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   675511篇
  免费   45604篇
  国内免费   1223篇
耳鼻咽喉   8595篇
儿科学   21488篇
妇产科学   16570篇
基础医学   107194篇
口腔科学   17632篇
临床医学   61512篇
内科学   126617篇
皮肤病学   14086篇
神经病学   51825篇
特种医学   23787篇
外国民族医学   121篇
外科学   99379篇
综合类   11004篇
现状与发展   1篇
一般理论   315篇
预防医学   54329篇
眼科学   16378篇
药学   52117篇
  1篇
中国医学   1291篇
肿瘤学   38096篇
  2021年   5954篇
  2019年   6307篇
  2018年   8304篇
  2017年   6097篇
  2016年   6918篇
  2015年   7726篇
  2014年   10771篇
  2013年   16327篇
  2012年   22854篇
  2011年   24912篇
  2010年   14197篇
  2009年   13230篇
  2008年   23244篇
  2007年   24758篇
  2006年   24604篇
  2005年   23953篇
  2004年   23207篇
  2003年   21805篇
  2002年   21469篇
  2001年   26573篇
  2000年   27389篇
  1999年   23002篇
  1998年   7370篇
  1997年   6365篇
  1996年   6390篇
  1995年   5977篇
  1994年   5491篇
  1992年   17336篇
  1991年   17925篇
  1990年   17893篇
  1989年   17196篇
  1988年   15979篇
  1987年   15701篇
  1986年   14810篇
  1985年   14219篇
  1984年   10820篇
  1983年   9288篇
  1982年   5581篇
  1979年   10371篇
  1978年   7659篇
  1977年   6509篇
  1976年   6258篇
  1975年   7005篇
  1974年   8294篇
  1973年   7784篇
  1972年   7501篇
  1971年   7136篇
  1970年   6587篇
  1969年   6296篇
  1968年   5991篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Variations of the medial and inferior choanal limits may facilitate snoring. These are: 1) short vomer without crista choanalis vomeris and adaptational formations, 2) extremely concave posterior margin of the hard palate leading to disproportion between the muscular and aponeurotic part of m. tensor veli palatini and hence to a flabby soft palate especially during sleep, and 3) neonatal relation of the height and width of the choane resulting in a very large choanal region instead of relative reduction of choanal width compared to its increasing height. All these variations result in a flabby soft palate especially during sleep and may lead to formation of whirles of inspired air and snoring.  相似文献   
53.
Most authors consider the principal advantage of FG anastomoses (compared to microsurgical anastomoses) to be shorter operating time, reduced surgical trauma to oviduct stumps, and absence of tissue ischemia. These features promote reparative regeneration and decrease adhesion formation, resulting in complete recanalization of fallopian tubes. To date, the majority of work on FG is confined to the experimental development of surgical techniques. Investigations in reconstructive gynecological surgery are quite uncommon. The physical properties of FG and the positive results of available experimental studies suggest that further development of surgical techniques using FG in obstetrics and gynecology is worthwhile.  相似文献   
54.
Background : The clinical course of chronic hepatitis B is variable. Patients with hepatic decompensation, bridging necrosis or an alpha-fetoprotein level greater than 100 ng/mL during an exacerbation of hepatitis have a high risk of developing cirrhosis. This study was conducted to evaluate the effect of colchicine in the prevention of cirrhosis in such patients.
Methods : Patients with risk factor(s) were randomized to receive either colchicine 5 mg/week or no specific treatment, the end point being development of cirrhosis.
Results : After a follow up period of 4 years, the treatment group had a marked reduction in exacerbations of acute hepatitis (32% vs. 63%/patient/year, P <0.005). Seven out of 38 patients in the treatment group and 10 out of 27 patients in the control group developed cirrhosis. The calculated cumulative incidence of cirrhosis by the end of first, second, third and fourth years in the treatment group was 8.7, 18.6, 32 and 32%, respectively. The corresponding figures in the control group were 30, 35.5, 46.3 and 73.2%, respectively, with a P -value of 0.057.
Conclusions : The results suggest that colchicine may prevent cirrhosis in chronic hepatitis B patients with risk factor(s), possibly by suppressing exacerbations of hepatitis through an anti-inflammatory effect.  相似文献   
55.
56.
Vaccine cuisine.   总被引:1,自引:0,他引:1       下载免费PDF全文
  相似文献   
57.
Eighty-nine cases of chronic bronchitis were matched against167 asymptomatic controls from the glass bangle industry ofFirozabad. Factors of age, social status, smoking habit andduration of exposure were studied. Duration of exposure wasfound to be a factor contributing significantly to the causationof disease. Requests for reprints should be addressed to: Dr B. N. Gupta, Division of Epidemilogy, Industrial Toxicology Research Centre, Mahatma Gandhi Marg, Lucknow P.O. Box 80, 226001, India  相似文献   
58.
59.
Vinylogous (Groups III and V ) and acetylenologous (Group IV ) analogs of the classical β-adrenergic agents — stimulants and blockers — were prepared in order to evaluate the effect of degree of saturation, position of unsaturation and rigidity of the chain linking the aromatic ring and the amino containing functional group on biological activity. Derivatives from Group III , which represent 4-aryl-3-butenyl-2-ol-amine analogs of Group II , retained β1-adrenoceptor antagonist activity albeit substantially less potent (50–200-fold) than that possessed by their aryloxy counterparts. Consistent with the SAR for Group II compounds, substitution at position 2 of the aromatic ring yielded the most potent antagonists ( 5a, 5d, 5g ), with KB's ranging from 73–93 nM while 3,4-dichloro substitution ( 5e ) markedly reduced antagonist potency (KB = 2,400 nM). Agonist activity was also noted for 5b and 5d , suggesting that these compounds may be best classified as partial agonists. Representatives from Groups IV and V were inactive as antagonists at the β1-adrenoceptor confirming the importance of the spatial relationship between the hydroxyl and the amino nitrogen.  相似文献   
60.
Although extracellular matrix (ECM) glycoproteins play important roles in neural development, their levels are generally believed to decrease in the adult brain. Immunohistochemical analysis indicates that the anti-adhesive ECM glycoprotein SPARC/osteonectin, which contains a follistatin ‘module’, is expressed in the adult rabbit nervous system. In the cerebellum, SPARC is present in Bergmann glia, with a strong signal along their radial fibres. SPARC, while enriched in membrane fractions, is not a transmembrane protein. In the hippocampus, colocalization of SPARC is observed in cells which express the astrocytic marker GFAP. The expression of SPARC by a subset of astrocytes, particularly in synaptic enriched areas, suggests a continuing role for the ECM in the adult brain.  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