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   4421篇
  免费   274篇
  国内免费   14篇
耳鼻咽喉   25篇
儿科学   111篇
妇产科学   84篇
基础医学   591篇
口腔科学   77篇
临床医学   460篇
内科学   1062篇
皮肤病学   60篇
神经病学   586篇
特种医学   67篇
外国民族医学   1篇
外科学   476篇
综合类   39篇
一般理论   1篇
预防医学   387篇
眼科学   41篇
药学   272篇
中国医学   6篇
肿瘤学   363篇
  2024年   11篇
  2023年   49篇
  2022年   105篇
  2021年   166篇
  2020年   94篇
  2019年   131篇
  2018年   148篇
  2017年   98篇
  2016年   119篇
  2015年   125篇
  2014年   195篇
  2013年   202篇
  2012年   346篇
  2011年   347篇
  2010年   169篇
  2009年   184篇
  2008年   247篇
  2007年   272篇
  2006年   260篇
  2005年   200篇
  2004年   214篇
  2003年   221篇
  2002年   197篇
  2001年   47篇
  2000年   42篇
  1999年   48篇
  1998年   33篇
  1997年   32篇
  1996年   27篇
  1995年   20篇
  1994年   24篇
  1993年   23篇
  1992年   22篇
  1991年   16篇
  1990年   10篇
  1989年   10篇
  1988年   14篇
  1987年   22篇
  1986年   13篇
  1985年   17篇
  1984年   14篇
  1983年   10篇
  1981年   13篇
  1979年   11篇
  1977年   10篇
  1974年   14篇
  1969年   16篇
  1968年   16篇
  1967年   12篇
  1966年   8篇
排序方式: 共有4709条查询结果,搜索用时 15 毫秒
41.
ContextAlterations in sleep-wake patterns of care recipients and their informal caregivers are common in the context of a chronic illness. Given the current notion that sleep may be regulated within and affected by close human relationships, concurrent and interrelated sleep problems may be present in care recipient-caregiver dyads.ObjectivesTo critically analyze evidence regarding concurrent sleep patterns or changes in care recipient-caregiver dyads in the context of a chronic illness and address methodological and research gaps.MethodsUsing a wide range of key terms and synonyms, three electronic databases (Medline, CINAHL, and Embase) were systematically searched for the period between January 1990 and July 2011.ResultsTen studies met prespecified selection criteria and were included for analysis. Study quality was fair to good on average. Seven studies were conducted in the context of dementia or Parkinson's disease, two in the context of cancer, and one study included a group of community elders with mixed related comorbidities and their informal caregivers. Bidirectional associations in the sleep of care recipient-caregiver dyads seem to exist. Concurrent and comparable nocturnal sleep disruptions also may be evident. Yet, inconsistencies in the methods implemented, and the samples included, as well as uncertainty regarding factors coaffecting sleep, still preclude safe conclusions to be drawn on.ConclusionThe dyadic investigation of sleep is a promising approach to the development of truly effective interventions to improve sleep quality of care recipients and their caregivers. Nevertheless, more systematic, longitudinal dyadic research is warranted to augment our understanding of co-occurrence and over time changes of sleep problems in care recipient-caregiver dyads, as well as to clarify covariates/factors that appear to contribute to these problems within the dyad and across time and context of illness.  相似文献   
42.
Abstract   The appearance of re-stenosis after repair of an interrupted aortic arch may be a surgical challenge due to adhesions. Here, we describe an approach using off-pump coronary artery bypass grafting techniques to reach the descending aorta through a median sternotomy in a patient with aortic arch stenosis after conduit repair. The 17-year-old patient with diagnoses of interrupted aortic arch and ventricular septal defect presented after two previous operations (one left lateral thoracotomy and one median sternotomy) with a stenosed vascular graft between ascending and descending aorta. Surgery was done via re-sternotomy without cardio-pulmonary bypass. An extraanatomic graft was used to connect ascending and descending aorta. When performing the distal anastomosis, the heart was exposed using a standard suction device. This case demonstrates that the use of modern techniques may facilitate surgical approaches dramatically. In our opinion the above-described technique is the first choice for all patients requiring arch repair following multiple previous operations, performed via sternotomy and thoracotomy.  相似文献   
43.
To develop a potential SPECT probe to evaluate the integrity of the serotoninergic system (5-HTT) whose dysfunction is linked to several disease conditions such as Parkinson's disease, Alzheimer's disease and depression, we report the synthesis, radiolabeling and in vivo baboon imaging of 2beta-carbomethoxy-3beta-(3'-[(123)I]iodophenyl) tropane (YP256, 6). The radiolabeling was performed by iododestannylation using sodium [(123)I]iodide and peracetic acid. Although the ligand displayed high selectivity for 5-HTT over dopamine transporter in vitro, SPECT imaging in baboons did not reveal selective 5-HTT accumulation in brain in vivo.  相似文献   
44.
45.
Background ACTH-independent macronodular adrenal hyperplasia (AIMAH) is a rare cause of Cushing’s syndrome. Bilateral adrenalectomy is considered the treatment of choice, with subsequent lifetime steroid replacement, but unilateral adrenalectomy has been recently proposed to reduce the secreting tissue. This prospective study was designed to evaluate the long-term results of unilateral adrenalectomy in AIMAH concerning the main laboratory and clinical abnormalities and the patient’s quality of life. Methods Seven consecutive patients with confirmed AIMAH underwent unilateral adrenalectomy of the largest gland. ACTH and cortisol levels, arterial blood pressure (BP), glycometabolic parameters, and patient’s subjective perception of health-related quality of life (by the SF-36 questionnaire) were measured preoperatively and postoperatively. Results No surgery-related morbidity occurred. One patient with a large contralateral adrenal enlargement required a completion adrenalectomy after 7 months because of persistent hypercortisolism. At a median follow-up of 53 (range, 27–68) months, the remaining six patients were cured, because serum and urinary free cortisol levels significantly decreased and ACTH increased, thus regaining the normal range. Both systolic and diastolic BP levels significantly reduced: 50% of patients definitively became normotensive, and the remaining patients reduced the need for antihypertensive treatment; 40% of patients suffering from preoperative diabetes were cured, whereas 40% reduced the need for hypoglycemizing drug. SF-36 evaluation of the health-related quality of life confirmed a significant amelioration. Conclusions Unilateral adrenalectomy of the largest gland can be an effective and safe treatment for AIMAH in case of asymmetric involvement. It may achieve long-term remission of Cushing’s syndrome and improve BP values, glycemic control, and patient’s quality of life.  相似文献   
46.
BACKGROUND: There is a paucity of data regarding whether sterile handling of endotracheal tubes (ETTs) impacts the incidence and prevalence of pneumonia in the emergency, urgent, or elective clinical scenarios. Intensive care units employ infection control and reduction schemes to reduce pneumonia rates. METHODS: A MEDLINE search of the English-language literature for the last 30 years was performed using the keywords "endotracheal intubation," "intubation," "pneumonia," "sinusitis," "tracheobronchitis," "nosocomial infection," and "infection." Data were limited to those papers addressing the role of sterile handling or passage of ETTs, infection with antibiotic-resistant micro-organisms, antibiotic prophylaxis, and the role of virulence determinants in supporting invasive infection. Also, a convenience sample of a single author's patients requiring tracheal intubation was undertaken. Data were acquired on tube handling, success of insertion, and subsequent occurrence of pneumonia. RESULTS: Virtually no data exist on the impact of sterile ETT handling, but unsterile manipulation of the ETT prior to insertion is common (112 of 154 intubation events). Within the limited patient sample, no conclusions may be drawn regarding the impact of unsterile handling on pneumonia rates, although sinusitis after nasotracheal intubation clearly increases the incidence of pneumonia. Biofilm generation as a facilitator of bacterial colonization of artificial airway surfaces is a ubiquitous virulence determinant that is not ameliorated by antibiotic administration. CONCLUSIONS: Unsterile ETT handling and insertion techniques are not clearly associated with pneumonia induction, but physiologically sound approaches that retard biofilm production may decrease pneumonia rates.  相似文献   
47.
AIM: We aimed to examine the distribution and activation of peripheral T cells in TTV positive (n = 32) and negative (n = 17) hemodialyzed patients. The control group (n = 20) consisted of healthy blood donors. METHOD: TTV-DNA was detected by seminested PCR. CD3, CD4, CD8, CD19, CD56, CD3/HLA-DR, CD3/CD69 and the Th1/Th2 ratio of T cells were analyzed by flow cytometry. Circulating IFN-gamma, IL-2, IL-4, IL-6, IL-10, IL-13, TNF-alpha, TGF-beta levels were measured by ELISA in the sera. RESULTS: There was no difference between the CD3, CD4, CD8 and CD19 values of HD subjects. In addition, the expression of both activation markers, HLA-DR and CD69, was significantly elevated in the TTV-positive and -negative HD groups compared to the controls, but not showing any difference from each other. The measurements of intracellular cytokines showed the enhanced occurrence of INF-gamma + CD4 T cells, and decreased appearance of IL-4 + CD4 lymphocytes in the HD groups without any significant difference between the TTV virus positive and negative patients. In addition, HD also elevated the expression of IL-10 in CD4 and CD8 (Th2) cells. There were only two significant changes in the levels of circulating cytokines: (a) IL-2 increased; (b) IL-13 decreased in both groups of HD patients compared to the controls, independently of TTV positivity or negativity. CONCLUSIONS: We assume that transfusion-transmitted virus does not cause any specific change in the distribution and activation of lymphocytes in the peripheral blood of hemodialyzed patients. Hemodialysis itself, however, results in a significant activation of peripheral T cells with the domination of increased production of Th1 type cytokines, IFN-gamma, IL-2, in contrast to the decreased synthesis of Th2 type cytokines, IL-4 and IL-13. Furthermore, the increased expression of IL-10 in the CD4 and CD8 cells of HD patients can be the sign of a contraregulatory Th2 activation as an answer on the Th1 effect.  相似文献   
48.
Hemorrhagic shock (HS) and resuscitation can be seen as a global body ischemia-reperfusion (I/R) injury characterized by neutrophil infiltration and organ damage. Liver dysfunction occurs early after HS. Adhesion molecules are needed for the first steps ofneutrophil migration. Thus, the purpose of this study was to investigate the role of L-selectin in the liver after uncontrolled HS and resuscitation. Forty-eight Sprague Dawley rats were subjected to uncontrolled HS and resuscitation. Animals were divided into three groups: sham, uncontrolled HS and resuscitation, and uncontrolled HS and resuscitation with anti-L-selectin treatment. At 6 we evaluated liver injury tests, liver tissue myeloperoxidase (MPO), and liver histology. Survival was followed for 3 days and compared between groups. Statistical analysis included Fisher's exact test and one-way analysis of variance. Survival significantly increased from 30% in the control group to 60% in the treated group (p < .05). Hepatocellular and structural injury as well as neutrophil infiltration was significantly decreased in treated animals (p < .05). Thus, blockade of L-selectin resulted in decreased hepatocellular injury and increased survival in our model of uncontrolled HS. Selectins may be important therapeutic targets for blockade in the treatment of HS.  相似文献   
49.

OBJECTIVE

Sympathetic nervous system (SNS) overactivity contributes to the pathogenesis and target organ complications of obesity. This study was conducted to examine the effects of lifestyle interventions (weight loss alone or together with exercise) on SNS function.

RESEARCH DESIGN AND METHODS

Untreated men and women (mean age 55 ± 1 year; BMI 32.3 ± 0.5 kg/m2) who fulfilled Adult Treatment Panel III metabolic syndrome criteria were randomly allocated to either dietary weight loss (WL, n = 20), dietary weight loss and moderate-intensity aerobic exercise (WL+EX, n = 20), or no treatment (control, n = 19). Whole-body norepinephrine kinetics, muscle sympathetic nerve activity by microneurography, baroreflex sensitivity, fitness (maximal oxygen consumption), metabolic, and anthropometric measurements were made at baseline and 12 weeks.

RESULTS

Body weight decreased by −7.1 ± 0.6 and −8.4 ± 1.0 kg in the WL and WL+EX groups, respectively (both P < 0.001). Fitness increased by 19 ± 4% (P < 0.001) in the WL+EX group only. Resting SNS activity decreased similarly in the WL and WL+EX groups: norepinephrine spillover by −96 ± 30 and −101 ± 34 ng/min (both P < 0.01) and muscle sympathetic nerve activity by −12 ± 6 and −19 ± 4 bursts/100 heart beats, respectively (both P < 0.01), but remained unchanged in control subjects. Blood pressure, baroreflex sensitivity, and metabolic parameters improved significantly and similarly in the two lifestyle intervention groups.

CONCLUSIONS

The addition of moderate-intensity aerobic exercise training to a weight loss program does not confer additional benefits on resting SNS activity. This suggests that weight loss is the prime mover in sympathetic neural adaptation to a hypocaloric diet.The metabolic syndrome (MetS) is an increasingly prevalent multidimensional risk factor for cardiovascular disease and type 2 diabetes (1). Its etiology is complex and incompletely understood, but thought to involve the interplay between metabolic susceptibility, lifestyle factors, and the acquisition of excess visceral adiposity (2). Scientific studies performed over the last 2 decades strongly support the relevance of the sympathetic nervous system (SNS) in both the pathogenesis and target organ complications of MetS obesity (3).Several indexes of SNS activity, such as urinary norepinephrine excretion, norepinephrine spillover from sympathetic nerves, and postganglionic muscle sympathetic nerve activity (MSNA) are increased in subjects with MetS, even in the absence of hypertension (47). Among the adiposity indexes, abdominal visceral fat is most strongly associated with elevated MSNA (8). Because of the bidirectional relationship between sympathetic activation and insulin resistance, much debate has focused on their chronology. Prospective studies with 10–20 years follow-up indicate that elevated plasma norepinephrine concentration (9) and sympathetic reactivity (10) precede and predict future rise in BMI and development of insulin resistance. Although seemingly counterintuitive, sympathetic activation may be causally linked to obesity via β-adrenoceptor desensitization (11) and insulin resistance (12,13). In established obesity, metabolic, cardiovascular (baroreflex impairment), and medical conditions (obstructive sleep apnea) contribute significantly to sympathetic neural drive and further aggravate insulin resistance, hence establishing a vicious cycle (3,7). Chronic sympathetic activation is associated with an increased prevalence of preclinical cardiovascular and renal changes that are recognized predictors of adverse clinical prognosis (3,14,15).Weight loss and exercise are recommended as first-line treatments for MetS. The Diabetes Prevention Program and the Oslo Diet and Exercise Study have shown the marked clinical benefits of intensive lifestyle intervention on the resolution of the MetS (16,17). Individually, both weight loss (5) and exercise training (18,19) cause sympathoinhibition and improvement in MetS components. We have previously reported that moderate weight loss (7% of body weight) by diet alone is accompanied by reductions in whole-body norepinephrine spillover and MSNA and improvement in spontaneous cardiac baroreflex function in middle-aged MetS subjects (5). Because exercise is often added to energy restriction in the treatment of obesity, it is pertinent to clarify its additive benefits. Augmented improvements in metabolic, anthropometric, and cardiovascular parameters have been observed after combined exercise training and dietary weight loss in some (17,20,21), but not other studies (22), and there are limited data regarding their combined effect on sympathetic activity (23). Exercise training may potentially augment weight loss induced sympathoinhibition by promoting a greater loss of fat relative to lean mass (20,21), by further improvement in insulin sensitivity (24) and reduction in plasma leptin concentration (21), and by potentiation of baroreceptor sensitivity (18).The present study was conducted to 1) test the hypothesis that weight loss by combined hypocaloric diet and aerobic exercise training would be associated with greater sympathoinhibition and improvement in MetS components than hypocaloric diet alone and 2) to examine the interrelationships between reduction in sympathetic tone and concurrent changes in anthropometric, metabolic (insulin sensitivity, plasma leptin concentration), and cardiovascular parameters. A moderate-intensity bicycle riding protocol was chosen as the exercise intervention, based on an earlier study that demonstrated attenuation in whole-body and renal norepinephrine spillover rates with this regimen in healthy men (19).  相似文献   
50.
Almost 75% of carotid body and cervical paragangliomas are adherent to or surround adjacent arteries and cranial nerves. Their resection can result in neurovascular injury, stroke, and excessive blood loss. To assess trends in neurovascular complications, we reviewed 153 carotid body and cervical paragangliomas that were surgically managed between 1935 and 1985. Results of the past 10 years were compared with two previous time periods: period I (1935 to 1965), when carotid artery reconstruction was uncommon at our institution, and period II (1966 to 1975), when methods of intraoperative electroencephalographic monitoring and carotid patch angioplasty were being developed. During the past 10 years (period III), surgical approach to these tumors has included intraoperative monitoring of cerebral blood flow, selective use of shunts, vein patch or graft reconstructions after extensive tumor resections, and mobilization of the parotid gland to facilitate adequate exposure of high tumors. Although tumor resection was attempted in 80% of patients in period I, surgical resection was complete in 98% during periods II and III. Three trends were observed: (1) The perioperative stroke rate has decreased dramatically from 23% in period I to 2.7% in period III (p = 0.007); (2) the perioperative mortality rate has been reduced from 6% in period I to no deaths in the past 10 years, but (3) the rate of postoperative cranial nerve dysfunction remains unchanged over 50 years (period I, 46%; period III, 40%). The median tumor size among patients with postoperative complications was significantly larger than those without complications (median size: 17 vs. 7 cm3, p = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)  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