A trade publication covers a specific industry for people who work in that industry. Trade publications therefore cover an industry in more minute details than a consumer publication or general magazine might. Trade publications deliver information that's of value to those who work in a certain field, but might not be of as much interest to the general public.
(1) Trade journals can be found full text in many library business and entrepreneur databases
(2) You may also be able to find trade journals online by simply doing a Web search for "trade journals" or "trade publications" and your industry.