TK Electrical engineering. Electronics Nuclear engineering HE Transportation and Communications 36 QA75 Electronic computers. Computer science 25 T Technology (General) 24 TJ Mechanical engineering and machinery 8 QA76 Computer software 7 TL Motor vehicles. Aeronautics. Astronautics 7 QA Mathematics 5 TA Engineering (General). Civil engineering (General) 4 QC Physics 3 T58.5-58.64 Information technology 2 TK5101-6720 Telecommunication 2 TK7885-7895 Computer engineer. Computer hardware 2 TP Chemical technology 2 TR Photography 2 HD28 Management. Industrial Management 1 HD61 Risk Management 1 HG Finance 1 Q Science (General) 1 QD Chemistry 1 QP Physiology 1 QR180 Immunology 1 R Medicine 1 R Medicine (General) 1 RZ Other systems of medicine 1 T Technology 1 TC Hydraulic engineering. Ocean engineering 1 TH Building construction 1 TK6570 Mobile Communication System 1 TN Mining engineering. Metallurgy 1