Currently, the Nature Publishing Group does not offer online only subscriptions.
All subscriptions are a combination of print journal and full-text unlimited online access.
We are investigating the possibility of such an option for the future. In the meantime, registering to any Nature Publishing Group web site will allow a limited degree of access to the site and its services, without the need for purchasing a subscription. The only exception to this is in Australia and New Zealand, where student and personal 1 year online-only Nature subscriptions are available.