TJ Mechanical engineering and machinery 133 QA Mathematics 105 TP Chemical technology 52 Q Science (General) 25 T Technology (General) 23 TA Engineering (General). Civil engineering (General) 22 Q Science 14 TK Electrical engineering. Electronics Nuclear engineering 13 QC Physics 5 TD Environmental technology. Sanitary engineering 5 QD Chemistry 4 TA1-2040 Engineering (General). Civil engineering (General) 4 Mechanical movements 3 Mechanics applied to machinery. Dynamics 3 TN Mining engineering. Metallurgy 3 Unspecified 3 CFD 2 Computational fluid dynamics 2 Heat 2 Heat engines 2 Numerical simulation 2 QA1-939 Mathematics 2 QA75 Electronic computers. Computer science 2 QH Natural history 2 QH301 Biology 2 TC Hydraulic engineering. Ocean engineering 2 TJ1-1570 Mechanical engineering and machinery 2 TL Motor vehicles. Aeronautics. Astronautics 2 VM Naval architecture. Shipbuilding. Marine engineering 2 Wind 2