By default articles containing any term in the query are returned (i.e., OR is implied)
Make sure that a word exists in an article by prefixing it with +; e.g., +journal +access scholarly academic
Combine multiple words with AND to find articles containing all terms; e.g., education AND research
Exclude a word by prefixing it with - or NOT; e.g., online -politics or online NOT politics
Search for an exact phrase by putting it in quotes; e.g., "open access publishing". Hint: Quoting Chinese or Japanese words will help you to find exact word matches in mixed-language fields, e.g. "中国".
Use parentheses to create more complex queries; e.g., archive ((journal AND conference) NOT theses)