Why can I logon to sciencedirect from my place of work?
It may be that the company subscribes to sciencedirect too but doesn’t use Athens username/password to authenticate its users, in which case it will be using IP address instead. This means that you will only be able to access the ejournals that the company subscribes to. Sciencedirect are aware of this problem and have provided an alternative link for such users; it is very long and doesn’t copy/paste in one go so be careful when using it.