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   8530篇
  免费   506篇
  国内免费   56篇
耳鼻咽喉   164篇
儿科学   196篇
妇产科学   121篇
基础医学   988篇
口腔科学   389篇
临床医学   638篇
内科学   2224篇
皮肤病学   161篇
神经病学   719篇
特种医学   303篇
外科学   1230篇
综合类   18篇
预防医学   334篇
眼科学   123篇
药学   620篇
中国医学   21篇
肿瘤学   843篇
  2023年   71篇
  2022年   188篇
  2021年   340篇
  2020年   186篇
  2019年   268篇
  2018年   305篇
  2017年   224篇
  2016年   288篇
  2015年   324篇
  2014年   364篇
  2013年   500篇
  2012年   673篇
  2011年   674篇
  2010年   358篇
  2009年   312篇
  2008年   518篇
  2007年   503篇
  2006年   490篇
  2005年   431篇
  2004年   392篇
  2003年   291篇
  2002年   267篇
  2001年   105篇
  2000年   87篇
  1999年   95篇
  1998年   57篇
  1997年   33篇
  1996年   28篇
  1995年   41篇
  1994年   26篇
  1993年   22篇
  1992年   56篇
  1991年   52篇
  1990年   43篇
  1989年   52篇
  1988年   45篇
  1987年   42篇
  1986年   38篇
  1985年   41篇
  1984年   29篇
  1983年   31篇
  1979年   23篇
  1978年   13篇
  1977年   11篇
  1976年   13篇
  1975年   14篇
  1974年   13篇
  1973年   13篇
  1971年   13篇
  1969年   11篇
排序方式: 共有9092条查询结果,搜索用时 15 毫秒
101.
A 67-year-old woman, who had symptoms of epigastric pain and abdominal distension, was found, on endoscopy, to have a large sessile villous adenoma of the periampullary duodenum. Despite the lack of evidence of malignancy, a pancreaticoduodenectomy procedure was performed, mainly because of the tumor size and site, involving the ampulla of Vater. The presence of the carcinoma was diagnosed only in the resected specimen by definitive histology. Because there is no general consensus on the optimal surgical procedure for the treatment of villous tumors of the duodenum, especially for the early stages, the indications for the operative procedure are discussed, based on a review of the literature.  相似文献   
102.
103.
104.
Subclinical hypothyroidism (sHT) is associated with enhanced cardiovascular risk. To test the hypothesis that patients with sHT are characterized by endothelial dysfunction and impaired nitric oxide (NO) availability, in 14 patients [serum cholesterol, 218 +/- 41 mg/dl (5.6 +/- 0.9 mM)] and 28 euthyroid subjects, subdivided into groups A and B [serum cholesterol, 170 +/- 19 mg/dl (4.4 +/- 0.5 mM) and 217 +/- 21 mg/dl (5.6 +/- 0.5 mM), respectively], we studied the forearm blood flow (strain-gauge plethysmography) response to intrabrachial acetylcholine, an endothelium-dependent vasodilator, at baseline and during infusion of N(G)-monomethyl-L-arginine (L-NMMA), a NO synthase inhibitor. Response to sodium nitroprusside and minimal forearm vascular resistances were also evaluated. In sHT patients, vasodilation to acetylcholine was reduced, compared with group B (+358 +/- 29% vs. +503 +/- 19%, P = 0.0003) and group A (663 +/- 65%, P = 0.02 vs. group B and P = 0.0002 vs. sHT). L-NMMA blunted the vasodilation to acetylcholine in groups A and B (49.1 +/- 6.3% and 42.7 +/- 5.5% maximal forearm blood flow reduction, respectively, P < 0.0001 vs. acetylcholine), whereas it was ineffective in sHT patients (12.8 +/- 2.5%). Response to sodium nitroprusside and minimal vascular resistances were similar. In sHT (n = 9) patients, 6 months of euthyroidism by levothyroxine replacement increased acetylcholine-vasodilation and restored L-NMMA inhibition. Patients with sHT are characterized by endothelial dysfunction resulting from a reduction in NO availability, an alteration partially independent of dyslipidemia and reversed by levothyroxine supplementation.  相似文献   
105.
Spironolactone improves lung diffusion in chronic heart failure.   总被引:1,自引:0,他引:1  
AIMS: To evaluate whether anti-aldosteronic treatment influences lung diffusion (DLCO) in chronic heart failure (HF) patients. Spironolactone improves clinical conditions and prognosis in chronic HF and reduces connective tissue matrix turnover; DLCO abnormalities in chronic HF are related to increase in fibrosis and connective tissue derangement. METHODS AND RESULTS: Thirty stable chronic HF patients, with reduced DLCO (<80% of predicted), were randomly assigned to active treatment (25 mg spironolactone daily) or placebo in addition to conventional anti-failure treatment. They were evaluated by quality of life questionnaire, laboratory investigations, cardiopulmonary exercise test, and pulmonary function test, which included DLCO and membrane diffusing capacity (DM). The evaluation was done before treatment and 6 months after. Quality of life score and standard pulmonary function tests were not significantly affected by spironolactone, while active treatment increased DLCO due to an increase of DM (DLCO: 18.3+/-3.9 vs. 19.9+/-5.5 mL/min/mmHg; DM: 28.1+/-7.7 vs. 33.3+/-8.6 mL/min/mmHg) and peak oxygen consumption (peak VO2 16.8+/-1.9 vs.18.6+/-2.2 mL/min/kg). Increments of DLCO and peak VO2 were linearly related (R=0.849, P<0.001). CONCLUSION: These data show a positive effect of spironolactone on gas diffusion and exercise capacity suggesting a novel mechanism by which anti-aldosteronic drugs improve HF clinical condition and prognosis.  相似文献   
106.
Digestive Diseases and Sciences - Mesenteric cysts are defined as a heterogeneous group of intra-abdominal cystic lesions of the mesentery or omentum that may be found in any portion of the...  相似文献   
107.
108.
The electrochemical behavior of some polybenzofulvene derivatives bearing bithiophene (BT) or terthiophene (TT) side chains was investigated by cyclic voltammetry. Very interestingly, the presence of unsubstituted terminal thiophene moieties allowed poly-6-BT-BF3k and poly-6-TT-BF3k to be cross-linked by electrochemical procedures. Conductive films were obtained by electrodeposition from solutions of these polymers onto electrode surfaces through the formation of covalent cross-linking due to dimerization (i.e. electrochemical oxidation) of the BT or TT side chains. The films showed electrochromic features and switched from yellow-orange (neutral) to green (positively charged) by switching the potential, and were stable to tenths of cycles, without degradation in the wet state in the electrolyte solution. Finally, the thin film obtained by electrodeposition of poly-6-TT-BF3k on a indium tin oxide (ITO) glass substrate showed in the neutral state a significantly red-shifted photoluminescence (PL) emission (∼40 nm red-shifted with respect to that of the corresponding film obtained by casting procedures), which was consistent with the presence of more conjugated moieties produced by the oxidative dimerization of the TT side chains. The innovative architecture and the easy preparation could lead to a broad range of applications in optoelectronics and bioelectronics for these cross-linked hybrid materials based on π-stacked polybenzofulvene backbones bearing oligothiophene side chains.

The electrochemical behavior of some polybenzofulvene derivatives bearing bithiophene (BT) or terthiophene (TT) side chains was investigated by cyclic voltammetry and cross-linked materials were obtained by dimerization of the BT or TT side chains.  相似文献   
109.
110.
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