全文获取类型
收费全文 | 2976篇 |
免费 | 262篇 |
出版年
2023年 | 9篇 |
2022年 | 29篇 |
2021年 | 46篇 |
2020年 | 25篇 |
2019年 | 35篇 |
2018年 | 47篇 |
2017年 | 44篇 |
2016年 | 68篇 |
2015年 | 110篇 |
2014年 | 155篇 |
2013年 | 141篇 |
2012年 | 174篇 |
2011年 | 207篇 |
2010年 | 142篇 |
2009年 | 122篇 |
2008年 | 152篇 |
2007年 | 155篇 |
2006年 | 161篇 |
2005年 | 118篇 |
2004年 | 157篇 |
2003年 | 140篇 |
2002年 | 140篇 |
2001年 | 66篇 |
2000年 | 66篇 |
1999年 | 59篇 |
1998年 | 43篇 |
1997年 | 36篇 |
1996年 | 35篇 |
1995年 | 18篇 |
1994年 | 24篇 |
1993年 | 24篇 |
1992年 | 40篇 |
1991年 | 38篇 |
1990年 | 35篇 |
1989年 | 31篇 |
1988年 | 29篇 |
1987年 | 20篇 |
1986年 | 29篇 |
1985年 | 30篇 |
1984年 | 22篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 24篇 |
1978年 | 21篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1972年 | 13篇 |
1971年 | 9篇 |
排序方式: 共有3238条查询结果,搜索用时 281 毫秒
131.
Eva Santermans Emmanuel Robesyn Tapiwa Ganyani Bertrand Sudre Christel Faes Chantal Quinten Wim Van Bortel Tom Haber Thomas Kovac Frank Van Reeth Marco Testa Niel Hens Diamantis Plachouras 《PloS one》2016,11(1)
Background
The Ebola outbreak in West Africa has infected at least 27,443 individuals and killed 11,207, based on data until 24 June, 2015, released by the World Health Organization (WHO). This outbreak has been characterised by extensive geographic spread across the affected countries Guinea, Liberia and Sierra Leone, and by localized hotspots within these countries. The rapid recognition and quantitative assessment of localised areas of higher transmission can inform the optimal deployment of public health resources.Methods
A variety of mathematical models have been used to estimate the evolution of this epidemic, and some have pointed out the importance of the spatial heterogeneity apparent from incidence maps. However, little is known about the district-level transmission. Given that many response decisions are taken at sub-national level, the current study aimed to investigate the spatial heterogeneity by using a different modelling framework, built on publicly available data at district level. Furthermore, we assessed whether this model could quantify the effect of intervention measures and provide predictions at a local level to guide public health action. We used a two-stage modelling approach: a) a flexible spatiotemporal growth model across all affected districts and b) a deterministic SEIR compartmental model per district whenever deemed appropriate.Findings
Our estimates show substantial differences in the evolution of the outbreak in the various regions of Guinea, Liberia and Sierra Leone, illustrating the importance of monitoring the outbreak at district level. We also provide an estimate of the time-dependent district-specific effective reproduction number, as a quantitative measure to compare transmission between different districts and give input for informed decisions on control measures and resource allocation. Prediction and assessing the impact of control measures proved to be difficult without more accurate data. In conclusion, this study provides us a useful tool at district level for public health, and illustrates the importance of collecting and sharing data. 相似文献132.
Yves Gleize Fanny Mendisco Marie-Hélène Pemonge Christophe Hubert Alexis Groppi Bertrand Houix Marie-France Deguilloux Jean-Yves Breuil 《PloS one》2016,11(2)
The rapid Arab-Islamic conquest during the early Middle Ages led to major political and cultural changes in the Mediterranean world. Although the early medieval Muslim presence in the Iberian Peninsula is now well documented, based in the evaluation of archeological and historical sources, the Muslim expansion in the area north of the Pyrenees has only been documented so far through textual sources or rare archaeological data. Our study provides the first archaeo-anthropological testimony of the Muslim establishment in South of France through the multidisciplinary analysis of three graves excavated at Nimes. First, we argue in favor of burials that followed Islamic rites and then note the presence of a community practicing Muslim traditions in Nimes. Second, the radiometric dates obtained from all three human skeletons (between the 7th and the 9th centuries AD) echo historical sources documenting an early Muslim presence in southern Gaul (i.e., the first half of 8th century AD). Finally, palaeogenomic analyses conducted on the human remains provide arguments in favor of a North African ancestry of the three individuals, at least considering the paternal lineages. Given all of these data, we propose that the skeletons from the Nimes burials belonged to Berbers integrated into the Umayyad army during the Arab expansion in North Africa. Our discovery not only discusses the first anthropological and genetic data concerning the Muslim occupation of the Visigothic territory of Septimania but also highlights the complexity of the relationship between the two communities during this period. 相似文献
133.
Immaculada Martínez-Rovira Rapha?l Boisgard Géraldine Pottier Bertrand Kuhnast Sébastien Jan 《PloS one》2016,11(3)
The development of a reliable dose monitoring system in hadron therapy is essential in order to control the treatment plan delivery. Positron Emission Tomography (PET) is the only method used in clinics nowadays for quality assurance. However, the accuracy of this method is limited by the loss of signal due to the biological washout processes. Up to the moment, very few studies measured the washout processes and there is no database of washout data as a function of the tissue and radioisotope. One of the main difficulties is related to the complexity of such measurements, along with the limited time slots available in hadron therapy facilities. Thus, in this work, we proposed an alternative in vivo methodology for the measurement and modeling of the biological washout parameters without any radiative devices. It consists in the implementation of a point-like radioisotope source by direct injection on the tissues of interest and its measurement by means of high-resolution preclinical PET systems. In particular, the washout of 11C carbonate radioisotopes was assessed, considering that 11C is is the most abundant β+ emitter produced by carbon beams. 11C washout measurements were performed in several tissues of interest (brain, muscle and 9L tumor xenograf) in rodents (Wistar rat). Results show that the methodology presented is sensitive to the washout variations depending on the selected tissue. Finally, a first qualitative correlation between 11C tumor washout properties and tumor metabolism (via 18F-FDG tracer uptake) was found. 相似文献
134.
Adrien Flahault Denis Trystram Marie Fouchard Bertrand Knebelmann Fran?ois Nataf Dominique Joly 《PloS one》2016,11(4)
BackgroundDespite a high prevalence of intracranial aneurysm (ICA) in autosomal dominant polycystic kidney disease (ADPKD), rupture events are rare. The current recommendations for ICA screening are based on expert opinions and studies with low levels of evidence.ObjectivesThe aim of our study was to describe the attitudes of practicing nephrologists in Europe towards screening for ICA using magnetic resonance angiography (MRA).MethodsWe conducted a web-based survey among 1315 European French-speaking nephrologists and nephrology residents. An anonymous, electronic questionnaire including 24 independent questions related to ICA screening modalities, indications and participant profiles was sent by email between September and December 2014. Four hundred and twenty nephrologists (mostly from France) participated, including 31 nephrology residents; the response rate was 32%.ResultsSystematic screening for ICA was advocated by 28% of the nephrologists. A family history of ICA rupture, sudden death, stroke and migraine were consensual indications for screening (> 90% of the panel). In other clinical situations largely not covered by the recommendations (pregnancy, nephrectomy, kidney transplantation, cardiac or hepatic surgery, uncontrolled hypertension, lack of familial ADPKD history, at-risk activity, tobacco use), the attitudes towards screening were highly divergent. ICA screening was influenced by nephrologists experience with ADPKD and by their practice setting. The majority of participants (57%) would not repeat a normal ICA screening. Only a few participants (22%) knew that non-contrast MRA was the reference diagnostic tool for ICA screening, whereas most participants thought that contrast enhancement was necessary to screen for ICA. The results from the nephrology residents were analyzed separately and yielded similar results.ConclusionThis practice survey revealed that most nephrologists follow the current recommendations for the initial screening of ICAs. However, more than a quarter of the panel was in favor of systematic ICA screening, most nephrologists did not know that contrast medium was not necessary to screen for ICA using MRA, and many areas of uncertainty remain. 相似文献
135.
Establishing nature reserves protects species from land cover conversion and the resulting loss of habitat. Even within a reserve, however, many factors such as fires and defoliating insects still threaten habitat and the survival of species. To address the risk to species survival after reserve establishment, reserve networks can be created that allow some redundancy of species coverage to maximize the expected number of species that survive in the presence of threats. In some regions, however, the threats to species within a reserve may be spatially correlated. As examples, fires, diseases, and pest infestations can spread from a starting point and threaten neighboring parcels’ habitats, in addition to damage caused at the initial location. This paper develops a reserve site selection optimization framework that compares the optimal reserve networks in cases where risks do and do not reflect spatial correlation. By exploring the impact of spatially-correlated risk on reserve networks on a stylized landscape and on an Oregon landscape, this analysis demonstrates an appropriate and feasible method for incorporating such post-reserve establishment risks in the reserve site selection literature as an additional tool to be further developed for future conservation planning. 相似文献
136.
Eveline Wijckmans Mieke Nys Sarah Debaveye Marijke Brams Els Pardon Katrien Willegems Daniel Bertrand Jan Steyaert Rouslan Efremov Chris Ulens 《PloS one》2016,11(3)
Cys-loop receptors are membrane spanning ligand-gated ion channels involved in fast excitatory and inhibitory neurotransmission. Three-dimensional structures of these ion channels, determined by X-ray crystallography or electron microscopy, have revealed valuable information regarding the molecular mechanisms underlying ligand recognition, channel gating and ion conductance. To extend and validate the current insights, we here present promising candidates for further structural studies. We report the biochemical and functional characterization of Cys-loop receptor homologues identified in the proteome of Alvinella pompejana, an extremophilic, polychaete annelid found in hydrothermal vents at the bottom of the Pacific Ocean. Seven homologues were selected, named Alpo1-7. Five of them, Alpo2-6, were unidentified prior to this study. Two-electrode voltage clamp experiments revealed that wild type Alpo5 and Alpo6, both sharing remarkably high sequence identity with human glycine receptor α subunits, are anion-selective channels that can be activated by glycine, GABA and taurine. Furthermore, upon expression in insect cells fluorescence size-exclusion chromatography experiments indicated that four homologues, Alpo1, Alpo4, Alpo6 and Alpo7, can be extracted out of the membrane by a wide variety of detergents while maintaining their oligomeric state. Finally, large-scale purification efforts of Alpo1, Alpo4 and Alpo6 resulted in milligram amounts of biochemically stable and monodisperse protein. Overall, our results establish the evolutionary conservation of glycine receptors in annelids and pave the way for future structural studies. 相似文献
137.
Andreas Hartmann Julia Muellner Niklaus Meier Helke Hesekamp Priscilla van Meerbeeck Marie-Odile Habert Aurélie Kas Marie-Laure Tanguy Merry Mazmanian Hervé Oya Nissen Abuaf Hafida Gaouar Sabrina Salhi Fanny Charbonnier-Beaupel Marie-Hélène Fievet Damien Galanaud Sophie Arguillere Emmanuel Roze Bertrand Degos David Grabli Lucette Lacomblez Cécile Hubsch Marie Vidailhet Anne-Marie Bonnet Jean-Christophe Corvol Michael Schüpbach 《PloS one》2016,11(9)
138.
139.
140.