Some sites do not provide RSS for their new content. In those cases, one can create one's own feed.
Here are two ways to go about it:
If you use Google Reader:
Google Reader has this function built in, just paste the URL of the website into the 'Add Subscription' box, and it will offer to search the site for any changes on its own.
For any other RSS Reader:
You can also create an RSS feed for a website at locations such as Feedburner (http://www.feedburner.com)
This guide is certainly far from exhaustive.
If you do not see the journal or publisher you are looking for listed here, take a look on their own website (not a content link through a database provider like Ebsco) and look around for either the RSS logo shown on the Home tab of the guide, the words RSS, or XML, and if you find it, click on it, then you ought to be able to subscribe.
For example, the Harvard Educational Review's website has an RSS link that looks like this in the footer of its homepage.
One you have located the URL of the RSS Feed, follow the instructions under Adding a Subscription to an RSS Reader to complete the process of subscribing to the feed.