An ontology of general science knowledge (SKIo) is developed to enhance machine representation and use of scientific theories in emerging e-Science Knowledge Infrastructures. SKIo specializes the DOLCE foundational ontology with science knowledge primitives, such as science theory, model, data, prediction, and induction. These are arranged to reflect the complex knowledge structures used in science, such as scientific ideas playing different roles within and between theories. SKIo is encoded with OWL-DL, uses the DOLCE Descriptions and Situations module, and provides defining conditions for its primitives to enable an extensible bridge between DOLCE and domain science ontologies. An application to environmental theories is demonstrated, and its utility to other natural sciences is promising.