全文获取类型
收费全文 | 286篇 |
免费 | 33篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 1篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 18篇 |
2015年 | 37篇 |
2014年 | 27篇 |
2013年 | 34篇 |
2012年 | 8篇 |
2011年 | 6篇 |
2010年 | 18篇 |
2009年 | 25篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1967年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有319条查询结果,搜索用时 15 毫秒
271.
Java language has been demonstrated to be an effective tool in supporting medical image viewing in Russia. This evaluation was completed by obtaining a maximum of 20 images, depending on the client's computer workstation from one patient using a commercially available computer tomography (CT) scanner. The images were compared against standard CT images that were viewed at the site of capture. There was no appreciable difference. The client side is a lightweight component that provides an intuitive interface for end users. Each image is loaded in its own thread and the user can begin work after the first image has been loaded. This feature is especially useful on slow connection speed, 9.6 Kbps for example. The server side, which is implemented by the Java Servlet Engine works more effective than common gateway interface (CGI) programs do. Advantages of the Java Technology place this program on the next level of application development. This paper presents a unique application of Java in telemedicine. 相似文献
272.
273.
274.
275.
Lindsay D. Leverett George F. Schieder IV Kathleen Donohue 《American journal of botany》2018,105(1):20-30
Premise of the Study
Phenology, the seasonal timing of development, can alter biotic interactions. Emergence from dormant or quiescent stages often occurs earlier when neighbors are present, which may reduce the neighbors' competitive effects. Delayed emergence in response to neighbors also has been observed, but the potential benefits of such delays are unclear. Further, emergence time may respond to neighbors experienced by parents, which may predict future competition in offspring.Methods
In the annual plant Arabidopsis thaliana (Brassicaceae), we quantified seed germination responses to neighbors in parental and offspring (seed) environments. To examine how observed changes in germination affect interactions with neighbors, we performed an outdoor experiment using neighbors of different sizes to represent different germination times.Key Results
Seeds were more likely to germinate if their parent had neighbors, but they were less likely to germinate if they themselves experienced a neighbor cue (canopy). As seeds lost dormancy over time, they gained the ability to germinate under a canopy, which suggests that they germinate later in the presence of neighbors. Neighbors of both sizes reduced growth, survival to reproduction, fecundity, and total fitness, but large neighbors increased seedling survival. Smaller neighbors provided no such benefit and had stronger negative effects.Conclusions
Delayed germination in response to neighbors can reduce negative interactions and promote positive ones if it occurs late enough to expose seedlings to larger neighbors. By altering relative phenologies and, in turn, the outcomes of biotic interactions, phenological responses to environmental change may influence species interactions and community dynamics. 相似文献276.
Pareto Optimal Spectrally Selective Emitters for Thermophotovoltaics via Weak Absorber Critical Coupling 下载免费PDF全文
Nari Jeon Jonathan J. Hernandez Daniel Rosenmann Stephen K. Gray Alex B. F. Martinson Jonathan J. Foley IV 《Liver Transplantation》2018,8(25)
Tailoring the emission spectra of a thermophotovoltaic (TPV) emitter away from that of a blackbody has the potential to minimize transmission and thermalization loss in a photovoltaic receiver. Selective TPV emitters can lead to solar energy conversion with efficiency greater than the Shockley–Queisser limit and can facilitate the generation of useful energy from waste heat. A new design is introduced to radically tune thermal emission that leverages the interplay between two resonant phenomena in simple planar nanostructures—absorption in weakly absorbing nanofilms and reflection in multilayer dielectric stacks. A virtual screening approach is employed to identify promising structures for a selective thermal emitter from a search space of millions, several of which approach the ideal values of a step‐function selective thermal emitter. One of these structures is experimentally fabricated and evaluated, which includes a weakly absorbing alloy with tailored optical properties fabricated by atomic layer deposition (ALD). The versatility of the design and fabrication approach result in an emitter with excellent spectral density (0.8 W cm?2 sr?1) and spectral efficiency (46.8%) at 1373 K. Future experimental challenges to a more accurate realization of the optimal structures calculated are also considered. 相似文献
277.
278.
Lida Xing W. Scott Persons IV Phil R. Bell Xing Xu Jianping Zhang Tetsuto Miyashita Fengping Wang Philip J. Currie 《Evolution; international journal of organic evolution》2013,67(8):2441-2445
The largest specimen of the four‐winged dromaeosaurid dinosaur Microraptor gui includes preserved gut contents. Previous reports of gut contents and considerations of functional morphology have indicated that Microraptor hunted in an arboreal environment. The new specimen demonstrates that this was not strictly the case, and offers unique insights into the ecology of nonavian dinosaurs early in the evolution of flight. The preserved gut contents are composed of teleost fish remains. Several morphological adaptations of Microraptor are identified as consistent with a partially piscivorous diet, including dentition with reduced serrations and forward projecting teeth on the anterior of the dentary. The feeding habits of Microraptor can now be understood better than that of any other carnivorous nonavian dinosaur, and Microraptor appears to have been an opportunistic and generalist feeder, able to exploit the most common prey in both the arboreal and aquatic microhabitats of the Early Cretaceous Jehol ecosystem. 相似文献
279.
Leigh C. Latta IV Kendall K. Morgan Casse S. Weaver Desiree Allen Sarah Schaack Michael Lynch 《Genetics》2013,193(2):539-544
Understanding how genetic variation is generated and how selection shapes mutation rates over evolutionary time requires knowledge of the factors influencing mutation and its effects on quantitative traits. We explore the impact of two factors, genomic background and generation time, on deleterious mutation in Daphnia pulicaria, a cyclically parthenogenic aquatic microcrustacean, using parallel mutation-accumulation experiments. The deleterious mutational properties of life-history characters for individuals from two different populations, and for individuals maintained at two different generation times, were quantified and compared. Mutational properties varied between populations, especially for clutch size, suggesting that genomic background influences mutational properties for some characters. Generation time was found to have a greater effect on mutational properties, with higher per-generation deleterious mutation rates in lines with longer generation times. These results suggest that differences in genetic architecture among populations and species may be explained in part by demographic features that significantly influence generation time and therefore the rate of mutation. 相似文献