BEIJING, Sept. 2 -- Firms listed on the Beijing Stock Exchange maintained steady operations in the first half of the year, according to data released by the bourse on Monday.

More than 60 percent of the 251 firms listed on the bourse reported revenue growth, and more than 80 percent achieved profitability in the period, the bourse said.

The combined operating revenue of the listed companies was 78.5 billion yuan (about 11.05 billion U.S. dollars) and their net profit attributable to shareholders stood at 5.4 billion yuan in the period, the data shows.

Currently, more than 50 percent of the firms listed on the bourse are included in the national catalogue of "little giants," which are the novel elites of small and medium-sized enterprises that are engaged in manufacturing, specialize in a niche market and boast cutting-edge technologies.

In the second quarter of the year, these firms' combined operating revenue and net profit attributable to shareholders stood at 22.01 billion yuan and 1.67 billion yuan, respectively.

In the first half, firms listed on the bourse invested a total of 3.73 billion yuan in research and development, up 2.47 percent year on year.

As of the end of June, the number of qualified investors on the bourse has neared 7.05 million, an increase of 292,300 from the end of last year, the data shows.