To combine terms: Use the connectors:
      &   (and)
      /   or
      !   not
To find phrases: Type words in exact order, without quotes:   physical education index
To truncate words: Use an asterisk:
canad*   (finds canada, canadian, etc.)
To group terms: Use parentheses:
(physical education) / sports   (finds the phrase "physical education" OR the word "sports")
To find words near each other: Use w# [words within, in either order] or p# [word preceding]: review w5 gastro* ; internat* p5 abstracts

For more search tips (including examples) consult:   Keyword Search Guide