  Graphene nanoribbons (GNRs) produced by means of bottom-up chemical
self-assembly are considered promising candidates for the next-generation
nanoelectronic devices. We address the electronic transport properties of
angled two-terminal GNR junctions, which are inevitable in the interconnects in
graphene-based integrated circuits. We construct a library of over 400000
distinct configurations of 60$^\circ$ and 120$^\circ$ junctions connecting
armchair GNRs of different widths. Numerical calculations combining the
tight-binding approximation and the Green's function formalism allow
identifying numerous junctions with conductance close to the limit defined by
the GNR leads. Further analysis reveals underlying structure-property
relationships with crucial roles played by the bipartite symmetry of graphene
lattice and the presence of resonant states localized at the junction. In
particular, we discover and explain the phenomenon of binary conductance in
120$^\circ$ junctions connecting metallic GNR leads that guarantees maximum
possible conductance. Overall, our study defines the guidelines for engineering
GNR junctions with desired electrical properties.
