fulltext is a package I maintain for text-mining the scholarly literature (package docs). You can search for articles, fetch article metadata and abstracts, and fetch full text of some articles. Text-mining the scholarly literature is a research tool used across disciplines. Full text of articles (entire article, not just the abstract) is the gold standard in text-mining in most cases.

pubchunks is a package grown out of the fulltext package. fulltextprovides a single interface to many sources of full text scholarly articles. Aspart of the user flow in fulltext there is an extraction step where fulltext::chunks()pulls parts of articles out of XML format article files.