全文获取类型
收费全文 | 1275篇 |
免费 | 113篇 |
专业分类
1388篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 40篇 |
2020年 | 28篇 |
2019年 | 36篇 |
2018年 | 25篇 |
2017年 | 27篇 |
2016年 | 46篇 |
2015年 | 75篇 |
2014年 | 82篇 |
2013年 | 79篇 |
2012年 | 143篇 |
2011年 | 97篇 |
2010年 | 55篇 |
2009年 | 44篇 |
2008年 | 48篇 |
2007年 | 56篇 |
2006年 | 42篇 |
2005年 | 40篇 |
2004年 | 30篇 |
2003年 | 32篇 |
2002年 | 25篇 |
2001年 | 26篇 |
2000年 | 21篇 |
1999年 | 13篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1971年 | 5篇 |
1887年 | 6篇 |
1886年 | 6篇 |
1885年 | 8篇 |
1884年 | 3篇 |
1883年 | 8篇 |
1882年 | 4篇 |
1875年 | 6篇 |
1874年 | 3篇 |
排序方式: 共有1388条查询结果,搜索用时 15 毫秒
151.
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: |
152.
Nicholls JA Austin JJ Moritz C Goldizen AW 《Evolution; international journal of organic evolution》2006,60(6):1279-1290
Geographic variation in vocalizations is widespread in passerine birds, but its origins and maintenance remain unclear. One hypothesis to explain this variation is that it is associated with geographic isolation among populations and therefore should follow a vicariant pattern similar to that typically found in neutral genetic markers. Alternatively, if environmental selection strongly influences vocalizations, then genetic divergence and vocal divergence may be disassociated. This study compared genetic divergence derived from 11 microsatellite markers with a metric of phenotypic divergence derived from male bower advertisement calls. Data were obtained from 16 populations throughout the entire distribution of the satin bowerbird, an Australian wet-forest-restricted passerine. There was no relationship between call divergence and genetic divergence, similar to most other studies on birds with learned vocalizations. Genetic divergence followed a vicariant model of evolution, with the differentiation of isolated populations and isolation-by-distance among continuous populations. Previous work on Ptilonorhynchus violaceus has shown that advertisement call structure is strongly influenced by the acoustic environment of different habitats. Divergence in vocalizations among genetically related populations in different habitats indicates that satin bowerbirds match their vocalizations to the environment in which they live, despite the homogenizing influence of gene flow. In combination with convergence of vocalizations among genetically divergent populations occurring in the same habitat, this shows the overriding importance that habitat-related selection can have on the establishment and maintenance of variation in vocalizations. 相似文献
153.
Singh RR Moritz KM Bertram JF Denton KM 《American journal of physiology. Regulatory, integrative and comparative physiology》2012,302(7):R868-R875
We have previously shown that fetal uninephrectomy (uni-x) at 100 days of gestation (term = 150 days) in male sheep results in a 30% nephron deficit, reduction in glomerular filtration rate (GFR) and renal blood flow, and elevation in arterial pressure at 6 mo of age. Furthermore, in response to an acute 0.9% saline load, sodium excretion was significantly delayed in uni-x animals leading us to speculate that tubuloglomerular feedback (TGF) activity was reset in uni-x animals. In the present study, we induced TGF blockade by furosemide administration (1.5 mg/kg iv over 90 min) and determined GFR, effective renal plasma flow, and urine and sodium excretion responses in 6-mo-old male sheep. In response to furosemide, a significant diuresis and natriuresis was observed in the sham group; however, the response was significantly delayed and reduced in uni-x animals (both, P(treatment×time) < 0.001). Cummulative urinary and sodium output was significantly less in the uni-x compared with the sham sheep (both, P(treatment×time) < 0.001). GFR was increased in the sham but not the uni-x sheep (P(treatment×time) < 0.0001). In conclusion, the excretory response to furosemide was attenuated in the uni-x sheep, and this suggests a rightward resetting of the TGF operating point. The TGF mechanism is important in the fine tuning of sodium homeostasis and is likely a contributing factor for the dysfunction in sodium regulation we have previously observed in the uni-x animals. 相似文献
154.
Mihai CM Mărghitaş LA Dezmirean DS Chirilă F Moritz RF Schlüns H 《Journal of invertebrate pathology》2012,110(1):68-72
Propolis is derived from plant resins, collected by honeybees (Apis mellifera) and renown for its antibacterial properties. Here we test the antibacterial effects of ethanolic extracts of propolis from different origins on Paenibacillus larvae, the bacterial pathogen that causes American Foulbrood, a larval disease that can kill the honeybee colony. All tested propolis samples inhibited significantly the growth of P. larvae tested in vitro. The extracts showed major differences in the content of total flavonoids (ranging from 2.4% to 16.4%) and the total polyphenols (ranging between 23.3% and 63.2%). We found that it is not only the content of compounds in propolis, which influences the strength of antimicrobial effects but there is also a significant interaction effect among flavonoids of the propolis extracts. We propose that interaction effects among the various chemical compounds in propolis should be taken into account when considering the antibacterial effects against honeybee pathogens. 相似文献
155.
Granzin J Cousin A Weirauch M Schlesinger R Büldt G Batra-Safferling R 《Journal of molecular biology》2012,416(5):611-618
Visual arrestin specifically binds to photoactivated and phosphorylated rhodopsin and inactivates phototransduction. In contrast, the p44 splice variant can terminate phototransduction by binding to nonphosphorylated light-activated rhodopsin. Here we report the crystal structure of bovine p44 at a resolution of 1.85 Å. Compared to native arrestin, the p44 structure reveals significant differences in regions crucial for receptor binding, namely flexible loop V–VI and polar core regions. Additionally, electrostatic potential is remarkably positive on the N-domain and the C-domain. The p44 structure represents an active conformation that serves as a model to explain the ‘constitutive activity’ found in arrestin variants. 相似文献
156.
157.
158.
Bell RC MacKenzie JB Hickerson MJ Chavarría KL Cunningham M Williams S Moritz C 《Proceedings. Biological sciences / The Royal Society》2012,279(1730):991-999
Though Pleistocene refugia are frequently cited as drivers of species diversification, comparisons of molecular divergence among sister species typically indicate a continuum of divergence times from the Late Miocene, rather than a clear pulse of speciation events at the Last Glacial Maximum. Community-scale inference methods that explicitly test for multiple vicariance events, and account for differences in ancestral effective population size and gene flow, are well suited for detecting heterogeneity of species' responses to past climate fluctuations. We apply this approach to multi-locus sequence data from five co-distributed frog species endemic to the Wet Tropics rainforests of northeast Australia. Our results demonstrate at least two episodes of vicariance owing to climate-driven forest contractions: one in the Early Pleistocene and the other considerably older. Understanding how repeated cycles of rainforest contraction and expansion differentially affected lineage divergence among co-distributed species provides a framework for identifying evolutionary processes that underlie population divergence and speciation. 相似文献
159.
In their widely noticed study, Gergely, Bekkering, and Király (2002) showed that 14-month-old infants imitated an unusual action only if the model freely chose to perform this action and not if the choice of the action could be ascribed to external constraints. They attributed this kind of selective imitation to the infants' capacity of understanding the principle of rational action. In the current paper, we present evidence that a simpler approach of perceptual distraction may be more appropriate to explain their results. When we manipulated the saliency of context stimuli in the two original conditions, the results were exactly opposite to what rational imitation predicts. Based on these findings, we reject the claim that the notion of rational action plays a key role in selective imitation in 14-month-olds. 相似文献
160.
Swearingen KE Hoopmann MR Johnson RS Saleem RA Aitchison JD Moritz RL 《Molecular & cellular proteomics : MCP》2012,11(4):M111.014985
High-field asymmetric waveform ion mobility spectrometry (FAIMS) is an atmospheric pressure ion mobility technique that can be used to reduce sample complexity and increase dynamic range in tandem mass spectrometry experiments. FAIMS fractionates ions in the gas-phase according to characteristic differences in mobilities in electric fields of different strengths. Undesired ion species such as solvated clusters and singly charged chemical background ions can be prevented from reaching the mass analyzer, thus decreasing chemical noise. To date, there has been limited success using the commercially available Thermo Fisher FAIMS device with both standard ESI and nanoLC-MS. We have modified a Thermo Fisher electrospray source to accommodate a fused silica pulled tip capillary column for nanospray ionization, which will enable standard laboratories access to FAIMS technology. Our modified source allows easily obtainable stable spray at flow rates of 300 nL/min when coupled with FAIMS. The modified electrospray source allows the use of sheath gas, which provides a fivefold increase in signal obtained when nanoLC is coupled to FAIMS. In this work, nanoLC-FAIMS-MS and nanoLC-MS were compared by analyzing a tryptic digest of a 1:1 mixture of SILAC-labeled haploid and diploid yeast to demonstrate the performance of nanoLC-FAIMS-MS, at different compensation voltages, for post-column fractionation of complex protein digests. The effective dynamic range more than doubled when FAIMS was used. In total, 10,377 unique stripped peptides and 1649 unique proteins with SILAC ratios were identified from the combined nanoLC-FAIMS-MS experiments, compared with 6908 unique stripped peptides and 1003 unique proteins with SILAC ratios identified from the combined nanoLC-MS experiments. This work demonstrates how a commercially available FAIMS device can be combined with nanoLC to improve proteome coverage in shotgun and targeted type proteomics experiments. 相似文献