History 253 Analysis 190 Enzymes 181 History and criticism 107 Social aspects 105 Mathematical models 100 Data processing 92 Mathematics 76 Research 66 Politics and government 65 Design and construction 59 Criticism and interpretation 50 Psychological aspects 50 Environmental aspects 49 Methodology 47 Design 45 Economic aspects 39 Materials 38 Social conditions 38 Food 36 Management 36 Study and teaching 36 Philosophy 34 Economic conditions 33 Signal processing 32 Chemistry, Organic 31 Political aspects 31 Psychology 30 Synthesis 30 Pollution 29