I don't have a grasp of the ins and outs of things here, but as of 2021 it seems most of the links in the above answers are broken. Currently it appears that archives of the journal "K-Theory" are available [here](https://access.portico.org/Portico/loviView?cs=ISSN_09203036&content=E-Journal%20Content) through Portico. "Journal of K-Theory" doesn't appear to be available through Portico: [here's](https://www.portico.org/coverage/titles/?keyword=k-theory&filter_by%5B%5D=e-journal) what you get if you just search Portico for journals called "K-Theory".