ChemBrain enables you to search the structure database for molecules by means of any fragment or combination of fragments. If you are looking for molecules which e. g. must contain at least two nitro groups and one or more phenyl rings, then just draw these groups in the graphical fragment-input window (see screenshots) and start the search. The result in most cases will be a list of hits. In order to see details of a specific hit molecule, just doubleclick it on the list and the corresponding molecule datasheet will appear.
This fragment-search feature also finds its use in ChemBrain's application of artificial neural networks.