  We report low-temperature transport experiments on single-wall nanotubes with
metallic leads of varying contact quality, ranging from weak tunneling to
almost perfect transmission. In the weak tunneling regime, where Coulomb
blockade dominates, the nanotubes act as one-dimensional quantum dots. For
stronger coupling to the leads the conductance can be strongly enhanced by
inelastic cotunneling and the Kondo effect. For open contacts Coulomb blockade
is completely suppressed, and the low-temperature conductance remains generally
high, although we often see distinct dips in the conductance versus gate
voltage which may result from resonant backscattering.
