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   4087078篇
  免费   278742篇
  国内免费   10120篇
耳鼻咽喉   56128篇
儿科学   133325篇
妇产科学   111855篇
基础医学   570040篇
口腔科学   115311篇
临床医学   376194篇
内科学   789223篇
皮肤病学   93159篇
神经病学   334941篇
特种医学   155411篇
外国民族医学   1310篇
外科学   604784篇
综合类   92870篇
现状与发展   7篇
一般理论   1620篇
预防医学   325935篇
眼科学   92806篇
药学   296182篇
  107篇
中国医学   8298篇
肿瘤学   216434篇
  2019年   33115篇
  2018年   44757篇
  2017年   34261篇
  2016年   39243篇
  2015年   44072篇
  2014年   61718篇
  2013年   93314篇
  2012年   123871篇
  2011年   132225篇
  2010年   79313篇
  2009年   75423篇
  2008年   122772篇
  2007年   130504篇
  2006年   132298篇
  2005年   127862篇
  2004年   122777篇
  2003年   118274篇
  2002年   114096篇
  2001年   190017篇
  2000年   195181篇
  1999年   164255篇
  1998年   48565篇
  1997年   43050篇
  1996年   43103篇
  1995年   41772篇
  1994年   38401篇
  1993年   36009篇
  1992年   129089篇
  1991年   124905篇
  1990年   121172篇
  1989年   116578篇
  1988年   107323篇
  1987年   105401篇
  1986年   99267篇
  1985年   95248篇
  1984年   71838篇
  1983年   61029篇
  1982年   36559篇
  1981年   32777篇
  1979年   64838篇
  1978年   46123篇
  1977年   38913篇
  1976年   36285篇
  1975年   38473篇
  1974年   45988篇
  1973年   44093篇
  1972年   41447篇
  1971年   38456篇
  1970年   35694篇
  1969年   33818篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.

Objective

The objective of this study was to investigate the feasibility of a specific custom-made fenestrated aortic cuff in the treatment of complex abdominal aortic aneurysms (AAAs).

Methods

Between 2013 and 2016, a total of 57 custom-made Fenestrated Anaconda (Vascutek, Inchinnan, Scotland, UK) aortic cuffs were placed in 38 centers worldwide. All centers were invited to participate in this retrospective analysis. Postoperative and follow-up data included the presence of adverse events, necessity for reintervention, and renal function.

Results

Fifteen clinics participated, leading to 29 cases. Median age at operation was 74 years (interquartile range [IQR], 71-78 years); five patients were female. Two patients were treated for a para-anastomotic AAA after open AAA repair, 19 patients were treated because of a complicated course after primary endovascular AAA repair, and 8 cases were primary procedures for AAA. A total of 76 fenestrations (mean, 2.6 per case) were used. Four patients needed seven adjunctive procedures. Two patients underwent conversion, one because of a dissection of the superior mesenteric artery and one because of perforation of a renal artery. Median operation time was 225 minutes (IQR, 150-260 minutes); median blood loss, 200 mL (IQR, 100-500 mL); and median contrast volume, 150 mL (IQR, 92-260 mL). Primary technical success was achieved in 86% and secondary technical success in 93%. The 30-day morbidity was 7 of 29 with a mortality rate of 4 of 29. Estimated glomerular filtration rate remained unchanged before and after surgery (76 to 77 mL/min/m2). Between preoperative and median follow-up of 11 months, estimated glomerular filtration rate was reduced statistically significantly (76 to 63 mL/min/m2). During follow-up, 9 cases had an increase in aneurysm sac diameter (5 cases >5 mm); 14 cases had a stable or decreased aneurysm sac diameter; and in 2 cases, no aneurysm size was reported. No type I endoleak was reported, and two cases with a type III endoleak were treated by endovascular means during follow-up. Survival, reintervention-free survival, and target vessel patency at 1 year were 81% ± 8%, 75% ± 9%, and 99% ± 1%, respectively. After 2 years, these numbers were 81% ± 8%, 67% ± 11%, and 88% ± 6%, respectively. During follow-up, the two patients with a type III endoleak needed endograft-related reinterventions.

Conclusions

Treatment with this specific custom-made fenestrated aortic cuff is feasible after complicated previous (endovascular) aortic repair or in complex AAAs. The complexity of certain AAA cases is underlined in this study, and the Fenestrated Anaconda aortic cuff is a valid option in selected cases in which few treatment options are left.  相似文献   
22.

Objectives

Arm swing is a distinctive characteristic of sprint-running with the arms working in a contralateral manner with the legs to propel the body in a horizontal direction. The purpose of this study was to determine the acute changes in kinematics and kinetics when wearable resistance (WR) of 1 kg (equivalent to ~1% body mass) was attached to each forearm during over ground short distance (20 m) maximal sprint-running.

Design

Cross-sectional study.

Methods

Twenty-two male amateur rugby athletes (19.4 ± 0.5 years; 97.0 ± 4.8 kg; 180.4 ± 7.2 cm) volunteered to participate in the study. Radar and Optojump were used to examine kinematic and kinetics between WR and unloaded sprint-running conditions.

Results

No significant (p < 0.05) differences were found at 2 m or 5 m between conditions, however, the WR condition resulted in a significant increase in 10 m, 20 m and 10–20 m split time (all, ~2%, small effect size) compared to the unloaded condition. Significant decreases were also found in theoretical maximum velocity (V0) (?1.4%, small effect size) and relative peak horizontal power production (Pmax) (?5.5%, small effect size). Step length (2.1%, small effect size) and contact time (6.5%, medium effect size) were significantly increased, while step frequency (?4.1%, small effect size) and flight time (?5.3%, medium effect size) were significantly decreased.

Conclusions

WR forearm loading provides a movement specific overload of the arms which significantly alters step kinematics and sprint times ≥10 m.  相似文献   
23.

Background

Epidemiology of patients with worsening heart failure and reduced ejection fraction (HFrEF) in the real-world setting is not well described.

Objectives

The purpose of this study was to describe incidence, clinical characteristics, treatment, and outcomes of patients with HFrEF who develop worsening heart failure (HF) in the real-world setting.

Methods

Data on patients with incident HFrEF from the National Cardiovascular Data Registry PINNACLE were linked to pharmacy, private practitioner, and hospital claims databases. Incidence, clinical characteristics, treatment (angiotensin-converting enzyme inhibitor/angiotensin receptor blocker, beta-blocker, and mineralocorticoid receptor antagonist) and outcomes of patients with worsening HF, defined as ≥90 days of stable HF with subsequent worsening requiring intravenous diuretic agents, were assessed.

Results

Of 11,064 HFrEF patients, 1,851 (17%) developed worsening HF on average 1.5 years following initial HF diagnosis. Patients who developed worsening HF were more likely to be African American, be octogenarians, and have higher comorbidity burden (p < 0.001). At the onset of worsening HF, 42.4% of patients were on monotherapy, 43.4% were on dual therapy, and 14.1% were on triple therapy. A total of 48%, 61%, and 98% of patients were on >50% target dose for angiotensin-converting enzyme inhibitor/angiotensin receptor blocker, beta-blocker, and mineralocorticoid receptor antagonist, respectively. The 2-year mortality rate was 22.5%, and 56% of patients were rehospitalized within 30 days of the worsening HF event.

Conclusions

In the real-world setting, 1 in 6 patients with HFrEF develop worsening HF within 18 months of HF diagnosis. These patients have a high risk for 2-year mortality and recurrent HF hospitalizations. The use of standard-of-care therapies both before and after the onset of worsening HF is low. With high unmet medical need, patients with worsening HF require novel treatment strategies as well as greater optimization of existing guideline-directed therapy.  相似文献   
24.
25.
26.
This study aimed to evaluate changes in sleep during the COVID‐19 outbreak, and used data‐driven approaches to identify distinct profiles of changes in sleep‐related behaviours. Demographic, behavioural and psychological factors associated with sleep changes were also investigated. An online population survey assessing sleep and mental health was distributed between 3 April and 24 June 2020. Retrospective questions were used to estimate temporal changes from before to during the outbreak. In 5,525 Canadian respondents (67.1% females, 16–95 years old: Mean ± SD = 55.6 ± 16.3 years), wake‐up times were significantly delayed relative to pre‐outbreak estimates (p < .001,  = 0.04). Occurrences of clinically meaningful sleep difficulties significantly increased from 36.0% before the outbreak to 50.5% during the outbreak (all p < .001, g ≥ 0.27). Three subgroups with distinct profiles of changes in sleep behaviours were identified: “Reduced Time in Bed”, “Delayed Sleep” and “Extended Time in Bed”. The “Reduced Time in Bed” and “Delayed Sleep” subgroups had more adverse sleep outcomes and psychological changes during the outbreak. The emergence of new sleep difficulties was independently associated with female sex, chronic illnesses, being employed, family responsibilities, earlier wake‐up times, higher stress levels, as well as heavier alcohol use and television exposure. The heterogeneity of sleep changes in response to the pandemic highlights the need for tailored interventions to address sleep problems.  相似文献   
27.
28.
Though cerebrovascular complications of pregnancy remain relatively rare, they represent a potentially devastating event that necessitates prompt identification and treatment. Eighteen percent of strokes occurring in young women are linked to pregnancy. They occur mostly in the third trimester or during the post-partum period. Their biggest risk factors are hypertension, preeclampsia/eclampsia and migraine. Cerebrovascular events occurring during this period may involve specific pathophysiological processes that include embolic phenomena or endothelial dysfunction, but can also have common etiologies that are simply favored by the context of pregnancy. Thus, posterior encephalopathy and vasoconstriction cerebral syndrome are relatively frequently involved in cerebrovascular complications of pregnancy. Other very specific causes like amniotic fluid embolism or postpartum cardiomyopathy can also be responsible for such events. The management of stroke during pregnancy must be multidisciplinary and include a neurovascular expertise. Some conditions can lead to a long-life follow-up and modify the management of a future pregnancy.  相似文献   
29.
30.
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