全文获取类型
收费全文 | 2799篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
2823篇 |
出版年
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 62篇 |
2012年 | 50篇 |
2011年 | 71篇 |
2010年 | 115篇 |
2009年 | 101篇 |
2008年 | 108篇 |
2007年 | 140篇 |
2006年 | 75篇 |
2005年 | 86篇 |
2004年 | 51篇 |
2003年 | 29篇 |
2002年 | 19篇 |
2001年 | 26篇 |
2000年 | 25篇 |
1999年 | 38篇 |
1998年 | 58篇 |
1997年 | 86篇 |
1996年 | 68篇 |
1995年 | 72篇 |
1994年 | 47篇 |
1993年 | 59篇 |
1992年 | 48篇 |
1991年 | 62篇 |
1990年 | 57篇 |
1989年 | 60篇 |
1988年 | 52篇 |
1987年 | 66篇 |
1986年 | 46篇 |
1985年 | 54篇 |
1984年 | 50篇 |
1983年 | 59篇 |
1982年 | 37篇 |
1981年 | 36篇 |
1980年 | 43篇 |
1979年 | 53篇 |
1978年 | 39篇 |
1977年 | 39篇 |
1976年 | 35篇 |
1975年 | 48篇 |
1974年 | 37篇 |
1973年 | 58篇 |
1972年 | 61篇 |
1971年 | 65篇 |
1970年 | 26篇 |
1969年 | 31篇 |
1968年 | 29篇 |
1967年 | 20篇 |
1966年 | 18篇 |
排序方式: 共有2823条查询结果,搜索用时 15 毫秒
41.
FITZ JOHN PORTER POOLE 《The Australian journal of anthropology》1984,14(3):191-216
The Bimin-Kuskusmin of the West Sepik interior of Papua New Guinea elaborate a complex folk theory of procreation that becomes the ‘natural’ foundation of some ideologically significant constructions of the individual, the person, gender, and societal continuity. Drawing on certain aspects of Weiner's model of reproduction and regeneration, symbols of substance and insubstantial ‘spirit’ that form this ‘natural’ foundation of the Bimin-Kuskusmin ideology of birth, death, and rebirth are explored in contexts of rites of passage that mark the course of the life-cycle from conception to death and ancestorhood. The key symbols of this cultural ideology are the enduring substances of bone, bone marrow, and finiik spirit, which are the basis of reckoning the cyclical regeneration of clan categories. 相似文献
42.
Topography and tectonics of the Taconic outer trench slope as revealed through gradient analysis of fossil assemblages 总被引:1,自引:1,他引:0
JOHN L. CISNE DANIEL E. KARIG BRUCE D. RABE BERNWARD J. HAY 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1982,15(3):229-246
Similarities in stratigraphic sequence, syndepositional topography and tectonics, and regional tectonic setting between the Mohawk Valley, New York, in the Middle Ordovician and the Australian flank of the Timor Trough today support the idea that the Taconic Foreland Basin orginated in an arc-continent collision. The Trenton Group strata studied - a roughly four million year long sequence correlated by bentonite beds along an 83 km downslope transect in the central Mohawk Valley - represent the continental shelf and outer trench slope. Bank limestones pass upward and downslope into deep water black shales in a manner reminiscent of the lateral and vertical sedimentary sequence on the Sahul Shelf and Australian flank of the Timor Trough. In studying topography, relative depth was measured through reciprocal averaging ordination of benthic macroinvertebrate fossil assemblages. Downslope bathymetric profiles show the development of a horst and graben topography coincident with regional tilting and transgression - a pattern associated with downward flexure of the Australian Plate approaching Timor. The net rate of transgression corresponds to an arc-continent convergence rate on the order of 2 cm per year. 相似文献
43.
The Upper Triassic fishes from Polzberg bei Lunz, Austria 总被引:1,自引:0,他引:1
JOHN GRIFFITH 《Zoological Journal of the Linnean Society》1977,60(1):1-93
Carnian (Upper Triassic) fishes from Polzberg bei Lunz have been known since 1886 but no comprehensive account has been published. Eleven species are described nine of which, Saurichthys calcaratus, Polzbergia brochatus, Peltopleurus dirumptus, Habroichthys gregarius, Nannolepis elegans, Phaidrosoma lunzensis, Elpistoichthys pectinatus, E. striolatus and Pholidophoretes salvus are new, and two others, Thoracopterus niederristi Bronn and Gigantopterus telleri Abel, previously little-known.
New supraspecific taxa defined are:the order Polzbergiiformes, the family Thoracopteridae and the genera Polzbergia, Nannolepis, Phaidrosoma, Elpistoichthys and Pholidophoretes.
Habroichthys, Thoracopterus, Gigantopterus and Nannolepis show an unusual skull-roof pattern and are included in the re-defined order Luganoiiformes.
Two new ichthyokentemids considerably extend the known time-range of this family.
The genus Pholidophoretes is intermediate between the Archaeomenidae Goodrich 1909, and the Pholidophoridae sensu stricto Nybelin 1966.
The Polzberg assemblage was probably mainly marine with a small freshwater contribution; it shows less similarity to the Besano and Raibl assemblages than these do to each other.
The Luganoiiformes are probably, but not certainly, monophyletic; relationships within the order are analyzed and a cladogram constructed.
The Platysiagiformes, Peltopleuriformes, Luganoiiformes and Cephaloxeniformes could all have been derived from a common ancestor at the Perleidus level and are probably offshoots of the perleidid radiation. 相似文献
New supraspecific taxa defined are:the order Polzbergiiformes, the family Thoracopteridae and the genera Polzbergia, Nannolepis, Phaidrosoma, Elpistoichthys and Pholidophoretes.
Habroichthys, Thoracopterus, Gigantopterus and Nannolepis show an unusual skull-roof pattern and are included in the re-defined order Luganoiiformes.
Two new ichthyokentemids considerably extend the known time-range of this family.
The genus Pholidophoretes is intermediate between the Archaeomenidae Goodrich 1909, and the Pholidophoridae sensu stricto Nybelin 1966.
The Polzberg assemblage was probably mainly marine with a small freshwater contribution; it shows less similarity to the Besano and Raibl assemblages than these do to each other.
The Luganoiiformes are probably, but not certainly, monophyletic; relationships within the order are analyzed and a cladogram constructed.
The Platysiagiformes, Peltopleuriformes, Luganoiiformes and Cephaloxeniformes could all have been derived from a common ancestor at the Perleidus level and are probably offshoots of the perleidid radiation. 相似文献
44.
DEMOGRAPHIC ANALYSIS OF THE GROWTH OF LINUM USITATISSIMUM 总被引:13,自引:13,他引:0
45.
JOHN W. M. WHITING JOHN A. SODERGREN and STEPHEN M. STIGLER 《American anthropologist》1982,84(2):279-298
The dispersion of preindustrial peoples is strongly related to winter temperature in two surprising respects. Based on a classification of societies by language, we introduce a statistical model for their dispersion and show that (1) the 10°C (50°F) winter temperature isotherm has been an effective constraint to migration and expansion, and (2) the dispersion of language phyla has been remarkably homogeneous in a certain temperature scale, in contrast to the marked heterogeneity in terms of geographical dispersion , [climate, language, migration] 相似文献
46.
Nonparametric tests of the Markov model for survival data 总被引:1,自引:0,他引:1
47.
JOHN C. W. COPE 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1992,25(4):439-441
A lappeted microconch specimen of the phylloceratid ammonoid Juraphyllites from the Tethyan Jurassic of Anatolia (Turkey) indicates that sexual dimorphism in this group was established as early as in the early Lower Pliensbachian (Lower Jurassic) and that dimorphism in this genus of the Phylloceratina follows the same pattern as that proven [or many groups of the Ammonitina. This is the earliest record of well-developed lateral lappets in the Mesozoic Ammonoidea 相似文献
48.
CROWE JOHN H.; CROWE LOIS M.; ROE PAMELA; WICKHAM DANIEL 《Integrative and comparative biology》1982,22(3):671-682
SYNOPSIS. Carcinonemertes errans is a nemertean worm, the juvenilesof which are found as epibionts on the Dungeness crab, Cancermagister, in close association with the arthrodial membranesof the crabs. The juvenile nemerteans appear to have no meansof taking in particulate food but survive for many months onthe surface of the host. We show that the juvenile C. erransare capable of removing amino acids from dilute solution insea water, that the water near the arthrodial membranes wherethe worms are found contains high concentrations of primaryamines, and that there is a low resistance pathway for low molecularweight amino acids across the arthrodial membrane examined invitro. 相似文献
49.
THE ENERGETICS OF FRESHWATER ALGAE; ENERGY REQUIREMENTS FOR BIOSYNTHESIS AND VOLUME REGULATION 总被引:10,自引:8,他引:2
JOHN A. RAVEN 《The New phytologist》1982,92(1):1-20
50.
MATTA NARENDER K.; GATEHOUSE JOHN A.; BOULTER DONALD 《Journal of experimental botany》1981,32(6):1295-1307
Pisum sativum legumin has been shown to be heterogeneous withrespect to the existence of different molecular forms, the molecularweights of subunit pairs, and the molecular weights and isoelectricpoints of constituent subunits. Disulphide-bonded subunit pairswith mol. wt. 54 000 constitute a major part of total legumin.In addition, subunit pairs varying in mol. wt. from 35 000 to58 000 have been observed which associate in various ways togive rise to at least three distinct molecular forms of leguminseparable on non-dissociating gels. Three-dimensionalgel electro-phoresis has been employed to understand the consitutionof these forms in detail. 相似文献