Articles in journals are found by searching in the databases and seeing if we have the content. Some databases cover a lot of ground (e.g. Agricola or CAB). Science Citation Index is interdisciplinary and shows who is citing whom within the journals that they index, among other features. There are links to Agricola, CAB, and several other databases in the box below this one.
For tips on using the databases, use the "Getting Started...." series, like "Getting Started with Agricola."