I agree. I have found though, that there's a neat workaround for some sites. I open them on incognito, and for some reason, I gain access to the whole article. Some sites are just too strict though, and even that trick doesn't work.
Did a bit of research and the eclipse mentioned in the novel was in the year 528, but I'm not sure if Mark Twain used the 1869 eclipse as an inspiration or whether he really was referring to the 528 eclipse.
This Is What China Looked Like 70 Years Ago
The People's Republic of China Was Born in Chains
Tissues: https://www.neatorama.com/2019/04/01/Bioengineers-Successfully-3D-Printed-Tissues/
Heart: https://www.neatorama.com/2019/04/16/Tel-Aviv-University-Team-Successfully-Makes-3D-Printed-Heart/
Air sac: https://www.neatorama.com/2019/06/11/This-is-a-3D-Printed-Air-Sac/