百度百科是一部内容开放、自由的网络百科全书，旨在创造一个涵盖所有领域知识，服务所有互联网用户的中文知识性百科全书。在这里你可以参与词条编辑，分享贡献你的知识。
Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.
Learn how to do anything with wikiHow, the world's most popular how-to website. Easy, well-researched, and trustworthy instructions for everything you want to know.
搜狗百科是搜狗搜索为广大用户所提供的一部自由、开放、共享的百科全书。旨在创造一个涵盖所有知识领域，服务于全部互联网用户的高质量内容平台。
提供精准知识问答，各种百科小知识，生活常识问答。
Explore the fact-checked online encyclopedia from Encyclopaedia Britannica with hundreds of thousands of objective articles, biographies, videos, and images from experts.
