1. A radiographic apparatus for obtaining radiographic images based on radiation detection signals, comprising a radiation emitting device for emitting radiation toward an object under examination, a radiation detecting device for detecting radiation transmitted through the object under examination, and a signal sampling device for taking radiation detection signals from the radiation detecting device at predetermined sampling time intervals, said apparatus being constructed to obtain radiographic images based on the radiation detection signals outputted from the radiation detecting device at the predetermined sampling time intervals as radiation is emitted to the object under examination, said apparatus further comprising a time lag removing device for removing lag-behind parts from the radiation detection signals by a recursive computation, on an assumption that a lag-behind part included in each of said radiation detection signals taken at the predetermined sampling time intervals is due to an impulse response formed of a single or a plurality of exponential functions with different attenuation time constants; and a pixel group sorting device for sorting pixel groups consisting of detection pixels respectively corresponding to positions on said radiation detection device, into locations subjected to said recursive computation and locations exempted from the recursive computation; wherein, for the locations subjected to the recursive computation, said time lag removing device removes lag-behind parts by the recursive computation to obtain corrected radiation detection signals.