  We present compiled radio continuum spectra for 200 Galactic supernova
remnants (SNRs) from 220 known and included in Green's (1998) catalog. These
spectra include most of the measurements available in literature, as well as
multi-frequency measurements of nearly 120 SNRs with the RATAN-600 radio
telescope in 1, 2 and 4 Galactic quadrants and from the Galactic plane survey
at 960 and 3900 MHz. The measurements have been placed on the same absolute
flux density scale. The presented compilation has given a possibility of
plotting quite accurate spectra with the thermal plasma free-free absorption in
fitting the spectra accounted for. An analysis of 190 spectra showed that 70
SNRs (37%) have clear low-frequency turnover caused, apparently, by absorption
in the thermal foreground of the Milky Way. We did not find considerable
correlation between spectral index and Galactic coordinates $l$ and $b$ of
SNRs. The turnover frequencies do not correlate with $l$ and $b$.
