TK Electrical engineering. Electronics Nuclear engineering 1,132 TJ Mechanical engineering and machinery 482 TA Engineering (General). Civil engineering (General) 280 TP Chemical technology 189 QA75 Electronic computers. Computer science 172 T Technology (General) 155 QA Mathematics 147 Q Science (General) 84 QC Physics 76 QD Chemistry 34 TH Building construction 31 QA76 Computer software 30 HE Transportation and Communications 28 Unspecified 25 TC Hydraulic engineering. Ocean engineering 24 TK5101-6720 Telecommunication 23 NA Architecture 20 TL Motor vehicles. Aeronautics. Astronautics 16 TK7885-7895 Computer engineer. Computer hardware 14 QH Natural history 12 R Medicine (General) 12 QH301 Biology 11 HD Industries. Land use. Labor 10 L Education (General) 10 TD Environmental technology. Sanitary engineering 10 TE Highway engineering. Roads and pavements 10 TK6570 Mobile Communication System 10 QE Geology 8 T58.5-58.64 Information technology 7 TS Manufactures 7