Ichthyology - The catalog of fishes - 
http://www.calacademy.org/research/ichthyology/catalog/fishcatsearch.html 

iCivilEngineer - http://www.icivilengineer.com/

IEEE Xplore - http://ieeexplore.ieee.org/  

IHS Specs & standards - http://library.lanl.gov/infores/stand/ihs/

IMB Jena image library of biological macromolecules - 
http://www.imb-jena.de/IMAGE.html

Immunology abstracts - http://www.csa.com/factsheets/immunology-set-c.php

Index Islamicus - 
http://www.columbia.edu/cu/lweb/eresources/databases/4256067.html

Index translationum - http://portal.unesco.org/culture/en/ev.php-
URL_ID=7810&URL_DO=DO_TOPIC&URL_SECTION=201.html

Industrial and applied microbiology - 
http://www.csa.com/factsheets/microbiology-a-set-c.php

IngentaConnect - http://www.ingentaconnect.com/

InsideWood - http://insidewood.lib.ncsu.edu/search/ 

INSPEC - http://www.ingentaconnect.com/

Institute of Physics: electronic journals - http://www.iop.org/Journals/

Integrated Taxonomic Information System - http://www.itis.usda.gov/ 

International abstracts of human resources - http://www.hrabstracts.com/ 

International index to music periodicals - http://iimp.chadwyck.com/home

international plant names index - http://www.ipni.org/

Internet library of early journals - http://www.bodley.ox.ac.uk/ilej/

Iter, gateway to the Middle Ages and Renaissance - 
http://www.itergateway.org