviewed. Here is the explanation about on the side top page.
arXiv is a free distribution service and an open-access archive for 2,035,119 scholarly articles in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics. Materials on this site are not peer-reviewed by arXiv.
The result by searching articles with a scientist "Heng Li" I respect is .
There is the site bioRxiv.org  that we can search only bio papers.
-  PubMed: https://pubmed.ncbi.nlm.nih.gov/
-  PubMed - The hallmarks of aging: https://pubmed.ncbi.nlm.nih.gov/23746838/
-  Google Scholar searched by "The hallmarks of aging": https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=The+hallmarks+of+aging&btnG=
-  arXiv.org: https://arxiv.org/
-  arXiv.org searched by "Heng Li": https://arxiv.org/search/?query=%22Heng+Li%22&searchtype=author&abstracts=show&order=-announced_date_first&size=50
-  bioRxiv.org: https://www.biorxiv.org/