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   106171篇
  免费   7929篇
  国内免费   386篇
耳鼻咽喉   1143篇
儿科学   2704篇
妇产科学   1710篇
基础医学   15014篇
口腔科学   2287篇
临床医学   10949篇
内科学   22412篇
皮肤病学   1832篇
神经病学   11191篇
特种医学   4342篇
外国民族医学   7篇
外科学   15079篇
综合类   1349篇
一般理论   78篇
预防医学   8373篇
眼科学   1756篇
药学   7137篇
中国医学   116篇
肿瘤学   7007篇
  2023年   592篇
  2022年   1103篇
  2021年   2188篇
  2020年   1345篇
  2019年   2016篇
  2018年   2471篇
  2017年   1831篇
  2016年   2175篇
  2015年   2534篇
  2014年   3331篇
  2013年   4442篇
  2012年   6797篇
  2011年   6872篇
  2010年   4044篇
  2009年   3686篇
  2008年   6101篇
  2007年   6561篇
  2006年   6082篇
  2005年   6018篇
  2004年   5673篇
  2003年   5059篇
  2002年   5021篇
  2001年   2019篇
  2000年   1898篇
  1999年   1783篇
  1998年   1256篇
  1997年   1045篇
  1996年   848篇
  1995年   855篇
  1994年   730篇
  1993年   671篇
  1992年   1252篇
  1991年   1143篇
  1990年   1088篇
  1989年   1048篇
  1988年   922篇
  1987年   884篇
  1986年   895篇
  1985年   906篇
  1984年   722篇
  1983年   623篇
  1982年   578篇
  1981年   477篇
  1980年   424篇
  1979年   580篇
  1978年   440篇
  1977年   390篇
  1974年   398篇
  1973年   390篇
  1972年   356篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Background: Neuraxial blockade is used as primary anesthetic technique in one third of surgical procedures. The authors tested whether bisoprolol would protect patients at risk for cardiovascular complications undergoing surgery with spinal block.

Methods: The authors performed a double-blinded, placebo-controlled, multicenter trial to compare the effect of bisoprolol with that of placebo on 1-yr composite outcome including cardiovascular mortality, nonfatal myocardial infarction, unstable angina, congestive heart failure, and cerebrovascular insult. Bisoprolol was given orally before and after surgery for a maximum of 10 days. Adrenergic receptor polymorphisms and safety outcome measures of bisoprolol therapy were also determined.

Results: A total of 224 patients were enrolled. Spinal block could not be established in 5 patients. One hundred ten patients were assigned to the bisoprolol group, and 109 patients were assigned to the placebo group. The mean duration of treatment was 4.9 days in the bisoprolol group and 5.1 days in the placebo group. Bisoprolol therapy reduced mean heart rate by 10 beats/min. The primary outcome was identical between treatment groups and occurred in 25 patients (22.7%) in the bisoprolol group and 24 patients (22.0%) in the placebo group during the 1-yr follow-up (hazard ratio, 0.97; 95% confidence interval, 0.55-1.69; P = 0.90). However, carriers of at least one Gly allele of the [beta]1-adrenergic receptor polymorphism Arg389Gly showed a higher number of adverse events than Arg homozygous (32.4% vs. 18.7%; hazard ratio, 1.87; 95% confidence interval, 1.04-3.35; P = 0.04).  相似文献   

64.
Human calcium absorption from whole-wheat products   总被引:1,自引:0,他引:1  
Fractional calcium absorption from wheat products and the influence of co-ingested wheat products on calcium absorption from milk were measured in a series of randomized crossover studies in healthy adult women. The wheat had been intrinsically labeled with 45Ca during growth. In the first study, fractional calcium absorption from leavened whole-wheat bread averaged 0.817 +/- 0.124. By comparison, absorption from milk, ingested at a comparable load in the same women, averaged only 0.589 +/- 0.111. When labeled bread was co-ingested with milk, at the same aggregate load as for bread alone, bread calcium absorption fell to 0.748 +/- 0.103 (P less than 0.05). In a second study, calcium absorption from an extruded cereal prepared from intrinsically labeled wheat bran was compared with milk. Calcium absorption from the cereal (0.223 +/- 0.046) was significantly less than from milk (0.375 +/- 0.072) (P less than 0.001). When the two were co-fed at the same total load, milk calcium absorption fell to 0.258 +/- 0.055 (P less than 0.001). In a third study, the effect of phytate hydrolysis through yeast fermentation and of Maillard browning on calcium absorption was investigated using leavened bread and underbaked and overbaked cookies, each made with intrinsically labeled wheat flour. Calcium absorption from cookies was not affected by the extent of browning and averaged 0.652 +/- 0.087. However, calcium absorption from bread in these same women averaged 0.703 +/- 0.108. This was significantly more than from the cookies (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
65.
Acquired supravalvar membranous stenosis of the left atrioventricular valve   总被引:1,自引:0,他引:1  
Acquired supravalvar membranous stenosis of the left atrioventricular valve developed in a nine year old boy with atrioventricular discordance. The supravalvar membrane had not been present when a partial annuloplasty was performed on the left atrioventricular valve eight years before. The stenosis was relieved by operative excision of the membrane.  相似文献   
66.
67.
68.
Sixteen patients underwent surgical treatment for severe renovascular hypertension with rapidly progressive renal failure. These patients were assessed preoperatively with the measurement of serum creatinine and blood-urea levels (means 271 +/- 204 mumol/l and 15.6 +/- 10.3 mmol/l respectively), and renal clearances. 5 patients underwent aorto-renal bypass (bilateral in one case) and 11 patients were treated by autotransplantation of the kidney. Operative mortality was 6.2%. Early results were assessed at 1 and 6 months postoperatively. Renal function was normal in 8 patients, improved in 5 (p less than 0.05), unchanged in 1 and worse in 1 by aorto-renal bypass thrombosis. At long-term with a minimum follow-up of 12 months (mean 31 +/- 12 months), the initial improvement in renal function remained steady in 12 patients whilst 1 patient has gone on to hemodialysis. At middle and long-term, 81% of the patients were normotensive without medication or had improved blood pressure (p less than 0.001). These good results confirm the reversibility of renal ischemic lesions and support an aggressive attitude towards the use of revascularization in the surgical treatment of such patients with renovascular hypertension and renal failure.  相似文献   
69.
70.
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