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   514113篇
  免费   33259篇
  国内免费   614篇
耳鼻咽喉   6893篇
儿科学   16839篇
妇产科学   13522篇
基础医学   85034篇
口腔科学   14473篇
临床医学   44342篇
内科学   93612篇
皮肤病学   12154篇
神经病学   36198篇
特种医学   18458篇
外国民族医学   63篇
外科学   77041篇
综合类   8471篇
一般理论   118篇
预防医学   38968篇
眼科学   12134篇
药学   40543篇
中国医学   1006篇
肿瘤学   28117篇
  2018年   4932篇
  2015年   4509篇
  2014年   6059篇
  2013年   9544篇
  2012年   12873篇
  2011年   14272篇
  2010年   8301篇
  2009年   7773篇
  2008年   13692篇
  2007年   14699篇
  2006年   14941篇
  2005年   14358篇
  2004年   14047篇
  2003年   13389篇
  2002年   13267篇
  2001年   24067篇
  2000年   25079篇
  1999年   20555篇
  1998年   5426篇
  1997年   4706篇
  1996年   5041篇
  1995年   4625篇
  1994年   4318篇
  1993年   4135篇
  1992年   15725篇
  1991年   16311篇
  1990年   16423篇
  1989年   15799篇
  1988年   14576篇
  1987年   14421篇
  1986年   13601篇
  1985年   12977篇
  1984年   9628篇
  1983年   8250篇
  1982年   4562篇
  1981年   4230篇
  1979年   9419篇
  1978年   6855篇
  1977年   5772篇
  1976年   5603篇
  1975年   6396篇
  1974年   7634篇
  1973年   7132篇
  1972年   6962篇
  1971年   6687篇
  1970年   6172篇
  1969年   5889篇
  1968年   5559篇
  1967年   5013篇
  1966年   4450篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
13.
14.
15.
16.
At this study a multi-criteria model was developed to examine the available procedures, techniques and methods of handling infectious waste in the large healthcare unit of University Regional General Hospital of Patras, Western Greece. Particularly, this study examined the: a) current legislation and Directives issued for medical waste management at Greece and among the other EU-members, b) contribution of healthcare wastes (HCW) generation rate on social and economic parameters in selected European countries, c) available procedures, techniques, and methods upon the disposal of infectious wastes at the healthcare studied, and, d) propositions for integrated management of such hazardous wastes. Specifically, the Analytic Hierarchy Process (AHP) methodology was applied under pair wise comparison matrices in two stages: 1) the scale factors and the indicators, and 2) the criteria and their sub–criteria. The assessment of these pair wise matrices included the indicators and the sub–criteria. Subsequently, two pair wise comparison matrices, upon a) the “Fulfillment of environmental objectives” indicator and b) the “Energy consumption” sub criterion, were denoted. The AHP methodology yielded good results; however there is still space of improving the environmental performance. The normalized relative weights obtained for the criteria and sub criteria motivated specific actions that have to be handled. Particularly, the results indicated a very good value in environmental management criteria due the values obtained for the commitment towards the environmental policy standards and the waste management procedures. However, further improvements on staff awareness (such as development programs to enhance sensitivity) and more green purchasing suppliers, should be further addressed.  相似文献   
17.
18.
ObjectiveIdentify factors associated with healthcare providers' frequency of depot medroxyprogesterone acetate (DMPA) provision to adolescents.Study designWe analyzed data from surveys mailed to a nationally representative sample of public-sector providers and office-based physicians (n=1984). We estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) of factors associated with frequent DMPA provision to adolescents in the past year.ResultsAlthough most providers (>95%) considered DMPA safe for adolescents, fewer reported frequent provision (89% of public-sector providers; 64% of office-based physicians). Among public-sector providers, factors associated with lower odds of frequent provision included working in settings without Title X funding (aOR 0.44, 95% CI 0.30–0.64), reporting primary care as their primary clinical focus versus reproductive or adolescent health (aOR 0.42, 95% CI 0.28–0.61), and providing fewer patients with family planning services. Among office-based physicians, factors associated with lower odds of frequent provision included specializing in obstetrics/gynecology (aOR 0.50, 95% CI 0.27–0.91) and family medicine (aOR 0.21, 95% CI 0.09–0.47) versus adolescent medicine, completing training ≥15 versus <5 years ago (aOR 0.27, 95% CI 0.09–0.83), and reporting that 0–24% of patients pay with Medicaid or other government healthcare assistance versus ≥50% (aOR 0.23, 95% CI 0.09–0.61). The reason most commonly reported by providers for infrequent DMPA provision was patient preference for another method.ConclusionsWhile most providers reported frequently providing DMPA to adolescents, training on evidence-based recommendations for contraception, focused on subgroups of providers with lower odds of frequent DMPA provision, may increase adolescents' access to contraception.ImplicationsAlthough >95% of providers considered depot medroxyprogesterone (DMPA) a safe contraceptive for adolescents, only 89% of public-sector providers and 64% of office-based physicians reported frequently providing DMPA to adolescents. Provider training on evidence-based recommendations for contraception counseling and provision may increase adolescents' access to DMPA and all methods of contraception.  相似文献   
19.
Rheological behaviour of pharmaceutical semisolid preparations significantly affects manufacturing process, administration, stability, homogeneity of incorporated drug, accuracy of dosing, adhesion in the place of application, drug release, and resulting therapeutic effect of the product. We performed test of consistency by penetrometry, rotational, oscillation and creep tests, and squeeze and tack tests of model samples to introduce methods suitable for characterization and comparison of semisolids in practice. Penetrometry is a simple method allowing sorting the semisolids to low and high stress-resistant materials but deficient for rheological characterization of semisolids. Value of yield stress, generally considered to be appropriate feature of semisolids, is significantly influenced by the method of testing and the way of evaluation. The hysteresis loops of model semisolids revealed incomplete thixotropy, therefore, three-step thixotropy test was employed. Semisolids showed nonlinear response in the creep phase of tests and partial recovery of structure by storing energy in the recovery phase. Squeeze and tack tests seem to be convenient ways for comparison of semisolids. Our study can contribute to a better understanding of different flow behaviour of semisolids given by different physicochemical properties of excipients and can bring useful approaches to evaluation and comparison of semisolids in practice.  相似文献   
20.
Microglia, the innate immune cells of the CNS, perform critical inflammatory and noninflammatory functions that maintain normal neural function. For example, microglia clear misfolded proteins, elaborate trophic factors, and regulate and terminate toxic inflammation. In Alzheimer’s disease (AD), however, beneficial microglial functions become impaired, accelerating synaptic and neuronal loss. Better understanding of the molecular mechanisms that contribute to microglial dysfunction is an important objective for identifying potential strategies to delay progression to AD. The inflammatory cyclooxygenase/prostaglandin E2 (COX/PGE2) pathway has been implicated in preclinical AD development, both in human epidemiology studies and in transgenic rodent models of AD. Here, we evaluated murine models that recapitulate microglial responses to Aβ peptides and determined that microglia-specific deletion of the gene encoding the PGE2 receptor EP2 restores microglial chemotaxis and Aβ clearance, suppresses toxic inflammation, increases cytoprotective insulin-like growth factor 1 (IGF1) signaling, and prevents synaptic injury and memory deficits. Our findings indicate that EP2 signaling suppresses beneficial microglia functions that falter during AD development and suggest that inhibition of the COX/PGE2/EP2 immune pathway has potential as a strategy to restore healthy microglial function and prevent progression to AD.  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