Q Science (General) T Technology (General) 23 TA Engineering (General). Civil engineering (General) 15 QA75 Electronic computers. Computer science 13 QA Mathematics 9 QC Physics 9 TP Chemical technology 9 GE Environmental Sciences 6 QD Chemistry 5 G Geography (General) 4 GC Oceanography 4 QA76 Computer software 3 H Social Sciences (General) 2 QH301 Biology 2 R Medicine (General) 2 T58.5-58.64 Information technology 2 TJ Mechanical engineering and machinery 2 GA Mathematical geography. Cartography 1 GB Physical geography 1 HA Statistics 1 HD61 Risk Management 1 L Education (General) 1 LB1501 Primary Education 1 LG Individual institutions (Asia. Africa) 1 PE English 1 QM Human anatomy 1 RE Ophthalmology 1 TK Electrical engineering. Electronics Nuclear engineering 1