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   2462篇
  免费   113篇
  国内免费   23篇
耳鼻咽喉   39篇
儿科学   73篇
妇产科学   166篇
基础医学   195篇
口腔科学   330篇
临床医学   175篇
内科学   559篇
皮肤病学   40篇
神经病学   191篇
特种医学   71篇
外科学   399篇
综合类   73篇
预防医学   57篇
眼科学   53篇
药学   85篇
中国医学   2篇
肿瘤学   90篇
  2024年   2篇
  2023年   25篇
  2022年   27篇
  2021年   55篇
  2020年   40篇
  2019年   46篇
  2018年   65篇
  2017年   57篇
  2016年   77篇
  2015年   86篇
  2014年   89篇
  2013年   103篇
  2012年   150篇
  2011年   201篇
  2010年   108篇
  2009年   86篇
  2008年   164篇
  2007年   175篇
  2006年   167篇
  2005年   140篇
  2004年   147篇
  2003年   149篇
  2002年   114篇
  2001年   82篇
  2000年   56篇
  1999年   50篇
  1998年   27篇
  1997年   31篇
  1996年   15篇
  1995年   7篇
  1994年   6篇
  1993年   7篇
  1992年   5篇
  1991年   10篇
  1990年   3篇
  1989年   7篇
  1988年   5篇
  1987年   2篇
  1985年   2篇
  1984年   3篇
  1982年   1篇
  1979年   2篇
  1978年   2篇
  1976年   1篇
  1965年   1篇
排序方式: 共有2598条查询结果,搜索用时 78 毫秒
91.
We report a case of “hugging balloon” dilatation of a giant right coronary artery using two dilatation catheters, a balloon “on a wire” and a balloon “rapid exchange” systems via a single guiding catheter. The necessity of larger PTCA balloon catheter (>4.0 mm) was stressed.  相似文献   
92.
OBJECTIVES: The purpose of this prospective study was to quantitate the diagnostic value of several tachycardia features and pacing maneuvers in patients with paroxysmal supraventricular tachycardia (PSVT) in the electrophysiology laboratory. BACKGROUND: No study has prospectively compared the value of multiple diagnostic tools in a large group of patients with PSVT. METHODS: One hundred ninety-six consecutive patients who had 200 inducible sustained PSVTs during an electrophysiology procedure were included. The diagnostic values of four baseline electrophysiologic parameters, nine tachycardia features and five diagnostic pacing maneuvers were quantified. RESULTS: The only tachycardia characteristic that was diagnostic of atrioventricular (AV) nodal reentry was a septal ventriculoatrial (VA) time of <70 ms, and no pacing maneuver was diagnostic for AV nodal reentry. An increase in the VA interval with the development of a bundle branch block was the only tachycardia characteristic that was diagnostic for orthodromic tachycardia, but it occurred in only 7% of all tachycardias. An atrial-atrial-ventricular response upon cessation of ventricular overdrive pacing was diagnostic of atrial tachycardia, and this maneuver could be applied to 78% of all tachycardias. Burst ventricular pacing excluded atrial tachycardia when the tachycardia terminated without depolarization of the atrium, but the result could be obtained only in 27% of patients. CONCLUSIONS: This prospective study quantitates the diagnostic value of multiple observations and pacing maneuvers that are commonly used during PSVT in the electrophysiology laboratory. The findings demonstrate that diagnostic techniques rarely provide a diagnosis when used individually. Therefore, careful observations and multiple pacing maneuvers are often required for an accurate diagnosis during PSVT. The results of this study provide a useful reference with which new diagnostic techniques can be compared.  相似文献   
93.
Mandibuloacral dysplasia (MAD) is a phenotypically heterogeneous, rare autosomal recessive disorder characterized by mandibular and clavicular hypoplasia, acroosteolysis, delayed closure of cranial sutures, joint contractures, and mottled cutaneous pigmentation. Patients with MAD develop two patterns of lipodystrophy: type A pattern, with loss of sc fat from the extremities and normal or slight excess in the neck and truncal regions; and type B pattern, with a more generalized loss of sc fat involving the face, trunk, and extremities. Recently, affected patients from five consanguineous Italian pedigrees with partial lipodystrophy (type A) were reported to have a homozygous R527H mutation in LMNA (lamin A/C) gene. We carried out mutational analysis of LMNA in affected patients from six pedigrees. Affected patients from two pedigrees with type A lipodystrophy had the homozygous R527H mutation in LMNA. The other four affected subjects who had type B lipodystrophy did not have any mutation in the exons and splice site junctions of LMNA; RNA extracted from lymphoblasts of two of these patients also revealed normal sequence. In these four subjects, sequencing of other known genes implicated in lipodystrophies, i.e. AGPAT2, Seipin, and PPARG also revealed no substantial alterations. We conclude that MAD is a genetically and phenotypically heterogeneous disorder. Besides LMNA gene, other as yet unmapped loci could be linked to MAD.  相似文献   
94.
OBJECTIVES: We prospectively investigated the prevalence and value of this criterion for identifying a target site for ablation in patients with postinfarction ventricular tachycardia (VT). BACKGROUND: Termination of postinfarction VT by pacing with nonglobal capture identifies a critical component of the reentrant circuit. METHODS: In a consecutive series of 34 patients with prior infarction (age 67 +/- 10 years, ejection fraction 0.26 +/- 0.1) referred for radiofrequency catheter ablation, mapping was performed in the left ventricle. At sites with abnormal electrograms, pacing was performed during VT. If VT terminated with nonglobal capture during the pacing train, radiofrequency energy was delivered. RESULTS: Sixty-two VTs (cycle length 450 +/- 84 ms) were mapped and targeted for radiofrequency ablation. Concealed entrainment was present at 101 endocardial sites. Among the 101 sites, VT terminated by pacing with nonglobal capture at 5 sites (5%). At 10 additional sites in 10 patients, VT terminated by pacing with nonglobal capture, and concealed entrainment could not be documented at these sites because of reproducible termination of the VT. An application of radiofrequency energy resulted in VT termination at all 15 sites where nonglobal capture was documented and the targeted VTs were no longer inducible after ablation. CONCLUSIONS: Termination of VT by pacing with nonglobal capture can be demonstrated in approximately one third of patients with postinfarction VT and is a specific criterion for identifying a critical component of the reentrant circuit, whether or not concealed entrainment can be documented at that site.  相似文献   
95.
INTRODUCTION: The anatomic arrangement of pulmonary veins (PVs) is variable. No prior studies have quantitatively analyzed the effects of segmental ostial ablation on the PVs. The aim of this study was to determine the effect of segmental ostial radiofrequency ablation on PV anatomy in patients with atrial fibrillation (AF). METHODS AND RESULTS: Three-dimensional models of the PVs were constructed from computed tomographic (CT) scans in 58 patients with AF undergoing segmental ostial ablation to isolate the PVs and in 10 control subjects without a history of AF. CT scans were repeated approximately 4 months later. PV and left atrial dimensions were measured with digital calipers. Four separate PV ostia were present in 47 subjects; 3 ostia were present in 2 subjects; and 5 ostia were present in 9 subjects. The superior PVs had a larger ostium than the inferior PVs. Patients with AF had a larger left atrial area between the PV ostia and larger ostial diameters than the controls. Segmental ostial ablation resulted in a 1.5 +/- 3.2 mm narrowing of the ostial diameter. A 28% to 61% focal stenosis was present 7.6 +/- 2.2 mm from the ostium in 3% of 128 isolated PVs. There were no instances of symptomatic PV stenosis during a mean follow-up of 245 +/- 105 days. CONCLUSION: CT of the PVs allows identification of anatomic variants prior to catheter ablation procedures. Segmental ostial ablation results in a significant but small reduction in ostial diameter. Focal stenosis occurs infrequently and is attributable to delivery of radiofrequency energy within the PV.  相似文献   
96.
We analyzed the postoperative short- and mid-term outcomes of a series of patients with annuloaortic ectasia who underwent a modified Bentall operation in our clinic from September 2000 through March 2006. The study included 44 patients. Their average age was 53.4 +/- 14.1 years. The underlying disease was degenerative aortic aneurysm in 42 patients (95.5%) and acute aortic dissection in 2 patients (4.5%). Six patients (13.6%) had Marfan phenotype. Aortic insufficiency was moderate in 30 patients (68.2%) and severe in 14 patients (31.8%). In our modification of the Bentall technique, we completed the resection of the aortic root while leaving 5 to 10 mm of native aortic wall tissue to support the anastomosis. A long piece of Teflon felt (width, 0.5-1 cm) was laid on the annulus, and nonpledgeted 2-0 polyester sutures were passed in turn through the Teflon felt, the preserved aortic tissue, and the aortic annulus. A thin piece of Teflon felt was also used in the coronary artery reimplantation sites. Fibrin glue was routinely applied to all anastomoses. There were no intraoperative deaths. One patient died in the hospital after surgery for acute type I aortic dissection. Another patient died 1 year after the operation from prosthetic-valve endocarditis. No patient required surgical correction of excessive postoperative bleeding. Kaplan-Meier curves showed overall survival of 0.94 (95% confidence intervals, 0.9-0.99). We consider our approach an easy, effective way to minimize bleeding from the anastomoses and at the aortic root--a common challenge in aortic surgery.  相似文献   
97.
Transcatheter aortic valve replacement can be an effective, reliable treatment for severe aortic stenosis in surgically high-risk or ineligible patients. However, various sequelae like coronary artery obstruction can occur, not only in the long term, but also immediately after the procedure. We present the case of a 78-year-old woman whose left main coronary artery became obstructed with calculus 2 hours after the transfemoral implantation of an Edwards Sapien XT aortic valve. Despite percutaneous coronary intervention in that artery, the patient died. This case reminds us that early recognition of acute coronary obstruction and prompt intervention are crucial in patients with aortic stenosis who have undergone transcatheter aortic valve replacement.  相似文献   
98.
Background: Fine particulate matter (PM) air pollution is associated with numerous adverse health effects, including increased blood pressure (BP) and vascular dysfunction. Coarse PM substantially contributes to global air pollution, yet differs in characteristics from fine particles and is currently not regulated. However, the cardiovascular (CV) impacts of coarse PM exposure remain largely unknown.Objectives: Our goal was to elucidate whether coarse PM, like fine PM, is itself capable of eliciting adverse CV responses.Methods: We performed a randomized double-blind crossover study in which 32 healthy adults (25.9 ± 6.6 years of age) were exposed to concentrated ambient coarse particles (CAP; 76.2 ± 51.5 μg/m3) in a rural location and filtered air (FA) for 2 hr. We measured CV outcomes during, immediately after, and 2 hr postexposures.Results: Both systolic (mean difference = 0.32 mmHg; 95% CI: 0.05, 0.58; p = 0.021) and diastolic BP (0.27 mmHg; 95% CI: 0.003, 0.53; p = 0.05) linearly increased per 10 min of exposure during the inhalation of coarse CAP when compared with changes during FA exposure. Heart rate was on average higher (4.1 bpm; 95% CI: 3.06, 5.12; p < 0.0001) and the ratio of low-to-high frequency heart rate variability increased (0.24; 95% CI: 0.07, 0.41; p = 0.007) during coarse particle versus FA exposure. Other outcomes (brachial flow-mediated dilatation, microvascular reactive hyperemia index, aortic hemodynamics, pulse wave velocity) were not differentially altered by the exposures.Conclusions: Inhalation of coarse PM from a rural location is associated with a rapid elevation in BP and heart rate during exposure, likely due to the triggering of autonomic imbalance. These findings add mechanistic evidence supporting the biological plausibility that coarse particles could contribute to the triggering of acute CV events.Citation: Brook RD, Bard RL, Morishita M, Dvonch JT, Wang L, Yang HY, Spino C, Mukherjee B, Kaplan MJ, Yalavarthi S, Oral EA, Ajluni N, Sun Q, Brook JR, Harkema J, Rajagopalan S. 2014. Hemodynamic, autonomic, and vascular effects of exposure to coarse particulate matter air pollution from a rural location. Environ Health Perspect 122:624–630; http://dx.doi.org/10.1289/ehp.1306595  相似文献   
99.
Hyperlipidemia is a major cardiovascular risk factor associated with progressive cerebrovascular dysfunction and diminished collateral perfusion in stroke. Rho-associated kinase (ROCK) may be an important mediator of hyperlipidemic vascular dysfunction. We tested the efficacy of acute or chronic ROCK inhibition on the size of dynamic perfusion defect using laser speckle flowmetry in hyperlipidemic apolipoprotein E knockout mice fed on a high-fat diet for 8 weeks. Mice were studied at an age before the development of flow-limiting atherosclerotic stenoses in aorta and major cervical arteries. Focal ischemia was induced by distal middle cerebral artery occlusion (dMCAO) during optical imaging. The ROCK inhibitor fasudil (10 mg/kg) was administered either as a single dose 1 hour before ischemia onset, or daily for 4 weeks. Fasudil decreased both baseline arterial blood pressure and cerebrovascular resistance (CVR) by ∼15%, and significantly improved tissue perfusion during dMCAO. Interestingly, peri-infarct depolarizations were also reduced. Chronic treatment did not further enhance these benefits compared with acute treatment with a single dose. These data show that ROCK inhibition improves CVR and ischemic tissue perfusion in hyperlipidemic mice.  相似文献   
100.
Neuromyelitis optica (NMO, Devic’s syndrome), long considered a clinical variant of multiple sclerosis, is now regarded as a distinct disease entity. Major progress has been made in the diagnosis and treatment of NMO since aquaporin-4 antibodies (AQP4-Ab; also termed NMO-IgG) were first described in 2004. In this review, the Neuromyelitis Optica Study Group (NEMOS) summarizes recently obtained knowledge on NMO and highlights new developments in its diagnosis and treatment, based on current guidelines, the published literature and expert discussion at regular NEMOS meetings. Testing of AQP4-Ab is essential and is the most important test in the diagnostic work-up of suspected NMO, and helps to distinguish NMO from other autoimmune diseases. Furthermore, AQP4-Ab testing has expanded our knowledge of the clinical presentation of NMO spectrum disorders (NMOSD). In addition, imaging techniques, particularly magnetic resonance imaging of the brain and spinal cord, are obligatory in the diagnostic workup. It is important to note that brain lesions in NMO and NMOSD are not uncommon, do not rule out the diagnosis, and show characteristic patterns. Other imaging modalities such as optical coherence tomography are proposed as useful tools in the assessment of retinal damage. Therapy of NMO should be initiated early. Azathioprine and rituximab are suggested as first-line treatments, the latter being increasingly regarded as an established therapy with long-term efficacy and an acceptable safety profile in NMO patients. Other immunosuppressive drugs, such as methotrexate, mycophenolate mofetil and mitoxantrone, are recommended as second-line treatments. Promising new therapies are emerging in the form of anti-IL6 receptor, anti-complement or anti-AQP4-Ab biologicals.  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