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   1833494篇
  免费   144070篇
  国内免费   2897篇
耳鼻咽喉   25214篇
儿科学   61233篇
妇产科学   52927篇
基础医学   263180篇
口腔科学   53206篇
临床医学   160535篇
内科学   357151篇
皮肤病学   39344篇
神经病学   146376篇
特种医学   73724篇
外国民族医学   516篇
外科学   280020篇
综合类   45879篇
现状与发展   4篇
一般理论   688篇
预防医学   138838篇
眼科学   42188篇
药学   137796篇
  36篇
中国医学   3593篇
肿瘤学   98013篇
  2018年   17557篇
  2016年   15316篇
  2015年   17740篇
  2014年   24205篇
  2013年   37074篇
  2012年   49588篇
  2011年   52152篇
  2010年   31247篇
  2009年   29598篇
  2008年   49759篇
  2007年   52723篇
  2006年   53389篇
  2005年   51747篇
  2004年   50975篇
  2003年   48653篇
  2002年   47437篇
  2001年   85453篇
  2000年   88344篇
  1999年   74796篇
  1998年   20108篇
  1997年   18448篇
  1996年   18315篇
  1995年   17940篇
  1994年   16848篇
  1993年   15901篇
  1992年   61575篇
  1991年   60158篇
  1990年   58847篇
  1989年   57055篇
  1988年   52844篇
  1987年   52028篇
  1986年   49475篇
  1985年   47894篇
  1984年   35721篇
  1983年   30746篇
  1982年   18054篇
  1981年   16024篇
  1980年   15119篇
  1979年   33839篇
  1978年   23508篇
  1977年   19931篇
  1976年   18612篇
  1975年   19842篇
  1974年   24120篇
  1973年   23371篇
  1972年   21376篇
  1971年   20142篇
  1970年   18574篇
  1969年   17353篇
  1968年   15927篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.

Background

Liver transplantation from donors after either controlled or uncontrolled cardiac death (DCD) is associated with considerable rates of primary nonfunction (PNF) and ischemic cholangiopathy (IC). Normothermic regional perfusion (NRP) could significantly reduce such rates.

Methods

Retrospective study to analyze short-term (mortality, PNF, vascular complications) and long-term (IC, survival) complications in 11 liver transplants from controlled DCDs using NRP with extracorporeal membrane oxygenation (ECMO) (group 1). They were compared with 51 patients transplanted with grafts from donors after brain death (DBD) (group 2). Mean recipient age, sex, and Model for End-stage Liver Disease (MELD) score were not significantly different.

Results

In group 1, mean functional warm ischemia time was 15.8 (range, 7–40) minutes and 94.1 (range, 20–150) minutes on NRP. The ischemic damage was minimal, as shown by the slight alanine aminotransferase (ALT) and aspartate aminotransferase (AST) rises in the donor serum after 1 hour on NRP and similar rises 24 hours after transplantation in both groups. No patient had IC or acute renal failure. No significant difference was found between the groups for vascular or biliary complications. One group 1 patient had PNF (9.1%), resulting in death. Overall retransplantation and in-hospital death rates were 8.1% and 4.8%, respectively, with no significant difference between groups. Estimated mean survival was 24.6 (95% confidence interval [CI], 20.2–29.1) months in group 1 and 32.3 (95% CI, 30.4–34.2) months in group 2 (not a statistically significant difference).

Conclusion

In our experience, liver transplants from controlled DCDs using NRP with ECMO is associated with a low risk of PNF and IC, with short- and long-term results comparable to those in DBD transplants.  相似文献   
82.
Introduction: Following life-threatening junctional trauma, the goal is to limit blood loss while expediting transfer to operative rescue. Unfortunately, life-threatening abdominal-pelvic or junctional hemorrhage is often not amenable to direct compression and few temporizing strategies are available beyond hemostatic dressings, hypotensive resuscitation, and balanced transfusion. Objectives: In this study, we evaluated proximal external aortic compression to arrest blood flow in healthy adult men. Methods: This was a simulation trial of proximal external aortic compression, for life-threatening abdominal-pelvic and junctional hemorrhage, in a convenience sample of healthy adult male volunteers. The primary end points were cessation of femoral blood flow as assessed by pulse wave Doppler ultrasound at the right femoral artery, caudal to the inguinal ligament. Secondary end points were discomfort and negative sequelae. Results: Aortic blood flow was arrested in 12 volunteers. Median time to blood flow cessation was 12.5?seconds. Median reported discomfort was 5 out of 10. No complications or negative sequelae were reported. Conclusion: This trial suggests that it may be reasonable to attempt temporization of major abdominal-pelvic and junctional hemorrhage using bimanual proximal external aortic compression. In the absence of immediate alternatives for this dangerous and vexing injury pattern, there appear to be few downsides to prehospital proximal external aortic compression while concomitantly expediting definite care.  相似文献   
83.

Background

Physicians treating nonvalvular atrial fibrillation (AF) assess stroke and bleeding risks when deciding on anticoagulation. The agreement between empirical and physician-estimated risks is unclear. Furthermore, the association between patient and physician sex and anticoagulation decision-making is uncertain.

Methods

We pooled data from 2 national primary care physician chart audit databases of patients with AF (Facilitating Review and Education to Optimize Stroke Prevention in Atrial Fibrillation and Coordinated National Network to Engage Physicians in the Care and Treatment of Patients with Atrial Fibrillation Chart Audit) with a combined 1035 physicians (133 female, 902 male) and 10,927 patients (4567 female and 6360 male).

Results

Male physicians underestimated stroke risk in female patients and overestimated risk in male patients. Female physicians estimated stroke risk well in female patients but underestimated the risk in male patients. Risk of bleeding was underestimated in all. Despite differences in risk assessment by physician and patient sex, > 90% of patients received anticoagulation across all subgroups. There was modest agreement between physician estimated and calculated (ie, CHADS2 score) stroke risk: Kappa scores were 0.41 (0.35-0.47) for female physicians and 0.34 (0.32-0.36) for male physicians.

Conclusions

Our study is the first to examine the association between patient and physician sex influences and stroke and bleeding risk estimation in AF. Although there were differences in agreement between physician estimated stroke risk and calculated CHADS2 scores, these differences were small and unlikely to affect clinical practice; further, despite any perceived differences in the accuracy of risk assessment by sex, most patients received anticoagulation.  相似文献   
84.
Abstract

Purpose: We aimed to evaluate the construct validity of the Eating Assessment Tool (EAT-10) by determining its dimensionality, rating scale integrity, item-person match, precision and relationship with the degree of airway invasion and functional oral intake.

Methods: We conducted a retrospective analysis of patients’ EAT-10 scores. We used the Rasch rating scale model. We investigated correlations between the EAT-10 and scores on the Penetration-Aspiration Scale (PAS) and Functional Oral Intake Scale (FOIS).

Results: The median score of the EAT-10 from 127 patients was 16 of 40 (range 0–40). Confirmatory factor analysis supported unidimensionality. The 5-point rating scale categories met published criteria. Two items misfit the Rasch model and two other items displayed differential item functioning. Rasch person reliability was 0.79. Our patient cohort was divided into three person-strata. Correlations between the EAT-10 and the PAS and FOIS were weak to moderate in strength (respectively: r?=?0.26, p?=?0.0036; r?=??0.27, p?=?0.0027).

Conclusions: Our analyses identified deficits in the construct validity of the EAT-10 suggestive of a need to improve the EAT-10 to support its frequent use in clinical practice and research.
  • Implications for Rehabilitation
  • Swallowing disorders are associated with severe complications, such as pneumonia and malnutrition, and impose both social and psychological burdens on patients.

  • The Eating Assessment Tool is a self-report instrument developed to estimate initial dysphagia severity and monitor change in patient-reported dysphagia symptoms as a response to treatment.

  • This study shows that the Eating Assessment Tool has deficits in its construct validity and a need to improve the instrument to support its frequent use in clinical practice and research.

  相似文献   
85.
86.

Objectives

This study reported a hospital outbreak due to an extensively drug-resistant (XDR) OXA-72-producing strain of Acinetobacter baumannii (A. baumannii).

Methods and Results

The isolates were found to be genotypically indistinguishable by whole-genome multiple locus sequence typing, and to belong to the international clonal complex CC2. One of these isolates sequentially developed a high resistance to colistin and rifampicin under treatment, as a result of mutations in genes pmrB and rpoB, respectively. The blaOXA-72 gene was localised on a 10-kb transferable plasmid, named pAB-STR-1, whose sequence is nearly identical to that of another plasmid previously found in Lithuanian strains, pAB120.

Conclusion

This report highlighted the need to carefully monitor the emergence of colistin and rifampicin resistance in patients treated for infections with multidrug-resistant A. baumannii.  相似文献   
87.
ABSTRACT

Various machine learning techniques have been developed for keratoconus detection and refractive surgery screening. These techniques utilize inputs from a range of corneal imaging devices and are built with automated decision trees, support vector machines, and various types of neural networks. In general, these techniques demonstrate very good differentiation of normal and keratoconic eyes, as well as good differentiation of normal and form fruste keratoconus. However, it is difficult to directly compare these studies, as keratoconus represents a wide spectrum of disease. More importantly, no public dataset exists for research purposes. Despite these challenges, machine learning in keratoconus detection and refractive surgery screening is a burgeoning field of study, with significant potential for continued advancement as imaging devices and techniques become more sophisticated.  相似文献   
88.

Purpose

The purpose of this study was to assess the potential of a deep learning model to discriminate between benign and malignant breast lesions using magnetic resonance imaging (MRI) and characterize different histological subtypes of breast lesions.

Materials and methods

We developed a deep learning model that simultaneously learns to detect lesions and characterize them. We created a lesion-characterization model based on a single two-dimensional T1-weighted fat suppressed MR image obtained after intravenous administration of a gadolinium chelate selected by radiologists. The data included 335 MR images from 335 patients, representing 17 different histological subtypes of breast lesions grouped into four categories (mammary gland, benign lesions, invasive ductal carcinoma and other malignant lesions). Algorithm performance was evaluated on an independent test set of 168 MR images using weighted sums of the area under the curve (AUC) scores.

Results

We obtained a cross-validation score of 0.817 weighted average receiver operating characteristic (ROC)-AUC on the training set computed as the mean of three-shuffle three-fold cross-validation. Our model reached a weighted mean AUC of 0.816 on the independent challenge test set.

Conclusion

This study shows good performance of a supervised-attention model with deep learning for breast MRI. This method should be validated on a larger and independent cohort.  相似文献   
89.
Background and purpose — No difference in outcome has been demonstrated comparing cemented taper-slip and composite beam designs in short-term randomised trials; we assessed outcome differences using a registry analysis.

Patients and methods — All cemented stems with > 100 implantations were identified in the National Joint Registry of England and Wales from April 1, 2003 to September 31, 2013 and categorised as taper-slip or composite beam. Survival analyses using Kaplan–Meier and Cox regression were performed.

Results — We identified 292,987 cemented arthroplasties, of which 16% (47,586) were composite beam stems, with taper-slip stems making up the remainder (n = 245,401). There was a statistically significant increased chance of revision in the composite beam group compared with the taper-slip group (1.7% vs 1.3%, p < 0.001) but statistically no significant differences of survival estimates (p = 0.06). When the 2 groups were segregated to delineate the most implanted model in each category, the differences became more profound with the most implanted taper-slip stem (Exeter V40) showing statistically and clinically significant superior 8-year survival: 97.9% compared with 97.6% for all other taper-slip; 97.5% for the most implanted composite beam (Charnley cemented stem); and 97.7% for all other composite beam.

Interpretation — There was an increased incidence of revision for composite beam stems. The most implanted taper-slip stem demonstrated significant survival advantage vs. all other stems.  相似文献   

90.
Abstract

Purpose: While a wide range of psychosocial oncological (PO) interventions has been developed, a systematic overview of interventions to inform patients, care providers, as well as researchers, policy makers and health insurers, is lacking. The aims of this paper were (1) to describe the attainment of this overview, which may be used in other jurisdictions and for other health conditions and (2) to reflect on what determines developments in this field.

Methods: Dutch researchers and care providers were invited to describe PO-interventions they apply in research or clinical practice. Selection criteria for what constituted a PO-intervention were determined. The input was organized in 12 predefined categories (e.g. physical functioning, genetics).

Findings: Sixty-six PO-interventions were included in the overview. Two major categories were psychosocial functioning (24%) and physical functioning and recovery (24%). Interventions are mostly directed at adults (65%) and not aimed at a specific type of cancer (61%). Nearly 25% of the interventions lacked scientific underpinning.

Conclusions: This paper provides an overview of Dutch PO-interventions and input on what drives their development. The categorizing method can be used in other jurisdictions and for other health care conditions. A next step would be to investigate the effectiveness and evidence of PO-interventions.

Implications for Psychosocial Providers and Policy: The open access overview of interventions provides referral information for care providers. By identifying possible gaps and overlap, the overview looks at possible drivers behind developments in this field which will be of interest to policy makers.  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