Stocks strengthened and were near session highs early Monday afternoon as news of another big merger in the tech sector kept sellers at bay. The Nasdaq rose 0.5%, while the Dow Jones industrial average and S&P 500 added 0.4%. Volume on the NYSE and Nasdaq was tracking higher than Friday’s levels. Intel (INTC) gave a lift to the stock market today, agreeing to buyAltera (ALTR) for nearly $17 billion. Shares of Altera surged 6%. Intel fell 1%.