Google Scholar searches for scholarly literature in a simple, familiar way. You can search across many disciplines and sources at once to find articles, books, theses, court opinions, and content from academic publishers, professional societies, some academic web sites, and more.
"PubChem is the world's largest collection of freely accessible chemical information. Search chemicals by name, molecular formula, structure, and other identifiers. Find chemical and physical properties, biological activities, safety and toxicity information, patents, literature citations and more."