Subclass Q Science (General)
Subclass QA Mathematics
Subclass QB Astronomy
Subclass QC Physics
Subclass QD Chemistry
Subclass QE Geology
Subclass QH Natural history - Biology 
Subclass QK Botany
Subclass QL Zoology
Subclass QM Human anatomy
Subclass QP Physiology
Subclass QR Microbiology
 
Subclass Q 
  Q1-390 Science (General)
  Q1-295   General
  Q300-390 Cybernetics
  Q350-390    Information theory
 
 
Subclass QA 
 QA1-939  Mathematics
 QA1-43       General
 QA47-59      Tables
 QA71-90      Instruments and machines
 QA75-76.95     Calculating machines
 QA75.5-76.95   Electronic computers. Computer science
 QA76.75-76.765   Computer software
 QA101-(145)  Elementary mathematics. Arithmetic
 QA150-272.5  Algebra
 QA273-280    Probabilities. Mathematical statistics
 QA299.6-433  Analysis
 QA440-699    Geometry. Trigonometry. Topology
 QA801-939    Analytic mechanics
 
Subclass QB 
 QB1-991 Astronomy
 QB1-139    General
 QB140-237  Practical and spherical astronomy
 QB275-343  Geodesy
 QB349-421  Theoretical astronomy and celestial mechanics
 QB455-456  Astrogeology
 QB460-466  Astrophysics
 QB468-480  Non-optical methods of astronomy
 QB495-903  Descriptive astronomy
 QB500.5-785  Solar system
 QB799-903    Stars
 QB980-991  Cosmogony. Cosmology

Subclass QC 
QC1-999   Physics
QC1-75      General
QC81-114      Weights and measures
QC120-168.85  Descriptive and experimental mechanics
QC170-197     Atomic physics. Constitution and properties of matter
                Including molecular physics, relativity,
                 quantum theory, and solid state physics
 QC221-246    Acoustics. Sound
 QC251-338.5  Heat
 QC310.15-319    Thermodynamics
 QC350-467    Optics. Light
 QC450-467       Spectroscopy
 QC474-496.9  Radiation physics (General)
 QC501-766    Electricity and magnetism
 QC501-(721)    Electricity
 QC669-675.8      Electromagnetic theory
 QC676-678.6      Radio waves (Theory)
 QC701-715.4      Electric discharge
 QC717.6-718.8    Plasma physics. Ionized gases
 QC750-766      Magnetism
 QC770-798    Nuclear and particle physics. Atomic energy. Radioactivity
 QC793-793.5    Elementary particle physics
 QC794.95-798   Radioactivity and radioactive substances
 QC801-809    Geophysics. Cosmic physics
 QC811-849    Geomagnetism
 QC851-999    Meteorology. Climatology 
                 Including the earth's atmosphere
 QC974.5-976    Meteorological optics
 QC980-999      Climatology and weather
 QC994.95-999      Weather forecasting
 
Subclass  QD 
 QD1-999 Chemistry
 QD1-65    General
             Including alchemy
 QD71-142  Analytical chemistry
 QD146-197 Inorganic chemistry
 QD241-441 Organic chemistry
 QD415-436    Biochemistry
 QD450-801 Physical and theoretical chemistry
 QD625-655    Radiation chemistry
 QD701-731    Photochemistry
 QD901-999 Crystallography
 
Subclass  QE 
 QE1-996.5  Geology
 QE1-350.62    General 
                  Including geographical divisions
 QE351-399.2   Mineralogy
 QE420-499     Petrology
 QE500-639.5   Dynamic and structural geology
 QE521-545       Volcanoes and earthquakes
 QE601-613.5     Structural geology
 QE640-699     Stratigraphy
 QE701-760     Paleontology
 QE760.8-899.2 Paleozoology
 QE901-996.5   Paleobotany
 
Subclass  QH 
QH1-278.5    Natural history (General)
QH1-(199.5)    General Including nature conservation, geographical distribution
 QH201-278.5   Microscopy
 QH301-705.5 Biology (General)
 QH359-425    Evolution
 QH426-470    Genetics
 QH471-489    Reproduction
 QH501-531    Life
 QH540-549.5  Ecology
 QH573-671    Cytology
 QH705-705.5  Economic biology
 
Subclass  QK 
QK1-989    Botany
 QK1-474.5   General 
               Including geographical distribution
 QK474.8-495 Spermatophyta. Phanerogams
 QK494-494.5    Gymnosperms
 QK495          Angiosperms
 QK504-(638) Cryptogams
 QK640-(707) Plant anatomy
 QK710-899   Plant physiology
 QK900-989   Plant ecology
 
Subclass  QL 
 QL1-991   Zoology
 QL1-355      General 
                Including geographical distribution
 QL360-599.82 Invertebrates
 QL461-599.82    Insects
 QL605-739.8  Chordates. Vertebrates
 QL614-639.8     Fishes
 QL640-669.3     Reptiles and amphibians
 QL671-699       Birds
 QL700-739.8     Mammals
 QL750-795    Animal behavior
 QL791-795       Stories and anecdotes
 QL799-799.5  Morphology
 QL801-950.9  Anatomy
 QL951-991    Embryology 
 
Subclass QM 
 QM1-695   Human anatomy
 QM1-511     General
 QM531-549   Regional anatomy
 QM550-577.8 Human and comparative histology
 QM601-695   Human embryology
 
Subclass QP 
 QP1-(981) Physiology
  QP1-345    General 
                  Including influence of the environment
 QP351-495     Neurophysiology and neuropsychology
 QP501-801     Animal biochemistry
 QP(901)-(981) Experimental pharmacology
 
Subclass  QR 
 QR1-502   Microbiology 
 QR1-74.5     General
 QR75-99.5    Bacteria
 QR99.6-99.8  Cyanobacteria
 QR100-130    Microbial ecology
 QR171        Microorganisms in the animal body
 QR180-189.5  Immunology
 QR355-502    Virology