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81.
Lisha A. Mathew Paul R. Staab Laura E. Rose Dirk Metzler 《Ecology and evolution》2013,3(11):3647-3662
With the advent of next‐generation sequencing technologies, large data sets of several thousand loci from multiple conspecific individuals are available. Such data sets should make it possible to obtain accurate estimates of population genetic parameters, even for complex models of population history. In the analyses of large data sets, it is difficult to consider finite‐sites mutation models (FSMs). Here, we use extensive simulations to demonstrate that the inclusion of FSMs is necessary to avoid severe biases in the estimation of the population mutation rate θ, population divergence times, and migration rates. We present a new version of Jaatha, an efficient composite‐likelihood method for estimating demographic parameters from population genetic data and evaluate the usefulness of Jaatha in two biological examples. For the first application, we infer the speciation process of two wild tomato species, Solanum chilense and Solanum peruvianum. In our second application example, we demonstrate that Jaatha is readily applicable to NGS data by analyzing genome‐wide data from two southern European populations of Arabidopsis thaliana. Jaatha is now freely available as an R package from the Comprehensive R Archive Network (CRAN). 相似文献
82.
83.
Svetec N Werzner A Wilches R Pavlidis P Alvarez-Castro JM Broman KW Metzler D Stephan W 《Molecular ecology》2011,20(3):530-544
Drosophila melanogaster is a cosmopolitan species that colonizes a great variety of environments. One trait that shows abundant evidence for naturally segregating genetic variance in different populations of D. melanogaster is cold tolerance. Previous work has found quantitative trait loci (QTL) exclusively on the second and the third chromosomes. To gain insight into the genetic architecture of cold tolerance on the X chromosome and to compare the results with our analyses of selective sweeps, a mapping population was derived from a cross between substitution lines that solely differed in the origin of their X chromosome: one originates from a European inbred line and the other one from an African inbred line. We found a total of six QTL for cold tolerance factors on the X chromosome of D. melanogaster. Although the composite interval mapping revealed slightly different QTL profiles between sexes, a coherent model suggests that most QTL overlapped between sexes, and each explained around 5–14% of the genetic variance (which may be slightly overestimated). The allelic effects were largely additive, but we also detected two significant interactions. Taken together, this provides evidence for multiple QTL that are spread along the entire X chromosome and whose effects range from low to intermediate. One detected transgressive QTL influences cold tolerance in different ways for the two sexes. While females benefit from the European allele increasing their cold tolerance, males tend to do better with the African allele. Finally, using selective sweep mapping, the candidate gene CG16700 for cold tolerance colocalizing with a QTL was identified. 相似文献
84.
Dirk Metzler 《Journal of computational biology》2006,13(4):882-896
We examine a Poisson heuristic for judging the significance of local sequence alignments with gaps. Model parameters are estimated directly from the sequences to be aligned, so that laborious prior simulation studies or database comparisons for the estimation of parameters describing the connection between score and E-value are unnecessary. Simulation studies give evidence that this method gives reasonable results even when the usual assumptions like the independence of sequence positions are violated. 相似文献
85.
Hanns Hubert Leuschner Andreas Bauerochse Alf Metzler 《Vegetation History and Archaeobotany》2007,16(2-3):183-195
This paper presents a detailed dendroecological analysis of remains from a sub-fossil pine forest at the Campemoor in the
Dümmer basin, NW Germany and of pine timbers from a contemporaneous Neolithic trackway Pr 32 through the Campemoor. Changes
in growth pattern and population dynamics of the pines are discussed in context with the time of construction of the trackway.
The findings date to the period around 3000 b.c. Together with palaeobotanical investigations (pollen and macro remains) and the archaeological results (trackway) the dendroecological
analysis mirrors environmental changes and the response of people to these changes. In order to test this local development
for a possible climate background, ring-width variability and population dynamics of the Campemoor pines and of the overall
data set of Lower Saxonian sub-fossil oaks from bogs have been compared. The results of these investigations clearly indicate
a common widespread turn from drier to more humid climate conditions as trigger for the transition period, initiating the
raised bog growth. It happened in two phases at the beginning of the 3rd millennium, interrupted by a drier period between
2825 and 2770 b.c. Afterwards large areas of former settlement sites within today's Campemoor became inaccessible and were covered by raised
bog. 相似文献
86.
Bernhard Metzler Johannes Jehle Igor Theurl Susanne Ludwiczek Peter Obrist Otmar Pachinger Günter Weiss 《Biometals》2007,20(2):205-215
The role of iron in the pathogenesis of cardio-vascular disorders is still controversial. We studied the effects of iron perturbations
on myocardial injury upon temporary ischemia/reperfusion. C57BL/6J male mice were injected with iron dextran for 2 weeks while
controls received saline. Mice were then subjected to 30 min of myocardial ischemia and subsequent reperfusion for 6–24 h.
Tissue damage was quantified histologically and by troponin T determination. The expressions of tumor necrosis factor-α (TNF-α),
superoxide dismutase (SOD) and inducible nitric oxide synthase (iNOS) were investigated in non-ischemic and ischemic regions
of both groups. After myocardial ischemia and reperfusion, troponin T levels, as a marker of myocardial damage, were significantly
reduced in iron-treated mice as compared to control mice (P < 0.05). Under the same conditions the infarction area and damage score were significantly lower in iron-treated animals.
In parallel, TNF-α and SOD expressions were increased in infarcted regions of iron-treated mice as compared to controls, whereas
myocardial iNOS expression was significantly lower in iron-treated mice. Although, iron challenge increased radical formation
and TNF-α expression in vivo, this did not result in myocardial damage which may be linked to the parallel induction of SOD. Importantly, iron treatment
inhibited iNOS expression. Since, an increased nitric oxide (NO) formation has been linked to cardiac damage after acute myocardial
infarction, iron may exert short time cardio-protective effects after induction of ischemia/reperfusion via decreasing iNOS
formation.
Both authors contributed equally to this work. 相似文献
87.
88.
Khatchadourian K Smith CE Metzler M Gregory M Hayden MR Cyr DG Hermo L 《Molecular reproduction and development》2007,74(3):341-359
Huntingtin interacting protein 1 (HIP1) is an endocytic adaptor protein with clathrin assembly activity that binds to cytoplasmic proteins, such as F-actin, tubulin, and huntingtin (htt). To gain insight into diverse functions of HIP1, we characterized the male reproductive defect of HIP1(-/-) mice from 7 to 30 weeks of age. High levels of HIP1 protein were expressed in the testis of wild-type mice as seen by Western blots and as a reaction over Sertoli cells and elongating spermatids as visualized by immunocytochemistry. Accordingly, major structural abnormalities were evident in HIP1(-/-) mice with vacuolation of seminiferous tubules caused by an apparent loss of postmeiotic spermatids and a significant reduction in mean profile area. Remaining spermatids revealed deformations of their heads, flagella, and/or acrosomes. In some Sertoli cells, ectoplasmic specializations (ES) were absent or altered in appearance accounting for the presence of spherical germ cells in the epididymal lumen. Quantitative analyses of sperm counts from the cauda epididymidis demonstrated a significant decrease in HIP1(-/-) mice compared to wild-type littermates. In addition, computer-assisted sperm analyses indicated that velocities, amplitude of lateral head displacements (ALH), and numbers and percentages of sperm in the motile, rapid, and progressive categories were all significantly reduced in HIP1(-/-) mice, while the numbers and percentages of sperm in the static category were greatly increased. Taken together, these various abnormalities corroborate reduced fertility levels in HIP1(-/-) mice and suggest a role for HIP1 in stabilizing actin and microtubules, which are important cytoskeletal elements enabling normal spermatid and Sertoli cell morphology and function. 相似文献
89.
Background
Obtaining an accurate sequence alignment is fundamental for consistently analyzing biological data. Although this problem may be efficiently solved when only two sequences are considered, the exact inference of the optimal alignment easily gets computationally intractable for the multiple sequence alignment case. To cope with the high computational expenses, approximate heuristic methods have been proposed that address the problem indirectly by progressively aligning the sequences in pairs according to their relatedness. These methods however are not flexible to change the alignment of an already aligned group of sequences in the view of new data, resulting thus in compromises on the quality of the deriving alignment. In this paper we present ReformAlign, a novel meta-alignment approach that may significantly improve on the quality of the deriving alignments from popular aligners. We call ReformAlign a meta-aligner as it requires an initial alignment, for which a variety of alignment programs can be used. The main idea behind ReformAlign is quite straightforward: at first, an existing alignment is used to construct a standard profile which summarizes the initial alignment and then all sequences are individually re-aligned against the formed profile. From each sequence-profile comparison, the alignment of each sequence against the profile is recorded and the final alignment is indirectly inferred by merging all the individual sub-alignments into a unified set. The employment of ReformAlign may often result in alignments which are significantly more accurate than the starting alignments.Results
We evaluated the effect of ReformAlign on the generated alignments from ten leading alignment methods using real data of variable size and sequence identity. The experimental results suggest that the proposed meta-aligner approach may often lead to statistically significant more accurate alignments. Furthermore, we show that ReformAlign results in more substantial improvement in cases where the starting alignment is of relatively inferior quality or when the input sequences are harder to align.Conclusions
The proposed profile-based meta-alignment approach seems to be a promising and computationally efficient method that can be combined with practically all popular alignment methods and may lead to significant improvements in the generated alignments.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2105-15-265) contains supplementary material, which is available to authorized users. 相似文献90.