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/