Pubget is like Pubmed, except you get the PDFs right away:
Simple search: nik gene cluster
Title and abstract: centrality[tiab] hub[tiab] network[tiab]
Latest issue: plos biol[latest]
Authors: carroll sb[au] AND (rokas[au] OR gompel[au]) NOT kassner[au]
Citation: chisholm sw[au] nature[ta] 2003[dp] 424:1047
Happy searching—wherever you are!