全文获取类型
收费全文 | 762篇 |
免费 | 14篇 |
国内免费 | 1篇 |
出版年
2017年 | 7篇 |
2015年 | 5篇 |
2013年 | 20篇 |
2012年 | 23篇 |
2011年 | 33篇 |
2010年 | 52篇 |
2009年 | 37篇 |
2008年 | 39篇 |
2007年 | 75篇 |
2006年 | 44篇 |
2005年 | 26篇 |
2004年 | 21篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 17篇 |
1997年 | 17篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1977年 | 6篇 |
1975年 | 5篇 |
1974年 | 10篇 |
1973年 | 4篇 |
1972年 | 13篇 |
1971年 | 12篇 |
1958年 | 4篇 |
1957年 | 15篇 |
1956年 | 5篇 |
1954年 | 10篇 |
1953年 | 8篇 |
1952年 | 4篇 |
1951年 | 4篇 |
1949年 | 4篇 |
排序方式: 共有777条查询结果,搜索用时 15 毫秒
91.
The Role of Exchange in Productive Specialization 总被引:1,自引:0,他引:1
Nomadic pastoralists are specialists in complex systems of land use. Their own productive strategies are dependent in large part upon the conversion rates of their products to imported items from other sectors of a larger economy. Changes in these conversion rates are likely to arise for a number of reasons; pastoralists respond to such changes in various ways, depending upon their past histories and current conditions. The case of the Yörük, specialized pastoralists of southeastern Turkey, is used to illustrate this process of changing productive strategies. Generalizations are sought concerning the ways in which large systems of land use become more or less specialized through time, in terms of the consequences of shifting exchange conditions for the productive strategies of component households. [economic anthropology, pastoralism, complex society, interpopulation exchange] 相似文献
92.
93.
ELISABETH RUNGGER-BRÄNDLE WERNER W. FRANKE MARY OSBORN KLAUS WEBER 《Differentiation; research in biological diversity》1978,10(1-3):187-191
Tubulin-containing structures of the male germ cells of Drosophila hydei crossreact in indirect immu-nofluorescence microscopy with antibody directed against homogeneous porcine brain tubulin. There is no detectable difference in reactivity between germ cells of wildtype flies and the mutant l(3)pl (lethal-polyploid) which is characterized by microtubular abnormalities. However, the technique of indirect immunofluorescence microscopy allows the direct visualization of several abnormalities in the arrangement of the microtubular system of the mutant, particularly in the axonemal complex. 相似文献
94.
CHRISTIAN M. TOBIAS DANIEL M. HAYDEN PAUL TWIGG GAUTAM SARATH 《Molecular ecology resources》2006,6(1):185-187
Switchgrass is a large, North American, perennial grass that is being evaluated as a potential energy crop. There is a need to assess genetic diversity in stored accessions and in remaining native stands to assist breeding and conservation efforts. Marker development will also be necessary for genetic linkage mapping. Toward this end, 32 switchgrass genic di‐, tri‐ and tetranucleotide repeat microsatellites were identified from expressed sequence tags (ESTs). These microsatellites were used to screen individuals from two different named cultivars. The markers displayed a high level of polymorphism consistent with the tetraploid, allogamous behaviour of the cultivars tested. 相似文献
95.
DANIEL J. C. KRONAUER JÜRGEN GADAU JACOBUS J. BOOMSMA 《Molecular ecology resources》2007,7(4):688-690
Here we describe 12 polymorphic microsatellite loci that were cloned and characterized for three species of army ants: the North American Neivamyrmex nigrescens, and the Asian Aenictus laeviceps and Aenictus dentatus. Observed and expected heterozygosities ranged from 0.37 to 0.97 (mean 0.70), and from 0.48 to 0.95 (mean 0.72), respectively. We observed 2–30 (mean 12) alleles per locus. These new genetic markers will be useful for studies of overall population structure and the complex pedigrees in colonies of army ants. 相似文献
96.
97.
98.
Following the traditions of ethnographic analysis, an account is given here of Best Value, the United Kingdom government's inspection of the services provided by municipalities and other local units of administration. My analysis is based largely upon the categories and terms used by the inspectorate itself. It is argued that in each of the main areas of inspection the results appear to contradict the intentions set out for the inspection. This appears to be the result of processes of abstraction which arise during the inspection. Such abstraction was located in the rise of jargon and bureaucracy as a result of the sheer scale of this audit, in the externalization of critical factors during market testing, in the emphasis on the representation of consulting over the results of consultation, and through the privileging of quantitative over qualitative information. Finally, the phrase 'owning the process' is analysed to show how the central ethos of serving the public is negated by these same forces. All these forms of abstraction are shown to occur despite, rather than because of, the intentions of the inspectorate. In the conclusion, they are analysed as contradictions which arise as a result of forces that are described by a theory of Virtualism. 相似文献
99.
Reproductive and Foraging Energetics of High Latitude Penguins, Albatrosses and Pinnipeds: Implications for Life History Patterns 总被引:3,自引:0,他引:3
Pinnipeds and seabirds feed at sea, but are tied to shore torear their young. Such a fundamental life history constraintshould lead to convergent adaptations in foraging and reproductiveecology. However, intrinsic differences in mammalian and avianreproductive biology may limitthe potential for convergence.In this paper I examine both reproductive and foraging energeticsof pinnipeds and seabirds. This is done in an attempt to identifytraits that might be considered convergent adaptations to lifein the marine environment and to show how divergent life historypatterns are optimal for different reasons. From this analysiswe find that seabirds invest a greater total amount of energyand protein into the offspring than pinnipeds, but this comesat the cost of making more trips to sea. Whereas pinnipeds foragein a manner more consistent with the predictions of centralplace foraging theory and exhibit a greater ability to compensateto the shortened breeding season typical of high latitude environments. 相似文献
100.
Dependence among responses in using the A-Not A or " Yes-No" task are accounted for in new hypothesis testing models. The new models involve adjustments to Pearson's and McNemar's chi-square statistics and to the variance of d', a measure of signal detectability or sensitivity. 相似文献