专业服务板块9月18日跌1.55%，钢研纳克领跌，主力资金净流出2.03亿元

Core Points - The professional services sector experienced a decline of 1.55% on September 18, with Steel Research Nack leading the drop [1] - The Shanghai Composite Index closed at 3831.66, down 1.15%, while the Shenzhen Component Index closed at 13075.66, down 1.06% [1] Sector Performance - The professional services sector saw a net outflow of 203 million yuan from major funds, while retail investors contributed a net inflow of 145 million yuan [2] - Key stocks in the sector showed mixed performance, with notable declines in Steel Research Nack, which fell by 4.78% to a closing price of 16.93 yuan [2] Individual Stock Analysis - Major stocks such as Jianyan Institute and Su Shi Testing saw increases of 2.19% and 1.76%, respectively, while others like Anbang Guard and Shike Nano experienced slight declines [1][2] - The trading volume and turnover for Jianyan Institute reached 411,100 shares and 194 million yuan, respectively, indicating strong investor interest [1] Fund Flow Analysis - The fund flow analysis indicates that Jianyan Institute had a net inflow of 21.56 million yuan from major funds, while Su Shi Testing experienced a net outflow of 25.34 million yuan [3] - Retail investors showed a preference for stocks like Jianyan Institute and Guandong Construction, with net inflows of 15.94 million yuan and 3.96 million yuan, respectively [3]