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   10542篇
  免费   978篇
  国内免费   5篇
  2023年   89篇
  2022年   204篇
  2021年   371篇
  2020年   207篇
  2019年   271篇
  2018年   291篇
  2017年   232篇
  2016年   398篇
  2015年   705篇
  2014年   722篇
  2013年   729篇
  2012年   1023篇
  2011年   937篇
  2010年   518篇
  2009年   384篇
  2008年   545篇
  2007年   573篇
  2006年   451篇
  2005年   411篇
  2004年   405篇
  2003年   317篇
  2002年   299篇
  2001年   59篇
  2000年   50篇
  1999年   52篇
  1998年   77篇
  1997年   37篇
  1996年   38篇
  1995年   30篇
  1994年   31篇
  1993年   34篇
  1992年   48篇
  1991年   40篇
  1990年   41篇
  1989年   32篇
  1988年   29篇
  1987年   30篇
  1985年   43篇
  1984年   41篇
  1983年   38篇
  1982年   36篇
  1981年   32篇
  1980年   37篇
  1979年   28篇
  1978年   44篇
  1977年   35篇
  1976年   38篇
  1975年   31篇
  1974年   40篇
  1973年   28篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
941.
Specimens of Starksia were collected throughout the western Atlantic, and a 650-bp portion of the mitochondrial gene cytochrome oxidase-c subunit I (COl) was sequenced as part of a re-analysis of species diversity of western Central Atlantic shorefishes. A neighbor-joining tree constructed from the sequence data suggests the existence of several cryptic species. Voucher specimens from each genetically distinct lineage and color photographs of vouchers taken prior to dissection and preservation were examined for diagnostic morphological characters. The results suggest that Starksia atlantica, Starksia lepicoelia, and Starksia sluiteri are species complexes, and each comprises three or more species. Seven new species are described. DNA data usually support morphological features, but some incongruence between genetic and morphological data exists. Genetic lineages are only recognized as species if supported by morphology. Genetic lineages within western Atlantic Starksia generally correspond to geography, such that members of each species complex have a very restricted geographical distribution. Increasing geographical coverage of sampling locations will almost certainly increase the number of Starksia species and species complexes recognized in the western Atlantic. Combining molecular and morphological investigations is bringing clarity to the taxonomy of many genera of morphologically similar fishes and increasing the number of currently recognized species. Future phylogenetic studies should help resolve species relationships and shed light on patterns of speciation in western Atlantic Starksia.  相似文献   
942.
A new method based on a mathematically natural local search framework for max cut is developed to uncover functionally coherent module and BPM motifs in high-throughput genetic interaction data. Unlike previous methods, which also consider physical protein-protein interaction data, our method utilizes genetic interaction data only; this becomes increasingly important as high-throughput genetic interaction data is becoming available in settings where less is known about physical interaction data. We compare modules and BPMs obtained to previous methods and across different datasets. Despite needing no physical interaction information, the BPMs produced by our method are competitive with previous methods. Biological findings include a suggested global role for the prefoldin complex and a SWR subcomplex in pathway buffering in the budding yeast interactome.  相似文献   
943.
The endoglucanase (E1) from Acidothermus cellulolyticus has been used extensively in cellulase research. The goal of this work was to produce high levels of this enzyme in a system that facilitates purification. A codon-optimized synthetic gene for A. cellulolyticus E1 with a C-terminal histidine tag was cloned into the genome of Pichia pastoris. Strain KM71H expressed the most enzyme, with a yield of 550mg/L culture supernatant. The temperature optimum (80°C) and pH optimum (5.1) of the purified enzyme agree with previously determined values for the enzyme produced in other systems. Michaelis-Menten kinetic parameters were determined, using a fluorescent substrate (methylumbelliferyl-β-d-cellobioside) at various temperatures. This thermostable enzyme can be used in future cellulosic biofuels-related research.  相似文献   
944.
945.
MOTIVATION: Business Architecture Models (BAMs) describe what a business does, who performs the activities, where and when activities are performed, how activities are accomplished and which data are present. The purpose of a BAM is to provide a common resource for understanding business functions and requirements and to guide software development. The cancer Biomedical Informatics Grid (caBIG?) Life Science BAM (LS BAM) provides a shared understanding of the vocabulary, goals and processes that are common in the business of LS research. RESULTS: LS BAM 1.1 includes 90 goals and 61 people and groups within Use Case and Activity Unified Modeling Language (UML) Diagrams. Here we report on the model's current release, LS BAM 1.1, its utility and usage, and plans for future use and continuing development for future releases. Availability and Implementation: The LS BAM is freely available as UML, PDF and HTML (https://wiki.nci.nih.gov/x/OFNyAQ).  相似文献   
946.
947.
948.
A paralog (here termed COG0212) of the ATP-dependent folate salvage enzyme 5-formyltetrahydrofolate cycloligase (5-FCL) occurs in all domains of life and, although typically annotated as 5-FCL in pro- and eukaryotic genomes, is of unknown function. COG0212 is similar in overall structure to 5-FCL, particularly in the substrate binding region, and has distant similarity to other kinases. The Arabidopsis thaliana COG0212 protein was shown to be targeted to chloroplasts and to be required for embryo viability. Comparative genomic analysis revealed that a high proportion (19%) of archaeal and bacterial COG0212 genes are clustered on the chromosome with various genes implicated in thiamin metabolism or transport but showed no such association between COG0212 and folate metabolism. Consistent with the bioinformatic evidence for a role in thiamin metabolism, ablating COG0212 in the archaeon Haloferax volcanii caused accumulation of thiamin monophosphate. Biochemical and functional complementation tests of several known and hypothetical thiamin-related activities (involving thiamin, its breakdown products, and their phosphates) were, however, negative. Also consistent with the bioinformatic evidence, the COG0212 proteins from A. thaliana and prokaryote sources lacked 5-FCL activity in vitro and did not complement the growth defect or the characteristic 5-formyltetrahydrofolate accumulation of a 5-FCL-deficient (ΔygfA) Escherichia coli strain. We therefore propose (a) that COG0212 has an unrecognized yet sometimes crucial role in thiamin metabolism, most probably in salvage or detoxification, and (b) that is not a 5-FCL and should no longer be so annotated.  相似文献   
949.
We report the development and optimization of reagents for in-solution, hybridization-based capture of the mouse exome. By validating this approach in a multiple inbred strains and in novel mutant strains, we show that whole exome sequencing is a robust approach for discovery of putative mutations, irrespective of strain background. We found strong candidate mutations for the majority of mutant exomes sequenced, including new models of orofacial clefting, urogenital dysmorphology, kyphosis and autoimmune hepatitis.  相似文献   
950.
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