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   453篇
  免费   2篇
  国内免费   2篇
系统科学   13篇
丛书文集   1篇
理论与方法论   15篇
现状及发展   80篇
研究方法   64篇
综合类   264篇
自然研究   20篇
  2021年   4篇
  2018年   3篇
  2017年   4篇
  2016年   6篇
  2015年   5篇
  2014年   3篇
  2013年   8篇
  2012年   32篇
  2011年   49篇
  2010年   18篇
  2009年   4篇
  2008年   39篇
  2007年   44篇
  2006年   31篇
  2005年   29篇
  2004年   23篇
  2003年   36篇
  2002年   24篇
  2001年   6篇
  2000年   6篇
  1999年   2篇
  1997年   1篇
  1996年   2篇
  1994年   3篇
  1992年   1篇
  1991年   4篇
  1990年   4篇
  1989年   7篇
  1988年   4篇
  1987年   2篇
  1986年   3篇
  1985年   2篇
  1979年   2篇
  1978年   2篇
  1977年   6篇
  1976年   2篇
  1975年   5篇
  1974年   6篇
  1973年   2篇
  1972年   2篇
  1971年   2篇
  1970年   2篇
  1968年   1篇
  1967年   3篇
  1966年   1篇
  1962年   3篇
  1961年   1篇
  1960年   1篇
  1955年   1篇
  1948年   2篇
排序方式: 共有457条查询结果,搜索用时 31 毫秒
261.
Parallel domestication of the Shattering1 genes in cereals   总被引:3,自引:0,他引:3  
  相似文献   
262.
Following homozygosity mapping in a single kindred, we identified nonsense and missense mutations in MYO5B, encoding type Vb myosin motor protein, in individuals with microvillus inclusion disease (MVID). MVID is characterized by lack of microvilli on the surface of enterocytes and occurrence of intracellular vacuolar structures containing microvilli. In addition, mislocalization of transferrin receptor in MVID enterocytes suggests that MYO5B deficiency causes defective trafficking of apical and basolateral proteins in MVID.  相似文献   
263.
Focal dermal hypoplasia (FDH) is an X-linked dominant multisystem birth defect affecting tissues of ectodermal and mesodermal origin. Using a stepwise approach of (i) genetic mapping of FDH, (ii) high-resolution comparative genome hybridization to seek deletions in candidate chromosome areas and (iii) point mutation analysis in candidate genes, we identified PORCN, encoding a putative O-acyltransferase and potentially crucial for cellular export of Wnt signaling proteins, as the gene mutated in FDH. The findings implicate FDH as a developmental disorder caused by a deficiency in PORCN.  相似文献   
264.
Familial clustering studies indicate that breast cancer risk has a substantial genetic component. To identify new breast cancer risk variants, we genotyped approximately 300,000 SNPs in 1,600 Icelandic individuals with breast cancer and 11,563 controls using the Illumina Hap300 platform. We then tested selected SNPs in five replication sample sets. Overall, we studied 4,554 affected individuals and 17,577 controls. Two SNPs consistently associated with breast cancer: approximately 25% of individuals of European descent are homozygous for allele A of rs13387042 on chromosome 2q35 and have an estimated 1.44-fold greater risk than noncarriers, and for allele T of rs3803662 on 16q12, about 7% are homozygous and have a 1.64-fold greater risk. Risk from both alleles was confined to estrogen receptor-positive tumors. At present, no genes have been identified in the linkage disequilibrium block containing rs13387042. rs3803662 is near the 5' end of TNRC9 , a high mobility group chromatin-associated protein whose expression is implicated in breast cancer metastasis to bone.  相似文献   
265.
266.
Pervasive and systemic barriers to collaborative university-community research make such studies highly challenging. Yet the necessity of participative research means that feasible ways to conduct high quality collaborative investigations must be sought. In a longitudinal action research study investigating adult literacy, issues facing community and academic researchers centred upon focus and integrity. Differing researchers defined focus and integrity in sharply varying ways, so that terminology employed within the programme formed contested sites of meaning and interpretation. This meant that ideas of research integrity held very different connotations for different actors. Yet the viability of the programme depended on both academics and community people attempting to expand their horizons by understanding and taking into account others’ perceptions.
Frank SligoEmail:
  相似文献   
267.
Community-based service learning helps students link subject matter to everyday life and developing sense of responsibility to their community. Corporate social responsibility (CSR) is a form of corporate self-regulation integrated into a business model. Both promote civic engagement but the two hardly come across each other. We explore the process that enriched service learning with its diversity by combining CSR practices of a multinational software company. It begins by exploring different forms of action research with a focus on action engagement to improve students’ involvement in marginalized communities. The article provides field-based reflections of the sustained engagement and suggests ways in which service learning experiences may create rooms for innovation and growth in the non-profit sector, local communities, businesses, and students themselves.  相似文献   
268.
Exposing the human nude phenotype   总被引:8,自引:0,他引:8  
  相似文献   
269.
Current views of the visual system assume that the primate brain analyses form and motion along largely independent pathways; they provide no insight into why form is sometimes interpreted as motion. In a series of psychophysical and electrophysiological experiments in humans and macaques, here we show that some form information is processed in the prototypical motion areas of the superior temporal sulcus (STS). First, we show that STS cells respond to dynamic Glass patterns, which contain no coherent motion but suggest a path of motion. Second, we show that when motion signals conflict with form signals suggesting a different path of motion, both humans and monkeys perceive motion in a compromised direction. This compromise also has a correlate in the responses of STS cells, which alter their direction preferences in the presence of conflicting implied motion information. We conclude that cells in the prototypical motion areas in the dorsal visual cortex process form that implies motion. Estimating motion by combining motion cues with form cues may be a strategy to deal with the complexities of motion perception in our natural environment.  相似文献   
270.
Molecular replacement procedures, which search for placements of a starting model within the crystallographic unit cell that best account for the measured diffraction amplitudes, followed by automatic chain tracing methods, have allowed the rapid solution of large numbers of protein crystal structures. Despite extensive work, molecular replacement or the subsequent rebuilding usually fail with more divergent starting models based on remote homologues with less than 30% sequence identity. Here we show that this limitation can be substantially reduced by combining algorithms for protein structure modelling with those developed for crystallographic structure determination. An approach integrating Rosetta structure modelling with Autobuild chain tracing yielded high-resolution structures for 8 of 13 X-ray diffraction data sets that could not be solved in the laboratories of expert crystallographers and that remained unsolved after application of an extensive array of alternative approaches. We estimate that the new method should allow rapid structure determination without experimental phase information for over half the cases where current methods fail, given diffraction data sets of better than 3.2?? resolution, four or fewer copies in the asymmetric unit, and the availability of structures of homologous proteins with >20% sequence identity.  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