全文获取类型
收费全文 | 147篇 |
免费 | 4篇 |
专业分类
化学 | 76篇 |
力学 | 3篇 |
数学 | 24篇 |
物理学 | 48篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 12篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1998年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1971年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有151条查询结果,搜索用时 61 毫秒
101.
Schmidt E Bail S Friedl SM Jirovetz L Buchbauer G Wanner J Denkova Z Slavchev A Stoyanova A Geissler M 《Natural product communications》2010,5(9):1365-1368
Commercially available aroma samples were evaluated for their olfactory quality by professional perfumers and tested for their antimicrobial activity. Agar diffusion and agar-dilution were used as test methods and a set of two Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and four Gram-negative bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris G, Klebsiella pneumoniae and Salmonella abony) and a yeast, Candida albicans, were the test microorganisms. All the investigated compounds were active against Gram-positive bacteria, especially beta-caryophyllene against Enterococcus faecalis (MIC 6 ppm), but only few substances showed activity towards Gram-negative bacteria, except for cinnamic acid, which was active against all (MIC 60 ppm) and Candida albicans, against which cinnamic acid and caryophyllene oxide showed high activity (MIC < 60 ppm). 相似文献
102.
103.
Snellen M Siemes K Simons DG 《The Journal of the Acoustical Society of America》2011,129(5):2878-2888
Acoustic remote sensing techniques for mapping sediment properties are of interest due to their low costs and high coverage. Model-based approaches directly couple the acoustic signals to sediment properties. Despite the limited coverage of the single-beam echosounder (SBES), it is widely used. Having available model-based SBES classification tools, therefore, is important. Here, two model-based approaches of different complexity are compared to investigate their practical applicability. The first approach is based on matching the echo envelope. It maximally exploits the information available in the signal but requires complex modeling and optimization. To minimize computational costs, the efficient differential evolution method is used. The second approach reduces the information of the signal to energy only and directly relates this to the reflection coefficient to obtain quantitative information about the sediment parameters. The first approach provides information over a variety of sediment types. In addition to sediment mean grain size, it also provides estimates for the spectral strength and volume scattering parameter. The need to account for all three parameters is demonstrated, justifying computational expenses. In the second approach, the lack of information on these parameters and the limited SBES beamwidth are demonstrated to hamper the conversion of echo energy to reflection coefficient. 相似文献
104.
Slobodan Nickovic Vladimir Djurdjevic Mirjam Vujadinovic Zavisa I. Janjic Milan Curcic Borivoj Rajkovic 《Journal of computational physics》2011,230(5):1865-1875
Generation of short gravity wave noise often occurs on semi-staggered rectangular grids as a result of sub-grid decoupling when there is a strong forcing in the mass field. In this study a numerical scheme has been proposed to prevent the generation of the gravity wave decoupling. The proposed numerical method provides efficient communication between decoupled gravity wave finite-difference solutions by a simple averaging of a term in the height tendency in the continuity equation. The proposed method is tested using a shallow water sink model developed for the purpose of this study. It has been demonstrated that this method outperforms other existing approaches. The new scheme is time efficient, based on explicit time integration and can be easily implemented. The proposed method is applicable in hydrodynamic models specified on semi-staggered B or E grids. 相似文献
105.
Mirjam Dür Charoenchai Khompatraporn Zelda B. Zabinsky 《Annals of Operations Research》2007,156(1):25-44
Fractional programming has numerous applications in economy and engineering. While some fractional problems are easy in the
sense that they are equivalent to an ordinary linear program, other problems like maximizing a sum or product of several ratios
are known to be hard, as these functions are highly nonconvex and multimodal. In contrast to the standard Branch-and-Bound
type algorithms proposed for specific types of fractional problems, we treat general fractional problems with stochastic algorithms
developed for multimodal global optimization. Specifically, we propose Improving Hit-and-Run with restarts, based on a theoretical
analysis of Multistart Pure Adaptive Search (cf. the dissertation of Khompatraporn (2004)) which prescribes a way to utilize problem specific information to sample until a certain level α of confidence is achieved. For this purpose, we analyze the Lipschitz properties of fractional functions, and then utilize
a unified method to solve general fractional problems. The paper ends with a report on numerical experiments.
This work was initiated while Mirjam Dür was spending a three-month research visit at the University of Washington. She would
like to thank the Fulbright Commission for financial support and the optimization group at UW for their warm hospitality.
The work of C. Khompatraporn and Z.B. Zabinsky was partially supported by the NSF grant DMI-0244286. 相似文献
106.
107.
Sebastian Wendl Lucien Eisenburger Mirjam Zipkat Daniel Günther Dr. Jonathan P. Wright Dr. Peter J. Schmidt Prof. Dr. Oliver Oeckler Prof. Dr. Wolfgang Schnick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):5010-5016
Barium imidonitridophosphate BaP6N10NH was synthesized at 5 GPa and 1000 °C with a high-pressure high-temperature approach using the multianvil technique. Ba(N3)2, P3N5 and NH4Cl were used as starting materials, applying a combination of azide and mineralizer routes. The structure elucidation of BaP6N10NH (P63, a=7.5633(11), c=8.512(2) Å, Z=2) was performed by a combination of transmission electron microscopy and single-crystal diffraction with microfocused synchrotron radiation. Phase purity was verified by Rietveld refinement. 1H and 31P solid-state NMR and FTIR spectroscopy are consistent with the structure model. The chemical composition was confirmed by energy-dispersive X-ray spectroscopy and CHNS analyses. Eu2+-doped samples of BaP6N10NH show blue emission upon excitation with UV to blue light (λem=460 nm, fwhm=2423 cm−1) representing unprecedented Eu2+-luminescence of an imidonitride. 相似文献
108.
109.
110.