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   269篇
  免费   13篇
  282篇
  2024年   4篇
  2022年   5篇
  2021年   8篇
  2020年   1篇
  2019年   1篇
  2018年   3篇
  2017年   4篇
  2016年   3篇
  2015年   10篇
  2014年   16篇
  2013年   24篇
  2012年   13篇
  2011年   15篇
  2010年   9篇
  2009年   8篇
  2008年   14篇
  2007年   10篇
  2006年   14篇
  2005年   6篇
  2004年   9篇
  2003年   4篇
  2002年   10篇
  2001年   6篇
  2000年   8篇
  1999年   4篇
  1998年   11篇
  1997年   3篇
  1996年   1篇
  1995年   3篇
  1994年   4篇
  1993年   2篇
  1992年   8篇
  1991年   11篇
  1990年   3篇
  1989年   6篇
  1988年   1篇
  1987年   5篇
  1986年   1篇
  1985年   3篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1968年   1篇
  1967年   2篇
  1929年   2篇
排序方式: 共有282条查询结果,搜索用时 0 毫秒
1.
Abstract  A series of specimens of the Asian citrus psyllid, Diaphorina citri , collected from the Northern Territory (NT) in 1915 was recently rediscovered in the Natural History Museum, London. Surveys were conducted in 2002 on suitable hosts in the locality of the 1915 collections to see if the infestation had persisted. These failed to detect either D. citri or the bacterium that it transmits and that causes huanglongbing disease in citrus. It is presumed that D. citri was eradicated fortuitously by the removal of all citrus plants above latitude 19°S during an eradication program for citrus canker in the NT from 1916 until 1922.  相似文献   
2.
Although it has been known for many years that beta1 integrins undergo differential glycosylation in accordance with changes in cell phenotype, the potential role of N-glycosylation as a modulator of integrin function has received little attention. One reason for the relatively limited interest in this topic likely relates to the fact that much of the prior research was correlative in nature. However, new results now bolster the hypothesis that there is a causal relationship between variant glycosylation and altered integrin activity. In this review, the evidence for variant glycosylation as a regulatory mechanism for beta1 integrins are summarized, with particular emphasis on: (1). outlining the instances in which cell phenotypic variation is associated with differential beta1 glycosylation, (2). describing the specific alterations in glycan structure that accompany phenotypic changes and (3). presenting potential mechanisms by which variant glycosylation might regulate integrin function.  相似文献   
3.
    
Both enantiomers of \"para-hydroxymexiletine\" (PHM), one of the main metabolites of mexiletine, were synthesized and fully characterized. Properties of (R)- and (S)-PHM, in terms of blocking potency and stereoselectivity on frog skeletal muscle Na(+) channels, were evaluated. The presence of a hydroxy group on the aryloxy moiety in the 4-position, as in PHM, reduced potency with respect to mexiletine in reducing I(Na max). However, PHM showed clear use-dependent behavior similar to that of mexiletine and, in contrast with what is observed with the parent compound, maintained its stereoselectivity during the use-dependent block. Chirality 16:72-78, 2004.  相似文献   
4.
5.
Abstract Aphis clerodendri Matsumura is newly recorded from Australia and is known from the Northern Territory, on islands in Torres Strait, and in rainforest in northern Queensland and New South Wales. It induces the formation of leaf pseudogalls on native species of Clerodendrum and is commonly attended by ants, which penetrate and may polydomously nest in the galls. Previously known only from eastern Asia, A. clerodendri can now be classified as native to Australia and Australasian in natural distribution. The species is also newly recorded from Papua New Guinea and Vietnam.  相似文献   
6.
    
Plasma lipidome is now increasingly recognized as a potentially important marker of chronic diseases, but the exact extent of its contribution to the interindividual phenotypic variability in family studies is unknown. Here, we used the rich data from the ongoing San Antonio Family Heart Study (SAFHS) and developed a novel statistical approach to quantify the independent and additive value of the plasma lipidome in explaining metabolic syndrome (MS) variability in Mexican American families recruited in the SAFHS. Our analytical approach included two preprocessing steps: principal components analysis of the high-resolution plasma lipidomics data and construction of a subject-subject lipidomic similarity matrix. We then used the Sequential Oligogenic Linkage Analysis Routines software to model the complex family relationships, lipidomic similarities, and other important covariates in a variance components framework. Our results suggested that even after accounting for the shared genetic influences, indicators of lipemic status (total serum cholesterol, TGs, and HDL cholesterol), and obesity, the plasma lipidome independently explained 22% of variability in the homeostatic model of assessment-insulin resistance trait and 16% to 22% variability in glucose, insulin, and waist circumference. Our results demonstrate that plasma lipidomic studies can additively contribute to an understanding of the interindividual variability in MS.  相似文献   
7.

Objective

To analyze hospitalization for lower extremity amputations (LEAs) and amputee rates in persons with and without diabetes in Italy.

Research Design and Methods

All patients with LEAs in the period 2001–2010 were identified analyzing the National Hospital Discharge Record database. For each year, amputee and hospitalization rates for LEAs were calculated either for persons with diabetes or without. Time trend for major and minor amputations were analysed.

Results

From 2001 to 2010 a mean annual number of 11,639 individuals underwent a lower extremity amputation: 58.6% had diabetes accounting for 60.7% of total hospitalizations. In 2010, the crude amputee rate for LEAs was 20.4 per 100,000 inhabitants: 247.2 for 100.000 persons with diabetes, and 8.6 for those without diabetes. Having diabetes was associated to an increased risk of amputation (Poisson estimated RR 10.9, 95%CI 9.4–12.8). Over the whole period, a progressive reduction of amputee rates was observed for major amputations either among persons with diabetes (−30.7%) or without diabetes (−12.5%), while the rates of minor amputations increased progressively (+22.4%) among people without diabetes and were nearly stable in people with diabetes (−4.6%). A greater number of minor amputations were performed among persons with than without diabetes: in 2010, the minor-to-major ratio among persons with diabetes (2.5) was more than twice than in those without diabetes (1.0).

Conclusions

The nationwide analyses confirm a progressive reduction of hospitalization and amputee rates for major LEAs, suggesting an earlier and more diffuse approach aimed at limb salvage.  相似文献   
8.
Hydrophobic interaction chromatography (HIC) has been used extensively for the separation of proteins and peptides by elution using a descending salt gradient, with and without the use of detergents or denaturing agents. In this paper we compare different hydrophobic interaction chromatographic media for the separation of multiple forms of hexokinase from rabbit reticulocytes. Among the different hydrophobic chromatographic media tested (Toyopearl Phenyl 650S, Ether 650S and Butyl 650S) Toyopearl Phenyl 650S offered the best separation of multiple forms of hexokinase, probably due to its intermediate hydrophobicity. In order to establish the optimal experimental conditions, we evaluated the effects of different salts, and the results obtained demonstrated that among the antichaotropic salts, ammonium sulphate is the most suitable for the separation of hexokinase sub-types. The sample loading capacity of the three Toyopearl supports was investigated and the recovery of enzymatic activity obtained ranged from 60% to 90%, depending on the different salts and hydrophobic media used. The chromatographic profiles of hexokinase activity from various mammalian and fungal tissues also demonstrate that Toyopearl Phenyl 650S can be successfully employed for the separation of multiple forms of enzymes from different biological sources.  相似文献   
9.
10.
A novel series of non-hydroxamate HDAC inhibitors (HDACi) showing a uracil group at the left and a 2-aminoanilide/2-aminoanilide-like portion at the right head have been reported. In particular, the new compounds incorporating a 2-aminoanilide moiety behaved as class I-selective HDACi. Compound 8, the most potent and class I-selective, showed weak apoptosis (higher than MS-275) joined to cytodifferentiating activity on U937 cells. Surprisingly, the highest differentiation was observed with 13, through an effect that seems to be unrelated to HDAC inhibition.  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