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   896篇
  免费   45篇
耳鼻咽喉   21篇
儿科学   15篇
妇产科学   39篇
基础医学   111篇
口腔科学   8篇
临床医学   111篇
内科学   144篇
皮肤病学   4篇
神经病学   100篇
特种医学   13篇
外科学   182篇
综合类   4篇
预防医学   120篇
眼科学   2篇
药学   38篇
肿瘤学   29篇
  2021年   12篇
  2020年   5篇
  2019年   21篇
  2018年   11篇
  2017年   12篇
  2016年   8篇
  2015年   23篇
  2014年   26篇
  2013年   52篇
  2012年   54篇
  2011年   52篇
  2010年   27篇
  2009年   43篇
  2008年   42篇
  2007年   48篇
  2006年   50篇
  2005年   46篇
  2004年   50篇
  2003年   34篇
  2002年   29篇
  2001年   6篇
  2000年   9篇
  1999年   8篇
  1998年   8篇
  1997年   12篇
  1995年   6篇
  1992年   7篇
  1991年   7篇
  1990年   8篇
  1989年   18篇
  1988年   13篇
  1987年   12篇
  1986年   12篇
  1985年   12篇
  1984年   5篇
  1983年   10篇
  1982年   8篇
  1981年   5篇
  1980年   10篇
  1978年   11篇
  1977年   9篇
  1976年   8篇
  1975年   8篇
  1974年   5篇
  1973年   13篇
  1971年   4篇
  1969年   10篇
  1968年   7篇
  1967年   5篇
  1966年   6篇
排序方式: 共有941条查询结果,搜索用时 31 毫秒
31.
The process of endothelial differentiation into a network of tube-like structures with patent lumens requires an integrated program of gene expression. To identify genes upregulated in endothelial cells during the process of tube formation, RNA was prepared from several different time points (0, 4, 8, 24, 40, and 48 hours) and from three different experimental models of human endothelial tube formation: in collagen gels and fibrin gels driven by the combination of PMA (80), bFGF (40 ng/ml) and bFGF (40 ng/ml) or in collagen gels driven by the combination of HGF (40 ng/ml) and VEGF (40 ng/ml). Gene expression was evaluated using Affymetrix Gene Chip oligonucleotide arrays. Over 1000 common genes were upregulated greater than twofold over baseline at one or more time points in the three different models. In the present study, we discuss the identified genes that could be assigned to major functional classes: apoptosis, cytoskeleton, proteases, matrix, and matrix turnover, pumps and transporters, membrane lipid turnover, and junctional molecules or adhesion proteins.  相似文献   
32.
Background Growth hormone (GH) replacement during childhood has been shown to increase stature; however, there is little information on its long-term effect on the heart is not yet clear. The aim of this study was to assess cardiac size and function in patients with childhood-onset GH deficiency in whom GH treatment had been stopped at the achievement of final height and the effect of a second course of GH replacement in adult age. Methods Cardiac dimensions and function, obtained with echocardiography, of 21 patients (5 women and 16 men, mean age 28 ± 8 years), all of whom were treated during childhood, were compared with 21 age- and sex-matched healthy control subjects. Eight of these patients (2 women and 6 men, mean age 28 ± 8 years) were given a second course of GH replacement therapy for 15 ± 3 months. Results The stature and all cardiac dimensions of patients with GH deficiency who were treated during childhood were significantly smaller than those of the control subjects. After the second course of GH in adulthood, the only significant change observed was an increase in left ventricular (LV) mass (93 ± 21 vs 106 ± 24 g, P = .007) and LV mass index (59 ± 12 vs 66 ± 13 g/body surface area, P = .005). Conclusion The stature and cardiac dimensions of patients with childhood-onset GH deficiency measured in adult age were smaller than those of control subjects, despite long-term GH replacement therapy during childhood. A second course of GH treatment during adulthood caused a significant increase in the estimated LV mass index in patients with both isolated and multiple pituitary hormone deficiency. (Am Heart J 2003;145:549-53.)  相似文献   
33.
Borderline personality disorder (BPD) is a serious mental health condition associated with severe symptoms of distress and poor quality of life (QoL). Research outside the field of BPD suggests that ego-resiliency is negatively associated with psychopathology and positively associated with a range of positive life outcomes. Thus, ego-resiliency may be a valuable construct for furthering our understanding and treatment of BPD. However, the mechanisms linking ego-resiliency to psychopathology and QoL in relation to BPD have not been examined and explored by research. This study has addressed this gap in the collective knowledge by evaluating whether within-person associations between daily reports of positive affect (PA) and negative affect (NA) mediated the relationship between ego-resiliency, BPD symptom severity, and QoL. For 21 consecutive days, 72 women diagnosed with BPD completed end-of-day electronic assessments regarding ego-resiliency, PA and NA, symptom severity, and QoL. Multilevel structural equation modelling established that PA and NA were parallel mediators linking ego-resiliency with BPD symptom severity and QoL. As hypothesized, the path to QoL was stronger through PA than through NA. The mediation paths through NA and PA to BPD symptom severity were both significant, but their strength did not differ. Our findings align with the assertions of theories on emotion, thus suggesting a two-factor approach to PA and NA. Future research can build on these findings by developing psychotherapeutic interventions designed not only to reduce symptom severity but also to enhance PA in individuals with BPD and determine whether an increase in PA is associated with improved QoL.  相似文献   
34.
35.
36.
37.
This article reviews theoretical and practical approaches for setting priorities in global child health research investments. It also provides an overview of previous attempts to develop appropriate tools and methodologies to define priorities in health research investments. A brief review of the most important theoretical concepts that should govern priority setting processes is undertaken, showing how different perspectives, such as medical, economical, legal, ethical, social, political, rational, philosophical, stakeholder driven, and others will necessarily conflict each other in determining priorities. We specially address present research agenda in global child health today and how it relates to United Nation's (UN) Millennium Development Goal 4, which is to reduce child mortality by two-thirds between 1990 and 2015. The outcomes of these former approaches are evaluated and their benefits and shortcomings presented. The case for a new methodology for setting priorities in health research investments is presented, as proposed by Child Health and Nutrition Research Initiative, and a need for its implementation in global child health is outlined. A transdisciplinary approach is needed to address all the perspectives from which investments into health research can be seen as priorities. This prioritization requires a process that is transparent, systematic, and that would take into account many perspectives and build on advantages of previous approaches.  相似文献   
38.

Aim

To identify main groups of stakeholders in the process of health research priority setting and propose strategies for addressing their systems of values.

Methods

In three separate exercises that took place between March and June 2006 we interviewed three different groups of stakeholders: 1) members of the global research priority setting network; 2) a diverse group of national-level stakeholders from South Africa; and 3) participants at the conference related to international child health held in Washington, DC, USA. Each of the groups was administered different version of the questionnaire in which they were asked to set weights to criteria (and also minimum required thresholds, where applicable) that were a priori defined as relevant to health research priority setting by the consultants of the Child Health and Nutrition Research initiative (CHNRI).

Results

At the global level, the wide and diverse group of respondents placed the greatest importance (weight) to the criterion of maximum potential for disease burden reduction, while the most stringent threshold was placed on the criterion of answerability in an ethical way. Among the stakeholders’ representatives attending the international conference, the criterion of deliverability, answerability, and sustainability of health research results was proposed as the most important one. At the national level in South Africa, the greatest weight was placed on the criterion addressing the predicted impact on equity of the proposed health research.

Conclusions

Involving a large group of stakeholders when setting priorities in health research investments is important because the criteria of relevance to scientists and technical experts, whose knowledge and technical expertise is usually central to the process, may not be appropriate to specific contexts and in accordance with the views and values of those who invest in health research, those who benefit from it, or wider society as a whole.When decisions on investments in health research are made, the term “stakeholders” refers to all individuals and/or groups who have interest in prioritization of those investments. The stakeholders will therefore comprise a large and highly heterogeneous group. Some apparent examples may include research funding agencies (eg, governmental agencies, private organizations, public-private partnerships, international and regional organizations, and taxpayers of a certain region), direct recipients of the funding (eg, researchers and research institutions), beneficiaries of the research (eg, policy makers and the general population of a country), and any other group with interest in prioritization process (eg, advocacy groups, journalists and media, lawyers, economists, experts in ethics, and many others).Two fundamental characteristics of any acceptable and successful priority setting process are legitimacy and fairness (1). In order to ensure the legitimacy and fairness of the priority setting decisions in health research investments, involvement of a wide range of stakeholders (and/or eliciting their values) is needed. Unfortunately, health research priorities are presently mainly driven by technical experts (2-5). The results of prioritization are therefore in danger of being mostly influenced by their personal views, with minimal input from representatives from the wider community who also may have interest in the process but lack technical expertise. Since the values and criteria important to scientists and technical experts may vary remarkably from those of other relevant stakeholders (6-8), the relevance of eliciting wider stakeholders’ input is increasingly being acknowledged (9-11). However, the main challenge is to develop a systematic, flexible, and repeatable strategy on how this can be achieved in different contexts.The literature on priority setting for health interventions identifies two main strategies: 1) stakeholders’ values may impact decisions through procedural processes (by having access to the decisions and the rationales behind the decisions, and by having the authority to deliberate on the decisions and influence the final outcome); 2) stakeholders’ values can be directly elicited using quantitative methods (through surveys where respondents rank, weigh, or rate their values) and qualitative methods (involving individual interviews, Delphi technique, complaints procedures or group discussions, concept mapping, citizen’s jury, and public meetings) (12). The main challenges in those attempts have mainly been the lack of capacity for some stakeholders to engage in meaningful deliberations (13) and how to practically incorporate the elicited stakeholders’ values in decision-making (12,14). This paper presents our suggestions and experiences on how the values and interests of large and diverse group of stakeholders could still be incorporated in decisions on health research investment priorities. We specified thresholds and weights needed to address stakeholders’ values within CHNRI methodology using three different versions of a questionnaire. We aimed to assess stakeholders’ values for priority setting in global health research investments. We tested questionnaires that presented different levels of complexity and detail of the questions that stakeholders’ representatives would be asked. We also aimed to evaluate different strategies of turning their responses into numerical thresholds and weights.  相似文献   
39.
40.

Introduction

The gold standard for diagnosis and immediate therapy of bladder cancer is a transurethral resection (TURB) followed by histopathologic evaluation. The aim of this study was to assess the reliability of visual diagnosis by the operating urologist concerning dignity (malignant/benign) and staging compared to histopathologic evaluation. This is especially crucial since early mitomycin C instillation is based on the urologist’s first impression.

Study design and methods

This prospective study included 311 cases of TURB from five German institutions. Surgeons were asked to estimate dignity of the neoplasm, tumor stage, and grade according to a standardized questionnaire.

Results

The subjective estimation/visual diagnosis of the operating urologist achieved a sensitivity with respect to identifying malignant tumors as such of 97%, while specificity was only 41%. Accordingly, the positive (PPV) and negative predictive values (NPV) were 76% and 88%, respectively. In general, muscle invasive cancer was predicted more often than confirmed by pathology (PPV 52%). However, whenever muscle invasive cancer was excluded by the urologist, this was confirmed by the pathologist in most the cases (NPV 95%). The educational degree did not influence the reliability and predictive value of visual diagnosis.

Conclusion

This study shows that urologists cannot reliably distinguish benign from malignant lesions of bladder mucosa—regardless of their educational degree. A reliable diagnosis of a pathologist is definitely needed to plan final therapeutic steps.  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