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   863篇
  免费   47篇
  2021年   10篇
  2020年   4篇
  2019年   4篇
  2018年   6篇
  2017年   7篇
  2016年   14篇
  2015年   28篇
  2014年   34篇
  2013年   34篇
  2012年   51篇
  2011年   44篇
  2010年   24篇
  2009年   26篇
  2008年   39篇
  2007年   39篇
  2006年   41篇
  2005年   46篇
  2004年   58篇
  2003年   35篇
  2002年   30篇
  2001年   26篇
  2000年   23篇
  1999年   10篇
  1998年   13篇
  1997年   7篇
  1996年   10篇
  1995年   10篇
  1994年   10篇
  1993年   4篇
  1992年   13篇
  1991年   16篇
  1990年   18篇
  1989年   12篇
  1988年   16篇
  1987年   16篇
  1986年   14篇
  1985年   17篇
  1984年   7篇
  1983年   10篇
  1982年   6篇
  1981年   9篇
  1980年   5篇
  1979年   6篇
  1978年   6篇
  1977年   6篇
  1976年   11篇
  1975年   7篇
  1974年   6篇
  1973年   6篇
  1966年   4篇
排序方式: 共有910条查询结果,搜索用时 15 毫秒
81.

Background

Depression and anxiety disorders have a high disease burden and as many as 15% of young people report mental health problems. Binge drinking, which is a particularly harmful way of consuming alcohol, is common among secondary school students. The aim of this study was to examine the association between binge drinking and self-reported mental health in boys and girls aged 12 to 18 years.

Findings

This cross-sectional analysis was performed on data collected by the Community Health Service (GGD) Brabant Zuidoost, the Netherlands, in 2007. In this Youth Survey, 10 090 randomly selected adolescents aged 12 tot 18 years were each sent a letter, a questionnaire, and a user name and log-in code for if they preferred to complete the Internet version of the questionnaire. Mental health was assessed using the Mental Health Inventory (MHI-5), a short 5-item questionnaire to detect feelings of depression and anxiety. Participants were asked about current alcohol consumption, their relationship with their parents, drug use, and sociodemographic data. Corrected for confounders, binge drinking and mental health problems were associated in the 12 to 15 year old girls (OR 2.43; 95% CI 1.86-3.17, p = 0.000) and boys (OR 1.64, 95% CI 1.19-2.27, p = 0.003). The majority of the 16 to 18 year old adolescents had been binge drinking in the previous 4 weeks (69.6% boys and 56.8% girls). In this age group, boys with mental health problems were less likely to be classified as binge drinkers than were boys without mental health problems (OR 0.63, 95% CI 0.45-0.87, p = 0.005). No such association between binge drinking and mental health was found in girls of this age.

Conclusion

Girls and boys aged 12-15 years were classified as binge drinkers significantly more often when they reported poor mental health. Because binge drinking damages the brain, especially at a young age, it is important that health professionals are alert to possible binge drinking when young adolescents report mental health problems and should ask their patients about their drinking behaviour. Likewise, if youngsters under 16 present with binge drinking, they should be asked whether they are anxious or depressed.  相似文献   
82.
Yang H  Zhao X  Xu Y  Wang L  He Q  Lundberg YW 《PloS one》2011,6(5):e20498
Otoconia are bio-crystals anchored to the macular sensory epithelium of the utricle and saccule in the inner ear for motion sensing and bodily balance. Otoconia dislocation, degeneration and ectopic calcification can have detrimental effects on balance and vertigo/dizziness, yet the mechanism underlying otoconia formation is not fully understood. In this study, we show that selected matrix components are recruited to form the crystal matrix and sequester Ca(2+) for spatial specific formation of otoconia. Specifically, otoconin-90 (Oc90) binds otolin through both domains (TH and C1q) of otolin, but full-length otolin shows the strongest interaction. These proteins have much higher expression levels in the utricle and saccule than other inner ear epithelial tissues in mice. In vivo, the presence of Oc90 in wildtype (wt) mice leads to an enrichment of Ca(2+) in the luminal matrices of the utricle and saccule, whereas absence of Oc90 in the null mice leads to drastically reduced matrix-Ca(2+). In vitro, either Oc90 or otolin can increase the propensity of extracellular matrix to calcify in cell culture, and co-expression has a synergistic effect on calcification. Molecular modeling and sequence analysis predict structural features that may underlie the interaction and Ca(2+)-sequestering ability of these proteins. Together, the data provide a mechanism for the otoconial matrix assembly and the role of this matrix in accumulating micro-environmental Ca(2+) for efficient CaCO(3) crystallization, thus uncover a critical process governing spatial specific otoconia formation.  相似文献   
83.
The treatment of mammalian cells with genotoxic substances can trigger DNA damage responses that include the hyperphosphorylation of replication protein A (RPA), a protein that plays key roles in the recognition, signaling, and repair of damaged DNA. We have previously reported that in the presence of a viral polymerase inhibitor, herpes simplex virus type 1 (HSV-1) infection induces the hyperphosphorylation of RPA (D. E. Wilkinson and S. K. Weller, J. Virol. 78:4783-4796, 2004). We initiated the present study to further characterize this genotoxic response to HSV-1 infection. Here we report that infection in the presence of polymerase inhibitors triggers an S-phase-specific response to DNA damage, as demonstrated by induction of the hyperphosphorylation of RPA and its accumulation within viral foci specific to the S phase of the cell cycle. This DNA damage response occurred in the presence of viral polymerase inhibitors and required the HSV-1 polymerase holoenzyme as well as the viral single-stranded-DNA binding protein. Treatment with an inhibitor of the viral helicase-primase did not induce the hyperphosphorylation of RPA or its accumulation in infected cells. Taken together, these results suggest that the S-phase-specific DNA damage response to infection is dependent on the specific inhibition of the polymerase. Finally, RPA hyperphosphorylation was not induced during productive infection, indicating that active viral replication does not trigger this potentially detrimental stress response.  相似文献   
84.
85.
86.
The proinflammatory cytokines IL-1beta and IL-18 are inactive until cleaved by the enzyme caspase-1. Stimulation of the P2X7 receptor (P2X7R), an ATP-gated ion channel, triggers rapid activation of caspase-1. In this study we demonstrate that pretreatment of primary and Bac1 murine macrophages with TLR agonists is required for caspase-1 activation by P2X7R but it is not required for activation of the receptor itself. Caspase-1 activation by nigericin, a K+/H+ ionophore, similarly requires LPS priming. This priming by LPS is dependent on protein synthesis, given that cyclohexamide blocks the ability of LPS to prime macrophages for activation of caspase-1 by the P2X7R. This protein synthesis is likely mediated by NF-kappaB, as pretreatment of cells with the proteasome inhibitor MG132, or the IkappaB kinase inhibitor Bay 11-7085 before LPS stimulation blocks the ability of LPS to potentiate the activation of caspase-1 by the P2X7R. Thus, caspase-1 regulation in macrophages requires inflammatory stimuli that signal through the TLRs to up-regulate gene products required for activation of the caspase-1 processing machinery in response to K+-releasing stimuli such as ATP.  相似文献   
87.
Cytokinins are plant hormones that can be glucosylated to form O-glucosides and N-glucosides. The glycoconjugates are inactive and are thought to play a role in homeostasis of the hormones. Although O-glucosyltransferases have been identified that recognize cytokinins, the enzymes involved in N-glucosylation have not been identified even though the process has been recognized for many years. This study utilizes a screening strategy in which 105 recombinant glycosyltransferases (UGTs) of Arabidopsis have been analyzed for catalytic activity toward the classical cytokinins: trans-zeatin, dihydrozeatin, N(6)-benzyladenine, N(6)-isopentenyladenine, and kinetin. Five UGTs were identified in the screen. UGT76C1 and UGT76C2 recognized all cytokinins and glucosylated the hormones at the N(7) and N(9) positions. UGT85A1, UGT73C5, and UGT73C1 recognized trans-zeatin and dihydrozeatin, which have an available hydroxyl group for glucosylation and formed the O-glucosides. The biochemical characteristics of the N-glucosyltransferases were analyzed, and highly effective inhibitors of their activities were identified. Constitutive overexpression of UGT76C1 in transgenic Arabidopsis confirmed that the recombinant enzyme functioned in vivo to glucosylate cytokinin applied to the plant. The role of the N-glucosyltransferases in cytokinin metabolism is discussed.  相似文献   
88.
Transthyretin (TTR) is an extracellular transport protein involved in the distribution of thyroid hormones and vitamin A. So far, TTR has only been found in vertebrates, of which piscine TTR displays the lowest sequence identity with human TTR (47%). Human and piscine TTR bind both thyroid hormones 3,5,3'-triiodo-l-thyronine (T(3)) and 3,5,3',5'-tetraiodo-l-thyronine (thyroxine, T(4)). Human TTR has higher affinity for T(4) than T(3), whereas the reverse holds for piscine TTR. X-ray structures of Sparus aurata (sea bream) TTR have been determined as the apo-protein at 1.75 A resolution and bound to ligands T(3) and T(4), both at 1.9 A resolution. The apo structure is similar to human TTR with structural changes only at beta-strand D. This strand forms an extended loop conformation similar to the one in chicken TTR. The piscine TTR.T(4) complex shows the T(4)-binding site to be similar but not identical to human TTR, whereas the TTR.T(3) complex shows the I3' halogen situated at the site normally occupied by the hydroxyl group of T(4). The significantly wider entrance of the hormone-binding channel in sea bream TTR, in combination with its narrower cavity, provides a structural explanation for the different binding affinities of human and piscine TTR to T(3) and T(4).  相似文献   
89.
90.
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