If you click on the link for the full text of an article and your access is refused, it could be for a number of reasons:
Does the information on Library Search for this journal say that the full text is available for the year/volume you want? Sometimes we subscribe only to specific years.
Does the information on Library Search for this journal say that a separate username/password is required? If so, Library Search should also tell you how to find out the login details.
What time of year is it? In January all the electronic journal suppliers have to update their subscription information from the various publishers & agents and this can take them several months resulting in some discrepancies in our holdings.