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   3801篇
  免费   234篇
  国内免费   11篇
耳鼻咽喉   31篇
儿科学   49篇
妇产科学   104篇
基础医学   614篇
口腔科学   38篇
临床医学   470篇
内科学   841篇
皮肤病学   46篇
神经病学   274篇
特种医学   117篇
外科学   487篇
综合类   39篇
一般理论   1篇
预防医学   275篇
眼科学   39篇
药学   238篇
中国医学   7篇
肿瘤学   376篇
  2023年   45篇
  2022年   28篇
  2021年   149篇
  2020年   89篇
  2019年   86篇
  2018年   117篇
  2017年   69篇
  2016年   76篇
  2015年   96篇
  2014年   114篇
  2013年   141篇
  2012年   214篇
  2011年   226篇
  2010年   135篇
  2009年   103篇
  2008年   204篇
  2007年   188篇
  2006年   186篇
  2005年   179篇
  2004年   165篇
  2003年   131篇
  2002年   146篇
  2001年   64篇
  2000年   58篇
  1999年   60篇
  1998年   22篇
  1997年   22篇
  1992年   33篇
  1991年   35篇
  1990年   49篇
  1989年   44篇
  1988年   29篇
  1987年   48篇
  1986年   33篇
  1985年   32篇
  1984年   32篇
  1983年   36篇
  1981年   24篇
  1980年   21篇
  1979年   52篇
  1978年   35篇
  1977年   34篇
  1976年   27篇
  1975年   31篇
  1974年   33篇
  1973年   23篇
  1972年   42篇
  1971年   23篇
  1970年   28篇
  1967年   25篇
排序方式: 共有4046条查询结果,搜索用时 250 毫秒
1.
International Journal of Mental Health and Addiction - One of the relatively new negative consequences of smartphone use is “phubbing” (snubbing someone while an individual checks their...  相似文献   
2.

Personality differences are important determinants of problematic online behaviors. The purpose of the present study was to investigate the mediating role of loneliness, depression, and online gaming motives and moderating role of age on the relationship between trait emotional intelligence (EI) and Internet gaming disorder (IGD) via the construction of a multiple mediation model. A total of 478 online gamers completed a self-report online survey, including validated psychometric scales assessing the aforementioned constructs. Results indicated that trait EI was directly and indirectly associated with IGD and that the motive of escape was a partial mediator between trait EI and IGD among the total sample and adult gamers, but not among adolescents. Moreover, trait EI was associated with coping, skill development, fantasy, and recreation gaming motives only among total sample and adult gamers, and the escape motive was positively associated with IGD among total sample and adult gamers. However, among these relationships, only the association between trait EI and fantasy was significantly moderated by age group. Furthermore, the direct effect of trait EI was stronger among adolescent gamers when compared to adult gamers. Results showed that trait EI is inversely associated with IGD and affects gaming for different motives among adolescent and adult gamers.

  相似文献   
3.
Unemployment causes ill health: the wrong track   总被引:1,自引:0,他引:1  
It is not unemployment per se that causes ill health. It can be a very desirable state. There are no diseases specific to unemployment. Contrast this with employment. Unemployment shares with all other socio-environmental situations risk of exposure to common physical, social and psychological stressors that predispose to disease. Focus for action and research should be on reducing such stressors and not on provision of full employment. The former is likely to be possible and beneficial. The latter is likely to be impossible and carries a risk of making matters worse. As an immediate first step, that will reduce 'cratogenic' disease, people in authority should stop misleading the public into believing that unemployment is the cause of ill health.  相似文献   
4.
5.
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   
6.
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   
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