We present average flux density measurements of 151 radio pulsars at 1.4 GHz with the Parkes 'Murriyang' radio telescope. We recommend our results be included in the next version of the Australia Telescope National Facility Pulsar Catalogue. The large sample of pulsars together with their wide dispersion measure (DM) range makes this data set useful for studying variability of flux density, pulsar spectra, and interstellar medium (ISM). We derive the modulation indices and structure-function from the flux density time series for 95 and 54 pulsars, respectively. We suggest the modulation index also be included in the next version of the pulsar catalogue to manifest the variability of pulsar flux density. The modulation index of flow density and DM are negatively correlated. The refractive scintillation (RISS) time-scales or its lower bound for a set of 15 pulsars are derived. They are very different from theoretical expectations, implying the complicated properties of the ISM along different lines of sight. The structure-function for other pulsars is flat. The RISS parameters for some of these pulsars possibly could be derived with different observing strategies in the future.