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   12208篇
  免费   945篇
  国内免费   431篇
耳鼻咽喉   41篇
儿科学   197篇
妇产科学   378篇
基础医学   461篇
口腔科学   73篇
临床医学   4675篇
内科学   1758篇
皮肤病学   79篇
神经病学   447篇
特种医学   662篇
外国民族医学   3篇
外科学   1414篇
综合类   2048篇
预防医学   302篇
眼科学   165篇
药学   393篇
  4篇
中国医学   61篇
肿瘤学   423篇
  2024年   77篇
  2023年   314篇
  2022年   347篇
  2021年   509篇
  2020年   513篇
  2019年   567篇
  2018年   354篇
  2017年   371篇
  2016年   345篇
  2015年   381篇
  2014年   616篇
  2013年   606篇
  2012年   510篇
  2011年   731篇
  2010年   616篇
  2009年   551篇
  2008年   575篇
  2007年   615篇
  2006年   729篇
  2005年   605篇
  2004年   535篇
  2003年   504篇
  2002年   443篇
  2001年   379篇
  2000年   221篇
  1999年   223篇
  1998年   280篇
  1997年   177篇
  1996年   148篇
  1995年   121篇
  1994年   101篇
  1993年   63篇
  1992年   69篇
  1991年   62篇
  1990年   60篇
  1989年   38篇
  1988年   27篇
  1987年   22篇
  1986年   23篇
  1985年   16篇
  1984年   21篇
  1983年   13篇
  1982年   18篇
  1981年   15篇
  1980年   12篇
  1979年   10篇
  1978年   9篇
  1977年   9篇
  1975年   10篇
  1973年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
BACKGROUND: Color Doppler ultrasonography of intrarenal arterial resistance index (RI), performed early after kidney transplant, has proven to reliably predict short-term allograft function. The aim of this study was to assess whether it could also predict long-term renal function. METHODS: We retrospectively analysed 76 kidney transplant patients who underwent RI assessment within 1 month after the transplant, subdivided into two groups according to RI values, lower (group A) or higher (group B) than its median value (0.635). RESULTS: Compared with group A subjects, the patients of group B were older at the time of transplant (42 +/- 9 vs 35 +/- 8 years; P = 0.001), the donor age was also older (41 +/- 16 vs 33 +/- 13 years; P = 0.02) and had a slightly higher proteinuria (0.54 +/- 0.5 vs 0.32 +/- 0.2 g/24 h; P = 0.02). Serum creatinine, ciclosporin or tacrolimus trough level, arterial blood pressure, number of human leukocyte antigen (HLA) mismatches, anti-hypertensive medications and incidence of delayed graft function were not significantly different between the two groups. By univariate analysis, RI turned out to directly correlate with the recipient age, donor age and daily proteinuria (P = 0.007, P = 0.0007 and P = 0.02, respectively). Multivariate analysis showed that only donor and recipient age maintained their independent predictive value on RI. Kaplan-Meier analysis, considering a serum creatinine increase >50% as the endpoint of the study, showed a statistically significant different graft survival in the two groups (log-rank test = 5.489; P = 0.01). The univariate relative risk of deterioration of graft function among patients with higher RI was 3.77. Proteinuria and recipient age increased the risk as well. CONCLUSIONS: Our data seem to suggest that early determination of RI can help predict long-term graft function in kidney transplant recipients.  相似文献   
32.
BACKGROUND: The pathophysiology leading to pulmonary side effects during haemodialysis and haemodiafiltration is not yet fully understood. Chronic microembolization, which can be demonstrated by pulsed Doppler ultrasound, may be one cause. METHODS: The study cohort consisted of 24 long-term dialysis patients undergoing haemodialysis (n=21) and online-haemodiafiltration (n=3), respectively. The subclavian vein downstream to the venous access was investigated during different phases of the procedure using a 2-MHz pulsed ultrasound device. RESULTS: In all periods investigated (connection, dialysis, disconnection), numerous microembolic signals (MES) were found in the subclavian vein. The numbers of MES detected during haemodiafiltration (314-709 MES per 10 min) were higher than during haemodialysis (0-81 MES per 10 min). CONCLUSIONS: The composition (gaseous or solid) and origin (pump, tubing system or shunt) of the microemboli detected remains unclear. Chronic microembolization may be one cause of pulmonary complications of haemodialysis and haemodiafiltration. The detection method described in this article will help us to better understand this process and to determine what role microemboli might play in pulmonary and central nervous system disorders. It may also help to optimize the devices and techniques used.  相似文献   
33.
目的:认识睾丸微石症(TM)的临床意义和诊断方法。方法:回顾性报告2例TM病例的临床资料,结合文献进行讨论。结果:2例分别因左精索静脉曲张和附睾炎就诊的患者行阴囊超声检查时发现睾丸内散在多发点状强回声,如针尖样,1~2mm,后无声影。分别诊断为局部TM、左精索静脉曲张和TM,左附睾炎。甲胎蛋白、人绒毛膜促性腺激素、乳酸脱氢酶和睾酮等检查均正常。对睾丸微石症未做特殊处置,随访6~8个月,体检和睾丸瘤标未见异常,阴囊超声睾丸图像无特征性改变。结论:TM是一种少见、无明显临床症状、相对稳定的疾病。多因阴囊其他疾病行超声检查时偶然发现,其是否属于癌前病变尚有争议,但是定期随访和阴囊超声检查是必要的。  相似文献   
34.
TCD观察动脉瘤性SAH后脑血管痉挛的血流动力学改变   总被引:4,自引:0,他引:4  
目的探讨动脉瘤性蛛网膜下腔出血(SAH)后脑血管痉挛的血流动力学改变。方法经CT、DSA证实为动脉瘤性SAH患者179例,床旁经颅超声多谱勒(TCD)在术前、术后1~3d、5~7d、9~11d、12~14d记录并分析大脑中动脉(M CA)的血流参数及频谱改变。结果M CA平均血流速度(Vm)于SAH后1~3d开始升高,5~7d、9~11d达到高峰;L I(血管痉挛指数)为3~6时预后良好;>6时可以出现神经系统功能损害,颅内压增高且有脑血管痉挛(CV S)者预后较差。结论TCD能无创、实时评价SAH后CV S的动态变化,可以推断SAH后CV S的严重程度及临床转归。  相似文献   
35.
目的 探讨大鼠中脑导水管周围灰质(PAG)NO对血压的影响及作用机制。方法 采用微量注射法,观察大鼠血压的变化,放免法检测Ach含量。结果 PAG内微量注射L-NNA后,大鼠平均动脉压升高,延髓头端腹外侧区(RVLM)内Ach含量增多,且这一升压效应可被PALG内预注L-Arg或RVLM内预注东莨菪碱所阻断。结论PAG内NO可能经RVLM内Ach介导对血压有紧张性抑制作用。  相似文献   
36.
目的 探讨胰岛素抵抗 (IR)在糖耐量减低 (IGT)大血管并发症中的作用。方法 测定 1 2 0名IGT患者和 96名糖耐量正常(NGT)对照者的空腹血糖 (FBG)、胆固醇 (TC)、甘油三酯 (TG)、胰岛素 (FINS)及餐后 2h血糖 (PBG) ,并测量身高、体重、腰围、臀围 ,计算相对胰岛素敏感指数 (RISI)、体重指数 (BMI)、腰臀比 (WHR) ,结合其颈动脉多普勒超声检测结果进行对比分析。结果 IGT组及NGT组颈动脉粥样斑块发生率有显著性差异 (P <0 .0 0 1 ) ,斑块面积与RISI呈负相关 (r =- 0 .45 ,P <0 .0 1 ) ,与餐后 2h血糖 (r =0 .39,P <0 .0 1 )、BMI(r=0 .48,P <0 .0 1 )及WHR(r=0 .41 ,P <0 .0 1 )正相关 ,而与TG、FBG、TC、FINS无相关性 (P >0 .0 5)。IGT组患者有斑块和无斑块者之间RISI、WHR、BMI、餐后 2h血糖、TG之间也存在显著性差异 (P <0 .0 1 )。结论 胰岛素抵抗与颈动脉粥样硬化的发生密切相关 ,是IGT患者发生大血管并发症的重要原因。  相似文献   
37.
A prospective study was carried out to evaluate the role of ultrasound in early detection of infections of bone. Presence of a hypoechoic collection adjacent to bone was considered highly suggestive of osteomyelitis whereas a hypoechoic collection away from the bone implied a soft tissue abscess. Cellulitis presented as increased subcutaneous thickness. Of the 31 patients clinically suspected to have osteomyelitis, and subjected to ultrasound, 25 were proven to be osteomyelitis at surgery or by subsequent radiological changes, 4 had soft tissue abscesses and the remaining 2 had cellulitis. Co-existent hip joint effusion was seen in 2 patients. It is felt that ultrasound is simple and non-invasive investigation, capable of detecting bone and soft tissue infections.  相似文献   
38.
The basilar artery is the only large artery in which two flows merge, and this is reflected in the flow downstream. We report quantitative flow — velocity measurements with a phase-based MR technique, i.e. the Fourier velocity encoding method, in the basilar artery of a volunteer. To our knowledge, this has not previously been performed successfully. A comparison is made with the results of flow velocity measurements in the basilar artery with transcranial Doppler ultrasonography; the techniques agreed very well. Although Doppler ultrasonography is still most widely used, no information on the flow rate and the flow velocity distribution in the basilar artery can be provided. MR flow measurement techniques appear promising when detailed information on the flow velocity distribution and flow rate is needed.  相似文献   
39.
Summary To evaluate the influence of the stomach and the cholinergic system on gallbladder contraction induced by physiological stimuli, the reduction in gallbladder volume in 7 healthy volunteers has been studied by real-time ultrasonography after the oral and intraduodenal administration of olive oil, preceded by pretreatment with cimetropium bromide or placebo. After an overnight fast, each subject swallowed 50 ml olive oil or it was administered through a naso-duodenal tube in the proximal duodenum. Cimetropium bromide 5 mg or placebo was given intravenously under double-blind control.After the placebo pretreatment, gallbladder contraction was greater and faster after intraduodenal oil than after oral oil. Cimetropium bromide decreased the extent, velocity and duration of gallbladder contraction induced by intraduodenal olive oil but it only reduced the velocity of the contraction induced by oil given orally.It is concluded that in normal human subjects the stomach modulates the extent and velocity of postprandial gallbladder contraction and that anticholinergic agents antagonize the gastric and duodenal phases of the response of the gallbladder to a meal.  相似文献   
40.
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