If I slipped and broke my shoulder because my landlord neglected to shovel snow and salt the ice, is he liable?

The landlord may be landlord. Liability will depend on two factors:

1) Was the landlord at fault in some way? For example, did the snowfall just occur, so he/she had no opportunity to shovel, salt, etc.? In that situation, there would generally not be fault; on the other hand, if there was opportunity to deal with the situation and the landlord failed to do so, he/she could be liable.

2) Is the landlord resposible for the shoveling? If it's a multi-family/mult-unit dwelling, he or she probably is; but if you leased the entirety of a single family home, then you, not the landlord, would most likely be responsible for shoveling (unless the lease said otherwise), since you are the one with possession and control over the outside areas.