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   127篇
  免费   0篇
系统科学   1篇
现状及发展   18篇
研究方法   30篇
综合类   68篇
自然研究   10篇
  2020年   1篇
  2016年   3篇
  2014年   1篇
  2013年   1篇
  2012年   13篇
  2011年   21篇
  2010年   3篇
  2009年   2篇
  2008年   4篇
  2007年   13篇
  2006年   12篇
  2005年   5篇
  2004年   4篇
  2003年   5篇
  2002年   2篇
  2000年   1篇
  1992年   1篇
  1991年   3篇
  1990年   3篇
  1988年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   5篇
  1976年   1篇
  1974年   3篇
  1973年   1篇
  1972年   3篇
  1971年   1篇
  1970年   1篇
  1969年   2篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
排序方式: 共有127条查询结果,搜索用时 15 毫秒
101.
Toll-like receptors (TLRs) and members of their signaling pathway are important in the initiation of the innate immune response to a wide variety of pathogens. The adaptor protein Mal (also known as TIRAP), encoded by TIRAP (MIM 606252), mediates downstream signaling of TLR2 and TLR4 (refs. 4-6). We report a case-control study of 6,106 individuals from the UK, Vietnam and several African countries with invasive pneumococcal disease, bacteremia, malaria and tuberculosis. We genotyped 33 SNPs, including rs8177374, which encodes a leucine substitution at Ser180 of Mal. We found that heterozygous carriage of this variant associated independently with all four infectious diseases in the different study populations. Combining the study groups, we found substantial support for a protective effect of S180L heterozygosity against these infectious diseases (N = 6,106; overall P = 9.6 x 10(-8)). We found that the Mal S180L variant attenuated TLR2 signal transduction.  相似文献   
102.
We previously mapped the type 2 diabetes mellitus-2 locus (T2dm2), which affects fasting insulin levels, to distal chromosome 19 in a leptin-deficient obese F2 intercross derived from C57BL/6 (B6) and BTBR T+ tf/J (BTBR) mice. Introgression of a 7-Mb segment of the B6 chromosome 19 into the BTBR background (strain 1339A) replicated the reduced insulin linked to T2dm2. The 1339A mice have markedly impaired insulin secretion in vivo and disrupted islet morphology. We used subcongenic strains derived from 1339A to localize the T2dm2 quantitative trait locus (QTL) to a 242-kb segment comprising the promoter, first exon and most of the first intron of the Sorcs1 gene. This was the only gene in the 1339A strain for which we detected amino acid substitutions and expression level differences between mice carrying B6 and BTBR alleles of this insert, thereby identifying variation within the Sorcs1 gene as underlying the phenotype associated with the T2dm2 locus. SorCS1 binds platelet-derived growth factor, a growth factor crucial for pericyte recruitment to the microvasculature, and may thus have a role in expanding or maintaining the islet vasculature. Our identification of the Sorcs1 gene provides insight into the pathway underlying the pathophysiology of obesity-induced type 2 diabetes mellitus.  相似文献   
103.
Solvent Extraction Developments in Southern Africa   总被引:1,自引:0,他引:1  
Introduction Solvent extraction (SX) has been an integral part of the hydrometallurgist’s arsenal in Southern Africa for many decades[1]. In the early 1970s, several SX plants were built to recover uranium, commonly occurring with the gold-bearing minera…  相似文献   
104.
Although thoracic aortic aneurysms and dissections (TAAD) can be inherited as a single-gene disorder, the genetic predisposition in the majority of affected people is poorly understood. In a multistage genome-wide association study (GWAS), we compared 765 individuals who had sporadic TAAD (STAAD) with 874 controls and identified common SNPs at a 15q21.1 locus that were associated with STAAD, with odds ratios of 1.6-1.8 that achieved genome-wide significance. We followed up 107 SNPs associated with STAAD with P < 1 × 10(-5) in the region, in two separate STAAD cohorts. The associated SNPs fall into a large region of linkage disequilibrium encompassing FBN1, which encodes fibrillin-1. FBN1 mutations cause Marfan syndrome, whose major cardiovascular complication is TAAD. This study shows that common genetic variants at 15q21.1 that probably act via FBN1 are associated with STAAD, suggesting a common pathogenesis of aortic disease in Marfan syndrome and STAAD.  相似文献   
105.
Cell-mediated cytotoxicity to SV40-specific tumour-associated antigens.   总被引:1,自引:0,他引:1  
G Trinchieri  D P Aden  B B Knowles 《Nature》1976,261(5558):312-314
  相似文献   
106.
Autosomal dominant retinal vasculopathy with cerebral leukodystrophy is a microvascular endotheliopathy with middle-age onset. In nine families, we identified heterozygous C-terminal frameshift mutations in TREX1, which encodes a 3'-5' exonuclease. These truncated proteins retain exonuclease activity but lose normal perinuclear localization. These data have implications for the maintenance of vascular integrity in the degenerative cerebral microangiopathies leading to stroke and dementias.  相似文献   
107.
The term ‘Sustainable Development’ is brandished by modern businesses as a marketing ploy used to suggest evidence of ethical conduct, innovative thinking and moral superiority. However, when analysing an organisations’ adoption of sustainable practices, it is often clear—within the UK—that there are few activities that have been undertaken as an ethical stance instead of legal obligation (McCormick in Environmental politics and policy in industrialized countries, MIT, London, 2002). Our hypothesis is that most methodologies and practices for environmental management do not adopt a holistic perspective, causing significant problems in implementation from inadequate structures and communication channels (Espinosa et al. in Eur J Oper Res, 187:636–651, 2008). In particular we consider that most organisations are currently stifled with management hierarchies that prevent informal/social networking, which may be one of the most powerful natural forms for self-organisation. It is proposed that sustainable development requires more efficient communication channels that foster self-organisation and self-regulation as a method for more productive change processes. In this paper, we explain the reasons why meta-systemic principles of self-organisation and distributed network management offer clear criteria to design an environmental management system that operates on the basis of self-controlled individuals and communities.  相似文献   
108.
STING is a direct innate immune sensor of cyclic di-GMP   总被引:1,自引:0,他引:1  
  相似文献   
109.
The concept of interactional expertise – characterized by sociologists Harry Collins and Robert Evans as the ability to speak the language of a discipline without the corresponding ability to practice – can serve as a powerful way of breaking down expert/non-expert dichotomies and providing a role for new voices in specialist communities. However, in spite of the vast uptake of this concept and its potential to fruitfully address many important issues related to scientific expertise, there has been surprisingly little critical analysis of it. We seek to remedy this situation by considering potential benefits of interactional expertise and the ways in which the current conception can – and cannot – realize those benefits. In particular, we argue that interactional expertise hasn't reached its full potential for addressing who ought to be involved in scientific research and decision-making, largely owing to an unnecessarily restrictive way of operationalizing the concept. In its place, we offer a broader, more pluralistic account of interactional expertise – one that is in line with the original spirit of the concept, but also captures the diversity that we see as being an important aspect of interactional experts and the value they can bring to the table.  相似文献   
110.
In many areas of the Rocky Mountains, elk ( Cervus elaphus ) migrate from low-elevation mountain valleys during spring to high-elevation subalpine and alpine areas for the summer. Research has focused on the impacts of elk herbivory on winter-range plant communities, particularly on woody species such as willow and aspen; however, little information is available on the effects of elk herbivory on alpine willows. In the Sangre de Cristo Mountains of south central Colorado, select alpine areas appear to receive high levels of summer elk herbivory, while other areas are nearly unbrowsed. In 2005 and 2008, we measured willow height, cover, and utilization on sites that appeared to be used heavily by elk, as well as on sites that appeared to be used lightly, to determine differences between these communities over time. We found less willow cover and shorter willows at sites that received higher levels of browsing compared to those that had lower levels of browsing. Human recreational use was greater at lightly browsed sites than at highly browsed sites. From 2005 to 2008, willow utilization declined, and willow cover and height increased at sites with heavy browsing, likely owing to ownership change of adjacent valley land which led to (1) removal of grazing competition from cattle at valley locations and (2) increased human use in alpine areas, which displaced elk. We discuss the implications of increased human use and climate change on elk use of these alpine habitats. En muchas &aacute;reas de las Monta&ntilde;as Rocosas, el ciervo rojo ( Cervus elaphus ) migra durante la primavera de valles monta&ntilde;osos de baja elevaci&oacute;n a &aacute;reas altas subalpinas y alpinas para el verano. Hasta ahora la investigaci&oacute;n se ha enfocado en el impacto de la herbivor&iacute;a del ciervo rojo sobre las comunidades de plantas en el invierno, particularmente en las especies le&ntilde;osas como el sauce y el &aacute;lamo; sin embargo, existe poca informaci&oacute;n disponible sobre el efecto de la herbivor&iacute;a del ciervo rojo en los sauces alpinos. En la cordillera Sangre de Cristo al centro-sur de Colorado, ciertas &aacute;reas alpinas parecen tener altos niveles de herbivor&iacute;a de verano por el ciervo rojo, en tanto que otras &aacute;reas quedan casi sin ramoneo. En 2005 y 2008 medimos la altura, cobertura y uso de los sauces en sitios en los que parec&iacute;a haber sido abundante el ramoneo y los comparamos con sitios donde parec&iacute;a haber sido m&aacute;s ligero, a fin de determinar las diferencias entre estas comunidades en el tiempo. Encontramos menos cobertura y altura de sauces en los sitios que recib&iacute;an niveles m&aacute;s altos de ramoneo en comparaci&oacute;n a los que ten&iacute;an menos evidencia de ello. El uso humano recreativo era mayor en los sitios de ramoneo ligero que en donde era abundante. De 2005 a 2008, disminuy&oacute; el uso y aument&oacute; la cobertura y la altura en sitios de ramoneo abundante, probablemente debido a que un valle adyacente cambi&oacute; de propietario, lo cual provoc&oacute; (1) la eliminaci&oacute;n de la competencia por el pastoreo en ganado en el valle; y (2) un aumento del uso humano en &aacute;reas alpinas, desplazando al ciervo rojo. Discutimos las implicaciones del aumento del uso humano y el cambio clim&aacute;tico en el uso por el ciervo rojo de estos h&aacute;bitats alpinos.  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