In the natural sciences a protocol is a written procedural method in the design and implementation of experiments.
excellent resource for recent protocols. (remember to use the UC Berkeley Link to get full text).
Cold Spring Harbor Protocols
collection of full-text scholarly monographs published by Cold Spring Harbor Laboratory Press
Current Protocols [Wiley]
Current Protocols includes in Bioinformatics, Field Analytical Chemistry, and others.
Methods in Molecular Biology & Methods in Molecular Medicine - covers biochemistry, biotechnology, genetics, microbiology, molecular and cell biology, neuroscience, oncology, and proteomics.
This contains subject-oriented libraries of handbooks in different areas. Many of these do contain methods information.
A clinical study involves research using human volunteers (also called participants) that is intended to add to medical knowledge. There are two main types of clinical studies: clinical trials (also called interventional studies) and observational studies. ClinicalTrials.gov includes both interventional and observational studies.