Classification
577 - Ecology
537
363 - Other social problems & services
227
333 - Economics of land & energy
202
628 - Sanitary & municipal engineering
128
551 - Geology, hydrology & meteorology
118
572 - Biochemistry
97
660 - Chemical engineering
83
620 - Engineering & allied operations
61
543 - Analytical chemistry
54
910 - Geography & travel
44
541 - Physical chemistry
42
630 - Agriculture & related technologies
41
631 - Techniques, equipment & materials
39
540 - Chemistry & allied sciences
38
550 - Earth sciences
35
621 - Applied physics
25
571 - Physiology & related subjects
23
613 - Personal health & safety
21
304 - Factors affecting social behavior
20
547 - Organic chemistry
16
579 - Microorganisms, fungi & algae
16
615 - Pharmacology & therapeutics
13
634 - Orchards, fruits & forestry
12
610 - Medicine & health
11
614 - Incidence & prevention of disease
11
670 - Manufacturing
10
344 - Labor, social, education & cultural law
8
546 - Inorganic chemistry
8
549 - Mineralogy
8
570 - Life sciences; biology
8
580 - Plants (Botany)
7
616 - Diseases
7
500 - Natural sciences & mathematics
6
578 - Natural history of organisms
6
590 - Animals (Zoology)
6
658 - General management
6
664 - Food technology
6
338 - Production
5
600 - Technology
5
624 - Civil engineering
5
700 - The arts; fine & decorative arts
5
581 - Specific topics in natural history
4
636 - Animal husbandry
4
641 - Food & drink
4
330 - Economics
3
523 - Specific celestial bodies & phenomena
3
592 - Invertebrates
3
629 - Other branches of engineering
3
000 - Computer science, information & general works
2
005 - Computer programming, programs & data
2
more ...