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   7700篇
  免费   749篇
  国内免费   28篇
耳鼻咽喉   88篇
儿科学   237篇
妇产科学   142篇
基础医学   1064篇
口腔科学   201篇
临床医学   829篇
内科学   1789篇
皮肤病学   159篇
神经病学   745篇
特种医学   205篇
外国民族医学   2篇
外科学   1065篇
综合类   72篇
一般理论   1篇
预防医学   704篇
眼科学   137篇
药学   434篇
中国医学   16篇
肿瘤学   587篇
  2023年   48篇
  2022年   87篇
  2021年   234篇
  2020年   102篇
  2019年   268篇
  2018年   302篇
  2017年   217篇
  2016年   204篇
  2015年   227篇
  2014年   264篇
  2013年   377篇
  2012年   447篇
  2011年   470篇
  2010年   280篇
  2009年   228篇
  2008年   353篇
  2007年   390篇
  2006年   389篇
  2005年   332篇
  2004年   277篇
  2003年   274篇
  2002年   282篇
  2001年   173篇
  2000年   200篇
  1999年   177篇
  1998年   73篇
  1997年   72篇
  1996年   59篇
  1995年   56篇
  1994年   50篇
  1993年   41篇
  1992年   143篇
  1991年   157篇
  1990年   128篇
  1989年   131篇
  1988年   119篇
  1987年   100篇
  1986年   111篇
  1985年   74篇
  1984年   67篇
  1983年   54篇
  1981年   27篇
  1980年   25篇
  1979年   50篇
  1977年   28篇
  1976年   29篇
  1974年   23篇
  1973年   35篇
  1970年   23篇
  1969年   24篇
排序方式: 共有8477条查询结果,搜索用时 15 毫秒
21.
The etiological diagnosis of obstruction is difficult during pregnancy. The authors report 3 cases of this rare association: obstruction due to adhesions [1], volvulus of the transverse colon on a common mesentery [1] and obstruction due to an appendix abscess [1]. Complementary investigations, obviously limited under these circumstances, were based on plain abdominal X-rays, repeated if necessary. The diagnosis must be made early and appropriate treatment given in order to ensure a good materno-fetal prognosis as was obtained in these 3 cases.  相似文献   
22.
23.
The brain is isolated behind a blood-tissue barrier that restricts the access of circulating proteins to neural cells. There is evidence that some of these proteins are synthesized within the central nervous system. The present study examines the synthesis and secretion of such proteins by cultured macroglial cells. Primary glial cultures were derived from cortical and subcortical regions of neonatal rat brains, and subsequent secondary cultures were enriched in type-1 astrocytes, type-2 astrocytes, or oligodendrocytes. Newly synthesized proteins were immunoprecipitated from the culture media using antisera directed against whole rat serum. All three types of glial cells secreted a range of plasma proteins. In general, type-1 astrocytes secreted more of these proteins than did type-2 astrocytes or oligodendrocytes, although the one-dimensional polyacrylamide gel electrophoresis (PAGE) profiles were specific for each cell type. Antisera directed against specific plasma proteins identified three of the most abundant proteins secreted by type-1 astrocytes as transferrin, α-2-macroglobulin, and ceruloplasmin. Northern blot analysis of cellular RNA confirmed that type-1 astrocytes contained transferrin mRNA, and that it was more abundant in cultures derived from subcortical regions than from cortical regions. In situ hybridization studies revealed that virtually all type-1 and type-2 astrocytes contained transferrin mRNA. Since the proteins identified in this study have been proposed to have a variety of neurotrophic roles in the central nervous system, these data further extend the range of possible functions that glial cells may serve in the CNS.  相似文献   
24.
25.
L-acetylcarnitine is a compound with cholinergic properties and putative action on the visual system and the glucose metabolism. Ten healthy, emmertropic volunteers (age range: 21 to 28 years) were studied. Each subject was administered 5, 10, and 30 mg/kg acute intravenous doses of L-acetylcarnitine and matching placebo. Retinal oscillatory potentials to full-field flash stimulation were recorded before and 30, 60, and 120 min after administration. A systematic reduction of the implicit time of the P2 and N2 oscillatory potential components was observed after administration of the 10 and 30 mg/kg doses: significant changes were not evident at the 5 mg dose or after placebo. The latency reduction was significantly correlated with the postdrug increment of the L-acetylcarnitine plasma concentration. No other systematic modification in latency of amplitude was observed.The results were presented in part at the XXV I.S.C.E.V. Symposium, Sarasota (Florida), April 26–30, 1987.  相似文献   
26.
OBJECTIVES: The purpose of this study was to determine quality of life (QOL) and exercise performance (EP) in patients with persistent atrial fibrillation (AF) converted to sinus rhythm (SR) compared with those remaining in or reverting to AF. BACKGROUND: Restoration of SR in patients with AF improving QOL and EP remains controversial. METHODS: Patients with persistent AF were randomized double-blind to amiodarone, sotalol, or placebo. Those not achieving SR at day 28 were cardioverted and classified into SR or AF groups at 8 weeks (n = 624) and 1 year (n = 556). The QOL (SF-36), symptom checklist (SCL), specific activity scale (SAS), AF severity scale (AFSS), and EP were assessed. RESULTS: Favorable changes were seen in SR patients at 8 weeks in physical functioning (p < 0.001), physical role limitations (p = 0.03), general health (p = 0.002), and vitality (p < 0.001), and at 1 year in general health (p = 0.007) and social functioning (p = 0.02). Changes in the scores for SCL severity (p = 0.01), functional capacity (p = 0.003), and AFSS symptom burden (p < 0.001) at 8 weeks and in SCL severity (p < 0.01) and AF symptom burden (p < 0.001) at 1 year showed significant improvements in SR versus AF. Symptomatic patients were more likely to have improvement. The EP in SR versus AF was greater from baseline to 8 weeks (p = 0.01) and to 1 year (p = 0.02). The EP correlated with physical functioning and functional capacity except in the AF group at 1 year. CONCLUSIONS: In patients with persistent AF, restoration and maintenance of SR was associated with improvements in QOL measures and EP. There was a strong correlation between QOL measures and EP.  相似文献   
27.
Hypertension in developing countries   总被引:2,自引:0,他引:2  
Population surveys carried out since the 1970s in 15 developing countries including 23 population groups show that the prevalence of hypertension ranges from as low as 1% in some African countries to over 30% in Brazil. A trend analysis of the mortality statistics for 35-74 year-olds from 16 countries in which data are available shows a downward trend in mortality from hypertension and cerebrovascular diseases in most of these countries. In spite of the current low prevalence in some countries, the total number of hypertensives in the developing world is high, and a cost assessment of possible antihypertensive drug treatment indicates that developing countries cannot afford the same drug treatment levels as developed countries.  相似文献   
28.
The aim of surgical treatment of a fixed stapes is to restore an as effective as possible impedance transfer of the ossicular chain and acoustic impedance of the annular ligament of the footplate, when it has lost elasticity, and this in order to achieve the best possible physiological vibration of the inner ear fluids.  相似文献   
29.
30.
Y Lopez  J Fioramonti  L Bueno 《Gastroenterology》1991,101(5):1249-1255
The role of endogenous opiates and cholecystokinin (CCK) in the control of postprandial pyloric myoelectric activity was investigated in conscious dogs with chronically implanted intraparietal electrodes at the gastroduodenal junction. Meals consisted of either 20 g/kg of canned food (standard meal) or the same food supplemented with 0.5 mL/kg of arachis oil (fat meal). During the 6 hours after standard and fat meals, the number of pyloric spike bursts, 2-4 seconds in duration, was 61.8 +/- 15.8 and 49.9 +/- 12.7/15 minutes, respectively. Administered 15 minutes before a fat meal, naloxone (50 micrograms/kg IV) decreased the number of spike bursts by 31.4%, whereas methyl-levallorphan, a peripheral opiate antagonist, increased postprandial spike activity by 22.2% when administered IV (0.5 mg/kg) and decreased it when administered intracerobroventricularly at a dose of 10 micrograms/kg. These two antagonists administered in the same conditions before a standard meal had no effect on the postprandial spike activity. A 1-hour infusion of cholecystokinin octapeptide (CCK-8), 500 ng.kg-1.h-1 IV and 50 ng.kg-1.h-1 intracerebroventricularly, performed 1 hour after a standard meal induced a 19.6% and 15.8% decrease in the number of pyloric spike bursts, respectively. Both naloxone IV (50 micrograms/kg) and methyl-levallorphan intracerebroventricularly (10 micrograms/kg) administered before the infusion of CCK-8 reinforced this pyloric inhibition, which was antagonized by methyl-levallorphan IV (0.5 mg/kg). The CCK antagonist asperlicin, 200 micrograms/kg IV and 20 micrograms/kg intracerebroventricularly, administered before a fat meal increased pyloric spike bursts by 22.0% and 31.5%, respectively. These results indicate that after a fat meal, endogenous opiates exert a peripheral inhibitory and central stimulatory control of pyloric motility; they suggest the involvement of both peripheral and central release of CCK.  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