Radio polarization observations of large supernova remnants at 6cm
  We have observed 79 supernova remnants (SNRs) with the Urumqi 25m telescope
at 6cm during the Sino-German 6cm polarization survey of the Galactic plane. We
measured flux densities of SNRs at 6cm, some of which are the first ever
measured or the measurements at the highest frequency, so that we can determine
or improve spectra of SNRs. Our observations have ruled out spectral breaks or
spectral flattening that were suggested for a few SNRs, and confirmed the
spectral break of S147. By combining our 6cm maps with 11cm and 21cm maps from
the Effelsberg 100 m telescope, we calculated the spectral index maps of
several large SNRs. For many remnants we obtained for the first time
polarization images, which show the intrinsic magnetic field structures at 6cm.
We disapproved three objects as being SNRs, OA184, G192.8-1.1 and G16.8-1.1,
which show a thermal spectrum and no polarization. We have discovered two large
supernova remnants, G178.2-4.2 and G25.1-2.3., in the survey maps.
