| CiteSeer | | Search engine for computer science and related matters. For all results number of citations are given which allows to estimate the importance of a paper in a given context. Most of the papers are cached and available for direct download as postscript or PDF. |
| ISI Highly Cited | | A search tool to identify individuals, departments and laboratories that have made fundamental contributions to the advancement of science and technology in recent decades. |
| iSpecies | | A species search engine from Rod Page of Glasgow University. Search on either the common or Latin name of a species. Results are generated by querying other data sources. |
| Scirus | | Search engine that fetches only scientific websites. |
| SciSeek | | Science search engine and directory. Also provides forums, tools and related news. |
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