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   2839篇
  免费   136篇
  国内免费   10篇
耳鼻咽喉   22篇
儿科学   35篇
妇产科学   57篇
基础医学   457篇
口腔科学   29篇
临床医学   319篇
内科学   815篇
皮肤病学   40篇
神经病学   155篇
特种医学   61篇
外科学   343篇
综合类   25篇
一般理论   1篇
预防医学   153篇
眼科学   30篇
药学   183篇
中国医学   7篇
肿瘤学   253篇
  2023年   35篇
  2022年   76篇
  2021年   141篇
  2020年   75篇
  2019年   72篇
  2018年   93篇
  2017年   45篇
  2016年   60篇
  2015年   74篇
  2014年   96篇
  2013年   114篇
  2012年   175篇
  2011年   177篇
  2010年   100篇
  2009年   75篇
  2008年   155篇
  2007年   152篇
  2006年   135篇
  2005年   142篇
  2004年   121篇
  2003年   100篇
  2002年   95篇
  2001年   34篇
  2000年   31篇
  1999年   32篇
  1998年   19篇
  1997年   13篇
  1996年   15篇
  1995年   12篇
  1992年   24篇
  1991年   30篇
  1990年   30篇
  1989年   33篇
  1988年   37篇
  1987年   28篇
  1986年   25篇
  1985年   28篇
  1984年   17篇
  1983年   19篇
  1979年   17篇
  1978年   13篇
  1977年   16篇
  1976年   15篇
  1975年   13篇
  1974年   19篇
  1973年   18篇
  1972年   18篇
  1971年   13篇
  1970年   27篇
  1969年   12篇
排序方式: 共有2985条查询结果,搜索用时 15 毫秒
1.
The use of multifactor statistic analysis for screening population of the northern part of the Ob river basin for helminthiasis allowed the authors to reveal a significant feedback between manifested opisthorchiasis and other types of this disease course in both sexes. The main component analysis indicates that the tentatively control group of males is presented by adolescents (14-17 years old) who are likely to be infected with Opisthorchis without evidence of its clinical manifestations. The correlation analysis demonstrated also a direct relationship between the age and manifest opisthorchiasis, as well as double mixed invasion of males (r-0.15 and 0.26, p less than 0.05 and 0.01, respectively). The first three main components explain about 55% variance in the correlation matrix of initial parameters and allow to reveal the variance source, taking into account, along with differentiation of 4 groups of opisthorchiasis patients, also the age- and sex-dependent combination of opisthorchiasis with other helminthic invasions.  相似文献   
2.
3.
Klein [Klein, A. S. (2006). Separating transducer nonlinearities and multiplicative noise in contrast discrimination. Vision Research, 46, 4279-4293] questions the existence of intrinsic singularities in two-alternative force-choice (2AFC) Signal Detection Theory (SDT) models, suggesting that the singularities found in Katkov et al. [Katkov, M., Tsodyks, M., & Sagi, D. (2006a). Singularities in the inverse modeling of 2AFC contrast discrimination data. Vision Research, 46, 259-266; Katkov, M., Tsodyks, M., & Sagi, D. (2006b). Analysis of two-alternative force-choice Signal Detection Theory model. Journal of Mathematical Psychology, 50, 411-420] are due to discarding higher order terms in the Taylor expansion of d' and/or limited to steep psychometric functions. Here we provide some simple intuitive examples that illustrate the results described in Katkov et al. (2006a, 2006b). We show, for the constant noise model, that singularities exist when exact values of d' are computed and that the singularities are not limited to steep psychometric functions. In these cases the disambiguation of the different models requires millions of trials.  相似文献   
4.
Background BMS-747158-02 is a novel fluorine 18-labeled pyridazinone derivative designed for cardiac imaging. The uptake and retention mechanisms of F-18 BMS-747158-02 in cardiac myocytes were studied in vitro, and the biodistribution of F-18 BMS-747158-02 was studied in vivo in mice. Methods and Results Fluorine 19 BMS-747158-01 inhibited mitochondrial complex I (MC-I) in bovine heart submitochondrial particles with an IC50 of 16.6±3 nmol/L that was comparable to the reference inhibitors of MC-1, rotenone, pyridaben, and deguelin (IC50 of 18.2±6.7 nmol/L, 19.8±2.6 nmol/L, and 23.1±1.5 nmol/L, respectively). F-18 BMS-747158-02 had high uptake in monolayers of neonatal rat cardiomyocytes (10.3%±0.7% of incubated drug at 60 minutes) that was inhibited by 200 nmol/L of rotenone (91%±2%) and deguelin (89%±3%). In contrast, an inactive pyridaben analog, P-0 (IC50 value>4 μmol/L in MC-1 assay), did not inhibit the binding of F-18 BMS-747158-02 in cardiomyocytes. Uptake and washout kinetics for F-18 BMS-747158-02 in rat cardiomyocytes indicated that the time to half-maximal (t1/2) uptake was very rapid (approximately 35 seconds), and washout t1/2 for efflux of F-18 BMS-747158-02 was greater than 120 minutes. In vivo biodistribution studies in mice showed that F-18 BMS-747158-02 had substatial myocardial uptake (9.5%±0.5% of injected dose per gram) at 60 minutes and heart-to-lung and heart-to-liver ratios of 14.1±2.5 and 8.3±0.5, respectively. Positron emission tomography imaging in the mouse allowed clear cardiac visualization and demonstrated sustained myocardial uptake through 55 minutes. Conclusions F-18 BMS-747158-02 is a novel positron emission tomography cardiac tracer targeting MC-I in cardiomyocytes with rapid uptake and slow washout. These characteristics allow fast and sustained accumulation in the heart.  相似文献   
5.
6.
Institute of Applied Physics. Scientific-Research Institute for Traumatology and Orthopedics, Nizhnii Novgorod. Translated from Meditsinskaya Tekhnika, No. 3, pp. 32–34, May–June, 1992.  相似文献   
7.
Various diseases of the central nervous system are characterized by induction of inflammatory events, which involve formation of prostaglandins. Production of prostaglandins is regulated by activity of phospholipases A(2) and cyclooxygenases. These enzymes release the prostaglandin precursor, the n-6 polyunsaturated fatty acid, arachidonic acid and oxidize it into prostaglandin H(2). Docosahexaenoic acid, which belongs to the n-3 class of polyunsaturated fatty acids, was shown to reduce production of prostaglandins after in vivo and in vitro administration. Nevertheless, the fact that in brain tissue cellular phospholipids naturally have a uniquely high content of docosahexaenoic acid was ignored so far in studies of prostaglandin formation in brain tissue. We consider the following possibilities: docosahexaenoic acid might attenuate production of prostaglandins by direct inhibition of cyclooxygenases. Such inhibition was found with the isolated enzyme. Another possibility, which has been already shown is reduction of expression of inducible cyclooxygenase-2. Additionally, we propose that docosahexaenoic acid could influence intracellular Ca(2+) signaling, which results in changes of activity of Ca(2+)-dependent phospholipase A(2), hence reducing the amount of arachidonic acid available for prostaglandin production. Astrocytes, the main type of glial cells in the brain control the release of arachidonic acid, docosahexaenoic acid and the formation of prostaglandins. Our recently obtained data revealed that the release of arachidonic and docosahexaenoic acids in astrocytes is controlled by different isoforms of phospholipase A(2), i.e. Ca(2+)-dependent phospholipase A(2) and Ca(2+)-independent phospholipase A(2), respectively. Moreover, the release of arachidonic and docosahexaenoic acids is differently regulated through Ca(2+)- and cAMP-dependent signal transduction pathways. Based on analysis of the current literature and our own data we put forward the hypothesis that Ca(2+)-independent phospholipase A(2) and docosahexaenoic acid are promising targets for treatment of inflammatory related disorders in brain. We suggest that Ca(2+)-independent phospholipase A(2) and docosahexaenoic acid might be crucially involved in brain-specific regulation of prostaglandins.  相似文献   
8.
Hutchinson's sign--pigmentation of the periungual tissues--is a valuable clue to the diagnosis of subungual melanoma. When present, this sign indicates malignant melanoma, however minimal the pigmentation or the histology may be. An illustrative case is presented.  相似文献   
9.
Chronic human health problems, namely arteriosclerosis, myocardial ischemia, and cancer, may be caused by highly active oxygen species and may be preventable by antioxidant vitamins. In humans, the sources of two major antioxidants, beta-carotene and alpha-tocopherol, are dietary. In this study, we measured the plasma concentrations of beta-carotene and alpha-tocopherol by reverse-phase high-pressure liquid chromatography in a cross-sectional sampling of 116 women. Significantly reduced plasma levels of beta-carotene and alpha-tocopherol were observed in women with histopathologically diagnosed cervical dysplasias or cancer (p less than 0.0001 and p less than 0.005, respectively). There was an inverse association between the plasma levels of both beta-carotene and alpha-tocopherol and increasingly severe graded cervical histopathology. In groups with advanced dysplasias, the percentage of smokers was markedly increased and the women were comparatively older (p less than 0.0001). A strong association was noted between smoking status and plasma beta-carotene levels, independent of cervical pathology. However, this was not evident with respect to alpha-tocopherol. The findings suggest that the antioxidants beta-carotene and alpha-tocopherol have biologic functions that are interdependent in the pathogenesis of cervical intraepithelial lesions and cervical cancer.  相似文献   
10.
Dexamethasone adjunctive treatment for tuberculous meningitis   总被引:3,自引:0,他引:3  
During a 5-year period, 280 of 2010 patients admitted to the meningitis ward of a referral hospital in Cairo, Egypt, were clinically diagnosed as having tuberculous meningitis and were treated with either antituberculous chemotherapy and dexamethasone or antituberculous chemotherapy alone. Fatality rates and neurologic sequelae were compared for the 2 treatment groups in the 160 patients who had cerebrospinal fluid cultures positive for Mycobacterium tuberculosis. The overall mortality rate of 51% reflects the delay in receiving appropriate therapy (79% with symptoms for more than 2 weeks) and the severity of illness on admission (56% in coma, 39% drowsy). The fatality rate was significantly lower in the group receiving dexamethasone (43% vs. 59%, P less than 0.05), particularly in the drowsy patients (15% vs. 40% P less than 0.04), and in patients surviving long enough to receive at least 10 days of treatment (14% vs. 33%, P less than 0.02). Development of neurologic complications after initiation of therapy (4 vs. 10) and permanent sequelae (6 vs. 13) were significantly lower in the dexamethasone-treated group (P less than 0.02).  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