  We conducted one blind and three targeted searches for millisecond and
submillisecond pulsars. The blind search was conducted within 3deg of the
Galactic plane and at longitudes between 20 and 110deg. It takes 22073
pointings to cover this region, and 5487 different positions in the sky. The
first targeted search was aimed at Galactic globular clusters, the second one
at 24 bright polarized and pointlike radiosources with steep spectra, and the
third at 65 faint polarized and pointlike radiosources. The observations were
conducted at the large radiotelescope of Nancay Observatory, at a frequency
near 1400 MHz. Two successive backends were used, first a VLBI S2 system,
second a digital acquisition board and a PC with large storage capacity
sampling the signal at 50 Mb/s on one bit, over a 24-MHz band and in one
polarization. The bandwidth of acquisition of the second backend was later
increased to 48 MHz and the sampling rate to 100 Mb/s. The survey used the
three successive setups, with respective sensitivities of 3.5, 2.2, and 1.7
mJy. The targeted-search data were obtained with the third setup and reduced
with a method based on the Hough transform, yielding a sensitivity of 0.9 mJy.
The processing of the data was done in slightly differed time by
soft-correlation in all cases. No new short-period millisecond pulsars were
discovered in the different searches. To better understand the null result of
the blind survey, we estimate the probability of detecting one or more
short-period pulsars among a given Galactic population of synthetic pulsars
with our setup: 25% for the actual incomplete survey and 79% if we had
completed the whole survey with a uniform nominal sensitivity of 1.7 mJy. The
alternative of surveying a smaller, presumably more densely populated, region
with a higher sensitivity would have a low return and would be impractical at a
transit instrument. (abridged)
