Most of the databases and journals of greatest interest to chemistry researchers are behind expensive paywalls, including SciFinder, Reaxys, and over 90% of primary journals. That means you need to be currently affiliated with a subscribing institution in order to use them. (Sorry, alumni don't qualify.) While there's a growing trend to make more research and data open and freely available to everyone, at present the chemical literature is far more closed than open.
Here's a list of some of the most important resources that alumni and the general public can use for free. In addition, many of the specialized web resources listed in the guide pages to the left are also free.
Just because a paper is published in a subscription journal doesn't mean that there's no free version of it lurking out there somewhere. See our Where to Find...Articles page for tricks to locate legal versions of papers that aren't behind paywalls: preprints, accepted deposited manuscripts, postprints, and more.
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