首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   68篇
  免费   7篇
  2023年   1篇
  2022年   2篇
  2021年   3篇
  2020年   1篇
  2019年   2篇
  2018年   3篇
  2017年   4篇
  2016年   2篇
  2015年   2篇
  2014年   5篇
  2013年   10篇
  2012年   8篇
  2011年   6篇
  2010年   1篇
  2009年   2篇
  2008年   5篇
  2007年   4篇
  2006年   3篇
  2005年   3篇
  2004年   1篇
  2003年   2篇
  2002年   3篇
  2001年   1篇
  1998年   1篇
排序方式: 共有75条查询结果,搜索用时 62 毫秒
31.
32.
The aim of this work was to analyze the magnitude of inherent errors associated with the fixed-frame counting method for corneal endothelial cell density (ECD) measurements. This technique is common among most eye banks worldwide. Three types of mosaics were used: regular and irregular tessellated mosaics (eight increasing densities ranging from 800 to 3,600 cells/mm2 by steps of 400 cells/mm2) generated by a computer, and real mosaics (four specimens) obtained from human corneal endothelium flat mounted and stained with Alizarin red. On the three mosaics, the fixed-frame counting method was applied using a computer program. The ECD was calculated for 3,000 successive random positions from calibrated grids which area ranged from 50 × 50 to 300 × 300 μm2 (incremental steps of 25 μm). For each grid, the ECD was expressed either as a single count, a mean of five or a mean of 10 measures. The fixed-frame count was constantly associated with an inherent variability but repeatability increased with larger grid size and ECD. The mean calculated out of 10 measures was the most reliable, but still, we noted ±5 % of residual variability from the real ECD. The 100 × 100 μm2 grid manual counts, performed in many eye banks, should be abandoned and upgraded to at least 200 × 200 μm2 grid counts. Digital image analysis with a variable frame counting method would be the best alternative.  相似文献   
33.
34.
The current existing enzymes have been identified from cultivable micro-organisms, most frequently from bacteria. These bacterial biocatalytic capabilities have been widely used for biotransformations, resulting in the development of profitable industrial bioprocesses in the fields of feed and food processing, textiles, agro-chemistry, cosmetics, pharmaceuticals and fine chemistry. However, the originality of this bioresource is progressively drying up, while requests from industry for novel biocatalytic activities are increasing in the face of economic and environmental pressure. Metagenomics, through access to the huge reservoir of uncultivated bacteria which represents the majority of the present biodiversity, opens the door to new industrial sources of enzymes. Surmounting hurdles encountered with this technology (e.g. DNA extraction to obtain high quality DNA libraries with proper statistical representativity, setting up of relevant high throughput screenings assays, combining functional and genome-based identifications), gives unique opportunities to access novel biocatalysts that better fit with the required industrial specifications, thus providing new biocatalysis tool boxes.  相似文献   
35.
Considering the increasing development of three dimensional (3D) imaging, the 3D assessment of the acetabular coverage is to become the most interesting tool for the detection of acetabular pathologies. Biplanar X-rays based methods allow a 3D reconstruction of the hip with a reduced radiation dose. This study proposes a 3D assessment method of the acetabular coverage from biplanar X-rays or from an anteroposterior X-ray (conventional clinical imaging). An in vitro evaluation of the method was performed on six hip joints in comparison with computed tomography. The global coverage, the local coverage and the acetabular rim orientation were estimated in 3D. The mean global acetabular coverage was 40% with an estimated mean accuracy of 1.3% for the biplanar X-rays based method. This study evaluated a 3D assessment method of the acetabular coverage from biplanar X-rays or anteroposterior X-ray and open the way for clinical in vivo applications.  相似文献   
36.
Zhou B  Latouche A  Rocha V  Fine J 《Biometrics》2011,67(2):661-670
For competing risks data, the Fine-Gray proportional hazards model for subdistribution has gained popularity for its convenience in directly assessing the effect of covariates on the cumulative incidence function. However, in many important applications, proportional hazards may not be satisfied, including multicenter clinical trials, where the baseline subdistribution hazards may not be common due to varying patient populations. In this article, we consider a stratified competing risks regression, to allow the baseline hazard to vary across levels of the stratification covariate. According to the relative size of the number of strata and strata sizes, two stratification regimes are considered. Using partial likelihood and weighting techniques, we obtain consistent estimators of regression parameters. The corresponding asymptotic properties and resulting inferences are provided for the two regimes separately. Data from a breast cancer clinical trial and from a bone marrow transplantation registry illustrate the potential utility of the stratified Fine-Gray model.  相似文献   
37.
ABSTRACT: BACKGROUND: Seqcrawler takes its roots in software like SRS or Lucegene. It provides an indexing platform to ease the search of data and meta-data in biological banks and it can scale to face the current flow of data. While many biological bank search tools are available on the Internet, mainly provided by large organizations to search in their data, there is a lack of free and open source solution to browse one own set of data with a flexible query system and able to scale from single computer to a cloud system. A personal index platform will help labs and bioinformaticians to search in their meta-data but also to build a larger information system with custom subsets of data. RESULTS: The software is scalable from a single computer to a cloud-based infrastructure. It has been successfully tested in a private cloud with 3 index shards (piece of index) hosting ~400 millions of sequence information (whole GenBank, UniProt, PDB and others) for a total size of 600 GB in a fault tolerant architecture (high-availability). It has also been successfully integrated with software to add extra meta-data from blast results to enhance user's result analysis. CONCLUSIONS: Seqcrawler provides a complete open source search and store solution for labs or platforms needing to manage large amount of data/meta-data with a flexible and customizable web interface. All components (search engine, visualization and data storage), though independent, share a common and coherent data system that can be queried with a simple HTTP interface. The solution scales easily and can also provide a high availability infrastructure.  相似文献   
38.
A crèche is an aggregation of chicks outside nesting territories, within chicks continue to be fed only by their own parents. Several adaptive functions of crèching have been proposed, the most frequent being a reduction in predator pressure. Using an evolutionary stable strategy approach based on the computation of individuals' fecundity, we examined which regime of aerial and terrestrial predation is likely to favour the evolution and stability of the crèching strategy (CS) in gulls. Our results confirm the hypothesis that habitat instability associated with high levels of terrestrial predation favours the evolution and maintenance of crèching behaviour. Moreover, our results suggest that a low aggressiveness against predators may be a pre-adaptation to a CS. In contrast, the high synchronisation often observed in crèching species does not favour the evolution of a crèching behaviour and is thus probably under selection pressures different from those modelled here.  相似文献   
39.
Dioscorea sansibarensis is a monocot species of inedible yam native of tropical Africa and Madagascar. Leaves of D. sansibarensis feature prominent acumen glands that are densely colonized by bacteria. We describe here the isolation and characterization of bacteria from leaf glands of D. sansibarensis specimens obtained from various botanical gardens. Phylogenetic and phenotypic characterizations indicate that the isolates belong to a novel genus and species of the Alcaligenaceae family for which we propose the name Orrella dioscoreae gen. nov. sp. nov., with type strain LMG 29303T [=CIP 111009T]. Strains isolated from different plants show limited phylogenetic and phenotypic diversity, indicating specific and tight association of the bacteria with the host plant. The analysis of the draft genome of strain LMG 29303T reveals features consistent with a recently evolved plant-associated lifestyle.  相似文献   
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号