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排序方式: 共有139条查询结果,搜索用时 15 毫秒
31.
From axon–glial signalling to myelination: the integrating role of oligodendroglial Fyn kinase 总被引:1,自引:1,他引:0
Central nervous system myelination requires recognition and signalling processes between neuronal axons and oligodendrocytes.
Complex cellular rearrangements occur in myelination-competent oligodendrocytes requiring spatio-temporal control mechanisms.
Although the molecular repertoire is becoming increasingly transparent, the signalling mechanisms governing myelination initiation
are only poorly understood. The non-receptor tyrosine kinase Fyn has been implicated in axon–glial signal transduction and
in several cellular processes required for oligodendrocyte maturation and myelination. Here, we review oligodendroglial Fyn
signalling and discuss the role of Fyn in axon–glia interaction mediating myelination. 相似文献
32.
33.
In this paper I defend, against Eric Scerri’s objections, the following theses: (i) that Lavoisier and Mendeleev shared a ‘core conception’ of chemical element, and (ii) that this core conception underwrites referential continuity in the names of particular elements. 相似文献
34.
Nanotechnology: high-speed integrated nanowire circuits 总被引:1,自引:0,他引:1
Macroelectronic circuits made on substrates of glass or plastic could one day make computing devices ubiquitous owing to their light weight, flexibility and low cost. But these substrates deform at high temperatures so, until now, only semiconductors such as organics and amorphous silicon could be used, leading to poor performance. Here we present the use of low-temperature processes to integrate high-performance multi-nanowire transistors into logical inverters and fast ring oscillators on glass substrates. As well as potentially enabling powerful electronics to permeate all aspects of modern life, this advance could find application in devices such as low-cost radio-frequency tags and fully integrated high-refresh-rate displays. 相似文献
35.
Evolutionary theory predicts that local population divergence will depend on the balance between the diversifying effect of selection and the homogenizing effect of gene flow. However, spatial variation in the expression of genetic variation will also generate differential evolutionary responses. Furthermore, if dispersal is non-random it may actually reinforce, rather than counteract, evolutionary differentiation. Here we document the evolution of differences in body mass within a population of great tits, Parus major, inhabiting a single continuous woodland, over a 36-year period. We show that genetic variance for nestling body mass is spatially variable, that this generates different potential responses to selection, and that this diversifying effect is reinforced by non-random dispersal. Matching the patterns of variation, selection and evolution with population ecological data, we argue that the small-scale differentiation is driven by density-related differences in habitat quality affecting settlement decisions. Our data show that when gene flow is not homogeneous, evolutionary differentiation can be rapid and can occur over surprisingly small spatial scales. Our findings have important implications for questions of the scale of adaptation and speciation, and challenge the usual treatment of dispersal as a force opposing evolutionary differentiation. 相似文献
36.
Saether BE Lande R Engen S Weimerskirch H Lillegård M Altwegg R Becker PH Bregnballe T Brommer JE McCleery RH Merilä J Nyholm E Rendell W Robertson RR Tryjanowski P Visser ME 《Nature》2005,436(7047):99-102
Theoretical studies have shown that variation in density regulation strongly influences population dynamics, yet our understanding of factors influencing the strength of density dependence in natural populations still is limited. Consequently, few general hypotheses have been advanced to explain the large differences between species in the magnitude of population fluctuations. One reason for this is that the detection of density regulation in population time series is complicated by time lags induced by the life history of species that make it difficult to separate the relative contributions of intrinsic and extrinsic factors to the population dynamics. Here we use population time series for 23 bird species to estimate parameters of a stochastic density-dependent age-structured model. We show that both the strength of total density dependence in the life history and the magnitude of environmental stochasticity, including transient fluctuations in age structure, increase with generation time. These results indicate that the relationships between demographic and life-history traits in birds translate into distinct population dynamical patterns that are apparent only on a scale of generations. 相似文献
37.
Reich D Patterson N De Jager PL McDonald GJ Waliszewska A Tandon A Lincoln RR DeLoa C Fruhan SA Cabre P Bera O Semana G Kelly MA Francis DA Ardlie K Khan O Cree BA Hauser SL Oksenberg JR Hafler DA 《Nature genetics》2005,37(10):1113-1118
Multiple sclerosis is a common disease with proven heritability, but, despite large-scale attempts, no underlying risk genes have been identified. Traditional linkage scans have so far identified only one risk haplotype for multiple sclerosis (at HLA on chromosome 6), which explains only a fraction of the increased risk to siblings. Association scans such as admixture mapping have much more power, in principle, to find the weak factors that must explain most of the disease risk. We describe here the first high-powered admixture scan, focusing on 605 African American cases and 1,043 African American controls, and report a locus on chromosome 1 that is significantly associated with multiple sclerosis. 相似文献
38.
M Germain J F Saluzzo J P Cornet J P Hervé P Sureau J L Camicas Y Robin J J Salaün G Hème 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,289(8):635-637
The yellow fever virus is isolated in natura from eggs of a Tick Amblyomma variegatum. It is then isolated from larvae issued from the same egg-cluster and also from blood of a monkey bitten by larvae of the same origin. It is reported that the same virus has been previously obtained from adults of the same species of Tick. An acarine appears for the first time as a sylvatic vector and reservoir (at least temporary) of yellow fever. 相似文献
39.
Takemoto T Uchikawa M Yoshida M Bell DM Lovell-Badge R Papaioannou VE Kondoh H 《Nature》2011,470(7334):394-398
The classical view of neural plate development held that it arises from the ectoderm, after its separation from the mesodermal and endodermal lineages. However, recent cell-lineage-tracing experiments indicate that the caudal neural plate and paraxial mesoderm are generated from common bipotential axial stem cells originating from the caudal lateral epiblast. Tbx6 null mutant mouse embryos which produce ectopic neural tubes at the expense of paraxial mesoderm must provide a clue to the regulatory mechanism underlying this neural versus mesodermal fate choice. Here we demonstrate that Tbx6-dependent regulation of Sox2 determines the fate of axial stem cells. In wild-type embryos, enhancer N1 of the neural primordial gene Sox2 is activated in the caudal lateral epiblast, and the cells staying in the superficial layer sustain N1 activity and activate Sox2 expression in the neural plate. In contrast, the cells destined to become mesoderm activate Tbx6 and turn off enhancer N1 before migrating into the paraxial mesoderm compartment. In Tbx6 mutant embryos, however, enhancer N1 activity persists in the paraxial mesoderm compartment, eliciting ectopic Sox2 activation and transforming the paraxial mesoderm into neural tubes. An enhancer-N1-specific deletion mutation introduced into Tbx6 mutant embryos prevented this Sox2 activation in the mesodermal compartment and subsequent development of ectopic neural tubes, indicating that Tbx6 regulates Sox2 via enhancer N1. Tbx6-dependent repression of Wnt3a in the paraxial mesodermal compartment is implicated in this regulatory process. Paraxial mesoderm-specific misexpression of a Sox2 transgene in wild-type embryos resulted in ectopic neural tube development. Thus, Tbx6 represses Sox2 by inactivating enhancer N1 to inhibit neural development, and this is an essential step for the specification of paraxial mesoderm from the axial stem cells. 相似文献
40.
Jacquemont S Reymond A Zufferey F Harewood L Walters RG Kutalik Z Martinet D Shen Y Valsesia A Beckmann ND Thorleifsson G Belfiore M Bouquillon S Campion D de Leeuw N de Vries BB Esko T Fernandez BA Fernández-Aranda F Fernández-Real JM Gratacòs M Guilmatre A Hoyer J Jarvelin MR Kooy RF Kurg A Le Caignec C Männik K Platt OS Sanlaville D Van Haelst MM Villatoro Gomez S Walha F Wu BL Yu Y Aboura A Addor MC Alembik Y Antonarakis SE Arveiler B Barth M Bednarek N Béna F Bergmann S Beri M Bernardini L 《Nature》2011,478(7367):97-102