Google - https://www.google.com/
Google Advanced Search - https://www.google.com/advanced_search
Google Search Guide - http://www.googleguide.com/print/adv_op_ref.pdf
Bing - https://www.bing.com/
Bing Search Guide - https://www.bruceclay.com/blog/bing-google-advanced-search-operators/
Yandex - https://yandex.com/
DuckDuckGo - https://duckduckgo.com/
DuckDuckGo Search Guide - https://help.duckduckgo.com/duckduckgo-help-pages/results/syntax/
Baidu - http://www.baidu.com/