It is generally recognized, however, that the introduction of the computer in the early 20th century, followed by the invention of the integrated circuit during the 1960s, radically changed the process, although its impact on the media was not immediately apparent.
句首it是形式主语，that引导真正的主语从句，主语从句中主语the introduction of the computer in the early 20th century后面是过去分词结构做后置定语，也可以看成是插入语，radically changed是谓语，the process是宾语，although引导让步状语从句。
it is generally recognized that…. 人们普遍认为
Because they are adjusting to their new bodies and a whole host of new intellectual and emotional challenges, teenagers are especially self-conscious and need the confidence