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321.
1.?Habitat use can influence individual performance in a wide range of animals, either immediately or through carry-over effects in subsequent seasons. Given that many animal species also show consistent individual differences in reproductive success, it seems plausible that individuals may have consistent patterns of habitat use representing individual specializations, with concomitant fitness consequences. 2.?Stable-carbon isotope ratios from a range of tissues were used to discern individual consistency in habitat use along a terrestrial-aquatic gradient in a long-distance migrant, the Bewick's swan (Cygnus columbianus bewickii). These individual specialisations represented <15% of the isotopic breadth of the population for the majority of individuals and were seen to persist throughout autumn migration and overwintering until aquatic habitats were no longer available. 3.?Individual foraging specialisations were then used to demonstrate two consecutive carry-over effects associated with macroscale habitat segregation: consequences of breeding season processes for autumn habitat use; and consequences of autumn habitat use for future reproductive success. Adults that were successful breeders in the year of capture used terrestrial habitats significantly more than adults that were not successful, revealing a substantial cost of reproduction and extended parental care. Use of aquatic habitats during autumn was, however, associated with increased body condition prior to spring migration; and increased subsequent breeding success in adults that had been unsuccessful the year before. Yet adults that were successful breeders in the year of capture remained the most likely to be successful the following year, despite their use of terrestrial habitats. 4.?Our results uniquely demonstrate not only individual foraging specializations throughout the migration period, but also that processes during breeding and autumn migration, mediated by individual consistency, may play a fundamental role in the population dynamics of long-distance migrants. These findings, therefore, highlight the importance of long-term consistency to our understanding of habitat function, interindividual differences in fitness, population dynamics and the evolution of migratory strategies. 相似文献
322.
Türke M Andreas K Gossner MM Kowalski E Lange M Boch S Socher SA Müller J Prati D Fischer M Meyhöfer R Weisser WW 《The American naturalist》2012,179(1):124-131
Seed dispersal by ants (myrmecochory) is widespread, and seed adaptations to myrmecochory are common, especially in the form of fatty appendices (elaiosomes). In a recent study, slugs were identified as seed dispersers of myrmecochores in a central European beech forest. Here we used 105 beech forest sites to test whether myrmecochore presence and abundance is related to ant or gastropod abundance and whether experimentally exposed seeds are removed by gastropods. Myrmecochorous plant cover was positively related to gastropod abundance but was negatively related to ant abundance. Gastropods were responsible for most seed removal and elaiosome damage, whereas insects (and rodents) played minor roles. These gastropod effects on seeds were independent of region or forest management. We suggest that terrestrial gastropods can generally act as seed dispersers of myrmecochorous plants and even substitute myrmecochory, especially where ants are absent or uncommon. 相似文献
323.
Schmidt Y Bannasch H Eisenhardt SU 《Plastic and reconstructive surgery》2012,129(1):174e-175e;author reply 175e-176e
324.
Schaper S Johnston IG Louis AA 《Proceedings. Biological sciences / The Royal Society》2012,279(1734):1777-1783
In evolution, the effects of a single deleterious mutation can sometimes be compensated for by a second mutation which recovers the original phenotype. Such epistatic interactions have implications for the structure of genome space--namely, that networks of genomes encoding the same phenotype may not be connected by single mutational moves. We use the folding of RNA sequences into secondary structures as a model genotype-phenotype map and explore the neutral spaces corresponding to networks of genotypes with the same phenotype. In most of these networks, we find that it is not possible to connect all genotypes to one another by single point mutations. Instead, a network for a phenotypic structure with n bonds typically fragments into at least 2(n) neutral components, often of similar size. While components of the same network generate the same phenotype, they show important variations in their properties, most strikingly in their evolvability and mutational robustness. This heterogeneity implies contingency in the evolutionary process. 相似文献
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327.
The permeability barrier of nuclear pore complexes (NPCs) controls all exchange of macromolecules between the cytoplasm and the cell nucleus. It consists of phenylalanine-glycine (FG) repeat domains apparently organized as an FG hydrogel. It has previously been demonstrated that an FG hydrogel derived from the yeast nucleoporin Nsp1p reproduces the selectivity of authentic NPCs. Here we combined time-resolved optical spectroscopy and X-ray scattering techniques to characterize such a gel. The data suggest a hierarchy of structures that form during gelation at the expense of unstructured elements. On the largest scale, protein-rich domains with a correlation length of ~16.5 nm are evident. On a smaller length scale, aqueous channels with an average diameter of ~3 nm have been found, which possibly represent the physical structures accounting for the passive sieving effect of nuclear pores. The protein-rich domains contain characteristic β-structures with typical inter-β-strand and inter-β-sheet distances of 1.3 and 0.47 nm, respectively. During gelation, the formation of oligomeric associates is accompanied by the transfer of phenylalanines into a hydrophobic microenvironment, supporting the view that this process is driven by a hydrophobic collapse. 相似文献
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329.
Schmidt C Peigneux P Leclercq Y Sterpenich V Vandewalle G Phillips C Berthomier P Berthomier C Tinguely G Gais S Schabus M Desseilles M Dang-Vu T Salmon E Degueldre C Balteau E Luxen A Cajochen C Maquet P Collette F 《PloS one》2012,7(1):e29658
Human morning and evening chronotypes differ in their preferred timing for sleep and wakefulness, as well as in optimal daytime periods to cope with cognitive challenges. Recent evidence suggests that these preferences are not a simple by-product of socio-professional timing constraints, but can be driven by inter-individual differences in the expression of circadian and homeostatic sleep-wake promoting signals. Chronotypes thus constitute a unique tool to access the interplay between those processes under normally entrained day-night conditions, and to investigate how they impinge onto higher cognitive control processes. Using functional magnetic resonance imaging (fMRI), we assessed the influence of chronotype and time-of-day on conflict processing-related cerebral activity throughout a normal waking day. Sixteen morning and 15 evening types were recorded at two individually adapted time points (1.5 versus 10.5 hours spent awake) while performing the Stroop paradigm. Results show that interference-related hemodynamic responses are maintained or even increased in evening types from the subjective morning to the subjective evening in a set of brain areas playing a pivotal role in successful inhibitory functioning, whereas they decreased in morning types under the same conditions. Furthermore, during the evening hours, activity in a posterior hypothalamic region putatively involved in sleep-wake regulation correlated in a chronotype-specific manner with slow wave activity at the beginning of the night, an index of accumulated homeostatic sleep pressure. These results shed light into the cerebral mechanisms underlying inter-individual differences of higher-order cognitive state maintenance under normally entrained day-night conditions. 相似文献
330.
Jan R. Thiele Kurt Goerendt G. Bjoern Stark Steffen U. Eisenhardt 《Journal of visualized experiments : JoVE》2012,(66)
Ischemia-reperfusion injury (IRI) has been implicated in a large array of pathological
conditions such as cerebral stroke, myocardial infarction, intestinal ischemia as well as
following transplant and cardiovascular surgery.1 Reperfusion of previously
ischemic tissue, while essential for the prevention of irreversible tissue injury, elicits
excessive inflammation of the affected tissue. Adjacent to the production of reactive
oxygen species, activation of the complement system and increased microvascular
permeability, the activation of leukocytes is one of the principle actors in the
pathological cascade of inflammatory tissue damage during reperfusion.2, 3
Leukocyte activation is a multistep process consisting of rolling, firm adhesion and
transmigration and is mediated by a complex interaction between adhesion molecules in
response to chemoattractants such as complement factors, chemokines, or
platelet-activating factor.4While leukocyte rolling in postcapillary venules is predominantly mediated by the
interaction of selectins5 with their counter ligands, firm adhesion of
leukocytes to the endothelium is selectin-controlled via binding to intercellular adhesion
molecules (ICAM) and vascular cellular adhesion molecules (VCAM).6, 7Gold standard for the in vivo observation of leukocyte-endothelial
interaction is the technique of intravital microscopy, first described in
1968.8Though various models of IRI (ischemia-reperfusion injury) have been described for
various organs, 9-12 only few are suitable for direct visualization of
leukocyte recruitment in the microvascular bed on a high level of image
quality.8We here promote the digital intravital epifluorescence microscopy of the postcapillary
venule in the cremasteric microcirculation of the rat 13 as a convenient method
to qualitatively and quantitatively analyze leukocyte recruitment for IRI-research in
striated muscle tissue and provide a detailed manual for accomplishing the technique. We
further illustrate common pitfalls and provide useful tips which should enable the reader
to truly appreciate, and safely perform the method.In a step by step protocol we depict how to get started with respiration controlled
anesthesia under sufficient monitoring to keep the animal firmly anesthetized for longer
periods of time. We then describe the cremasteric preparation as a thin flat sheet for
outstanding optical resolution and provide a protocol for leukocyte imaging in IRI that
has been well established in our laboratories.Download video file.(88M, mov) 相似文献