Under what conditions you are allowed to distribute a scientific work are governed by the licence terms under which that work is made available. Most often journals or repositories of other research outputs will have clear indications regarding reuse, redistribution, etc. Often, all rights will be reserved by default and only certain rights for reuse/redistribution, if any, will be explicitly stated. If no specific rights are stated then you have no rights to reuse/redistribute.
In order to distribute a scientific work where no rights are automatically granted you are required to contact the copyright holder to request those rights.
This is one reason why Creative Commons licences were developed; so that authors of works can be explicit about what reuse rights they allow so users are not forced to individually contact creators to request rights.
Even when a work such as a dataset may not have copyright protection in the strict sense (e.g. facts), it may well have database rights protecting the specific compilation of the data into a whole. It is important to request permission, especially where you are unsure of the restrictions that might be in place.