where can i download free scientific papers and books?

There are several legitimate platforms and repositories where you can access free scientific papers and books. Here are some options:

**Google Scholar** (scholar.google.com): Use this search engine to find scholarly articles. Sometimes you'll find links to free PDFs or related resources.

**PubMed Central** (www.ncbi.nlm.nih.gov/pmc/): This is a free repository for biomedical and life sciences literature, offering access to a wide variety of research articles.

**arXiv** (arxiv.org): A repository of preprints in physics, mathematics, computer science, quantitative biology, quantitative finance, and statistics.

**Directory of Open Access Journals (DOAJ)** (www.doaj.org): A community-curated list of open access journals that provide free access to articles.

**Project Gutenberg** (www.gutenberg.org): While primarily focused on classic literature, it also has some scientific texts available for free download.

**Open Textbook Library** (open.umn.edu/opentextbooks/): A collection of open-access textbooks that are freely available for download and use.

**ResearchGate** (www.researchgate.net): A social networking site for researchers where authors often share their publications. You can request full-text copies directly from authors if they are not available.

**Academia.edu** (www.academia.edu): Similar to ResearchGate, this platform allows researchers to share their papers. Some articles are available for free download.

**Sci-Hub**: Note that while Sci-Hub provides access to a large number of paywalled academic papers, it operates in a legally and ethically gray area, as it bypasses publisher paywalls. Use this with caution, as accessing materials this way may violate copyright laws in your jurisdiction.

**Library Genesis (LibGen)**: This is another controversial site that offers access to a wide array of scientific books and articles. Like Sci-Hub, it operates in a legally ambiguous space.

Always ensure you comply with copyright laws and the terms of use of any platform you use.