Access to real-time streams of tweets for research purpose?



I am PhD student and my current project involves developing techniques for analyzing social media data. I want to access real-time Twitter streams for testing my topic detection and evaluation algorithms, and ideally, the data must be complete (so the partial data provided by POST endpoint would not be as useful). Is there any API or endpoint that allows me to do this? I heard I can use Firehose to access the complete Twitter stream, but it is extremely difficult to obtain.

Yihong Zhang