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   11933篇
  免费   746篇
  国内免费   60篇
耳鼻咽喉   104篇
儿科学   182篇
妇产科学   142篇
基础医学   1558篇
口腔科学   212篇
临床医学   1170篇
内科学   2830篇
皮肤病学   394篇
神经病学   1134篇
特种医学   653篇
外国民族医学   5篇
外科学   1779篇
综合类   39篇
一般理论   2篇
预防医学   512篇
眼科学   149篇
药学   695篇
中国医学   19篇
肿瘤学   1160篇
  2024年   8篇
  2023年   56篇
  2022年   114篇
  2021年   224篇
  2020年   168篇
  2019年   236篇
  2018年   276篇
  2017年   230篇
  2016年   298篇
  2015年   350篇
  2014年   454篇
  2013年   591篇
  2012年   970篇
  2011年   945篇
  2010年   644篇
  2009年   546篇
  2008年   875篇
  2007年   936篇
  2006年   898篇
  2005年   860篇
  2004年   738篇
  2003年   644篇
  2002年   661篇
  2001年   111篇
  2000年   70篇
  1999年   108篇
  1998年   102篇
  1997年   100篇
  1996年   69篇
  1995年   68篇
  1994年   40篇
  1993年   61篇
  1992年   22篇
  1991年   34篇
  1990年   19篇
  1989年   30篇
  1988年   15篇
  1987年   21篇
  1986年   17篇
  1985年   13篇
  1984年   15篇
  1983年   13篇
  1982年   17篇
  1981年   14篇
  1980年   7篇
  1979年   6篇
  1978年   5篇
  1977年   4篇
  1976年   7篇
  1975年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Objective: The use of non-heart-beating donors (NHBD) has been propagated as an alternative to overcome the scarcity of pulmonary grafts. Formation of microthrombi after circulatory arrest, however, is a major concern for the development of reperfusion injury. We looked at the effect and the best route of pulmonary flush following topical cooling in NHBD. Methods: Non-heparinized pigs were sacrificed by ventricular fibrillation and divided into three groups (n = 6 per group). After 1 h of in situ warm ischaemia and 2.5 h of topical cooling, lungs in group I were retrieved unflushed (NF). In group II, lungs were explanted following an anterograde flush (AF) through the pulmonary artery with 50 ml/kg Perfadex® (6 °C). Finally, in group III, lungs were retrieved after an identical but retrograde flush (RF) via the left atrium. Flush effluent was sampled at intervals to measure haemoglobin concentration. Performance of the left lung was assessed during 60 min in our ex vivo reperfusion model. Wet-to-dry weight ratio (W/D) of both lungs was calculated as an index of pulmonary oedema. IL-1ß and TNF- protein levels in bronchial lavage fluid from both lungs were compared between groups. Results: Haemoglobin concentration (g/dl) was higher in the first effluent in RF versus AF (3.4 ± 1.1 vs 0.6 ± 0.1; p < 0.05). Pulmonary vascular resistance (dynes × s × cm−5) was 975 ± 85 RF versus 1567 ± 98 AF and 1576 ± 88 NF at 60 min of reperfusion (p < 0.001). Oxygenation (mmHg) and compliance (ml/cmH2O) were higher (491 ± 44 vs 472 ± 61 and 430 ± 33 NS, 22 ± 3 vs 19 ± 3 and 14 ± 1 NS, respectively) and plateau airway pressure (cmH2O) was lower (11 ± 1 vs 13 ± 1 and 13 ± 1 NS) after RF versus AF and NF, respectively. No differences in cytokine levels or in W/D ratios were observed between groups after reperfusion. Histology demonstrated microthrombi more often present after AF and NF compared to RF. Conclusion: Retrograde flush of the lung following topical cooling in the NHBD results in a better washout of residual blood and microthrombi and subsequent reduced pulmonary vascular resistance upon reperfusion.  相似文献   
72.
Diagnostic and therapeutic strategies for acute biliary inflammation/infection (acute cholangitis and acute cholecystitis), according to severity grade, have not yet been established in the world. Therefore we formulated flowcharts for the management of acute biliary inflammation/infection in accordance with severity grade. For mild (grade I) acute cholangitis, medical treatment may be sufficient/appropriate. For moderate (grade II) acute cholangitis, early biliary drainage should be performed. For severe (grade III) acute cholangitis, appropriate organ support such as ventilatory/circulatory management is required. After hemodynamic stabilization is achieved, urgent endoscopic or percutaneous transhepatic biliary drainage should be performed. For patients with acute cholangitis of any grade of severity, treatment for the underlying etiology, including endoscopic, percutaneous, or surgical treatment should be performed after the patient's general condition has improved. For patients with mild (grade I) cholecystitis, early laparoscopic cholecystectomy is the preferred treatment. For patients with moderate (grade II) acute cholecystitis, early laparoscopic or open cholecystectomy is preferred. In patients with extensive local inflammation, elective cholecystectomy is recommended after initial management with percutaneous gallbladder drainage and/or cholecystostomy. For the patient with severe (grade III) acute cholecystitis, multiorgan support is a critical part of management. Biliary peritonitis due to perforation of the gallbladder is an indication for urgent cholecystectomy and/or drainage. Delayed elective cholecystectomy may be performed after initial treatment with gallbladder drainage and improvement of the patient's general medical condition.  相似文献   
73.
Spontaneous pneumomediastinum is an uncommon, self-limiting condition resulting from alveolar rupture in young adults. Because of the ambiguous presentation and the general lack of awareness of this condition, its diagnosis is often delayed, missed, or confused with spontaneous esophageal perforation. We report our experience of treating six patients who were referred to our unit with vomiting-induced pneumomediastinum, subcutaneous emphysema, and an initial diagnosis of spontaneous esophageal perforation. Ultimately, we diagnosed spontaneous pneumomediastinum in all six patients, who recovered uneventfully without any surgical intervention. We review the literature with particular emphasis on differentiating spontaneous pneumomediastinum from spontaneous esophageal perforation.  相似文献   
74.
The blood-brain barrier is a natural diffusion barrier, which expresses active carriers extruding drugs on their way to the brain back into the blood against concentration gradients. Whereas these so-called adenosine triphosphate-binding cassette (ABC) transporters prevent the brain entry of toxic compounds under physiological conditions, they complicate pharmacotherapies in neurological disease. Recent observations in animal models of ischemic stroke, drug-resistant epilepsy, and brain cancer showed that the prototype of ABC transporters, ABCB1, is upregulated on brain injury, deactivation of this carrier considerably enhancing the accumulation of neuroprotective, antiepileptic, and chemotherapeutic compounds. These studies provide the proof of concept that the efficacy of brain-targeting drugs may significantly be improved when drug efflux is blocked. Under clinical conditions, efforts currently are made to enhance drug accumulation by selecting new compounds that do not bind to efflux carriers or deactivating ABC transporters by targeted downregulation or pharmacological inhibition. We predict that strategies aiming at circumventing drug efflux may greatly facilitate progress in neurological therapies.  相似文献   
75.
In our prospective study of diffusion tensor imaging (DTI), we measured hippocampal mean diffusivity (MD) and volumes in amnestic mild cognitive impairment (MCI). Thirteen MCI patients were followed-up by clinical assessment over a mean 112-year period. MCI patients who converted to dementia (6 of 13) during the observation period had slightly elevated left hippocampal mean diffusivity at baseline compared with MCI patients who remained clinically stable. Hippocampal volumes as well as baseline verbal memory and MMSE did not differ significantly between stable MCI patients and converters. Hippocampal diffusivity was superior to hippocampal volumes for prediction of conversion to dementia in MCI patients during a 112-year period.  相似文献   
76.

Study objective

To determine longitudinal trends in mortality, and the contribution of specific injury characteristics and treatment modalities to the risk of a fatal outcome after severe and complex pelvic trauma.

Methods

We studied 5048 patients with pelvic ring fractures enrolled in the German Pelvic Trauma Registry Initiative between 1991 and 1993, 1998 and 2000, and 2004 and 2006. Complete datasets were available for 5014 cases, including 508 complex injuries, defined as unstable fractures with severe peri-pelvic soft tissue and organ laceration. Multivariable mixed-effects logistic regression analysis was employed to evaluate the impact of demographic, injury- and treatment-associated variables on all-cause in-hospital mortality.

Results

All-cause in-hospital mortality declined from 8% (39/466) in 1991 to 5% (33/638) in 2006. Controlling for age, Injury Severity Score, pelvic vessel injury, the need for emergency laparotomy, and application of a pelvic clamp, the odds ratio (OR) per annum was 0.94 (95% confidence interval [CI] 0.91–0.96). However, the risk of death did not decrease significantly in patients with complex injuries (OR 0.98, 95% CI 0.93–1.03). Raw mortality associated with this type of injury was 18% (95% CI 9–32%) in 2006.

Conclusion

In contrast to an overall decline in trauma mortality, complex pelvic ring injuries remain associated with a significant risk of death. Awareness of this potentially life-threatening condition should be increased amongst trauma care professionals, and early management protocols need to be implemented to improve the survival prognosis.  相似文献   
77.
Aim of this study was to collect information about oral health of patients before and after SOT as well as information about center‐based recommendations for dental care. In a single center cross‐sectional study, the oral situation of 20 patients before and 20 after SOT were examined including dental (DMF‐T), periodontal (PSR®/PSI), and oral hygiene findings (modified QHI). In a second project, a survey among 50 transplant centers in Germany was questioned regarding their recommendations for dental care of SOT recipients. Patients before and after SOT showed similar quality of dental findings (DMF‐T), but worse compared to the general population. In addition, most patients in both groups showed pronounced periodontal treatment need (PSR®/PSI score 3 or 4). Oral hygiene findings (modified QHI) after SOT were significantly worse than in patients on the waiting list (P = 0.032). In a second project, the questionnaire was returned by 28 of 50 centers. Interpretation of data showed that 89% carry out a dental examination before SOT and 67% contacted the patients’ dentists. After SOT, 83% of the transplant centers recommend antibiotic cover before dental measures. The results of our study revealed lacks in the dental care of SOT recipients. Consistent recommendations regarding the dental care of patients before and after SOT should be determined.  相似文献   
78.
Purpose: To assess the success of percutaneous transluminal angioplasty (PTA) in treating peripheral bypass stenoses. Methods: Patients who received a femoropopliteal or femorocrural bypass graft for limb ischemia were included in a duplex surveillance program. If duplex ultrasound revealed a short (<2 cm) severe (peak systolic velocity ratio ≥ 4.5) stenosis, patients were scheduled for arteriography and PTA. Fifty-eight peripheral bypass stenoses in 39 grafts in 37 patients were treated with PTA. The cumulative primary patency of treated stenoses was calculated. Results: During the first year after PTA 31 (53%) treated lesions remained patent, 15 (26%) lesions restenosed at a median interval of 5.0 (range 1–12) months and 4 (7%) bypasses occluded. The cumulative primary patency of 58 treated graft stenoses at 1 year was 60% [95% confidence interval (CI) 46%–74%] and 55% (95% CI 41%–70%) at 2 years. Graft body stenoses showed a better 2-year cumulative primary patency (86%; 95% CI 68%–100%) compared with juxta-anastomotic lesions (45%; 95% CI 29%–62%; p < 0.05). Conclusion: PTA is justifiable as the initial treatment of peripheral bypass stenoses. Nevertheless, the restenosis rate is rather high, especially in juxta-anastomotic lesions. Continuation of duplex surveillance after PTA and timely reintervention is recommended.  相似文献   
79.
OBJECTIVE: To report a rare cause of spinal cord injury. STUDY DESIGN: Case report. CASE REPORT: A 36-year-old woman presented with acute onset of paresis of the upper and lower extremity (level C5, ASIA B) the day after delivering a healthy daughter (39 weeks' gestation). Prior to giving birth, she was admitted with gestational hypertension. Directly postpartum, blood pressure increased markedly, and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome was diagnosed. The next day, tetraplegia developed. Magnetic resonance imaging showed multiple epidural and subdural hematomas in the cervical and thoracic spinal canal extending from C2 to T8, with displacement and compression of the cord. Three weeks after treatment with intravenous labetalol, she made a significant recovery (level T1, ASIA D). CONCLUSIONS: This rare cause of spinal cord injury shows the importance of closely monitoring pregnant patients with hypertension complicated with HELLP syndrome both pre- and postpartum.  相似文献   
80.
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