科学技术类搜索引擎及目录索引

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化学 Chemistry：

Analytical Chemistry Springboard - Directory of analytical chemistry resources on the Internet.

ChemDex - Directory of chemistry on the WWW.

ChemFinder - An index to chemical information on the Internet, with structures and physical properties, searchable by name, structure, CAS Number, and physical properties.

Chemical Analysis.com - Analytical chemistry guide.

Chemistry - Links for Chemists - A huge index of Chemistry resources on the WWW arranged into 75 chemical categories.

Information Retrieval in Chemistry - Chemistry and sciences resource compendium by field and by topic.

Virtual Chemistry Center - Directory of chemistry sites.

World-Wide Web Virtual Library: Chemistry