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   862065篇
  免费   70589篇
  国内免费   1839篇
耳鼻咽喉   12799篇
儿科学   24635篇
妇产科学   25099篇
基础医学   124215篇
口腔科学   25484篇
临床医学   75307篇
内科学   164553篇
皮肤病学   16974篇
神经病学   70070篇
特种医学   35190篇
外国民族医学   171篇
外科学   136145篇
综合类   24604篇
现状与发展   2篇
一般理论   263篇
预防医学   66873篇
眼科学   20517篇
药学   64685篇
中国医学   1594篇
肿瘤学   45313篇
  2018年   7346篇
  2015年   7723篇
  2014年   11109篇
  2013年   16782篇
  2012年   22718篇
  2011年   23833篇
  2010年   13866篇
  2009年   13062篇
  2008年   22572篇
  2007年   24617篇
  2006年   24487篇
  2005年   24140篇
  2004年   23704篇
  2003年   22832篇
  2002年   21924篇
  2001年   35822篇
  2000年   36464篇
  1999年   30896篇
  1998年   9221篇
  1997年   8548篇
  1996年   8475篇
  1995年   8006篇
  1994年   7723篇
  1992年   26658篇
  1991年   26098篇
  1990年   25617篇
  1989年   24677篇
  1988年   23219篇
  1987年   22883篇
  1986年   21740篇
  1985年   21097篇
  1984年   16385篇
  1983年   13996篇
  1982年   8854篇
  1981年   8201篇
  1980年   7671篇
  1979年   16736篇
  1978年   12114篇
  1977年   10181篇
  1976年   9328篇
  1975年   10147篇
  1974年   12641篇
  1973年   12136篇
  1972年   11538篇
  1971年   10685篇
  1970年   10218篇
  1969年   9909篇
  1968年   8900篇
  1967年   8230篇
  1966年   7653篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
111.
The efficacy of radiology in evaluating dysphagia was studied in 86 patients by comparison to endoscopic findings. In the 66 patients with endoscopic abnormalities radiology was correct in 54, for a sensitivity of 82%. Sensitivity of radiology improved to 95% if mild esophagitis was excluded. In the 20 patients with normal endoscopy, radiology was normal in 18 (90%). Thus radiology proved to be a reliable means of evaluating the esophagus in patients with dysphagia.  相似文献   
112.
A crossover double-blind controlled trial was performed on 36 patients with rheumatoid arthritis to assess the necessity for serum salicylate monitoring in determining optimal dosage. There was no clinically or statistically significant increase in the clinical improvement of patients associated with serum monitoring but potentially toxic serum levels occurred without tinnitus when serum monitoring was not used.  相似文献   
113.
114.
Transient transfection of pLB2CAT constructs bearing short synthetic oligonucleotides derived either from the tyrosine hydroxylase (TH) promoter or other sources was used to examine functional cAMP regulatory element (CRE) activity in a variety of cell lines. The region containing only the putative TH CRE was found to be as or more effective in conferring cAMP responsiveness onto pLB2CAT (which employs the TK promoter) than the immediate 272 bp region of the TH promoter. Increases in CAT activity of 10- to 20-fold were observed in JEG-3 cells with a single insert of the TH CRE region (-31 to -54) in pLB2CAT, and the presence of a second insert generated only a modest further increase. This construct also responded to cAMP in 4 other cell lines tested but the degree of increase was less dramatic. Inserts containing the consensus 8 bp CRE motif embedded in other natural or artificial contexts served generally as weak functional CREs in all cell lines tested. In vitro analysis revealed that a specific protein-DNA complex apparently containing a single protein with a MW of 45-50 kDa was formed equally well with JEG-3 cell nuclear extract and CRE-bearing-TH and other fragments which produced dramatically different cAMP effects in vivo. These results suggest specificity in the effects of cAMP on different CREs which are dictated by contextual differences.  相似文献   
115.
116.
Pregnant rats were injected with a single dose of methylazoxymethanol (MAM, 25 mg/kg) on gestational day 14, 15, 16, 17, 18 or 19 and offspring were tested for their physical development, reflex development and spontaneous activity. MAM treatment did not affect gestational and litter parameters at any of the time of administration studied. Treatment at gestational day 14 (GD14) had the most severe effect on functional neurodevelopment until weaning: righting reflex at surface, chimney test, horizontal wire test resulted altered. Administration at GD15, 16, 18, 19 did not affect the performance in these tests. Offspring treated at GD17 showed a delayed eye opening and an impaired performance in the horizontal wire test. When tested at 50 days of age on the rotarod, all the treated groups performed worse than controls with the exception of GD19 treated offspring. Administration at GD14 and GD15 resulted in increased spontaneous activity of the offspring at 21 days but not at 60 days of age. Different degrees of microencephaly were observed for all treated groups. The results indicate that alterations of physical and behavioral development induced by MAM treatment are dependent on the time of MAM administration, and specific behavioral tests are able to detect different abnormalities and differentiate among treatment groups. Some alterations observed in MAM rats undergo to adaptive changes during maturation of the CNS.  相似文献   
117.
118.
Although the initial phase of receptor-mediated Ca2+ signaling, involving Ca2+ release from intracellular stores by inositol 1,4,5-trisphosphate, is relatively well characterized, the nature of the organelle releasing Ca2+ is a controversial subject. At issue is the question of whether Ca2+ is released from the endoplasmic reticulum, or from a more specialized organelle called the 'calciosome'. In this review, we attempt to analyse the arguments for and against these two views, and attempt to reconcile some of the apparently conflicting findings by proposing a hypothetical model of the inositol 1,4,5-trisphosphate-sensitive Ca2+ pool.  相似文献   
119.
BACKGROUND AND PURPOSE: The familial occurrence of intracranial aneurysms and cervical artery dissections has been described in different families and supports the hypothesis that a primary arteriopathy may play a role in the pathogenesis of these disorders. Although the basis for this arteriopathy is generally not believed to be similar among cases of intracranial aneurysms and cervical artery dissections, several similarities exist in the epidemiology of these disorders and a common underlying arterial abnormality may be suspected. SUMMARY OF REPORTS: The medical records of all 175 patients with spontaneous dissections of the cervical arteries who were seen at the Mayo Clinic between 1970 and 1989 were reviewed to identify families in which intracranial aneurysms and cervical dissections coexisted. Three families were identified in which intracranial aneurysms and cervical artery dissections were observed among siblings. These families are described in detail. CONCLUSIONS: The familial occurrence of intracranial aneurysms and cervical artery dissections within the same families provides support to the importance of a common underlying arteriopathy in the pathogenesis of both these disorders. The underlying vascular defect may, at least in some cases, be inherited.  相似文献   
120.
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