article 252 nitrogen 230 Nitrogen 155 nonhuman 115 unclassified drug 96 priority journal 90 metabolism 82 chemistry 80 controlled study 77 carbon 76 Argentina 74 Nitrogen compounds 73 pH 58 Nitrogen oxides 56 Carbon 52 Nitrogen Oxides 48 phosphorus 48 Animals 47 Article 46 nitric oxide 44 Oxidation-Reduction 42 nitrogen oxide 42 chemical structure 41 Kinetics 39 enzyme activity 39 South America 38 Hydrogen-Ion Concentration 35 Culture Media 34 aqueous solution 34 Nitric Oxide 32