Classification
577 - Ecology
1,744
333 - Economics of land & energy
1,130
581 - Specific topics in natural history
717
363 - Other social problems & services
643
551 - Geology, hydrology & meteorology
461
330 - Economics
399
580 - Plants (Botany)
395
630 - Agriculture & related technologies
316
579 - Microorganisms, fungi & algae
286
304 - Factors affecting social behavior
271
000 - Computer science, information & general works
251
700 - The arts; fine & decorative arts
237
571 - Physiology & related subjects
223
910 - Geography & travel
215
576 - Genetics & evolution
197
600 - Technology
190
320 - Political science
180
140 - Specific philosophical schools
151
590 - Animals (Zoology)
141
620 - Engineering & allied operations
141
900 - History & geography
140
570 - Life sciences; biology
139
610 - Medicine & health
132
572 - Biochemistry
130
550 - Earth sciences
124
634 - Orchards, fruits & forestry
109
500 - Natural sciences & mathematics
105
616 - Diseases
94
591 - Specific topics in natural history
90
380 - Commerce, communications & transportation
82
660 - Chemical engineering
81
631 - Techniques, equipment & materials
74
300 - Social sciences
66
100 - Philosophy & psychology
65
578 - Natural history of organisms
63
338 - Production
56
628 - Sanitary & municipal engineering
55
592 - Invertebrates
53
370 - Education
52
301 - Sociology & anthropology
47
658 - General management
45
200 - Religion
43
720 - Architecture
43
340 - Law
41
636 - Animal husbandry
41
540 - Chemistry & allied sciences
40
307 - Communities
35
612 - Human physiology
33
414 - Phonology & phonetics
32
624 - Civil engineering
31
more ...