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101.
102.
The extracellular patch clamp technique developed by Neher et al. to record the responses of single channels in skeletal muscle has provided firm evidence for the two-state nature of the conductance event in nicotinic endplate channels. We report here the use of the extracellular patch technique to record single-channel responses from tissue-cultured chick skeletal muscle cells. The temperature dependence of channel conductance and gating kinetics shows no evidence of discontinuous behaviour between 17 and 37 degrees C. 相似文献
103.
本书的第一版是汇集1987年12月28日至1988年1月6日在耶路撒冷举行的第5届“薄膜和表面的统计力学”讲学会的所有演讲,于1989年出版。这次出版第2版更新了一些章的内容,并增加了最后三章。此书应用聚合物物理、微分几何、场论和临界现象等领域的工具来探讨几何和统计力学在一些材料中的微弱的相互作用。这些材料包括微乳状液、湿润的与生长的表面、易溶的液晶块、硫族化合物的眼镜和片状聚合物。 相似文献
104.
David L. Nelson 《西北部美国博物学家》2011,42(3)
Larvae of the phalacrid beetle Phalacropsis dispar (LeConte) consumed aeciospores and the underlying sporogenous mycelium, thereby destroying the aecia of all native western pine stem rust fungi studied. Aecia of the introduced white pine blister rust fungus ( Cronartium ribicola ) were not found to be infested by the beetle. A close, if not obligate, biosis of the beetle apparently exists with the native rust fungi, and their geographic distributions closely coincide. Laboratory tests and field observations indicate that the beetle completes its life cycle in 30 to 40 days and apparently overwinters as an adult. Quantitative data on aeciospore inoculum destruction were beyond the means of this study; however, observations over a 12 - year period evidenced widespread and extensive destruction of aeciospores. The beetle may be an effective element in the natural control of native pine stem rust fungi. Natural control by secondary organisms could significantly reduce the selective pressure for high host resistance in a naturally evolving host - parasite population. 相似文献
105.
The theory of quasi-rational expectations was tested under the controlled conditions of the economics laboratory. Five experiments were conducted with a variety of stochastic processes. In each experiment, subjects produced one-step-ahead forecasts of the variable generated by a Monte Carlo process. Comparisons of the performance of an aggregate of subjects' forecasts versus an ARIMA model showed that for relatively simple series (such as those generated by autoregressive processes of first or second order) the aggregate forecast was indistinguishable from that of the model. These results lend support to the theory that forecasts from an ARIMA model can serve as substitutes for aggregate expectations in macroeconomic policy models under some conditions. 相似文献
106.
Locke DP Hillier LW Warren WC Worley KC Nazareth LV Muzny DM Yang SP Wang Z Chinwalla AT Minx P Mitreva M Cook L Delehaunty KD Fronick C Schmidt H Fulton LA Fulton RS Nelson JO Magrini V Pohl C Graves TA Markovic C Cree A Dinh HH Hume J Kovar CL Fowler GR Lunter G Meader S Heger A Ponting CP Marques-Bonet T Alkan C Chen L Cheng Z Kidd JM Eichler EE White S Searle S Vilella AJ Chen Y Flicek P Ma J Raney B Suh B Burhans R Herrero J Haussler D Faria R Fernando O Darré F Farré D Gazave E Oliva M 《Nature》2011,469(7331):529-533
'Orang-utan' is derived from a Malay term meaning 'man of the forest' and aptly describes the southeast Asian great apes native to Sumatra and Borneo. The orang-utan species, Pongo abelii (Sumatran) and Pongo pygmaeus (Bornean), are the most phylogenetically distant great apes from humans, thereby providing an informative perspective on hominid evolution. Here we present a Sumatran orang-utan draft genome assembly and short read sequence data from five Sumatran and five Bornean orang-utan genomes. Our analyses reveal that, compared to other primates, the orang-utan genome has many unique features. Structural evolution of the orang-utan genome has proceeded much more slowly than other great apes, evidenced by fewer rearrangements, less segmental duplication, a lower rate of gene family turnover and surprisingly quiescent Alu repeats, which have played a major role in restructuring other primate genomes. We also describe a primate polymorphic neocentromere, found in both Pongo species, emphasizing the gradual evolution of orang-utan genome structure. Orang-utans have extremely low energy usage for a eutherian mammal, far lower than their hominid relatives. Adding their genome to the repertoire of sequenced primates illuminates new signals of positive selection in several pathways including glycolipid metabolism. From the population perspective, both Pongo species are deeply diverse; however, Sumatran individuals possess greater diversity than their Bornean counterparts, and more species-specific variation. Our estimate of Bornean/Sumatran speciation time, 400,000?years ago, is more recent than most previous studies and underscores the complexity of the orang-utan speciation process. Despite a smaller modern census population size, the Sumatran effective population size (N(e)) expanded exponentially relative to the ancestral N(e) after the split, while Bornean N(e) declined over the same period. Overall, the resources and analyses presented here offer new opportunities in evolutionary genomics, insights into hominid biology, and an extensive database of variation for conservation efforts. 相似文献
107.
108.
Subsidence risk from thawing permafrost 总被引:19,自引:0,他引:19
109.
The family of hyperpolarization-activated, cyclic nucleotide-modulated (HCN) channels are crucial for a range of electrical signalling, including cardiac and neuronal pacemaker activity, setting resting membrane electrical properties and dendritic integration. These nonselective cation channels, underlying the I(f), I(h) and I(q) currents of heart and nerve cells, are activated by membrane hyperpolarization and modulated by the binding of cyclic nucleotides such as cAMP and cGMP. The cAMP-mediated enhancement of channel activity is largely responsible for the increase in heart rate caused by beta-adrenergic agonists. Here we have investigated the mechanism underlying this modulation by studying a carboxy-terminal fragment of HCN2 containing the cyclic nucleotide-binding domain (CNBD) and the C-linker region that connects the CNBD to the pore. X-ray crystallographic structures of this C-terminal fragment bound to cAMP or cGMP, together with equilibrium sedimentation analysis, identify a tetramerization domain and the mechanism for cyclic nucleotide specificity, and suggest a model for ligand-dependent channel modulation. On the basis of amino acid sequence similarity to HCN channels, the cyclic nucleotide-gated, and eag- and KAT1-related families of channels are probably related to HCN channels in structure and mechanism. 相似文献
110.