ScienceDirect gives you the option of using email alerts or RSS feeds to subscribe to content.
You can create an alert or an RSS feed for your search
You can also create an alert or RSS feed for new articles for a specific journal
ScienceDirect also has preset topic alerts available for many subdisciplines. Choose a category, then a subdiscipline. *You must be logged in to access the topic alerts page.*
If you change your mind and how to recieve your content, you can create an RSS feed from an alert. You cannot, however, create an alert from an RSS feed.