Humans human 70 article 58 mass spectrometry 50 nonhuman 48 unclassified drug 48 controlled study 46 Animals 44 chemistry 32 priority journal 32 metabolism 28 animal 26 human cell 24 Article 22 Magnetic Resonance Spectroscopy 20 Cell Line, Tumor 18 Spectrometry, Mass, Electrospray Ionization 18 electrospray mass spectrometry 18 protein protein interaction 18 Chromatography, High Pressure Liquid 16 Mass Spectrometry 16 matrix assisted laser desorption ionization time of flight mass spectrometry 16 Mice 14 Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization 14 chemical structure 14 enzyme activity 14 in vitro study 14 Molecular Structure 12 animal cell 12 drug structure 12