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   3001篇
  免费   166篇
  2023年   6篇
  2022年   16篇
  2021年   33篇
  2020年   18篇
  2019年   38篇
  2018年   48篇
  2017年   47篇
  2016年   73篇
  2015年   106篇
  2014年   143篇
  2013年   170篇
  2012年   215篇
  2011年   211篇
  2010年   151篇
  2009年   144篇
  2008年   239篇
  2007年   198篇
  2006年   214篇
  2005年   204篇
  2004年   205篇
  2003年   159篇
  2002年   183篇
  2001年   21篇
  2000年   18篇
  1999年   28篇
  1998年   38篇
  1997年   31篇
  1996年   30篇
  1995年   12篇
  1994年   17篇
  1993年   18篇
  1992年   12篇
  1991年   8篇
  1990年   8篇
  1989年   7篇
  1988年   5篇
  1987年   4篇
  1986年   5篇
  1985年   9篇
  1984年   17篇
  1983年   16篇
  1982年   8篇
  1981年   4篇
  1980年   6篇
  1979年   6篇
  1978年   5篇
  1977年   4篇
  1973年   2篇
  1972年   3篇
  1971年   1篇
排序方式: 共有3167条查询结果,搜索用时 312 毫秒
241.
242.
In the introduction to this theme issue, Honing et al. suggest that the origins of musicality—the capacity that makes it possible for us to perceive, appreciate and produce music—can be pursued productively by searching for components of musicality in other species. Recent studies have highlighted that the behavioural relevance of stimuli to animals and the relation of experimental procedures to their natural behaviour can have a large impact on the type of results that can be obtained for a given species. Through reviewing laboratory findings on animal auditory perception and behaviour, as well as relevant findings on natural behaviour, we provide evidence that both traditional laboratory studies and studies relating to natural behaviour are needed to answer the problem of musicality. Traditional laboratory studies use synthetic stimuli that provide more control than more naturalistic studies, and are in many ways suitable to test the perceptual abilities of animals. However, naturalistic studies are essential to inform us as to what might constitute relevant stimuli and parameters to test with laboratory studies, or why we may or may not expect certain stimulus manipulations to be relevant. These two approaches are both vital in the comparative study of musicality.  相似文献   
243.
Mast cells (MCs) produce soluble mediators such as histamine and prostaglandins that are known to influence dendritic cell (DC) function by stimulating maturation and antigen processing. Whether direct cell–cell interactions are important in modulating MC/DC function is unclear. In this paper, we show that direct contact between MCs and DCs occurs and plays an important role in modulating the immune response. Activation of MCs through FcεRI cross-linking triggers the formation of stable cell–cell interactions with immature DCs that are reminiscent of the immunological synapse. Direct cellular contact differentially regulates the secreted cytokine profile, indicating that MC modulation of DC populations is influenced by the nature of their interaction. Synapse formation requires integrin engagement and facilitates the transfer of internalized MC-specific antigen from MCs to DCs. The transferred material is ultimately processed and presented by DCs and can activate T cells. The physiological outcomes of the MC–DC synapse suggest a new role for intercellular crosstalk in defining the immune response.  相似文献   
244.
IntroductionTocilizumab (TCZ), an anti-interleukin-6 receptor antibody, is clinically effective against rheumatoid arthritis (RA), and several reports have indicated how TCZ influences a number of mechanisms underlying RA pathogenesis. However, it is still unclear whether TCZ affects inflammatory cells in peripheral blood and whether any such changes are associated with clinical response. We evaluated associations between proportions of subsets of peripheral immune cells and clinical response in patients with RA treated with TCZ.MethodsThirty-nine consecutive patients with RA who started to receive TCZ as their first biologic between March 2010 and April 2012 were enrolled. The proportions of several subsets of peripheral cells with their levels of expression of differentiation markers, activation markers and costimulatory molecules were measured sequentially from baseline to week 52 by flow cytometry analysis.ResultsClinical Disease Activity Index (CDAI) remission was achieved in 53.8% of patients at week 52 of TCZ therapy. The proportions of CD4+CD25+CD127low regulatory T cells (Treg) and HLA-DR+ activated Treg cells significantly increased with TCZ therapy (P < 0.001 and P < 0.001, respectively), whereas proportions of CD3+CD4+CXCR3CCR6+CD161+ T helper 17 cells did not change over the 52 weeks. The proportions of CD20+CD27+ memory B cells, HLA-DR+CD14+ and CD69+CD14+ activated monocytes, and CD16+CD14+ monocytes significantly decreased (P < 0.001, P < 0.001, P < 0.001 and P < 0.001, respectively). Among them, only the change in Treg cells was inversely correlated with the change in CDAI score (ρ = −0.40, P = 0.011). The most dynamic increase in Treg cells was observed in the CDAI remission group (P < 0.001).ConclusionThis study demonstrates that TCZ affected proportions of circulating immune cells in patients with RA. The proportion of Treg cells among CD4+ cells correlated well with clinical response.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0526-4) contains supplementary material, which is available to authorized users.  相似文献   
245.
Satellite cells, which are skeletal muscle stem cells, divide to provide new myonuclei to growing muscle fibers during postnatal development, and then are maintained in an undifferentiated quiescent state in adult skeletal muscle. This state is considered to be essential for the maintenance of satellite cells, but their molecular regulation is unknown. We show that Hesr1 (Hey1) and Hesr3 (Heyl) (which are known Notch target genes) are expressed simultaneously in skeletal muscle only in satellite cells. In Hesr1 and Hesr3 single-knockout mice, no obvious abnormalities of satellite cells or muscle regenerative potentials are observed. However, the generation of undifferentiated quiescent satellite cells is impaired during postnatal development in Hesr1/3 double-knockout mice. As a result, myogenic (MyoD and myogenin) and proliferative (Ki67) proteins are expressed in adult satellite cells. Consistent with the in vivo results, Hesr1/3-null myoblasts generate very few Pax7(+) MyoD(-) undifferentiated cells in vitro. Furthermore, the satellite cell number gradually decreases in Hesr1/3 double-knockout mice even after it has stabilized in control mice, and an age-dependent regeneration defect is observed. In vivo results suggest that premature differentiation, but not cell death, is the reason for the reduced number of satellite cells in Hesr1/3 double-knockout mice. These results indicate that Hesr1 and Hesr3 are essential for the generation of adult satellite cells and for the maintenance of skeletal muscle homeostasis.  相似文献   
246.
Coffee is a globally consumed beverage with potential health benefits. However, there are few reports about the effects of coffee on immunological functions. We previously reported that in an allergic mouse model, coffee intake prevented allergy development through augmentation of interleukin (IL)-12p40. In order to investigate the anti-allergic activity of coffee, we examined the effect of coffee on antigen (Ag)-specific responses of immune cells in vitro. Coffee treatment suppressed proliferation and IL-2 secretion of mouse splenocytes in the same way as splenocytes from mice administered coffee orally. However, IL-12p40 secretion decreased significantly as a result of in vitro coffee treatment, which was contrary to the results obtained from experiments of mice administered coffee orally. Therefore, modification associated with oral administration might influence the anti-allergic activity of coffee.  相似文献   
247.
Japanese horse chestnut (Aesculus turbinata: Hippocastanaceae) is one of the typical woody plants that grow in temperate riparian forests in the Japanese Archipelago. To analyze the phylogeography of this plant in the Japanese Archipelago, we determined cpDNA haplotypes for 337 samples from 55 populations covering the entire distribution range. Based on 1,313 bp of two spacers, we determined ten haplotypes that are distinguished from adjacent haplotypes by one or two steps. Most of the populations had a single haplotype, suggesting low diversity. Spatial analysis of molecular variance suggested three obvious phylogeographic structures in western Japan, where Japanese horse chestnut is scattered and isolated in mountainous areas. Conversely, no clear phylogeographic structure was observed from the northern to the southern limit of this species, including eastern Japan, where this plant is more common. Rare and private haplotypes were also found in southwestern Japan, where Japanese horse chestnuts are distributed sparsely. These findings imply that western Japan might have maintained a relatively large habitat for A. turbinata during the Quaternary climatic oscillations, while northerly regions could not.  相似文献   
248.
A small library of 25 triazole/tetrazole-based sulfonamides have been synthesized and further evaluated for their inhibitory activity against thrombin, trypsin, tryptase and chymase. In general, the triazole-based sulfonamides inhibited thrombin more efficiently than the tetrazole counterparts. Particularly, compound 26 showed strong thrombin inhibition (K(i)=880 nM) and significant selectivity against other human related serine proteases like trypsin (K(i)=729 μM). Thrombin binding affinity of the same compound was determined by ITC and demonstrated that the binding of this new triazole-based scaffold is enthalpically driven, making it a good candidate for further development.  相似文献   
249.
Lysine-nitrile derivatives having a trisubstituted benzene, which belongs to a new chemical class, were prepared and tested for inhibitory activities against plasmin and the highly homologous plasma kallikrein and urokinase. The use of the novel chemotype in the development of plasmin inhibitors has been demonstrated by derivatives of compound 9.  相似文献   
250.
The single-nucleotide polymorphisms (SNPs) in the human DNase I gene (DNASE1) might be involved in susceptibility to some common diseases; however, only limited population data are available. Further, the effects of these SNPs on in vivo DNase I activity remain unknown. The genotype and haplotype of all the SNPs in DNASE1 were determined in 3 ethnic groups including 14 populations using newly developed methods. Together with our previous data on the nonsynonymous SNPs, two major haplotypes based on the five exonic SNPs were identified; genetic diversity in the Asian population was low. Among 10 SNPs, other than exonic SNPs in the gene, only 3 were polymorphic among all the populations. Haplotype distribution, based on all the polymorphic SNPs, was clarified to be generally varied in an ethnic-dependent manner. Thus, the genetic aspects of DNASE1 with regard to all the SNPs in wide-ranging ethnic groups could be first demonstrated. Further, there was no correlation of all the polymorphic SNPs other than nonsynonymous ones with serum DNase I activity levels. Polymorphic SNPs other than the exonic SNPs might not be directly related to common diseases through alterations in in vivo levels of the activity.  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