In the natural sciences a protocol is a defined written procedural method in the design and implementation of experiments.
an excellent resource for recent protocols.
Cold Spring Harbor Protocols
collection of full-text scholarly monographs published by Cold Spring Harbor Laboratory Press
Current Protocols [Wiley]
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Methods in Molecular Biology and Methods in Molecular Medicine. Content 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.
Free Online Resources
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.