首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   365篇
  免费   36篇
  2024年   1篇
  2023年   5篇
  2022年   1篇
  2021年   16篇
  2020年   5篇
  2019年   14篇
  2018年   6篇
  2017年   10篇
  2016年   20篇
  2015年   23篇
  2014年   25篇
  2013年   27篇
  2012年   31篇
  2011年   38篇
  2010年   24篇
  2009年   20篇
  2008年   18篇
  2007年   17篇
  2006年   13篇
  2005年   14篇
  2004年   8篇
  2003年   8篇
  2002年   10篇
  2001年   5篇
  2000年   5篇
  1999年   4篇
  1998年   2篇
  1997年   1篇
  1996年   2篇
  1993年   1篇
  1992年   2篇
  1990年   1篇
  1987年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
  1975年   1篇
  1972年   1篇
  1969年   4篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
  1963年   2篇
  1962年   2篇
  1960年   1篇
  1957年   1篇
排序方式: 共有401条查询结果,搜索用时 15 毫秒
1.
2.
Carroll A. Laurin 《CMAJ》1966,94(1):36-39
The indications for and contraindications to cervical traction are discussed. The social and economic advantages to be obtained from carrying out such treatment at home are obvious. A special technique is described which does not make use of weights and in which traction is applied in a position of flexion rather than of extension.  相似文献   
3.
In the Maritime Alps, the Middle and Upper Bathoniancorresponds to a transgressive episode on the Provençal platform. The advancement of the marine invasion is very noticeable between Grasse and Antibes. The sediment shows the existence of a shallow marine environment in which benthic organisms were predominant.The deposits are at first varied: marly layers withbivalves (burrowers for the most part) and calcareous layers with monospecific populations of brachiopods (Burmirhynchia mediterranea nov. sp. in a calm environment, and B. turgidaBuckman in a more turbulent environment).The deposits then become uniform and show theexistence of very shallows environments: B. decorata kiliani nov. subsp. is the only representative of macrofauna in the micritic limestones that can be attributed to the Upper Bathonian.The Rhynchonellids, as on the other Bathonian carbonateplatforms of Western Europe, seem to be the only organisms likely to stay alive and proliferate in the specific environments in which entirely carbonate sediments are deposited in shallow water. Due to their relationships to those existing in other platforms, the species described in this article permit the clarification of biostratigraphic correlations.  相似文献   
4.
Monitoring ecosystem functions in forests is a priority in a climate change scenario, as climate‐induced events may initially alter the functions more than slow‐changing attributes, such as biomass. The ecosystem functional properties (EFPs) are quantities that characterize key ecosystem processes. They can be derived by point observations of gas and energy exchanges between the ecosystems and the atmosphere that are collected globally at FLUXNET flux tower sites and upscaled at ecosystem level. The properties here considered describe the ability of ecosystems to optimize the use of resources for carbon uptake. They represent functional forest information, are dependent on environmental drivers, linked to leaf traits and forest structure, and influenced by climate change effects. The ability of vegetation optical depth (VOD) to provide forest functional information is investigated using 2011–2014 satellite data collected by the Soil Moisture and Ocean Salinity mission and using the EFPs as reference dataset. Tropical forests in Africa and South America were analyzed, also according to ecological homogeneous units. VOD jointly with water deficit information explained 93% and 87% of the yearly variability in both flux upscaled maximum gross primary productivity and light use efficiency functional properties, in Africa and South America forests respectively. Maps of the retrieved properties evidenced changes in forest functional responses linked to anomalous climate‐induced events during the study period. The findings indicate that VOD can support the flux upscaling process in the tropical range, affected by high uncertainty, and the detection of forest anomalous functional responses. Preliminary temporal analysis of VOD and EFP signals showed fine‐grained variability in periodicity, in signal dephasing, and in the strength of the relationships. In selected drier forest types, these satellite data could also support the monitoring of functional dynamics.  相似文献   
5.
Good manufacturing practices guidelines require safer and standardized cell substrates especially for those cell therapy products to treat ocular diseases where fibroblasts are used as feeder layers. However, if these are unavailable for stem cells culturing, murine fibroblasts are regularly used, raising critical issues as accidentally transplanting xenogenous graft and adversely affecting stem cell clinical trials. Moreover, human fibroblasts play a significant role in testing novel ophthalmologic drugs. Accordingly, we developed a standardized laboratory and surgical approach to isolate normal and undamaged Tenon’s fibroblasts to implement the setting up of banks for both stem cells-based ocular cell therapy and in vitro drug testing. A 2–3 cm2 undamaged Tenon’s biopsy was surgically obtained from 28 patients without mutually correlated ocular diseases. Nineteen dermal biopsies were used as control. Fibroblasts were isolated with or without collagenase, cultured in autologous, fetal bovine or AB serum, tested for viability by trypan blue, vimentin expression and standardized until passage 6. Successful Tenon’s fibroblasts isolation was age dependent (P = 0.001) but not sex, pathology or surgery related. A significant rate of successful cultures were obtained when biopsies were not digested by collagenase (P = 0.013). Moreover, cultures in autologous or fetal bovine serum had comparable proliferative properties (P = 0.77; P = 0.82). Through our surgical and laboratory standardized procedure, we elucidated for the first time key points of this human primary culture system, the role of the autologous serum, comparing Tenon’s and dermal fibroblasts. Our protocol may be clinically useful to reduce the risk above mentioned and may be potentially more effective for ophthalmological clinical purposes.  相似文献   
6.
A hallmark of the central nervous system is its spatial and functional organization in synaptic layers. During neuronal development, axons form transient contacts with potential post-synaptic elements and establish synapses with appropriate partners at specific layers. These processes are regulated by synaptic cell-adhesion molecules. In the Drosophila visual system, R7 and R8 photoreceptor subtypes target distinct layers and form en passant pre-synaptic terminals at stereotypic loci of the axonal shaft. A leucine-rich repeat transmembrane protein, Capricious (Caps), is known to be selectively expressed in R8 axons and their recipient layer, which led to the attractive hypothesis that Caps mediates R8 synaptic specificity by homophilic adhesion. Contradicting this assumption, our results indicate that Caps does not have a prominent role in synaptic-layer targeting and synapse formation in Drosophila photoreceptors, and that the specific recognition of the R8 target layer does not involve Caps homophilic axon-target interactions. We generated flies that express a tagged synaptic marker to evaluate the presence and localization of synapses in R7 and R8 photoreceptors. These genetic tools were used to assess how the synaptic profile is affected when axons are forced to target abnormal layers by expressing axon guidance molecules. When R7 axons were mistargeted to the R8-recipient layer, R7s either maintained an R7-like synaptic profile or acquired a similar profile to r8s depending on the overexpressed protein. When R7 axons were redirected to a more superficial medulla layer, the number of presynaptic terminals was reduced. These results indicate that cell-surface molecules are able to dictate synapse loci by changing the axon terminal identity in a partially cell-autonomous manner, but that presynapse formation at specific sites also requires complex interactions between pre- and post-synaptic elements.  相似文献   
7.
Mitochondria actively contribute to apoptotic cell death through mechanisms including the loss of integrity of the outer mitochondrial membrane, the release of intermembrane space proteins, such as cytochrome c, in the cytosol and the caspase cascade activation. This process is the result of careful cooperation not only among members of the Bcl‐2 family but also dynamin‐related proteins. These events are often accompanied by fission of the organelle, thus linking mitochondrial dynamics to apoptosis. Emerging evidences are suggesting a fine regulation of mitochondrial morphology by Bcl‐2 family members and active participation of fission–fusion proteins in apoptosis. The debate whether in mitochondrial morphogenesis the role of Bcl‐2 family members is functionally distinct from their role in apoptosis is still open and, above all, which morphological changes are associated with cell death sensitisation. This review will cover the findings on how the mitochondrial fission and fusion machinery may intersect apoptotic pathways focusing on recent advances on the key role played by Mcl‐1.  相似文献   
8.
To increase fitness, a wide range of vertebrates preferentially mate with partners that are dissimilar at the major histocompatibility complex (MHC) or that have high MHC diversity. Although MHC often can be assessed through olfactory cues, the mechanism by which MHC genes influence odour remains largely unclear. MHC class IIB molecules, which enable recognition and elimination of extracellular bacteria, have been suggested to influence odour indirectly by shaping odour‐producing microbiota, i.e. bacterial communities. However, there is little evidence of the predicted covariation between an animal's MHC genotype and its bacterial communities in scent‐producing body surfaces. Here, using high‐throughput sequencing, we tested the covariation between MHC class IIB genotypes and feather microbiota in the blue petrel (Halobaena caerulea), a seabird with highly developed olfaction that has been suggested to rely on oduor cues during an MHC‐based mate choice. First, we show that individuals with similar MHC class IIB profiles also have similar bacterial assemblages in their feathers. Then, we show that individuals with high MHC diversity have less diverse feather microbiota and also a reduced abundance of a bacterium of the genus Arsenophonus, a genus in which some species are symbionts of avian ectoparasites. Our results, showing that feather microbiota covary with MHC, are consistent with the hypothesis that individual MHC genotype may shape the semiochemical‐producing microbiota in birds.  相似文献   
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号