Al Goldstein, the scabrous publisher whose Screw magazine pushed hard-core pornography into the cultural mainstream, died on Thursday at a nursing home in Cobble Hill, Brooklyn. He was 77. The cause was believed to be renal failure, his lawyer, Charles C. DeStefano, said. Mr. Goldstein did not invent the dirty magazine, but he was the first to present it to a wide audience without the slightest pretense of classiness or subtlety.