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Using the Urumqi 25 m radio telescope,sources from the first three months of the Fermi-large area telescope detected active galactic nuclei (AGN) catalog with a declination of ＞ 0° were observed in 2009 at 4.8 GHz.The radio flux density appeared to correlate with the γ-ray intensity.Intra-day variability (IDV) observations were performed in March,April and May 2009 for 42 selected γ-ray bright blazars,and ～60％ of them showed evidence of flux variability at 4.8 GHz during the IDV observations.The IDV detection rate was higher than that in previous flat-spectrum AGN samples.IDV appeared more often in the very long baseline interferometry-core dominant blazars,and the non-IDV blazars showed relatively “steeper” spectral indices than the IDV blazars.Pronounced inter-month variability was also found in two BL Lac objects:J0112+2244 and J0238+1636.