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51.
52.
C. Mark Maupin Gregory A. Voth 《Biochimica et Biophysica Acta - Proteins and Proteomics》2010,1804(2):332-341
This article reviews the insights gained from molecular simulations of human carbonic anhydrase II (HCA II) utilizing non-reactive and reactive force fields. The simulations with a reactive force field explore protein transfer and transport via Grotthuss shuttling, while the non-reactive simulations probe the larger conformational dynamics that underpin the various contributions to the rate-limiting proton transfer event. Specific attention is given to the orientational stability of the His64 group and the characteristics of the active site water cluster, in an effort to determine both of their impact on the maximal catalytic rate. The explicit proton transfer and transport events are described by the multistate empirical valence bond (MS-EVB) method, as are alternative pathways for the excess proton charge defect to enter/leave the active site. The simulation results are interpreted in light of experimental results on the wild-type enzyme and various site-specific mutations of HCA II in order to better elucidate the key factors that contribute to its exceptional efficiency. 相似文献
53.
Estimates of (co)variance components and genetic parameters for body weights and first greasy fleece weight in Bharat Merino sheep 总被引:2,自引:0,他引:2
Gowane GR Chopra A Prince LL Paswan C Arora AL 《Animal : an international journal of animal bioscience》2010,4(3):425-431
(Co)variance components and genetic parameters of weight at birth (BWT), weaning (3WT), 6, 9 and 12 months of age (6WT, 9WT and 12WT, respectively) and first greasy fleece weight (GFW) of Bharat Merino sheep, maintained at Central Sheep and Wool Research Institute, Avikanagar, Rajasthan, India, were estimated by restricted maximum likelihood, fitting six animal models with various combinations of direct and maternal effects. Data were collected over a period of 10 years (1998 to 2007). A log-likelihood ratio test was used to select the most appropriate univariate model for each trait, which was subsequently used in bivariate analysis. Heritability estimates for BWT, 3WT, 6WT, 9WT and 12WT and first GFW were 0.05 ± 0.03, 0.04 ± 0.02, 0.00, 0.03 ± 0.03, 0.09 ± 0.05 and 0.05 ± 0.03, respectively. There was no evidence for the maternal genetic effect on the traits under study. Maternal permanent environmental effect contributed 19% for BWT and 6% to 11% from 3WT to 9WT and 11% for first GFW. Maternal permanent environmental effect on the post-3WT was a carryover effect of maternal influences during pre-weaning age. A low rate of genetic progress seems possible in the flock through selection. Direct genetic correlations between body weight traits were positive and ranged from 0.36 between BWT and 6WT to 0.94 between 3WT and 6WT and between 6WT and 12WT. Genetic correlations of 3WT with 6WT, 9WT and 12WT were high and positive (0.94, 0.93 and 0.93, respectively), suggesting that genetic gain in post-3WT will be maintained if selection age is reduced to 3 months. The genetic correlations of GFW with live weights were 0.01, 0.16, 0.18, 0.40 and 0.32 for BWT, 3WT, 6WT, 9WT and 12WT, respectively. Correlations of permanent environmental effects of the dam across different traits were high and positive for all the traits (0.45 to 0.98). 相似文献
54.
Derek V. Banthorpe Clifford A. Bunton Osvaldo Cori Martin J.O. Francis 《Phytochemistry》1985,24(2):251-252
Biosynthesis of several mono- and sesqui-terpenes that possess E or Z double bonds, or which are generally considered to be derived from precursors possessing such geometries, involved loss of the pro-4S hydrogen of mevalonate in the construction of the double bond. These results confirm and extend previous observations. A recent claim to have newly discovered such a stereochemical correlation is rejected. 相似文献
55.
Wise MJ 《The New phytologist》2007,175(4):773-784
As part of a study of the ecological and evolutionary dynamics of herbivore resistance in Solanum carolinense (horsenettle), potential genetic constraints to the evolution of resistance to 11 of its most common herbivores were investigated. Leaf, flower, fruit, and stem herbivory were measured in a field experiment involving 24 ramets of each of 40 horsenettle genets. The experimental plant population contained significant genetic variation for resistance to all 11 species of herbivore. For only one species was there an indication of a genotype-by-environment interaction in the expression of resistance that might constrain its evolution. Genetic correlations in resistance to different species were common but not universal, with seven negative and 12 positive correlations out of the 55 pairwise species comparisons. Correlations were independent of plant part fed upon. The evolution of the resistance of horsenettle to most of its diverse community of herbivores does not appear to be prevented by a lack of genetic variation or by genotype-by-environment interactions in resistance. Negative genetic correlations in resistance to different herbivores may play a small role in slowing the evolution of resistance, but positive correlations may play at least as large a role in facilitating its evolution. 相似文献
56.
Allen MR 《Oecologia》2007,153(1):135-143
Habitat fragmentation poses an inherent problem for metacommunity dynamics, as dispersal among communities is hindered by
increasing isolation and the loss of patches. Wetlands are one such system that have undergone excessive destruction and fragmentation
in recent years. Zooplankton within these communities have historically been considered frequent and widespread dispersers,
but direct, quantitative measures of zooplankton dispersal are rare. In this study, I performed two experiments to quantify
zooplankton dispersal and to identify the primary dispersal vectors. I first set up an array of traps at 10, 30, 60, 120 and
180 m around an isolated pond to collect dispersing individuals. Nearly 1,500 adult zooplankton were captured in traps up
to 180 m from the pond, with approximately 60% of dispersers being captured in traps at 10 m from the pond. A second experiment
using open and animal-excluded traps suggested that large animals were the primary dispersal vector for these zooplankton.
Using a subset of these data, I fit four models to describe the shape and magnitude of adult cladoceran dispersal at this
site. All models showed the majority of cladocerans were deposited very close to the source pond, with three models suggesting
that the trapping area encompassed 67% or more of the dispersal distances. These results suggest that adult zooplankton movement
among ponds may be significant in areas where aquatic habitats are plentiful. Yet, in recent years climate change and anthropogenic
disturbances have reduced the number and size of aquatic habitats in many regions of the world, likely curtailing effective
transport of individuals in many cases. As a result, fragmented zooplankton metacommunities may experience increased dispersal
limitation, stronger priority effects, higher levels of inbreeding and selection against traits engendering high dispersability.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
57.
The conservation of Himalayan forests is big concern in view of global agenda. Many studies in this endeavor reported that
the rate of forests degradation is posing a severe threat to the landscape and existing biodiversity in the Himalayas. Currently
there many conservation approaches exists and of them four are widely recognized (1) Conservation through traditional religious
beliefs “traditional conserved forests” (TCF); (2) Conservation through governmental planning and schemes “government conserved
forests” (GCF); (3) Conservation through creation of protected areas (PAF); and (4) Conservation through community efforts
“community conserved forests” (CCF). Our hypothesis in this direction says that all the conservation approaches lead to same
results concerning to forest conservation. To testify our hypothesis we have studied the forests of each conservation regimes
and evaluated them based on the identified indicators. We have done empirical studies and following the cloud-free satellite
data were used for last three decades (such as Multi-Spectral Scanner, Linear Imaging and Self Scanning, and Enhanced Thematic
Mapper ) to study a change in vegetation dynamics of the mountain forests in multi-temporal dimension. Our research concluded
that community conservation approach have greater significance for biodiversity conservation and management in the Himalayan
region. Here we support the model of CCF for forest ecosystem conservation, alongside the sustainable livelihood of the mountain
societies. But every conservation regimes has its own importance in viewpoint of the particular objectives. Therefore, we
suggests advancement and revision of PAF and GCF however, some elements of CCF can be introduced in TCF for making up it more
sound in view of rapid socio-economic and cultural changes taking place in the communities.
An erratum to this article can be found at 相似文献
58.
A novel approach to the detection of synchronisation in EEG based on empirical mode decomposition 总被引:1,自引:0,他引:1
Transient neural assemblies mediated by synchrony in particular frequency ranges are thought to underlie cognition. We propose
a new approach to their detection, using empirical mode decomposition (EMD), a data-driven approach removing the need for
arbitrary bandpass filter cut-offs. Phase locking is sought between modes. We explore the features of EMD, including making
a quantitative assessment of its ability to preserve phase content of signals, and proceed to develop a statistical framework
with which to assess synchrony episodes. Furthermore, we propose a new approach to ensure signal decomposition using EMD.
We adapt the Hilbert spectrum to a time-frequency representation of phase locking and are able to locate synchrony successfully
in time and frequency between synthetic signals reminiscent of EEG. We compare our approach, which we call EMD phase locking
analysis (EMDPL) with existing methods and show it to offer improved time-frequency localisation of synchrony.
Action Editor: Carson C. Chow 相似文献
59.
Alice Brambilla Iris Biebach Bruno Bassano Giuseppe Bogliani Achaz von Hardenberg 《Proceedings. Biological sciences / The Royal Society》2015,282(1798)
Heterozygosity–fitness correlations (HFCs) are a useful tool to investigate the effects of inbreeding in wild populations, but are not informative in distinguishing between direct and indirect effects of heterozygosity on fitness-related traits. We tested HFCs in male Alpine ibex (Capra ibex) in a free-ranging population (which suffered a severe bottleneck at the end of the eighteenth century) and used confirmatory path analysis to disentangle the causal relationships between heterozygosity and fitness-related traits. We tested HFCs in 149 male individuals born between 1985 and 2009. We found that standardized multi-locus heterozygosity (MLH), calculated from 37 microsatellite loci, was related to body mass and horn growth, which are known to be important fitness-related traits, and to faecal egg counts (FECs) of nematode eggs, a proxy of parasite resistance. Then, using confirmatory path analysis, we were able to show that the effect of MLH on horn growth was not direct but mediated by body mass and FEC. HFCs do not necessarily imply direct genetic effects on fitness-related traits, which instead can be mediated by other traits in complex and unexpected ways. 相似文献
60.
Multicollinearity in spatial genetics: separating the wheat from the chaff using commonality analyses
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Direct gradient analyses in spatial genetics provide unique opportunities to describe the inherent complexity of genetic variation in wildlife species and are the object of many methodological developments. However, multicollinearity among explanatory variables is a systemic issue in multivariate regression analyses and is likely to cause serious difficulties in properly interpreting results of direct gradient analyses, with the risk of erroneous conclusions, misdirected research and inefficient or counterproductive conservation measures. Using simulated data sets along with linear and logistic regressions on distance matrices, we illustrate how commonality analysis (CA), a detailed variance‐partitioning procedure that was recently introduced in the field of ecology, can be used to deal with nonindependence among spatial predictors. By decomposing model fit indices into unique and common (or shared) variance components, CA allows identifying the location and magnitude of multicollinearity, revealing spurious correlations and thus thoroughly improving the interpretation of multivariate regressions. Despite a few inherent limitations, especially in the case of resistance model optimization, this review highlights the great potential of CA to account for complex multicollinearity patterns in spatial genetics and identifies future applications and lines of research. We strongly urge spatial geneticists to systematically investigate commonalities when performing direct gradient analyses. 相似文献