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   4314309篇
  免费   353017篇
  国内免费   14471篇
耳鼻咽喉   59558篇
儿科学   136511篇
妇产科学   114046篇
基础医学   660172篇
口腔科学   121854篇
临床医学   389181篇
内科学   776455篇
皮肤病学   107637篇
神经病学   360525篇
特种医学   172893篇
外国民族医学   686篇
外科学   661349篇
综合类   128221篇
现状与发展   23篇
一般理论   2537篇
预防医学   353007篇
眼科学   101622篇
药学   310178篇
  24篇
中国医学   11865篇
肿瘤学   213453篇
  2021年   55867篇
  2019年   58476篇
  2018年   73283篇
  2017年   55723篇
  2016年   61872篇
  2015年   75242篇
  2014年   109781篇
  2013年   175152篇
  2012年   114904篇
  2011年   118238篇
  2010年   123382篇
  2009年   125892篇
  2008年   105345篇
  2007年   111101篇
  2006年   120949篇
  2005年   115456篇
  2004年   117460篇
  2003年   107496篇
  2002年   97091篇
  2001年   160889篇
  2000年   156617篇
  1999年   144942篇
  1998年   71287篇
  1997年   67502篇
  1996年   65508篇
  1995年   61064篇
  1994年   55043篇
  1993年   51262篇
  1992年   107490篇
  1991年   103100篇
  1990年   99539篇
  1989年   97403篇
  1988年   89977篇
  1987年   88198篇
  1986年   83879篇
  1985年   82509篇
  1984年   68595篇
  1983年   61131篇
  1982年   48663篇
  1981年   45092篇
  1980年   42507篇
  1979年   60246篇
  1978年   47830篇
  1977年   42917篇
  1976年   39440篇
  1975年   39408篇
  1974年   43460篇
  1973年   41882篇
  1972年   39128篇
  1971年   36447篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
921.
922.
923.
924.
925.
Between the 1930s and 1960s Puerto Rico was transformed from a marginal United States territory into an industrialised ‘showcase of development’. This article investigates the organisation of milk station programmes on the island during this crucial period and how these reflected the circulation of child welfare knowledge, nutrition expertise and public health practices. During the Depression, these perspectives fostered a recast of the eugenic regeneration ideologies motivating medical assessments of and sanitary interventions with Puerto Rico’s rural poor since the nineteenth century. Innovations in nutrition knowledge and an emerging rural hygiene movement highlighted the negative health effects of the island’s monocrops economy. In this context, the nourishment of children’s bodies assumed symbolic and instrumental significance for the reconfiguration of colonial and developmental models promoted by the new Popular Democratic Party (PPD). The experience of public health professionals in relief work during the 1930s contributed to the articulation of food and nutrition as key elements of this party’s populist discourse. Programmes like milk stations became part of strategies to rear and manage the labour force needed in the industrial development model promoted by the PPD. From the perspective of poor Puerto Ricans, however, they were part of the materialisation of its promise of social justice for the poorer classes.  相似文献   
926.
Die Ophthalmologie - Die Filtrationsverfahren sind im Gegensatz zu allen anderen Glaukomoperationen mit einer biomikroskopisch sichtbaren Wundheilung assoziiert, sodass eine Vielzahl von...  相似文献   
927.
928.
929.
  1. Butyrylcholinesterase (BChE) is a serine esterase that plays a role in the detoxification of natural as well as synthetic ester-bond-containing compounds. Alterations in BChE activity are associated with a number of diseases. Cholinergic system abnormalities in particular are correlated with the formation of senile plaques in Alzheimer’s disease (AD), and administration of cholinesterase inhibitors is a common therapeutic approach used to treat AD.

  2. Here, our aim was to study the interaction between BChE and fluoxetine.

  3. Molecular docking simulations revealed that fluoxetine penetrated deep into the active-site gorge of BChE and that it was engaged in stabilizing noncovalent interactions with multiple subsites. In substrate kinetic studies, the Vm, Km, kcat and kcat/Km values were found to be 20.59?±?0.36?U mg?1 protein, 194?±?14?µM, 1.3?×?108?s?1 and 6.7?×?105?µM?1s?1, respectively. Based on inhibitory studies, fluoxetine appeared to inhibit BChE competitively, with an IC50 value of 104?µM and a Ki value of 36.3?±?4.7?µM.

  4. Overall, both the low Ki value and the high number of BChE–fluoxetine interactions suggest that fluoxetine is a potent inhibitor of BChE, although in vivo mechanisms for the direct effects of BChE inhibition on various pathologies remain to be further investigated.

  相似文献   
930.

Objectives

Short successive periods of skeletal muscle disuse have been suggested to substantially contribute to the observed loss of skeletal muscle mass over the life span. Hospitalization of older individuals due to acute illness, injury, or major surgery generally results in a mean hospital stay of 5 to 7 days, during which the level of physical activity is strongly reduced. We hypothesized that hospitalization following elective total hip arthroplasty is accompanied by substantial leg muscle atrophy in older men and women.

Design and participants

Twenty-six older patients (75 ± 1 years) undergoing elective total hip arthroplasty participated in this observational study.

Measurements

On hospital admission and on the day of discharge, computed tomographic (CT) scans were performed to assess muscle cross-sectional area (CSA) of both legs. During surgery and on the day of hospital discharge, a skeletal muscle biopsy was taken from the m. vastus lateralis of the operated leg to assess muscle fiber type–specific CSA.

Results

An average of 5.6 ± 0.3 days of hospitalization resulted in a significant decline in quadriceps (?3.4% ± 1.0%) and thigh muscle CSA (?4.2% ± 1.1%) in the nonoperated leg (P < .05). Edema resulted in a 10.3% ± 1.7% increase in leg CSA in the operated leg (P < .05). At hospital admission, muscle fiber CSA was smaller in the type II vs type I fibers (3326 ± 253 μm2 vs 4075 ± 279 μm2, respectively; P < .05). During hospitalization, type I and II muscle fiber CSA tended to increase, likely due to edema in the operated leg (P = .10).

Conclusions

Six days of hospitalization following elective total hip arthroplasty leads to substantial leg muscle atrophy in older patients. Effective intervention strategies are warranted to prevent the loss of muscle mass induced by short periods of muscle disuse during hospitalization.  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