Robert is right about free access to some of the IAU proceedings. Not all are free downloads, though, and some are truncated data. IAU is playing it nice, while some other publishers are a bit less forthcoming. Luckily, we can access almost all the pricey professional papers by copying down the lead (or other) author names and the key words of the article title, then searching them as key words on
arXiv.org,
IOP,
ADS (Astronomical Data Service), or the
yandex.com search engine. There are scads of other resources, but the above four seem to come up with the best & the most.
If you are interested in the original historical papers which are the founding documents of astronomy as we know it, a search on the
UK Google Scholar or USA equivalent
Google Scholar comes up with papers by the likes of Edwin Hubble, Fritz Zwicky, Harlow Shapley, the Burbidge-Fowler-Hoyle collaboration, etc. You'll also find how windy and proceduralized papers have become since the flood of aspiring Ph.Ds came onto the market looking for jobs starting in the early 2000s. There are now roughly 20,000 professional astronomers (i.e., getting paid) in the world. A r-e-a-l-l-y big plus-mark for this profession is that nearly half of all the professionals are women, and a perusal of author names on the papers shows just how many of them can write as well as they can crunch data.