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   2967篇
  免费   195篇
  国内免费   1篇
  2023年   21篇
  2022年   33篇
  2021年   68篇
  2020年   39篇
  2019年   47篇
  2018年   82篇
  2017年   43篇
  2016年   89篇
  2015年   140篇
  2014年   157篇
  2013年   221篇
  2012年   272篇
  2011年   226篇
  2010年   165篇
  2009年   132篇
  2008年   195篇
  2007年   171篇
  2006年   160篇
  2005年   146篇
  2004年   130篇
  2003年   132篇
  2002年   141篇
  2001年   27篇
  2000年   12篇
  1999年   24篇
  1998年   26篇
  1997年   21篇
  1996年   31篇
  1995年   20篇
  1994年   31篇
  1993年   22篇
  1992年   14篇
  1991年   14篇
  1990年   12篇
  1989年   5篇
  1988年   7篇
  1987年   9篇
  1986年   4篇
  1985年   5篇
  1984年   10篇
  1983年   13篇
  1982年   6篇
  1980年   7篇
  1979年   6篇
  1978年   7篇
  1975年   3篇
  1974年   4篇
  1973年   3篇
  1971年   2篇
  1964年   2篇
排序方式: 共有3163条查询结果,搜索用时 15 毫秒
231.
Single nucleotide polymorphisms (SNPs) represent a valuable resource for the mapping of human disease genes and induced mutations in model organisms. SNPs may become the markers of choice also for population ecology and evolutionary studies, but their isolation for non-model organisms with unsequenced genomes is often difficult. Here, we describe a rapid and cost-effective strategy to isolate SNPs that exploits the property of the bacteriophage Mu transposition machinery to target mismatched DNA sites and thereby to effectively detect polymorphic loci. To demonstrate the methodology, we isolated 164 SNPs from the unsequenced genome of the Glanville fritillary butterfly (Melitaea cinxia), a much-studied species in population biology, and we validated 24 of them. The strategy involves standard molecular biology techniques as well as undemanding MuA transposase-catalyzed in vitro transposition reactions, and it is applicable to any organism.  相似文献   
232.
We investigated the stability of expression constructs based on Potato virus X (PVX) as a function of insert length. Five different inserts ranging in length from 261 to 1,758 bp (human proinsulin, murine interleukin-10, HIV-1 nef, petunia expansin-1 and human gad65) were expressed using a PVX vector in Nicotiana benthamiana plants for three sequential passages. Using a competitive RT-PCR approach we demonstrated that insert–deletion could occur in the first infection cycle for all inserts, but that this was much more likely to be the case for longer ones. This suggested a negative correlation between insert length and vector stability. Sequence analysis of the deleted constructs suggested that recombination usually occurred at sites close to the duplicated sub-genomic promoter, but in a smaller number of cases the foreign gene itself was probably involved, resulting in partially deleted constructs containing transgene fragments. The implications of these results in the context of recombinant protein expression and its risks are discussed.  相似文献   
233.
Enantiopure constrained 1-aminocyclopentane-1,2,4-tricarboxylic acids containing the glutamic acid skeleton were prepared as two diastereomers characterized by having the carboxylic groups in position two and four cis-oriented to each other and trans with respect to 1-carboxylic group and all cis-oriented carboxylic groups, respectively. A biochemical screening of activity of the above amino acids was investigated on glutamate and 5-HT receptors to find a possible metabotropic agonist, acting on the serotoninergic system.  相似文献   
234.
We describe herein the discovery of LASSBio-881 (3c) as a novel in vivo antinociceptive, anti-inflammatory, and in vitro antiproliferative and antioxidant compound, with a cannabinoid ligand profile. We observed that LASSBio-881 (3c) was able to bind to CB1 receptors (71% at 100microM) and also to inhibit T-cell proliferation (66% at 10microM) probably by binding to CB2 receptors, in a non-proapoptotic manner, different from anandamide (1). It was also demonstrated that LASSBio-881 (3c) had an important antioxidant profile toward free radicals (DPPH and hydroxyl), probably due to its particular redox behavior, which reflects the presence of both nitro and 3,5-di-tert-butyl-4-hydroxyphenyl sub-units, as demonstrated by cyclic voltammetry studies. In addition, we showed that these structural sub-units are essential for the observed pharmacological activity.  相似文献   
235.
The emerging domain of epigenetics in molecular medicine finds application for a variety of patient populations. Here, we present fundamental neuroendocrine immune evidence obtained in patients with senile dementia of the Alzheimer's type (sDAT), and discuss the implications of these data from the viewpoint of translational epigenetics of Alzheimer's disease. We followed 18 subjects with mild sDAT treated with acetylcholinesterase inhibitors, and 10 control subjects matched for age in a repeated measure design every six months for 18 months. We monitored psychosocial profile (Mini-Mental State Examination, Functional Assessment Staging, Independence in Activities of Daily Living, Depression, Profile of Moods States) in parallel to immunophenotypic parameters of T cell subpopulations by flow cytometry. Based on change in the mini-mental state score at entry and at 18 months, patients with sDAT were assigned to a "fast progression" (delta greater than 2 points) or to a "slow progression" group (delta less than or equal to 2 points). The change in circulating activated T cells (CD3+Dr+) with time in patients with sDAT was significantly inversely correlated with the change in time in natural killer (NK) cytotoxic activity to cortisol modulation in these patients, which was greater in patients with fast progression, compared to slow progression sDAT. These data indicate underlying neuroendocrine immune processes during progression of sDAT. Our observations suggest that psychoimmune measures such as those we have monitored in this study provide relevant information about the evolving physiological modulation in patients with sDAT during progression of Alzheimer's disease, and point to new or improved translational epigenetic treatment interventions.  相似文献   
236.
Patients with Alzheimer's disease (AD) are characterized by an altered sensitivity to cortisol-mediated modulation of circulating lymphocytes. Longitudinal studies are needed to address the clinical applicability of these abnormalities as prognostic factors. Therefore, we designed a longitudinal study to address the clinical applicability of physiologic modulation of Natural Killer (NK) cell activity as a prognostic factor in AD. NK activity was assessed as baseline measurement and in response to modulation by cortisol at 10(-6)M. To verify the immunophysiological integrity of the NK cell population, we tested augmentation of NK cytotoxicity by human recombinant interleukin (IL)-2 (100 IU/ml) as control. The response to modulation by cortisol or by IL-2 was significantly greater in patients with AD. Based on change in the Mini-Mental State score at entry and at 18 months, patients with AD could be assigned to a "fast progression" (Delta > 2 points) or to a "slow progression" group (Delta 相似文献   
237.
238.
Metabolic syndrome includes most widely distributed clinical conditions such as obesity, hypertension, dislipidemia, and diabetes. Pomegranate fruit extract (PFE), rich in polyphenolic antioxidants, reduces the expression of oxidation-sensitive genes at the sites of perturbed shear-stress. The aim of this study was to evaluate the effect of PFE in comparison to regular pomegranate juice (PJ) and seed oil on the biological actions of nitric oxide (NO) and the arterial function in obese Zucker rats, a model of metabolic syndrome. Our results indicated that supplementation with PFE or PJ significantly decreased the expression of vascular inflammation markers, thrombospondin (TSP), and cytokine TGFbeta1 (P<0.05), whereas seed oil supplementation had a significant effect only on TSP-1 expression (P <0.05). Plasma nitrate and nitrite (NO(x)) levels were significantly increased by PFE and PJ (P<0.05). Furthermore, the effect of PFE in increasing endothelial NO synthase (eNOS) expression was comparable to that of PJ. These data highlight possible clinical applications of PFE in metabolic syndrome.  相似文献   
239.
A wealth of molecular interaction data is available in the literature, ranging from large-scale datasets to a single interaction confirmed by several different techniques. These data are all too often reported either as free text or in tables of variable format, and are often missing key pieces of information essential for a full understanding of the experiment. Here we propose MIMIx, the minimum information required for reporting a molecular interaction experiment. Adherence to these reporting guidelines will result in publications of increased clarity and usefulness to the scientific community and will support the rapid, systematic capture of molecular interaction data in public databases, thereby improving access to valuable interaction data.  相似文献   
240.
Curcumin is a phytochemical with antiinflammatory, antioxidant and anticarcinogenic activities. Apparently, curcumin is not genotoxic in vivo, but in vitro copper and curcumin interactions induce genetic damage. The aim of this study was to test if in vivo copper excess induces DNA damage measured by comet and micronucleus assays in the presence of curcumin. We tested 0.2% curcumin in Balb-C mice at normal (13 ppm) and high (65, 130 and 390 ppm) copper ion concentrations. The comet and micronucleus assays were performed 48 hr after chemical application. Comet tail length in animals treated with 0.2% curcumin was not significantly different from the control. Animals exposed to copper cations (up to 390 ppm) exhibited higher oxidative DNA damage. Curcumin reduced the DNA damage induced by 390 ppm copper. We observed statistically significant increase in damage in individuals exposed to 390 ppm copper versus the control or curcumin groups, which was lowered by the presence of curcumin. Qualitative data on comets evidenced that cells from individuals exposed to 390 ppm copper had longer tails (categories 3 and 4) than in 390 ppm copper + curcumin. A statistically significant increase in frequency of micronucleated erythrocytes (MNE/10000TE) was observed only in 390 ppm copper versus the control and curcumin alone. Also cytotoxicity measured as the frequency of polychromatic erythrocytes (PE/1000TE) was attributable to 390 ppm copper. The lowest cytotoxic effect observed was attributed to curcumin. In vivo exposure to 0.2% curcumin for 48 hr did not cause genomic damage, while 390 ppm copper was genotoxic, but DNA damage induced by 390 ppm copper was diminished by curcumin. Curcumin seems to exert a genoprotective effect against DNA damage induced by high concentrations of copper cations. The comet and micronucleus assays prove to be suitable tools to detect DNA damage by copper in the presence of curcumin.  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