The New Yorker, as the only widely circulated general-interest American magazine without an active Web presence, is one of the last holdouts against the barbarians at the digital gate. Which is why we were surprised when, not long ago, a piece by Malcolm Gladwell, a New Yorker staff writer, popped up in our online Nexis search. A modern marvel, Nexis offers a full-text compendium of more than 30,000 publications. But until recently, The New Yorker has been conspicuously absent from the vast database.