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   72349篇
  免费   3904篇
  国内免费   221篇
耳鼻咽喉   1111篇
儿科学   2625篇
妇产科学   1716篇
基础医学   8906篇
口腔科学   4011篇
临床医学   5609篇
内科学   15944篇
皮肤病学   2025篇
神经病学   6285篇
特种医学   2104篇
外国民族医学   1篇
外科学   10128篇
综合类   325篇
一般理论   24篇
预防医学   5351篇
眼科学   1777篇
药学   4986篇
  1篇
中国医学   395篇
肿瘤学   3150篇
  2024年   66篇
  2023年   609篇
  2022年   850篇
  2021年   1919篇
  2020年   1108篇
  2019年   1721篇
  2018年   2549篇
  2017年   1725篇
  2016年   1853篇
  2015年   1875篇
  2014年   2389篇
  2013年   3375篇
  2012年   5274篇
  2011年   5914篇
  2010年   2883篇
  2009年   2072篇
  2008年   4763篇
  2007年   4971篇
  2006年   4682篇
  2005年   4523篇
  2004年   4310篇
  2003年   3864篇
  2002年   3644篇
  2001年   1549篇
  2000年   1681篇
  1999年   1135篇
  1998年   441篇
  1997年   351篇
  1996年   325篇
  1995年   280篇
  1994年   240篇
  1993年   205篇
  1992年   319篇
  1991年   303篇
  1990年   284篇
  1989年   236篇
  1988年   242篇
  1987年   208篇
  1986年   170篇
  1985年   158篇
  1984年   140篇
  1983年   131篇
  1982年   91篇
  1981年   82篇
  1980年   84篇
  1979年   98篇
  1978年   82篇
  1977年   75篇
  1973年   53篇
  1967年   66篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Data are presented on hospital stay for the population 65 years-old and over, measured in percentage over the total for Spain, for the 1978 to 1988 period, by gender, for each province and autonomous region (Comunidad Autónoma). The country's total for the last available year was 35%. Except in Baleares and Murcia, the proportion of hospital stays increased in all Regions, especially in Navarra, where it increased from 23% to 51%. After adjusting for age, the increase in the proportion of hospital stays in the study population was due to an increase in utilization per person. The proportion, which was 13.3% in 1978, raised to 23.8% in 1988, with an adjusted value of 21.3%.  相似文献   
64.
65.
Carcinoma of the papilla of Vater is classified as periampullary cancer representing 5% of all gastrointestinal tract malignancies. Early and accurate diagnosis is important for those patients with a tumor of the papilla, as the prognosis is more favorable than in other periampullary neoplasms. Endoscopically obtained biopsies from suspicious papillae can detect an early tumor, although even for skilled pathologists it is often difficult to differentiate carcinomas from noninvasive lesions on the basis of forceps biopsies. The purpose of this study was to assess the preoperative diagnostic accuracy of duodenoscopy appearance and biopsy in all cases with suspicion of tumor. Thirty patients with suspicion of carcinoma of the papilla of Vater and with final diagnosis established by pancreatoduodenectomy were included in this retrospective study. In each case, a comparison was made between endoscopic biopsy and duodenoscopic appearance. Duodenoscopic appearance sensitivity and accuracy for malignancy were 86% and 83%, respectively, whereas endoscopic biopsy sensitivity and accuracy were 65% and 67%, respectively. Although preoperative diagnosis of carcinoma of the papilla of Vater is useful for making therapeutic decisions, the diagnostic value of the endoscopic appearance was superior to endoscopic biopsy in this series. Presented at the 2003 American Hepato-Pancreato-Biliary Association Congress, Miami, Florida, February 27-March 3, 2003. Supported by FADA-CAPES/PROP 200J (M.L.D.).  相似文献   
66.
Heterotopic pregnancy is the combination of intrauterine and ectopic pregnancy. This potentially fatal condition rarely occurs in spontaneous conception cycles and consequently its diagnosis requires a high index of suspicion. We report a case of heterotopic pregnancy in a 30-year old primipara with no known risk factors who presented with acute abdominal pain due to a spontaneous heterotopic pregnancy. The ectopic pregnancy was resected via laparoscopy. After surgery, the intrauterine pregnancy was uneventful.  相似文献   
67.
The spectrometric analysis of extracts from tobacco and tobacco smoke revealed the presence of pentobarbital in the analyzed substances. Tobacco samples and tobacco smoke were extracted with chloroform, determinations were performed with the Perkin-Elmer Autosystem XL system, on a Turbo Mass spectrometer. Subject to analysis were 4 cigarette brands manufactured in Poland and raw, unprocessed tobacco. The presence of pentobarbital in the analyzed samples was confirmed by the analysis of the mass spectrum of the substance, as well as by comparison of retention time with standard of pentobarbital. The determined pentobarbital concentrations in tobacco amounted to 3-6 microg/cigarette, and in tobacco smoke they were approximately 45% lower. In case of tobacco extracts it can with high probability be excluded that pentobarbital is synthesized during chromatographical analysis. The presence of pentobarbital in tobacco is thus beyond question.  相似文献   
68.
Plants traditionally employed for the treatment of malaria in certain areas of Brazil, where this disease is prevalent, were surveyed by interviewing natives and migrants in the Amazon Region. Forty-one plants used for malarial treatment and/or for the related symptoms (fever and liver disorders) were collected and identified. Given the potential of Brazil's forests and medicinal plants, research on traditional plant-based remedies in this country may lead to the development of new drugs.  相似文献   
69.
Excitatory amino acids may cause neuronal damage and death in cerebral hypoxia and ischemia, through the activation of different subtypes of glutamate receptors, in particular of the (NMDA) receptor. In the present work, the effect of hypoxia on the component of the field excitatory postsynaptic potential (fepsp) mediated by the NMDA receptor was studied in the hippocampal CA1 area of the rat. A period of 15 min of hypoxia induced virtual abolition of the NMDA receptor-mediated fepsp and a 94.8 ± 0.7% maximal decrease in the fepsp. A period of 3 min of hypoxia induced a 89.3 ± 12.3% maximal decrease in the NMDA receptor-mediated component of the fepsp and only a 50.8 ± 11.5% maximal decrease in the fepsp. Both periods of hypoxia thus induced a more pronounced depression of the NMDA receptor-mediated component of the fepsp than of the fepsp. We found that 48.5 ± 9.1% decrease (about half of the total decrease) in the NMDA receptor-mediated fepsp, and 51.6 ± 19.6% decrease (approximately all decrease) in the fepsp induced by hypoxia (3 min) were reversed in the presence of the selective adenosine A1 receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) (50 nM), and thus likely to be mediated by endogenous adenosine, through the activation of adenosine A1 receptors. On the other hand, under the conditions we assumed to be normoxic in our slices, DPCPX (50 nM) induced a much larger increase in the amplitude of the NMDA receptor-mediated fepsp compared to the increase in the fepsp, which suggest that endogenous adenosine is inhibiting predominantly the NMDA receptor-mediated fepsp under these conditions. Hypoxia markedly decreases the NMDA receptor-mediated fepsp in the hippocampal CA1 area. The contribution of endogenous adenosine to the inhibition of the NMDA receptor-mediated fepsp may be fundamental for its neuroprotective effects.  相似文献   
70.
A 32-year old woman, with endocarditis caused by Streptococcus mitis, and systolic murmur is presented. The Doppler examination was found a systolic gradient of 150 mmHg. Aortography showed a multiple membranous supravalvular aortic stenosis, with aneurysmal dilatation of the left main coronary artery and circumflex artery, associated with bicuspid aortic valve and mild aortic insufficiency. The patient died suddenly by cardiac arrest in stand by to cardiac surgery. Anatomic comprobation was not possible. The coronary artery anomalies associated with the supravalvular aortic stenosis syndrome are reviewed.  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