Stocks launched into broad gains, led by steel, mining, coal and anything else related to economic growth in China. Early Thursday, the Dow Jones industrial average climbed 0.6%. The S&P 500 rose 0.4% and the Nasdaq 0.2%. Volume was firm, up 8% on the Nasdaq and 22% higher on the NYSE compared with the same time Wednesday. Strong gains by Akamai Technologies (AKAM) and F5 Networks (FFIV)bolstered the Nasdaq 100. Caterpillar (CAT) and Alcoa (AA)