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   572篇
  免费   5篇
  国内免费   8篇
系统科学   9篇
丛书文集   1篇
教育与普及   1篇
理论与方法论   9篇
现状及发展   113篇
研究方法   71篇
综合类   351篇
自然研究   30篇
  2021年   3篇
  2020年   2篇
  2019年   5篇
  2018年   3篇
  2017年   5篇
  2016年   4篇
  2015年   6篇
  2014年   6篇
  2013年   12篇
  2012年   47篇
  2011年   76篇
  2010年   13篇
  2009年   6篇
  2008年   36篇
  2007年   38篇
  2006年   46篇
  2005年   43篇
  2004年   34篇
  2003年   24篇
  2002年   27篇
  2001年   8篇
  2000年   12篇
  1999年   3篇
  1998年   2篇
  1996年   3篇
  1995年   6篇
  1994年   5篇
  1991年   2篇
  1990年   5篇
  1989年   7篇
  1987年   9篇
  1986年   4篇
  1985年   6篇
  1984年   6篇
  1983年   2篇
  1982年   2篇
  1979年   5篇
  1978年   2篇
  1977年   3篇
  1975年   4篇
  1974年   5篇
  1973年   7篇
  1972年   7篇
  1971年   4篇
  1970年   3篇
  1968年   2篇
  1966年   9篇
  1965年   5篇
  1956年   1篇
  1945年   1篇
排序方式: 共有585条查询结果,搜索用时 78 毫秒
461.
This study was performed to examine the effect of chronic renal impairment and renin-angiotensin system (RAS) activation induced by unilateral nephrectomy (UNX) on the development of pancreatic islet β-cell deficit and glucose intolerance. Sprague-Dawley rats were randomized into three groups: untreated UNX (n = 10), UNX treated with the angiotensin-converting enzyme inhibitor lisinopril (n = 8) and sham operation (n = 10). Blood glucose, serum insulin, renal function and histological changes of kidney and pancreas were examined 8 months postoperation. Compared with the sham rats, UNX rats developed renal impairment, insulin deficiency and glucose intolerance. Histological staining revealed an islet β-cell deficit associated with increased immunoreactivity for angiotensin and angiotensin type 1 receptor in UNX rats. Treatment with lisinopril significantly improved renal dysfunction, hyperglycemia, insulin secretion and islet RAS expression. These data suggest that chronic renal impairment and RAS activation may contribute to islet β-cell loss and glucose intolerance. RAS blockade may therefore prevent these disorders. Received 29 August 2007; received after revision 25 September 2007; accepted 27 September 2007  相似文献   
462.
Joubert syndrome-related disorders (JSRD) are a group of syndromes sharing the neuroradiological features of cerebellar vermis hypoplasia and a peculiar brainstem malformation known as the 'molar tooth sign'. We identified mutations in the CEP290 gene in five families with variable neurological, retinal and renal manifestations. CEP290 expression was detected mostly in proliferating cerebellar granule neuron populations and showed centrosome and ciliary localization, linking JSRDs to other human ciliopathies.  相似文献   
463.
The genome-wide distribution of linkage disequilibrium (LD) determines the strategy for selecting markers for association studies, but it varies between populations. We assayed LD in large samples (200 individuals) from each of 11 well-described population isolates and an outbred European-derived sample, using SNP markers spaced across chromosome 22. Most isolates show substantially higher levels of LD than the outbred sample and many fewer regions of very low LD (termed 'holes'). Young isolates known to have had relatively few founders show particularly extensive LD with very few holes; these populations offer substantial advantages for genome-wide association mapping.  相似文献   
464.
Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disorder of skeletal malformations and progressive extraskeletal ossification. We mapped FOP to chromosome 2q23-24 by linkage analysis and identified an identical heterozygous mutation (617G --> A; R206H) in the glycine-serine (GS) activation domain of ACVR1, a BMP type I receptor, in all affected individuals examined. Protein modeling predicts destabilization of the GS domain, consistent with constitutive activation of ACVR1 as the underlying cause of the ectopic chondrogenesis, osteogenesis and joint fusions seen in FOP.  相似文献   
465.
Physiogenomic resources for rat models of heart, lung and blood disorders   总被引:6,自引:0,他引:6  
Cardiovascular disorders are influenced by genetic and environmental factors. The TIGR rodent expression web-based resource (TREX) contains over 2,200 microarray hybridizations, involving over 800 animals from 18 different rat strains. These strains comprise genetically diverse parental animals and a panel of chromosomal substitution strains derived by introgressing individual chromosomes from normotensive Brown Norway (BN/NHsdMcwi) rats into the background of Dahl salt sensitive (SS/JrHsdMcwi) rats. The profiles document gene-expression changes in both genders, four tissues (heart, lung, liver, kidney) and two environmental conditions (normoxia, hypoxia). This translates into almost 400 high-quality direct comparisons (not including replicates) and over 100,000 pairwise comparisons. As each individual chromosomal substitution strain represents on average less than a 5% change from the parental genome, consomic strains provide a useful mechanism to dissect complex traits and identify causative genes. We performed a variety of data-mining manipulations on the profiles and used complementary physiological data from the PhysGen resource to demonstrate how TREX can be used by the cardiovascular community for hypothesis generation.  相似文献   
466.
Congenital hereditary endothelial dystrophy (CHED) is a heritable, bilateral corneal dystrophy characterized by corneal opacification and nystagmus. We describe seven different mutations in the SLC4A11 gene in ten families with autosomal recessive CHED. Mutations in SLC4A11, which encodes a membrane-bound sodium-borate cotransporter, cause loss of function of the protein either by blocking its membrane targeting or nonsense-mediated decay.  相似文献   
467.
468.
低糖型金耳饮料口感调配研究初探   总被引:1,自引:0,他引:1  
以金耳发酵液为主要原料,用木糖醇和低聚异麦芽糖作甜味剂,柠檬酸为酸味剂制成低糖型金耳饮料并进行口感调配。经正交试验,当添加木糖醇5.0%、低聚异麦芽糖3.5%、柠檬酸0.10%时产品口感较佳。且还原糖含量仅为0.52%。  相似文献   
469.
Reversing EphB2 depletion rescues cognitive functions in Alzheimer model   总被引:1,自引:0,他引:1  
Cissé M  Halabisky B  Harris J  Devidze N  Dubal DB  Sun B  Orr A  Lotz G  Kim DH  Hamto P  Ho K  Yu GQ  Mucke L 《Nature》2011,469(7328):47-52
Amyloid-β oligomers may cause cognitive deficits in Alzheimer's disease by impairing neuronal NMDA-type glutamate receptors, whose function is regulated by the receptor tyrosine kinase EphB2. Here we show that amyloid-β oligomers bind to the fibronectin repeats domain of EphB2 and trigger EphB2 degradation in the proteasome. To determine the pathogenic importance of EphB2 depletions in Alzheimer's disease and related models, we used lentiviral constructs to reduce or increase neuronal expression of EphB2 in memory centres of the mouse brain. In nontransgenic mice, knockdown of EphB2 mediated by short hairpin RNA reduced NMDA receptor currents and impaired long-term potentiation in the dentate gyrus, which are important for memory formation. Increasing EphB2 expression in the dentate gyrus of human amyloid precursor protein transgenic mice reversed deficits in NMDA receptor-dependent long-term potentiation and memory impairments. Thus, depletion of EphB2 is critical in amyloid-β-induced neuronal dysfunction. Increasing EphB2 levels or function could be beneficial in Alzheimer's disease.  相似文献   
470.
This paper investigates the role of corporate social responsibility (CSR) performance in forecasting companys' stock prices and future returns. The forecasting analysis identifies a negative association between CSR performance and proxies of price delay. The negative CSR–delay association is weak for state‐owned enterprises (SOEs) because of their politically oriented motivation of CSR activities, but significantly strong for non‐SOEs. Furthermore, we find that forecasting delayed firms is expected to have higher future returns. In particular, the returns premium is most attributable to the CSR component of delay, compared with the non‐CSR component. Taken together, these results suggest that CSR performance plays a positive role in enhancing stock price efficiency, and a potential explanation is that CSR performance can be considered as additional information for equity predictions.  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