If it is not open source, you can generally find its DOI number or link with DOI number on the paper query page. All DOI numbers start with 10, and you can download the literature after you get the DOI number.

Open-source journals refer to academic information resources that anyone can get for free on the Internet, and are not restricted by copyright or registration. Open source periodical is a kind of free online periodical, which aims to make all users get the full text of periodical papers through the Internet without restriction. This kind of periodical generally adopts the operation mode of paid publication by the author, free access by readers and unlimited use, and the copyright of the paper is reserved by the author.