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1.
The increased use of induction heating (IH) cooktops in Japan and Europe has raised public concern on potential health effects of the magnetic fields generated by IH cooktops. In this study, we evaluated the effects of intermediate frequency (IF) magnetic fields generated by IH cooktops on gene expression profiles. Human fetus‐derived astroglia cells were exposed to magnetic fields at 23 kHz and 100 µTrms for 2, 4, and 6 h and gene expression profiles in cells were assessed using cDNA microarray. There were no detectable effects of the IF magnetic fields at 23 kHz on the gene expression profile, whereas the heat treatment at 43 °C for 2 h, as a positive control, affected gene expression including inducing heat shock proteins. Principal component analysis and hierarchical analysis showed that the gene profiles of IF‐exposed groups were similar to the sham‐exposed group and were different than the heat treatment group. These results demonstrated that exposure of human fetus‐derived astroglia cells to an IF magnetic field at 23 kHz and 100 µTrms for up to 6 h did not induce detectable changes in gene expression profile. Bioelectromagnetics 33:662–669, 2012. © 2012 Wiley Periodicals, Inc.  相似文献   
2.
在自然环境中,人和动物常在一定的背景噪声下感知信号声刺激,然而,关于低强度的弱背景噪声如何影响听皮层神经元对声刺激频率的编码尚不清楚.本研究以大鼠听皮层神经元的频率反应域为研究对象,测定了阈下背景噪声对79个神经元频率反应域的影响.结果表明,弱背景噪声对大鼠初级听皮层神经元的听反应既有抑制性影响、又有易化性影响.一般来说,抑制性影响使神经元的频率调谐范围和最佳频率反应域缩小,易化性影响使神经元的频率调谐范围和最佳频率反应域增大.对于少数神经元,弱背景噪声并未显著改变其频率调谐范围,但却改变了其最佳频率反应域范围.弱背景噪声对63.64%神经元的特征频率和55.84%神经元的最低阈值无显著影响.神经元频率调谐曲线的尖部比中部更容易受到弱背景噪声的影响.该研究结果有助于我们进一步理解复杂声环境下大脑听皮层对听觉信息的编码机制.  相似文献   
3.
Understanding the mechanism(s) that favour cooperation among individuals competing for the same resources provides direct insights into the evolution of grouping behaviour. In a hybrid zone between golden-/yellow-collared (Manacus vitellinus) and white-collared (Manacus candei) manakins, males form aggregations composed of white and yellow males solely to attract females ('mixed leks'). Previous work shows that yellow males in these mixed leks experience a clear mating advantage over white males, resulting in the preferential introgression of yellow plumage allele(s) into the white species. However, the yellow male mating advantage only occurs in mixed leks with high frequencies of yellow males, and only a few of these males probably mate. Hence, it remains unclear why unsuccessful males join leks. Here, we used microsatellite markers to estimate pairwise relatedness among males within and between leks to test whether indirect genetic benefits of helping kin ('kin selection') can promote grouping. We found that yellow males are significantly more related to each other within than between leks, while relatedness among white males did not differ within and between leks. This suggests that yellow males may indirectly enhance their own reproductive success by preferentially lekking with relatives because yellow plumage is under positive frequency-dependent selection (positive FDS). Our results are consistent with the hypothesis that kin selection may promote grouping and facilitate positive FDS for yellow males, mediating the movement of yellow plumage across this hybrid zone.  相似文献   
4.
Continuous progress in empirical population genetics based on the whole‐genome polymorphism data requires the theoretical analysis of refined models in order to interpret the evolutionary history of populations with adequate accuracy. Recent studies focus prevalently on the aspects of demography and adaptation, whereas age structure (for example, in plants via the maintenance of seed banks) has attracted less attention. Germ banking, that is, seed or egg dormancy, is a prevalent and important life‐history trait in plants and invertebrates, which buffers against environmental variability and modulates species extinction in fragmented habitats. Within this study, we investigate the combined effect of germ banking and time‐varying population size on the neutral coalescent and particularly derive the allele frequency spectrum under some simplifying assumptions. We then perform an ABC analysis using two simple demographic scenarios—a population expansion and an instantaneous decline. We demonstrate the appreciable influence of seed banks on the estimation of demographic parameters depending on the germination rate with biases scaled by the square of the germination rate. In the more complex case of a population bottleneck, which comprises an instantaneous decline and an expansion phase, ignoring information on the germination rate denies reliable estimates of the bottleneck parameters via the allelic spectrum. In particular, when seeds remain in the bank over several generations, recent expansions may remain invisible in the frequency spectrum, whereas ancient declines leave signatures much longer than in the absence of seed bank.  相似文献   
5.
We assessed the variability of chloroplast DNA sequences in populations of the dipterocarp forest tree, Shorea curtisii. This species is widely distributed in hill and coastal hill dipterocarp forests of the Malay Peninsula, whereas isolated populations are found in the coastal hills of north Borneo. Two chloroplast DNA regions (1555 bp of trnHpsbAtrnK and 925 bp of trnLtrnF) were sequenced from 123 individuals collected from six Malay Peninsula and two Bornean populations. There were 15 chloroplast haplotypes derived from 16 polymorphic sites. A haplotype network revealed two distinct haplogroups that correlate with two geographic regions, the Malay Peninsula and Borneo. These two haplogroups differed by a number of mutations, and no haplotypes were shared between populations from the different geographic regions. This suggests an ancient diversification of these haplogroups, and that long‐distance seed dispersal was unlikely to have occurred during the Pleistocene when the Sunda Shelf was a contiguous landmass. Phylogenetic analysis of the haplotypes together with those found in other Shorea species showed that two haplogroups in S. curtisii appear in different positions of the phylogenetic tree. This could be explained by the persistence of ancestral polymorphisms or by ancient chloroplast capture. Low levels of genetic differentiation were found between populations within each geographic region. Signature of a bottleneck followed by demographic expansion was detected in the Malay Peninsula haplogroup. The presence of two distinct evolutionary lineages in the different regions suggests that they should be managed independently to conserve the major sources of genetic diversity in S. curtisii.  相似文献   
6.
7.
Recent work on the evolution of behaviour is set in a structured population, providing a systematic way to describe gene flow and behavioural interactions. To obtain analytical results one needs a structure with considerable regularity. Our results apply to such "homogeneous" structures (e.g., lattices, cycles, and island models). This regularity has been formally described by a "node-transitivity" condition but in mathematics, such internal symmetry is powerfully described by the theory of mathematical groups. Here, this theory provides elegant direct arguments for a more general version of a number of existing results. Our main result is that in large "group-structured" populations, primary fitness effects on others play no role in the evolution of the behaviour. The competitive effects of such a trait cancel the primary effects, and the inclusive fitness effect is given by the direct effect of the actor on its own fitness. This result is conditional on a number of assumptions such as (1) whether generations overlap, (2) whether offspring dispersal is symmetric, (3) whether the trait affects fecundity or survival, and (4) whether the underlying group is abelian. We formulate a number of results of this type in finite and infinite populations for both Moran and Wright-Fisher demographies.  相似文献   
8.
Male sailfin mollies Poecilia latipinna were tested in five different treatments that varied in the relative frequency of heterospecific gynogens (Amazon molly Poecilia formosa) to conspecific females to determine whether social interactions among males within a population causes some males to mate with heterospecific females. Male P. latipinna inseminated a significantly higher proportion of conspecific females and fertilized a significantly higher number of conspecific eggs regardless of the treatment. Nonetheless, preference for conspecific females was not exclusive as a range of 20 to 50% of heterospecific females were fertilized. Social interactions among males may best explain the results and may therefore play an important role in the maintenance of unisexual--bisexual mating complexes.  相似文献   
9.
Using genetic data to study the process of population divergence is central to understanding speciation, yet distinguishing between recent divergence and introgressive hybridization is challenging. In a previous study on the phylogeography of the yellow‐rumped warbler complex using mitochondrial (mt)DNA data, we reported limited sequence divergence and a lack of reciprocal monophyly between myrtle and Audubon's warblers (Dendroica coronata and Dendroica auduboni, respectively), suggesting very recent isolation. In the present study, we report the results obtained from a subsequent sampling of Audubon's warbler in Arizona and Utah (‘memorabilis’ race), which shows that, although this taxon is similar to auduboni in plumage colour, most memorabilis individuals sampled (93%) carry haplotypes that belong to the divergent black‐fronted warbler lineage (Dendroica nigrifrons) of Mexico. Furthermore, the auduboni and nigrifrons lineages mix in southern Utah at a narrow, yet apparently ‘cryptic’ contact zone. Newly‐available evidence from nuclear markers indicating marked differentiation between auduboni and coronata has focused attention on the possibility of mtDNA introgression in the absence of nuclear gene flow, and the results of the present study are consistent with the hypothesis that the mtDNA of auduboni was indeed historically introgressed from the coronata lineage. Analysis of morphological traits shows that memorabilis is significantly differentiated from auduboni and nigrifrons in some traits, yet is overall intermediate between the two, which is consistent with a shared common ancestor for the auduboni/memorabilis/nigrifrons group. The striking, unexpected mtDNA pattern reported in the present study reveals a complex evolutionary history of the yellow‐rumped warbler complex, and cautions against the exclusive use of mtDNA to infer evolutionary relationships. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 696–706.  相似文献   
10.
HapStar: automated haplotype network layout and visualization   总被引:1,自引:0,他引:1  
Haplotype networks are commonly used for representing associations between sequences, yet there is currently no straightforward way to create optimal layouts. Automated optimal layouts are particularly useful not only because of the time-saving element but also because they avoid both human error and human-induced biases in the presentation of figures. HapStar directly uses the network connection output data generated from Arlequin (or a simple user-generated input file) and uses a force-directed algorithm to automatically lay out the network for easy visualization. In addition, this program is able to use the alternative connections generated by Arlequin to create a minimum spanning tree. HapStar provides a straightforward user-friendly interface, and publication-ready figures can be exported simply. HapStar is freely available (under a GPLv3 licence) for download for MacOSX, UNIX and Windows, at http://fo.am/hapstar.  相似文献   
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