An embargo is a period during which access to academic journals is not allowed to users who have not paid for access (or have access through their institution). During this time, the only access allowed is if one has a subscription to the specific journal. If a user's institution has access via a database, an abstract may be available. After the embargo period, users may have access to full text through a database that licenses the content or other means.
To search within a publication, use the "search within publication" link that is usually located above the title of the publication.
If you know which year the article may have appeared or you just want to peruse issues to see what turns up, you can also click on the issue year (usually listed on the right) and look through issues.