Chemistry 82 Article 75 physical chemistry 69 chemistry 65 controlled study 56 Physical chemistry 55 Research & information: general 51 QD Chemistry 46 Physical and theoretical chemistry 42 nonhuman 39 Spectrum analysis, spectrochemistry, mass spectrometry 34 Physics 33 Technology: general issues 32 human 32 Quantum chemistry 30 unclassified drug 25 Humans 23 particle size 23 metabolism 22 Materials science 20 Research and information: general 19 Inorganic chemistry 17 pH 17 physical parameters 16 Animals 15 X ray diffraction 15 nanoparticle 15 Analytical chemistry 14 Biology, life sciences 14 Condensed matter physics (liquid state and solid state physics) 14