URL of search engines

(d) DuckDuckGo

https://duckduckgo.com/?q=%s

(ewiki) English Wikipedia

https://en.wikipedia.org/wiki/Special:Search?search=%s

(g) Google

https://www.google.com/search?q=%s

(gs) Google Scholar

https://scholar.google.co.jp/scholar?q=%s

(doi) DOI

http://dx.doi.org/%s

(alc) 英辞郎

http://eowf.alc.co.jp/search?q=%s

(dic) Dictionary.com

http://www.dictionary.com/browse/%s

(wol) Wolfram Alpha

http://www.wolframalpha.com/input/?i=%s

(ref) Chemistry Reference Resolver

http://chemsearch.kovsky.net/index.php?q=%s

(jwiki) Japanese Wikipedia

https://ja.wikipedia.org/wiki/%s