全文获取类型
收费全文 | 2728篇 |
免费 | 215篇 |
国内免费 | 53篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 8篇 |
妇产科学 | 11篇 |
基础医学 | 77篇 |
口腔科学 | 45篇 |
临床医学 | 368篇 |
内科学 | 210篇 |
皮肤病学 | 17篇 |
神经病学 | 57篇 |
特种医学 | 38篇 |
外科学 | 79篇 |
综合类 | 399篇 |
预防医学 | 1189篇 |
眼科学 | 5篇 |
药学 | 344篇 |
1篇 | |
中国医学 | 116篇 |
肿瘤学 | 24篇 |
出版年
2024年 | 5篇 |
2023年 | 43篇 |
2022年 | 70篇 |
2021年 | 113篇 |
2020年 | 111篇 |
2019年 | 112篇 |
2018年 | 85篇 |
2017年 | 82篇 |
2016年 | 85篇 |
2015年 | 103篇 |
2014年 | 171篇 |
2013年 | 216篇 |
2012年 | 155篇 |
2011年 | 163篇 |
2010年 | 146篇 |
2009年 | 132篇 |
2008年 | 134篇 |
2007年 | 178篇 |
2006年 | 125篇 |
2005年 | 109篇 |
2004年 | 129篇 |
2003年 | 95篇 |
2002年 | 75篇 |
2001年 | 60篇 |
2000年 | 61篇 |
1999年 | 34篇 |
1998年 | 35篇 |
1997年 | 17篇 |
1996年 | 19篇 |
1995年 | 19篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有2996条查询结果,搜索用时 911 毫秒
91.
Petersen AM Riccaboni M Stanley HE Pammolli F 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(14):5213-5218
Understanding how institutional changes within academia may affect the overall potential of science requires a better quantitative representation of how careers evolve over time. Because knowledge spillovers, cumulative advantage, competition, and collaboration are distinctive features of the academic profession, both the employment relationship and the procedures for assigning recognition and allocating funding should be designed to account for these factors. We study the annual production n(i)(t) of a given scientist i by analyzing longitudinal career data for 200 leading scientists and 100 assistant professors from the physics community. Our empirical analysis of individual productivity dynamics shows that (i) there are increasing returns for the top individuals within the competitive cohort, and that (ii) the distribution of production growth is a leptokurtic "tent-shaped" distribution that is remarkably symmetric. Our methodology is general, and we speculate that similar features appear in other disciplines where academic publication is essential and collaboration is a key feature. We introduce a model of proportional growth which reproduces these two observations, and additionally accounts for the significantly right-skewed distributions of career longevity and achievement in science. Using this theoretical model, we show that short-term contracts can amplify the effects of competition and uncertainty making careers more vulnerable to early termination, not necessarily due to lack of individual talent and persistence, but because of random negative production shocks. We show that fluctuations in scientific production are quantitatively related to a scientist's collaboration radius and team efficiency. 相似文献
92.
93.
94.
Aznar JA Marco A Jiménez-Yuste V Fernández-Fontecha E Pérez R Soto I Parra R Moreno M Mingot ME Moret A;ON BEHALF OF THE SPANISH HAEMOPHILIA EPIDEMIOLOGICAL STUDY WORKING GROUP 《Haemophilia》2012,18(5):738-742
Summary. On‐demand therapy enables stopping haemorrhages rapidly, reducing joint pain and restoring joint mobility, but does not prevent the beginning and subsequent development of haemophilic arthropathy. The main objective of this study was to identify the clinical and orthopaedic status of severe haemophilic patients with bleeding phenotype receiving on‐demand treatment in Spain. We conducted an epidemiological, observational, retrospective study, recruiting 167 patients from 36 centres (92% of them with haemophilia A), median age at enrolment of 35 years. Forty per cent of the patients received a combination of on‐demand and short‐term prophylaxis regimen; the rest was under on‐demand treatment. One hundred and forty‐five patients (87%) reported at least one bleeding episode and 22 (13%) of the biologically severe patients had no bleeding phenotype. Seventy‐one per cent of the studied population presented established haemophilic arthropathy, reaching 80% if we exclude patients without bleeding phenotype. Forty‐three per cent of these patients had one or two joints affected, 28% of them had three or four affected joints, 20% reported five or six affected joints and 9% more than six injured joints. An increase in established haemophilic arthropathy with age was observed. Forty‐six patients underwent orthopaedic surgery at least once. These data show that on‐demand therapy is not effective in preventing the development of haemophilic arthropathy in severe haemophilic population with bleeding phenotype. Therefore, we suggest that the optimal treatment in these patients should be based on prophylaxis. We recommend analysing the reasons for ending prophylaxis, in case its reinstatement should be necessary. 相似文献
95.
Summary. Inpatient costs comprise >50% of annual healthcare costs for haemophilia patients with inhibitors but no reports exist on inpatient resource use and costs at a US national level. To quantify inpatient resource use and costs for on‐demand treatment of bleeds of US haemophilia patients with inhibitors and compare costs and treatment duration between Factor VIII bypassing agents (BAs). Stays with haemophilia A from 2003–2008 were identified from inpatient billing records. Presence of inhibitors was inferred through use of BA; recombinant activated Factor VII and plasma‐derived activated prothrombin complex concentrate. Duration and number of infusions of BA, length of stay, use of opioid‐containing analgesics and costs were assessed and compared. Among 1322 stays mean BA treatment duration was 4.6 days with 4.9 infusions, 6.1 nights spent in hospital, and 58% administered opioid‐containing analgesics. In unadjusted analyses there were significant differences in the above mentioned outcomes by BA use, reflecting underlying differences between the two patient populations. Average inpatient costs were $82 911. In adjusted analyses, African‐American race, greater disease severity, hospital region outside the southern US and older age (cost model only) were significant predictors of longer BA treatment duration and higher costs. The economic burden of inpatient on‐demand treatment of haemophilia with inhibitors is substantial and is associated with lengthy stays, high costs and inadequate pain relief. Availability of more effective BAs could reduce the need for re‐treatment, reducing treatment costs and other medical costs, while improving health related quality of life. 相似文献
96.
Frequent evaluation of haemophilia treatment is necessary to improve patient care. The 2010 Practice Patterns Survey (PPS) investigated current trends in haemophilia treatment in the United States, as reported by nurses. The aim was to document practice patterns for haemophilia A and haemophilia B Survey questionnaires were sent to nurses at haemophilia treatment centres (HTCs) across the United States. Seventy-one of 126 HTCs (56%) responded to the survey. Factor dosage across treatment modalities ranged from 20 to 50 IU kg(-1) for severe haemophilia A. Dosage for severe haemophilia B was more variable (<40 to >100 IU kg(-1)). On-demand dosing regimens were inconsistent for haemophilia A and more so for haemophilia B. Rates of adherence to prescribed treatment were similar for both haemophilia types (~80%). The main barrier to adherence was identified as inconvenience. More bleeding episodes occurred in adults (16.6 bleeding episodes per year) with severe haemophilia A than in younger patients (11.3 bleeding episodes per year) before switching patients to prophylaxis. For both haemophilia types, most patients who switched from prophylaxis to on-demand treatment were aged 13-24 years; these patients also had the lowest adherence (60-71%). More paediatric patients with severe haemophilia A and inhibitors (53%) received prophylactic bypassing therapy than their haemophilia B counterparts (38%). Adults with severe haemophilia A faced challenges in relation to co-morbidities and long-term care. This PPS provides insights into previously unexplored aspects of haemophilia care that will serve to increase awareness and promote discussion of current issues affecting haemophilia patient care. 相似文献
97.
A large body of behavioural research has used the cued task‐switching paradigm to characterize the nature of trial‐by‐trial preparatory adjustments that enable fluent task implementation when demands on cognitive flexibility are high. This work reviews the growing number of fMRI studies on the same topic, mostly focusing on the central hypothesis that preparatory adjustments should be indicated by enhanced prefrontal and parietal BOLD activation in task switch when compared with task repeat trials under conditions that enable advance task preparation. The evaluation of this straight‐forward hypothesis reveals surprisingly heterogeneous results regarding both the precise localization and the very existence of switch‐related preparatory activation. Explanations for these inconsistencies are considered on two levels. First, we discuss methodological issues regarding (i) the possible impact of different fMRI‐specific experimental design modifications and (ii) statistical uncertainty in the context of massively multivariate imaging data. Second, we discuss explanations related to the multidimensional nature of task preparation itself. Specifically, the precise localization and the size of switch‐related preparatory activation might depend on the differential interplay of hierarchical control via abstract task goals and attentional versus action‐directed preparatory processes. We argue that different preparatory modes can be adopted relying either on advance goal activation alone or on the advance resolution of competition within action sets or attentional sets. Importantly, while either mode can result in a reduction of behavioral switch cost, only the latter two are supposed to be associated with enhanced switch versus repeat BOLD activation in prepared trial conditions. Hum Brain Mapp, 2013. © 2011 Wiley Periodicals, Inc. 相似文献
98.
Marica Ferri Sonia Dias Alessandra Bo Danilo Ballotta Roland Simon Giuseppe Carrá 《Drugs (Abingdon, England)》2018,25(2):198-204
Background: The EMCDDA, through its network of National Focal Points, collects information on the quality assurance systems for drugs-related interventions across European countries. European National Drug Strategies include recommendations for systems and approaches for the assurance of the quality of interventions.Methods: We searched National Drug Strategies for elements related to quality assurance in drug demand reduction and summarised information through questionnaires administered to the EMCDDA Network of National Focal Points.Results: In total, 15 National Drug Strategies and 60 questionnaires were analysed. Almost all the strategies include quality-related topics. Frequently, the Ministry of Health leads quality assurance although sometimes jointly with the Ministries of Education, Labour, Family and Social Welfare. Accreditation systems are common, but implemented in different ways. Training and education are widely provided, for the vast majority of countries, consisting of short-term training to keep professionals updated. Guidelines and Standards are gathering momentum as the major tools for the implementation of evidence-based recommendations and are usually available across countries.Conclusions: Although the evidence base for interventions in drug demand reduction is becoming available and accepted, attention needs to be given to implementation issues. The European countries are rapidly moving towards paying greater attention to the quality of interventions. 相似文献
99.
100.