Research on semantic search has become heated these years. In this paper we propose an approach focusing on searching for resources with descriptions. The knowledge representation we employ is based on conceptual graphs and is expressive with negation. We carry out semantic search by graph matching, which can be performed in polynomial time. Before matching we enrich the resource graphs with background knowledge by a deductive graph inference, so as to improve the search performance. The processing of negations and the graph inference method are two important contributions of this paper.