Human-curated database focusing on high quality scientific journals. Offers many more sophisticated searching features. Search strategies should lead to stable (repeatable) results.
Searches the whole internet, presenting machine curated results. Inclusion of "scholarly" materials is based on self-reporting by publishers rather than selected by experts for quality. Advanced search features are limited. May search the full text, not just title and abstract, meaning you often get many irrelevant results. Search strategies will not usually lead to stable results.
Search Chemical Abstracts for journal articles; searchable by author, title, subject, chemical name or formula, and by drawing chemical substructures. NOTE: First time users must use registration link