Crossref, as the largest digital object identifier (DOI) Registration Agency, has indexed over 100 million publications, and the total number of scientific journal articles published in electronic format increases by 2-3 million annually. This increase currently climbs by 8-9% every year.
However, it may be questioned if the quality of individual digital publications is the same as those of printed publications now and before the 21st century. Publication of "predatory journals" ("Beall's List") has become a standard feature within the "open-access" publishing concept. While determining the success or failure of publishing concepts takes decades/generations, Jeffrey Beall favored the "traditional scholarly publishing system" with no monetary relationship between publishers and authors. Other excesses of ever-increasing numbers of "World Journals" include "scholarly refereed" journals in which the journal's editor publishes three or more self-authored articles in a single issue.
While electronic publishing of scientific articles has become standard during the past ca. 20 years, there is a wealth of information available only in print. The total number of articles published only in print can only be estimated and might be a count of 100 million publications or presumably many, many more. To get hold of this information is difficult since there is no universal index of such literature like Crossref's DOI, nor have most printed journals and books ever been scanned. Besides tables of contents (TOC), the cited literature ("references"), which is usually included at the end of journal articles, book chapters, and books, has traditionally been the most significant resource for identifying such texts. Digitizing the TOCs of journals and books, as well as digitizing the reference sections of individual articles, appears to be the only way of elevating the "analog anonymity" of printed texts into the digital age.
Identification and localization of print articles based upon references in print media is not easy either. Particularly before the 1960s, references were kept as short as possible for saving space. By then and now, the "styles" of many journals mandate/mandated the use of journal abbreviations. The use of "initialisms in abbreviations of journal titles" was rampant throughout the 19th and 20th centuries and resulted in an "analog mess" of variations of journal citations. For example, the journal "Chemisches Zentralblatt" was and is being abbreviated as: C. Z., Ch. Z., Chem. Centb., Chem. Zentb., Chem. Centbl., Chem. Zentbl., Chem. Centr. and Chem. Zentr. making it challenging to identify the journal's single-most important identifier, i.e., the International Standard Serial Number (ISSN, in this case: 2194-2080). While not every journal is associated with an ISSN (alternatively ISBN for books) and not every library catalog contains the ISSN for every journal on the shelf, knowledge of this number is exceptionally important for correctly and quickly identifying and ultimately duplicating a journal article.
While duplicating journal articles or book chapters used to be restricted to (analog) photocopying before the 21st century, it is now usually a digitization process. Libraries now scan texts and deliver these in picture-PDF ("portable document format") file format. Good document-delivery providers apply optical character recognition (OCR) to these files to complete the digitization process.
EurekaMag is a digital biomedical library that performs all of the above tasks to deliver a fully digitized journal article or book chapter within only one workday. EurekaMag (1) identifies every ordered text, (2) matches the reference with the holdings of over 45 libraries worldwide, (3) retrieves the scanned picture files, and (4) applies OCR to the files in their native language. It holds records of over 40 million non-electronic articles that are not associated with a digital object identifier but can only be retrieved from printed media professionally preserved in libraries. Besides this vast stock, which can be ordered with one click, EurekaMag also offers a "Custom Request" feature through which any article or chapter not already referenced on the website can be ordered.
