全文获取类型
收费全文 | 171篇 |
免费 | 1篇 |
专业分类
系统科学 | 11篇 |
理论与方法论 | 2篇 |
现状及发展 | 54篇 |
研究方法 | 25篇 |
综合类 | 65篇 |
自然研究 | 15篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 13篇 |
2011年 | 21篇 |
2010年 | 8篇 |
2008年 | 14篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 15篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1963年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有172条查询结果,搜索用时 31 毫秒
31.
The pudu (Pudu puda) is a small, endemic deer, and the only native ungulate found in Chilean and Argentinean temperate forests. Its ecology, including its double role as an herbivore and as a prey, is poorly known. Therefore, it is pressing to gain a better understanding of the pudu given that its habitat is being transformed rapidly by anthropogenic causes. On a coastal mountain range in south-central Chile, we conducted a habitat use study and examined the activity patterns of the pudu using camera traps. The study area was a large native forest patch, surrounded by commercial plantations which would not constitute a habitat for this deer. Using a sampling effort of 7559 camera days, we found that this deer was largely nocturnal with little activity during daytime. The pudu selected Araucaria forests, and avoided Nothofagus forests. These behaviours suggest that the pudu traded off habitat use patterns and activity time to avoid predation, mainly by puma which is the top predator in the rich local community of carnivores occurring in the latter habitat. 相似文献
32.
Samuel Cardozo Ribeiro Diego Alves Teles Daniel Oliveira Mesquita Waltécio de Oliveira Almeida Luciano Alves dos Anjos Miriam Camargo Guarnieri 《Journal of Natural History》2019,53(39-40):2365-2377
ABSTRACTWe evaluated the activity period, thermal ecology, habitats, and preference for microhabitats of the skink Mabuya arajara in a humid forest environment on the slope of the Araripe Plateau, Brazil. A total of 283 lizards were observed. The lizards were found to be diurnally active (unimodal type pattern), with peak activity during the hottest hours of the day (1100 to 1200). About habitat use, the majority of individuals (73.8% N = 209) were recorded in the narrow transitional area, in the edges of the forest; while 26.4% of individuals were observed in open areas and no observations were made in dense forest. Seven different types of microhabitats were used, with fallen palm leaves (Arecaceae) being the preferred (47.7% N = 135). Considering all lizards, microhabitat niche breadth was 3.27. Males and females presented a high overlap (0.95) in microhabitat use. The average Tc recorded for M. arajara was 32.06 ± 2.72°C. Body size (SVL) did not influence body temperature (F = 0.51, P = > 0.05). Most of the animals were observed with their bodies completely exposed (67.84%, N = 192), 18.37% (N = 52) were semi-exposed and 13.79% (N = 39) were in shelters. Among animals with some degree of sunlight exposure, 57.59% (N = 163) were in shadows, 25.10% (N = 71) were under sunlight filtered by vegetation, and 17.31% (N = 49) were under direct sunlight.A review of the ecology of Mabuya spp. shows that several features appear to be conserved among members of the genus. 相似文献
33.
This paper offers an account of a process to build up relations of trust as a necessary condition for developing a new concept of auditing. The conceptual base of the discussion is centered upon the idea of managing complexity. Specifically, trust is observed not only as a form of reducing the complexity of our world relevant to each of us, but also as a most powerful amplifier of social complexity. In the paper the distinction is made between contextual trust and responsible trust. It is argued that responsible trust is necessary in order to accept diversity and increase the organization's performance in a demanding environment. This, in turn, suggests the necessity to move from hierarchical organizations to recursive organizations. The system in focus in this work was the Colombian State and, in particular, the National Audit Office of Colombia, which has begun a process to support the development of self-controlled organizational systems. 相似文献
34.
Miriam Beer Torchinsky J. Magarian Blander 《Cellular and molecular life sciences : CMLS》2010,67(9):1407-1421
In the few years since their discovery, T helper 17 cells (TH17) have been shown to play an important role in host defense against infections, and in tissue inflammation during autoimmunity.
TH17 cells produce IL-17, IL-21, IL-10, and IL-22 cytokines, and thus have broad effects on a variety of tissues. Notably, the
requirement for the immunosuppressive cytokine TGF-β along with the pro-inflammatory cytokine IL-6 for TH17 differentiation supports the intimate relationship between the TH17 subset and FOXP3+ regulatory T cells. Here, we discuss current knowledge on effector functions and differentiation of the TH17 lineage. Furthermore, we now know of a physiological stimulus for TH17 differentiation: innate immune recognition of cells undergoing apoptosis as a direct result of infection induces unique
development of this subset. As our knowledge of TH17 and T regulatory cells grows, we are building on a new framework for the understanding of effector T cell differentiation
and the biology of CD4+ T cell adaptive immune responses. 相似文献
35.
36.
Large-Scale Corruption: Definition,Causes, and Cures 总被引:1,自引:0,他引:1
Corruption is a social pathology. It has much the same effect on the development of a nation that cancer has on the life of a biological organism. Through a review of the literature, a definition of corruption is derived. Large-scale corruption is supported by power networks. In order to function and survive, power networks require five capabilities: economic, technical, political, physical, and ideological. Large-scale corruption is an emergent social process. The same governing factors that sustain large-scale corruption are in direct opposition to efforts to promote development. The history and evolution of a government agency for small farmers in a developing country are reviewed. While extracting wealth, corrupt power networks generated waste, reduced production, and caused acrimony on the part of the victims. For each dollar embezzled there was a resulting loss of $2.5. The corrupt networks reached such a level that the government had to disassemble the agencies. The ability to detect and neutralize corrupt networks is essential to development. 相似文献
37.
J L Arsuaga C Lorenzo J M Carretero A Gracia I Martínez N García J M Bermúdez de Castro E Carbonell 《Nature》1999,399(6733):255-258
The Middle Pleistocene site of Sima de los Huesos in Sierra de Atapuerca, Spain, has yielded around 2,500 fossils from at least 33 different hominid individuals. These have been dated at more than 200,000 years ago and have been classified as ancestors of Neanderthals. An almost complete human male pelvis (labelled Pelvis 1) has been found, which we associate with two fragmentary femora. Pelvis 1 is robust and very broad with a very long superior pubic ramus, marked iliac flare, and a long femoral neck. This pattern is probably the primitive condition from which modern humans departed. A modern human newborn would pass through the birth canal of Pelvis 1 and this would be even larger in a female individual. We estimate the body mass of this individual at 95 kg or more. Using the cranial capacities of three specimens from Sima de los Huesos, the encephalization quotients are substantially smaller than in Neanderthals and modern humans. 相似文献
38.
Neuronal activity in the motor cortex is understood to be correlated with movements, but the impact of action potentials (APs) in single cortical neurons on the generation of movement has not been fully determined. Here we show that trains of APs in single pyramidal cells of rat motor cortex can evoke long sequences of small whisker movements. For layer-5 pyramids, we find that evoked rhythmic movements have a constant phase relative to the AP train, indicating that single layer-5 pyramids can reset the rhythm of whisker movements. Action potentials evoked in layer-6 pyramids can generate bursts of rhythmic whisking, with a variable phase of movements relative to the AP train. An increasing number of APs decreases the latency to onset of movement, whereas AP frequency determines movement direction and amplitude. We find that the efficacy of cortical APs in evoking whisker movements is not dependent on background cortical activity and is greatly enhanced in waking rats. We conclude that in vibrissae motor cortex sparse AP activity can evoke movements. 相似文献
39.
Allen M Heinzmann A Noguchi E Abecasis G Broxholme J Ponting CP Bhattacharyya S Tinsley J Zhang Y Holt R Jones EY Lench N Carey A Jones H Dickens NJ Dimon C Nicholls R Baker C Xue L Townsend E Kabesch M Weiland SK Carr D von Mutius E Adcock IM Barnes PJ Lathrop GM Edwards M Moffatt MF Cookson WO 《Nature genetics》2003,35(3):258-263
Asthma is a common disease in children and young adults. Four separate reports have linked asthma and related phenotypes to an ill-defined interval between 2q14 and 2q32 (refs. 1-4), and two mouse genome screens have linked bronchial hyper-responsiveness to the region homologous to 2q14 (refs. 5,6). We found and replicated association between asthma and the D2S308 microsatellite, 800 kb distal to the IL1 cluster on 2q14. We sequenced the surrounding region and constructed a comprehensive, high-density, single-nucleotide polymorphism (SNP) linkage disequilibrium (LD) map. SNP association was limited to the initial exons of a solitary gene of 3.6 kb (DPP10), which extends over 1 Mb of genomic DNA. DPP10 encodes a homolog of dipeptidyl peptidases (DPPs) that cleave terminal dipeptides from cytokines and chemokines, and it presents a potential new target for asthma therapy. 相似文献
40.
Daniele R. Parizotto Danúncia Urban Gabriel A. R. Melo 《Journal of Natural History》2018,52(1-2):53-71
A taxonomic revision for the species of Austrostelis Michener and Griswold is provided. Ten species are recognized, one of which is newly described, A. saltensis Parizotto and Urban sp. nov., from Argentina. Additionally one new synonym is proposed and a lectotype for Stelis iheringi Friese, 1925 is designated. A revised diagnosis for the genus, illustrations and identification key for all species are also provided.
http://zoobank.org/urn:lsid:zoobank.org:pub:8397FEAE-45CB-444C-8B3C-6D706E752068 相似文献