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   400篇
  免费   35篇
  435篇
  2023年   2篇
  2022年   7篇
  2021年   14篇
  2020年   7篇
  2019年   3篇
  2018年   5篇
  2017年   9篇
  2016年   14篇
  2015年   34篇
  2014年   22篇
  2013年   24篇
  2012年   32篇
  2011年   39篇
  2010年   15篇
  2009年   19篇
  2008年   13篇
  2007年   21篇
  2006年   20篇
  2005年   25篇
  2004年   23篇
  2003年   10篇
  2002年   16篇
  2001年   3篇
  2000年   4篇
  1999年   4篇
  1998年   4篇
  1997年   2篇
  1994年   3篇
  1993年   2篇
  1992年   2篇
  1991年   2篇
  1990年   3篇
  1989年   2篇
  1985年   3篇
  1982年   1篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1978年   1篇
  1977年   2篇
  1976年   1篇
  1971年   1篇
  1970年   2篇
  1969年   1篇
  1966年   1篇
  1928年   1篇
  1910年   1篇
  1903年   1篇
  1888年   1篇
  1887年   1篇
排序方式: 共有435条查询结果,搜索用时 31 毫秒
41.
42.
Climate change is a significant future driver of change in coastal social-ecological systems. Our knowledge of impacts, adaptation options, and possible outcomes for marine environments and coastal industries is expanding, but remains limited and uncertain. Alternative scenarios are a way to explore potential futures under a range of conditions. We developed four alternative future scenarios for the Great Barrier Reef and its fishing and tourism industries positing moderate and more extreme (2–3 °C above pre-industrial temperatures) warming for 2050 and contrasting ‘limited’ and ‘ideal’ ecological and social adaptation. We presented these scenarios to representatives of key stakeholder groups to assess the perceived viability of different social adaptation options to deliver desirable outcomes under varied contexts.  相似文献   
43.
44.
45.
Long-chain acyl CoA synthetase 1 (ACSL1) plays an important role in fatty acid metabolism and triacylglycerol (TAG) synthesis. Disturbance of these pathways may result in dyslipidemia and insulin resistance, hallmarks of the metabolic syndrome (MetS). Dietary fat is a key environmental factor that may interact with genetic determinants of lipid metabolism to affect MetS risk. We investigated the relationship between ACSL1 polymorphisms (rs4862417, rs6552828, rs13120078, rs9997745, and rs12503643) and MetS risk and determined potential interactions with dietary fat in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1,754). GG homozygotes for rs9997745 had increased MetS risk {odds ratio (OR) 1.90 [confidence interval (CI) 1.15, 3.13]; P = 0.01}, displayed elevated fasting glucose (P = 0.001) and insulin concentrations (P = 0.002) and increased insulin resistance (P = 0.03) relative to the A allele carriers. MetS risk was modulated by dietary fat, whereby the risk conferred by GG homozygosity was abolished among individuals consuming either a low-fat (<35% energy) or a high-PUFA diet (>5.5% energy). In conclusion, ACSL1 rs9997745 influences MetS risk, most likely via disturbances in fatty acid metabolism, which was modulated by dietary fat consumption, particularly PUFA intake, suggesting novel gene-nutrient interactions.  相似文献   
46.
ABSTRACT

Pasteurella haemolytica serovar A1 is the causative agent of acute fibrinohemorrahgic pneumonia also known as shipping fever. Many pathogens, including P. haemolytica, survive in their respective hosts through the up-regulation of an iron acquisition system. In this study we identified, purified and characterized a 35-kDa periplasmic iron-regulated protein. The N-terminal sequence of the iron-regulated protein ANEVNVYSYRQP YLIEPMLK was identical to the deduced amino acid sequence of the ferric binding protein, FbpA, of P. haemolytica. Growth of P. haemolytica in a synthetic medium (RPMI-1640), without iron and supplemented with 50 μM 2,2' dipyridyl, facilitated the expression, isolation and purification of the native P. haemolytica FbpA.  相似文献   
47.

Background

Chagas disease, caused by infection with the protozoan Trypanosoma cruzi, remains a serious public health issue in Latin America. Genetically diverse, the species is sub-divided into six lineages, known as TcI–TcVI, which have disparate geographical and ecological distributions. TcII, TcV, and TcVI are associated with severe human disease in the Southern Cone countries, whereas TcI is associated with cardiomyopathy north of the Amazon. T. cruzi persists as a chronic infection, with cardiac and/or gastrointestinal symptoms developing years or decades after initial infection. Identifying an individual''s history of T. cruzi lineage infection directly by genotyping of the parasite is complicated by the low parasitaemia and sequestration in the host tissues.

Methodology/Principal Findings

We have applied here serology against lineage-specific epitopes of the T. cruzi surface antigen TSSA, as an indirect approach to allow identification of infecting lineage. Chagasic sera from chronic patients from a range of endemic countries were tested by ELISA against synthetic peptides representing lineage-specific TSSA epitopes bound to avidin-coated ELISA plates via a biotin labelled polyethylene glycol-glycine spacer to increase rotation and ensure each amino acid side chain could freely interact with their antibodies. 79/113 (70%) of samples from Brazil, Bolivia, and Argentina recognised the TSSA epitope common to lineages TcII/TcV/TcVI. Comparison with clinical information showed that a higher proportion of Brazilian TSSApep-II/V/VI responders had ECG abnormalities than non-responders (38% vs 17%; p<0.0001). Among northern chagasic sera 4/20 (20%) from Ecuador reacted with this peptide; 1/12 Venezuelan and 1/34 Colombian samples reacted with TSSApep-IV. In addition, a proposed TcI-specific epitope, described elsewhere, was demonstrated here to be highly conserved across lineages and therefore not applicable to lineage-specific serology.

Conclusions/Significance

These results demonstrate the considerable potential for synthetic peptide serology to investigate the infection history of individuals, geographical and clinical associations of T. cruzi lineages.  相似文献   
48.
Recent advances in the developmental biology, genetics and cell biology of the inner ear are guiding research to novel therapeutic modalities - a market currently estimated to be at least US Dollars 10 billion. This article highlights prospects to manipulate the mammalian hearing organ with gene and stem cell delivery to the inner ear to protect, repair or regenerate the hair cells, supporting cells and associated nerves.  相似文献   
49.
AimsEstimate the prevalence of cannabis dependence and its contribution to the global burden of disease.MethodsSystematic reviews of epidemiological data on cannabis dependence (1990-2008) were conducted in line with PRISMA and meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. Culling and data extraction followed protocols, with cross-checking and consistency checks. DisMod-MR, the latest version of generic disease modelling system, redesigned as a Bayesian meta-regression tool, imputed prevalence by age, year and sex for 187 countries and 21 regions. The disability weight associated with cannabis dependence was estimated through population surveys and multiplied by prevalence data to calculate the years of life lived with disability (YLDs) and disability-adjusted life years (DALYs). YLDs and DALYs attributed to regular cannabis use as a risk factor for schizophrenia were also estimated.ResultsThere were an estimated 13.1 million cannabis dependent people globally in 2010 (point prevalence0.19% (95% uncertainty: 0.17-0.21%)). Prevalence peaked between 20-24 yrs, was higher in males (0.23% (0.2-0.27%)) than females (0.14% (0.12-0.16%)) and in high income regions. Cannabis dependence accounted for 2 million DALYs globally (0.08%; 0.05-0.12%) in 2010; a 22% increase in crude DALYs since 1990 largely due to population growth. Countries with statistically higher age-standardised DALY rates included the United States, Canada, Australia, New Zealand and Western European countries such as the United Kingdom; those with lower DALY rates were from Sub-Saharan Africa-West and Latin America. Regular cannabis use as a risk factor for schizophrenia accounted for an estimated 7,000 DALYs globally.ConclusionCannabis dependence is a disorder primarily experienced by young adults, especially in higher income countries. It has not been shown to increase mortality as opioid and other forms of illicit drug dependence do. Our estimates suggest that cannabis use as a risk factor for schizophrenia is not a major contributor to population-level disease burden.  相似文献   
50.
The PTEN/PI3K pathway is commonly mutated in cancer and therefore represents an attractive target for therapeutic intervention. To investigate the primary phenotypes mediated by increased pathway signaling in a clean, patient-relevant context, an activating PIK3CA mutation (H1047R) was knocked-in to an endogenous allele of the MCF10A non-tumorigenic human breast epithelial cell line. Introduction of an endogenously mutated PIK3CA allele resulted in a marked epithelial-mesenchymal transition (EMT) and invasive phenotype, compared to isogenic wild-type cells. The invasive phenotype was linked to enhanced PIP(3) production via a S6K-IRS positive feedback mechanism. Moreover, potent and selective inhibitors of PI3K were highly effective in reversing this phenotype, which is optimally revealed in 3-dimensional cell culture. In contrast, inhibition of Akt or mTOR exacerbated the invasive phenotype. Our results suggest that invasion is a core phenotype mediated by increased PTEN/PI3K pathway activity and that therapeutic agents targeting different nodes of the PI3K pathway may have dramatic differences in their ability to reverse or promote cancer metastasis.  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