There are several ways to keep up with your favourite journals. You can, for example, subscribe to receive a notification email every time a new (electronic) article is published in a journal, or receive the table of contents of the newest issue. Publishers have their own tools for subscribing (see Springer below), but there are also services, such as the Researcher app and JournalTOCs specialised in notifying you of the latest updates in electronic journals.
Books, whether printed or electronic, are a slow but valuable scientific publication type especially in humanities, social sciences, and economics. In these fields, literature does not age as quickly as in some of the STEM disciplines.
The homepages of different libraries are a convenient way to find new titles purchased by the library, yet the newest information comes directly from publishers. They often release announcements of new publications even before they actually come out. You can easily subscribe to newsletters on publishers’ homepages to receive information on new and soon-to-be-released publications, sales and so on. Below are some examples from the Palgrave Macmillan's web page.
Pictures: Palgrave Macmillan
Most academic publishers are not concentrated on only one discipline or type of publication, even though they often specialise in something. For example, book publishers may have some high quality journals and journal publishers may also have databases. However, there are some publishers that concentrate strictly on specific disciplines or subjects.
In some fields, for example in law studies, academic research comes second to practical cases and their documentation. The European Court of Human Rights (ECHR) RSS feeds is a good example of a non-commercial service that functions similarly to disclipine specific publishers. The service delivers news of and about the European Court of Human Rights and operates via RSS.
A vast majority of scientific journals are published online or also in electronic format, even though publication practises still obey the procedures of printed publishing. This is why articles may be published (i.e. printed) several months to a year after they have been written. Often these articles are released on the web as e-pubs (electronic publication, online first publication, e-pub ahead of print, etc.) before the official publication date. This means the article does not yet have all the reference information, such as issue number or page numbers. Pre-release of articles is typical for medicine and other STEM disciplines, such as physics.
Another typical publication feature in STEM disciplines are pre-prints, which are versions of manuscripts that have already been accepted to be published later and are saved in either an open access or in a restricted-use repository. Depending on the publisher policy, articles can be self-archived before or after they have been peer-reviewed, or even in their final published form. Most of the parallel publications in institutional repositories and CRIS systems are pre-prints.
arXiv.org is one on the most popular open e-print repositories – among other things. It is a multi-disciplinary service for mathematics, physics, IT, and other technical sciences and it is updated constantly with new publications coming in almost daily. There is also a search engine on arXiv. In the wake of arXiv, there has been an emergence of other pre-print repositories with a similar name, such as PsyArXiv for psychological sciences, bioRxiv for biology, and medRxiv for health sciences.