  Yebes 40\,m radio telescope is the main and largest observing instrument at
Yebes Observatory and it is devoted to Very Long Baseline Interferometry (VLBI)
and single dish observations since 2010. It has been covering frequency bands
between 2\,GHz and 90\,GHz in discontinuous and narrow windows in most of the
cases, to match the current needs of the European VLBI Network (EVN) and the
Global Millimeter VLBI Array (GMVA). Nanocosmos project, a European Union
funded synergy grant, opened the possibility to increase the instantaneous
frequency coverage to observe many molecular transitions with single tunnings
in single dish mode. This reduces the observing time and maximises the output
from the telescope. We present the technical specifications of the recently
installed 31.5-50 GHz (Q band) and 72-90.5 GHz (W band) receivers along with
the main characteristics of the telescope at these frequency ranges. We have
observed IRC+10216, CRL 2688 and CRL 618, which harbour a rich molecular
chemistry, to demonstrate the capabilities of the new instrumentation for
spectral observations in single dish mode. The results show the high
sensitivity of the telescope in the Q band. The spectrum of IRC+10126 offers a
signal to noise ratio never seen before for this source in this band. On the
other hand, the spectrum normalised by the continuum flux towards CRL\,618 in
the W band demonstrates that the 40~m radio telescope produces comparable
results to those from the IRAM 30~m radio telescope, although with a smaller
sensitivity. The new receivers fulfil one of the main goals of Nanocosmos and
open the possibility to study the spectrum of different astrophysical media
with unprecedented sensitivity.
