Editor's Note: TheStreet ratings do not represent the views of TheStreet's staff or its contributors. Ratings are established by computer based on metrics for performance (which includes growth, stock performance, efficiency and valuation) and risk (volatility and solvency). Companies with poor cash flow or high debt levels tend to earn lower ratings in our model Two out of the three major indices are trading lower today with the Dow Jones Industrial Average ( ^DJI) trading down 5 points (0.0%) at 15,100 as of Thursday, May 9, 2013, 12:45 PM ET. The NYSE advances/declines ratio sits at 1,176 issues advancing vs. 1,742 declining with 136 unchanged. The Basic Materials sector currently sits up 0.2% versus the S&P 500, which is down 0.21. On the negative front, top decliners within the sector include Seadrill ( SDRL), down 2.52, Cenovus Energy ( CVE), down 1.47, Enbridge ( ENB), down 1.34, LyondellBasell Industries ( LYB), down 1.34 and National Oilwell Varco ( NOV), down 0.93. Top gainers within the sector include Apache Corporation ( APA), up 4.2%, CF Industries Holdings ( CF), up 2.8%, Chesapeake Energy ( CHK), up 2.8%, Williams Companies ( WMB), up 2.7% and Energy Transfer Partners L.P ( ETP), up 2.4%. TheStreet Ratings group would like to highlight 5 stocks pushing the sector lower today: 5. PetroChina ( PTR) is one of the companies pushing the Basic Materials sector lower today. As of noon trading, PetroChina is down $1.13 (-0.9%) to $130.90 on light volume Thus far, 33,730 shares of PetroChina exchanged hands as compared to its average daily volume of 97,800 shares. The stock has ranged in price between $130.64-$132.19 after having opened the day at $132.19 as compared to the previous trading day's close of $132.03. PetroChina Company Limited produces and sells oil and gas in the People's Republic of China. The company operates in four segments: Exploration and Production, Refining and Chemicals, Marketing, and Natural Gas and Pipeline. PetroChina has a market cap of $236.1 billion and is part of the energy industry. The company has a P/E ratio of 204.8, above the S&P 500 P/E ratio of 17.7. Shares are down 8.2% year to date as of the close of trading on Wednesday. TheStreet Ratings rates PetroChina as a buy. The company's strengths can be seen in multiple areas, such as its revenue growth and attractive valuation levels. We feel these strengths outweigh the fact that the company has had sub par growth in net income. Get the full PetroChina Ratings Report now. Exclusive Offer: Jim Cramer's 'go-to' small/mid-cap guru Bryan Ashenberg only buys stocks he thinks could return 50-100%. See his top picks for 14-days FREE.