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   446篇
  免费   28篇
  474篇
  2022年   2篇
  2021年   1篇
  2019年   10篇
  2018年   5篇
  2017年   4篇
  2016年   7篇
  2015年   22篇
  2014年   19篇
  2013年   29篇
  2012年   20篇
  2011年   19篇
  2010年   30篇
  2009年   27篇
  2008年   19篇
  2007年   17篇
  2006年   23篇
  2005年   20篇
  2004年   15篇
  2003年   9篇
  2002年   8篇
  2001年   8篇
  2000年   11篇
  1999年   10篇
  1998年   12篇
  1997年   13篇
  1996年   8篇
  1995年   8篇
  1994年   3篇
  1993年   11篇
  1992年   3篇
  1991年   8篇
  1990年   3篇
  1989年   3篇
  1988年   8篇
  1987年   2篇
  1986年   3篇
  1985年   5篇
  1984年   4篇
  1983年   3篇
  1982年   17篇
  1981年   4篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1977年   6篇
  1976年   3篇
  1975年   3篇
  1972年   1篇
  1971年   1篇
  1921年   1篇
排序方式: 共有474条查询结果,搜索用时 15 毫秒
1.
The Aspergillus nidulans endoxylanase X24 and the Aspergillus oryzae (alpha)-amylase cDNAs were placed under the control of the Saccharomyces cerevisiae actin promoter (pACT1) and introduced into baker's yeast. Bread made with transformants expressing both enzymes (YEpACT-AMY-ACT-X24) showed a 30% increase in volume and reduced firmness in comparison with that produced with a commercial strain. Endoxylanase X24 and (alpha)-amylase seem to act synergistically to improve the quality of bread in terms of volume and density.  相似文献   
2.
3.
4.
Movement is a trait of fundamental importance in ecosystems subject to frequent disturbances, such as fire‐prone ecosystems. Despite this, the role of movement in facilitating responses to fire has received little attention. Herein, we consider how animal movement interacts with fire history to shape species distributions. We consider how fire affects movement between habitat patches of differing fire histories that occur across a range of spatial and temporal scales, from daily foraging bouts to infrequent dispersal events, and annual migrations. We review animal movements in response to the immediate and abrupt impacts of fire, and the longer‐term successional changes that fires set in train. We discuss how the novel threats of altered fire regimes, landscape fragmentation, and invasive species result in suboptimal movements that drive populations downwards. We then outline the types of data needed to study animal movements in relation to fire and novel threats, to hasten the integration of movement ecology and fire ecology. We conclude by outlining a research agenda for the integration of movement ecology and fire ecology by identifying key research questions that emerge from our synthesis of animal movements in fire‐prone ecosystems.  相似文献   
5.
6.
The transposon Mutator was first identified in maize, and is one of the most active mobile elements in plants. The Arabidopsis thaliana genome contains at least 200 Mutator-like elements (MULEs), which contain the Mutator-like transposase gene, and often additional genes. We have detected a novel type of MULEs in melon (CUMULE), which, besides the transposase, contains two ubiquitin-like specific protease-like sequences (ULP1). This element is not present in the observed location in some melon cultivars. Multiple copies of this element exist in the Cucumis melo genome, and it has been detected in other Cucurbitaceae species. Analysis of the A. thaliana genome revealed more than 90 CUMULE-like elements, containing one or two Ulp1-like sequences, although no evidence of mobility exists for these elements. We detected various putative transposable elements containing ULP1-like sequences in rice. The discovery of these MULEs in melon and Arabidopsis, and the existence of similar elements in rice and maize, suggest that a proteolytic function may be important for this subset of the MULE transposable elements. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. Nucleotide sequence data reported are available in the GenBank database under the accession number AY524004.  相似文献   
7.
The Cape Gannet Morus capensis is one of several seabird species endemic to the Benguela upwelling ecosystem (BUS) but whose population has recently decreased, leading to an unfavourable IUCN Red List assessment. Application of ‘JARA’ (‘Just Another Red-List Assessment,’ a Bayesian state-space tool used for IUCN Red List assessments) to updated information on the areas occupied by Cape Gannets and the nest densities of breeding birds at their six colonies, suggested that the species should be classified as Vulnerable. However, the rate of decrease of Cape Gannets in their most-recent generation exceeded that of the previous generation, primarily as a result of large decreases at Bird Island, Lambert’s Bay, and Malgas Island, off South Africa’s west coast (the western part of their range). Since the 1960s, there has been an ongoing redistribution of the species from northwest to southeast around southern Africa, and ~70% of the population now occurs on the south coast of South Africa, at Bird Island in Algoa Bay, on the eastern border of the BUS. Recruitment rather than adult survival may be limiting the present population; however, information on the seabird’s demographic parameters and mortality in fisheries is lacking for colonies in the northern part of the BUS. Presently, major threats to Cape Gannet include: substantially decreased availability of their preferred prey in the west; heavy mortalities of eggs, chicks and fledglings at and around colonies, inflicted by Cape Fur Seals Arctocephalus pusillus and other seabirds; substantial disturbance at colonies caused by Cape Fur Seals attacking adult gannets ashore; oiling; and disease.  相似文献   
8.
9.
10.
The signal produced by fluorescence in situ hybridization (FISH) often is inconsistent among cells and sensitivity is low. Small DNA targets on the chromatin are difficult to detect. We report here an improved nick translation procedure for Texas red and Alexa Fluor 488 direct labeling of FISH probes. Brighter probes can be obtained by adding excess DNA polymerase I. Using such probes, a 30 kb yeast transgene, and the rp1, rp3 and zein multigene clusters were clearly detected.  相似文献   
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