In this study we are concerned with describing written discourse tools employed by university PhD students to access specialized information and to construct knowledge across disciplines. In this vein, the research objectives are to identify and to describe the academic discourse genres based on a corpus of 3,147 texts collected in six disciplines in Social Sciences and Humanities and Basic Sciences (PUCV-2010 Corpus). Once the genres are identified, their occurrence is quantified across the disciplines under study: Biotechnology, Chemistry, History, Linguistics, Literature, and Physics. Among the most important findings, 30 genres were identified. The most recurrent genres are: Disciplinary Text, Research Article, and Textbook. Literature academic discourse shows the principal genre variation (15), while Chemistry and Physics academic discourse reveals the least genre variation (5).