全文获取类型
收费全文 | 486篇 |
免费 | 42篇 |
国内免费 | 1篇 |
出版年
2022年 | 6篇 |
2021年 | 7篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 23篇 |
2014年 | 24篇 |
2013年 | 33篇 |
2012年 | 30篇 |
2011年 | 42篇 |
2010年 | 20篇 |
2009年 | 21篇 |
2008年 | 19篇 |
2007年 | 11篇 |
2006年 | 12篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 9篇 |
2002年 | 17篇 |
2001年 | 19篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 6篇 |
1971年 | 2篇 |
1970年 | 3篇 |
排序方式: 共有529条查询结果,搜索用时 31 毫秒
51.
Paul Scholte Saïdou Kari Mark Moritz Herbert Prins 《Human ecology: an interdisciplinary journal》2006,34(1):27-51
This paper examines the responses of mobile pastoralists to a floodplain rehabilitation program in north Cameroon. From 1993
to 1999, we measured changes in number of camps and herds, and the time they spent in the 600 km2 of the Logone floodplain that was reflooded in 1994. The first year, few pastoralists anticipated the reflooding or its impact,
and the increase in grazing intensity was caused by a prolonged stay of pastoralists who already used the area for transit.
The following three years showed a sharp increase in the number of camps and herds, which stabilized from 1997 onwards. Overall,
grazing intensity increased threefold, following the gradually recovering perennial grasslands, with no signs of overexploitation
of the area. These developments closely match the ideal preemptive distribution model. We also examined how reflooding affected
pastoral incursions in the Waza National Park located in the floodplain.
相似文献
Paul ScholteEmail: |
52.
Hybrids in divers (Gaviiformes) 总被引:1,自引:0,他引:1
C. S. Roselaar Tineke G. Prins Mansour Aliabadian Vincent Nijman 《Journal of Ornithology》2006,147(1):24-30
The incidence of hybridisation in birds differs greatly between orders and is expected to be low in orders comprising few
species. The divers or loons (Gaviiformes) are a species-poor group in which apparent hybridisation has been reported infrequently.
Here we report on a hybrid diver stored in the collections of the Zoological Museum Amsterdam. The bird shows a heterogeneous
set of characters, some shared with the putative parent species White-billed Diver Gavia adamsii and Great Northern Diver G. immer, others being intermediate between the two. A Canonical Discriminant Function analysis positions the bird between these two
putative parent species, making a hybrid status quite likely. We evaluate the evidence for hybridisation in the order Gaviiformes
and conclude that hybridisation has been suspected in four of the five species, though documentation is limited. If this high
incidence could be confirmed, it would rank among the highest of any avian order, contradicting the assumption that incidence
of hybridisation in small orders is relatively low. 相似文献
53.
A.K. Shrestha S.E. van Wieren F. van Langevelde A. Fuller R.S. Hetem L.C.R. Meyer S. de Bie H.H.T. Prins 《Journal of thermal biology》2012
To understand the adaptive capacity of a species in response to rapid habitat destruction and climate change, we investigated variation in body temperature (Tb) of three species of antelope, namely eland, blue wildebeest and impala, using abdominally-implanted temperature data loggers. The study was conducted at two climatically contrasting environments in South Africa, one with a less seasonal and mild winter (Mapungubwe National Park) and the other with a more seasonal, long and cold winter (Asante Sana Game Reserve). Since the habitat with long and cold winters would be suboptimal for these African antelopes, which evolved in less seasonal and hot environments, antelopes in Asante Sana were expected to exhibit a larger amplitude in Tb and a lower minimum body temperature (Min Tb) during winter to reduce Tb and the ambient temperature (Tb−Ta) gradient to save energy. In both eland and impala, 24-h body temperature amplitude did not differ between the study sites, regardless of season. Conversely, wildebeest in Mapungubwe showed a higher variability in the 24-h amplitude of body temperature and also a lower Min Tb during winter and spring than the wildebeest in Asante Sana. This variation in Tb among Mapungubwe wildebeest was influenced by both the amplitude of ambient temperature (positive) and cumulative rainfall (negative), which was not the case for wildebeest in Asante Sana. We propose that the low Min Tb of wildebeest in Mapungubwe was the result of nutritional stress during winter and spring; an evident response even during a year of average rainfall. Therefore, these wildebeest apparently live in a physiologically stressful environment. With the predicted increase in the frequency and intensity of drought periods in southern Africa, wildebeest and other grazers, will likely experience greater nutritional stress in the future. 相似文献
54.
55.
Rudy M. Jonker R. H. J. M. Kurvers A. van de Bilt M. Faber S. E. Van Wieren H. H. T. Prins R. C. Ydenberg 《Evolutionary ecology》2012,26(3):657-667
The optimal duration of parental care is shaped by the trade-off between investment in current and expected future reproductive
success. A change in migratory behaviour is expected to affect the optimal duration of parental care, because migration and
non-migration differ in expectations of future reproductive success as a result of differential adult and/or offspring mortality.
Here we studied how a recent emergence of non-migratory behaviour has affected the duration of parental care in the previously
(until the 1980s) strictly migratory Russian breeding population of the barnacle geese Branta leucopsis. As a measure of parental care, we compared the vigilance behaviour of parents and non-parents in both migratory and non-migratory
barnacle geese throughout the season. We estimated the duration of parental care at 233 days for migratory and 183 days for
non-migratory barnacle geese. This constitutes a shortening of the duration of parental care of 21% in 25 years. Barnacle
geese are thus able to rapidly adapt their parental care behaviour to ecological conditions associated with altered migratory
behaviour. Our study demonstrates that a termination of migratory behaviour resulted in a drastic reduction in parental care
and highlights the importance of studying the ecological and behavioural consequences of changes in migratory behaviour and
the consequences of these changes for life-history evolution. 相似文献
56.
Kathleen C. Prins Gaia Vasiliver-Shamis Michael Cammer David Depoil Michael L. Dustin Catarina E. Hioe 《Journal of visualized experiments : JoVE》2012,(61)
Human immunodeficiency virus type 1 (HIV-1) infection occurs most efficiently via cell to cell transmission2,10,11. This cell to cell transfer between CD4+ T cells involves the formation of a virological synapse (VS), which is an F-actin-dependent cell-cell junction formed upon the engagement of HIV-1 envelope gp120 on the infected cell with CD4 and the chemokine receptor (CKR) CCR5 or CXCR4 on the target cell 8. In addition to gp120 and its receptors, other membrane proteins, particularly the adhesion molecule LFA-1 and its ligands, the ICAM family, play a major role in VS formation and virus transmission as they are present on the surface of virus-infected donor cells and target cells, as well as on the envelope of HIV-1 virions1,4,5,6,7,13. VS formation is also accompanied by intracellular signaling events that are transduced as a result of gp120-engagement of its receptors. Indeed, we have recently showed that CD4+ T cell interaction with gp120 induces recruitment and phosphorylation of signaling molecules associated with the TCR signalosome including Lck, CD3ζ, ZAP70, LAT, SLP-76, Itk, and PLCγ15.In this article, we present a method to visualize supramolecular arrangement and membrane-proximal signaling events taking place during VS formation. We take advantage of the glass-supported planar bi-layer system as a reductionist model to represent the surface of HIV-infected cells bearing the viral envelope gp120 and the cellular adhesion molecule ICAM-1. The protocol describes general procedures for monitoring HIV-1 gp120-induced VS assembly and signal activation events that include i) bi-layer preparation and assembly in a flow cell, ii) injection of cells and immunofluorescence staining to detect intracellular signaling molecules on cells interacting with HIV-1 gp120 and ICAM-1 on bi-layers, iii) image acquisition by TIRF microscopy, and iv) data analysis. This system generates high-resolution images of VS interface beyond that achieved with the conventional cell-cell system as it allows detection of distinct clusters of individual molecular components of VS along with specific signaling molecules recruited to these sub-domains. 相似文献
57.
Casper D. J. den Heijer Mari?lle A. J. Beerepoot Jan M. Prins Suzanne E. Geerlings Ellen E. Stobberingh 《PloS one》2012,7(11)
For women with recurrent urinary tract infections (rUTI), the contribution of antibiotic use versus patient-related factors in determining the presence of antimicrobial resistance in faecal and urinary Escherichia coli, obtained from the same patient population, has not been assessed yet. Within the context of the ‘Non-antibiotic prophylaxis for recurrent urinary tract infections’ (NAPRUTI) study, the present study assessed determinants of antimicrobial resistance in E. coli isolated from urinary and faecal samples of women with rUTIs collected at baseline. Potential determinants of resistance were retrieved from self-administered questionnaires. From 434 asymptomatic women, 433 urinary and 424 faecal samples were obtained. E. coli was isolated from 146 (34%) urinary samples and from 336 (79%) faecal samples, and subsequently tested for antimicrobial susceptibility. Multivariable analysis showed trimethoprim/sulfamethoxazole (SXT) use three months prior to inclusion to be associated with urine E. coli resistance to amoxicillin (OR 3.6, 95% confidence interval: 1.3–9.9), amoxicillin-clavulanic acid (OR 4.4, 1.5–13.3), trimethoprim (OR 3.9, 1.4–10.5) and SXT (OR 3.2, 1.2–8.5), and with faecal E. coli resistance to trimethoprim (OR 2.0, 1.0–3.7). The number of UTIs in the preceding year was correlated with urine E. coli resistance to amoxicillin-clavulanic acid (OR 1.11, 1.01–1.22), trimethoprim (OR 1.13, 1.03–1.23) and SXT (OR 1.10, 1.01–1.19). Age was predictive for faecal E. coli resistance to amoxicillin (OR 1.02, 1.00–1.03), norfloxacin and ciprofloxacin (both OR 1.03, 1.01–1.06). In conclusion, in women with rUTI different determinants were found for urinary and faecal E. coli resistance. Previous antibiotic use and UTI history were associated with urine E. coli resistance and age was a predictor of faecal E. coli resistance. These associations could best be explained by cumulative antibiotic use. 相似文献
58.
Vrisekoop N van Gent R de Boer AB Otto SA Borleffs JC Steingrover R Prins JM Kuijpers TW Wolfs TF Geelen SP Vulto I Lansdorp P Tesselaar K Borghans JA Miedema F 《Journal of immunology (Baltimore, Md. : 1950)》2008,181(2):1573-1581
It remains uncertain whether full T cell reconstitution can be established in HIV-infected children and adults with long-term sustained virological control by highly active antiretroviral therapy (HAART). In this study, we comprehensively analyzed various phenotypical markers of CD4 T cell recovery. In addition to measuring T cell activation and proliferation markers, CD4 T cell generation and aging of the CD4 T cell compartment were assessed by measuring TCR excision circles and the fraction of CD31-expressing naive CD4 T cells. In all children and in adults with relatively high CD4 T cell counts at start of therapy (>200 cells/microl), total CD4 T cell numbers normalized within 1 year of therapy. After long-term HAART (4.4-9.6 years), naive CD4 T cell counts had normalized in both groups. Although in adults with low baseline CD4 T cell counts (<200 cells/microl) total CD4 T cell numbers normalized eventually after at least 7 years of HAART, naive CD4 T cell counts had still not recovered. TCR excision circle data showed that thymic T cell production contributed to naive T cell recovery at all ages. The fraction of CD31-expressing naive CD4 T cells was found to be normal, suggesting that the CD4 T cell repertoire was diverse after long-term HAART. Hence, under sustained viral suppression during long-term HAART, the T cell compartment has the potential to fully recover by generating new naive T cells both in children and in adults with high baseline CD4 T cells counts. Irrespective of baseline CD4 T cell counts, reconstitution occurred without a significant effect on T cell aging as reflected by markers for replicative history. 相似文献
59.
Mollah ZU Pai S Moore C O'Sullivan BJ Harrison MJ Peng J Phillips K Prins JB Cardinal J Thomas R 《Journal of immunology (Baltimore, Md. : 1950)》2008,180(5):3166-3175
Dendritic cell (DC) differentiation is abnormal in type 1 diabetes mellitus (T1DM). However, the nature of the relationship between this abnormality and disease pathogenesis is unknown. We studied the LPS response in monocytes and monocyte-derived DCs isolated from T1DM patients and from non-T1DM controls. In T1DM patients, late LPS-mediated nuclear DNA binding by RelA, p50, c-Rel, and RelB was impaired as compared with type 2 DM, rheumatoid arthritis, and healthy subjects, associated with impaired DC CD40 and MHC class I induction but normal cytokine production. In TIDM monocytes, RelA and RelB were constitutively activated, and the src homology 2 domain-containing protein tyrosine phosphatase (SHP-1), a negative regulator of NF-kappaB, was overexpressed. Addition of sodium stibogluconate, a SHP-1 inhibitor, to DCs differentiating from monocyte precursors restored their capacity to respond to LPS in approximately 60% of patients. The monocyte and DC NF-kappaB response to LPS is thus a novel phenotypic and likely pathogenetic marker for human T1DM. SHP-1 is at least one NF-kappaB regulatory mechanism which might be induced as a result of abnormal inflammatory signaling responses in T1DM monocytes. 相似文献
60.
Alpha-dystrobrevin is a component of the dystrophin-glycoprotein complex (DGC) and is thought to have both structural and signaling roles in skeletal muscle. Mice deficient for alpha-dystrobrevin (adbn(-/-)) exhibit extensive myofiber degeneration and neuromuscular junction abnormalities. However, the biochemical stability of the DGC and the functional performance of adbn(-/-) muscle have not been characterized. Here we show that the biochemical association between dystrophin and beta-dystroglycan is compromised in adbn(-/-) skeletal muscle, suggesting that alpha-dystrobrevin plays a structural role in stabilizing the DGC. However, despite muscle cell death and DGC destabilization, costamere organization and physiological performance is normal in adbn(-/-) skeletal muscle. Our results demonstrate that myofiber degeneration alone does not cause functional deficits and suggests that more complex pathological factors contribute to the development of muscle weakness in muscular dystrophy. 相似文献