全文获取类型
收费全文 | 530篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
化学 | 328篇 |
晶体学 | 4篇 |
力学 | 48篇 |
数学 | 110篇 |
物理学 | 65篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 21篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 29篇 |
2015年 | 25篇 |
2014年 | 19篇 |
2013年 | 31篇 |
2012年 | 27篇 |
2011年 | 41篇 |
2010年 | 29篇 |
2009年 | 30篇 |
2008年 | 27篇 |
2007年 | 42篇 |
2006年 | 30篇 |
2005年 | 31篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 18篇 |
2001年 | 4篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1941年 | 1篇 |
1937年 | 1篇 |
1926年 | 1篇 |
1913年 | 1篇 |
1907年 | 1篇 |
1869年 | 1篇 |
排序方式: 共有555条查询结果,搜索用时 15 毫秒
541.
Marcello D'Abbicco 《Mathematical Methods in the Applied Sciences》2015,38(6):1032-1045
In this paper, we obtain the global existence of small data solutions to the Cauchy problem in space dimension n ≥ 1, for p > 1 + 2 ∕ n, where μ is sufficiently large. We obtain estimates for the solution and its energy with the same decay rate of the linear problem. In particular, for μ ≥ 2 + n, the damping term is effective with respect to the L1 ? L2 low‐frequency estimates for the solution and its energy. In this case, we may prove global existence in any space dimension n ≥ 3, by assuming smallness of the initial data in some weighted energy space. In space dimension n = 1,2, we only assume smallness of the data in some Sobolev spaces, and we introduce an approach based on fractional Sobolev embedding to improve the threshold for global existence to μ ≥ 5 ∕ 3 in space dimension n = 1 and to μ ≥ 3 in space dimension n = 2. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
542.
Marcello Mascini Camilla Montesano Manuel Sergi German Perez Maristella De Cicco Roberta Curini Dario Compagnone 《Analytica chimica acta》2013
Two different hexapeptides were computationally designed and tested as selective SPE sorbent for cocaine. The amino acid residues used for designing the two hexapeptides, tested in SPE experiments, were, according to chemical function and interatomic distances, the most (QHWWDW) and the lowest (ESSIDH) preserved sequences in 4 proteins binding cocaine. The hexapeptide–cocaine complex was docked with different scoring functions combinations and resulting binding scores were compared with the SPE results. The extraction procedure for SPE was optimized considering volume loading, pH effect, and human plasma matrix interferences. Cocaine was loaded onto the modified resin cartridge at 10 ng mL−1 and the peptide QHWWDW was found to have the highest recovery with the best retention at pH 7.5, in agreement with docking simulation. Retention experiments were carried out also on cocaine metabolites nor-cocaine, benzoylecgonine and ecgonine methyl ester. Except for nor-cocaine the retention of metabolites on resin modified with peptide QHWWDW decreased drastically confirming the peptide selectivity, and validating the simulation data. Compared to standard solutions, only a slight decrease in cocaine recovery was observed loading human plasma samples after a partial protein precipitation. 相似文献
543.
Trabattoni S Moret M Miozzo L Campione M 《Journal of colloid and interface science》2011,360(2):422-429
The utilization of metal nanoparticles (NPs) to fabricate metal electrodes under mild conditions is one of the most studied topic in recent years. In this work, colloidal Au NPs were deposited on two isostructural molecular crystals, namely 1,2,3,4-tetrafluoro-7-thiomethyl-acridine (MeSAcr) and 1,2,3,4-tetrafluoro-7-methoxy-acridine (MeOAcr), exposing S atoms and O atoms, respectively, at their largest crystal faces. The depositions were carried out mainly by drop casting under ambient conditions, increasing the contact time from 1 to 120 min, and the samples were then analyzed by atomic force microscopy (AFM) to evaluate the coverage. Thanks to the affinity between S and Au atoms, Au NPs are observed to adhere on the MeSAcr surface within 1-min contact time, whereas at least 1h is required to find NPs on the MeOAcr surface. NP adsorption is also affected by the substrate surface morphology; indeed, step edges represent preferential adsorption sites even in the absence of Au-S interaction. Experiments under different conditions were performed to maximize the coverage on MeSAcr, reaching values up to 13%. AFM equipped with fluid cell was also employed to simultaneously depositing and imaging NPs, achieving a better understanding of the adsorption mechanism. 相似文献
544.
M. Abdel-Bary S. Abdel-Samad K. -Th. Brinkmann H. Clement J. Dietrich E. Doroshkevich S. Dshemuchadse K. Ehrhardt A. Erhardt W. Eyrich A. Filippi H. Freiesleben M. Fritsch W. Gast A. Gillitzer J. Gottwald H. J?ger B. Jakob R. J?kel L. Karsch K. Kilian H. Koch M. Krapp J. Kre? E. Kuhlmann A. Lehmann S. Marcello S. Mauro P. Michel K. Móller H. P. Morsch L. Naumann N. Paul C. Pizzolotto Ch. Plettner S. Reimann M. Richter J. Ritman E. Roderburg A. Schamlott P. Sch?nmeier W. Schroeder M. Schulte-Wissermann T. Sefzick M. Steinke G. Y. Sun A. Teufel W. Ullrich G. J. Wagner M. Wagner R. Wenzel A. Wilms P. Wintz P. Wüstner P. Zupranski 《The European Physical Journal A - Hadrons and Nuclei》2010,44(1):7-22
545.
M. Abdel-Bary S. Abdel-Samad K-Th. Brinkmann H. Clement J. Dietrich E. Doroshkevich S. Dshemuchadse K. Ehrhardt A. Erhardt W. Eyrich D. Filges A. Filippi H. Freiesleben M. Fritsch W. Gast J. Georgi A. Gillitzer J. Gottwald D. Hesselbarth H. J?ger B. Jakob R. J?kel L. Karsch K. Kilian H. Koch M. Krapp J. Kre? E. Kuhlmann A. Lehmann S. Marcello S. Marwinski S. Mauro W. Meyer P. Michel K. M?ller H. P. Morsch H. M?rtel L. Naumann N. Paul L. Pinna C. Pizzolotto Ch. Plettner S. Reimann M. Richter J. Ritman E. Roderburg A. Schamlott P. Sch?nmeier W. Schroeder M. Schulte-Wissermann T. Sefzick F. Stinzig M. Steinke G. Y. Sun A. Teufel W. Ullrich G. J. Wagner M. Wagner R. Wenzel A. Wilms P. Wintz S. Wirth P. Wüstner P. Zupranski 《The European Physical Journal A - Hadrons and Nuclei》2010,46(3):435-436
546.
The Drude weight is a central quantity for the transport properties of quantum spin chains. The canonical definition of Drude weight is directly related to Kubo formula of conductivity. However, the difficulty in the evaluation of such expression has led to several alternative formulations, accessible to different methods. In particular, the Euclidean, or imaginary-time, Drude weight can be studied via rigorous renormalization group. As a result, in the past years several universality results have been proven for such quantity at zero temperature; remarkably, the proofs work for both integrable and non-integrable quantum spin chains. Here we establish the equivalence of Euclidean and canonical Drude weights at zero temperature. Our proof is based on rigorous renormalization group methods, Ward identities, and complex analytic ideas. 相似文献
547.
Maurizio Aceto Elisa Cal Federica Gulino Francesca Gullo Maria Labate Angelo Agostino Marcello Picollo 《Molecules (Basel, Switzerland)》2022,27(15)
The identification of gemstones is an important topic in the field of cultural heritage, given their enormous value. Particularly, the most important precious stones, namely diamond, emerald, ruby and sapphire, are frequently subjected to counterfeit by substitution with objects of lesser value with similar appearance, colour or shape. While a gemmologist is able to recognise a counterfeit in most instances, more generally, it is not easy to do this without resorting to instrumental methods. In this work, the use of UV-visible diffuse reflectance spectrophotometry with optic fibres (FORS) is proposed as a fast and easy method for the preliminary identification of gemstones, alternative to the classical methods used by gemmologists or to Raman spectroscopy, which is by far the instrumental method with the best diagnostic potential, but it cannot be used in situations of problematic geometric hindrance. The possibilities and the limitations given by the FORS technique are critically discussed together with the spectral features of the most important gemstones. Finally, the application of chemometric pattern recognition methods is described for the treatment of large sets of spectral data deriving from gemstones identification. 相似文献
548.
Rosa Sparaco Antonia Scognamiglio Angela Corvino Giuseppe Caliendo Ferdinando Fiorino Elisa Magli Elisa Perissutti Vincenzo Santagada Beatrice Severino Paolo Luciano Marcello Casertano Anna Aiello Gilberto De Nucci Francesco Frecentese 《Molecules (Basel, Switzerland)》2023,28(1)
We recently identified 6-nitrodopamine and other nitro-catecholamines (6-nitrodopa, 6-nitroadrenaline), indicating that the endothelium has the ability to nitrate the classical catecholamines (dopamine, noradrenaline, and adrenaline). In order to investigate whether drugs could be subject to the same nitration process, we synthesized 4-nitro- and 7-nitropropranolol as probes to evaluate the possible nitration of the propranolol by the endothelium. The separation of the enantiomers in very high yields and excellent enantiopurity was achieved by chiral HPLC. Finally, we used Riguera’s method to determine the absolute configuration of the enantiomers, through double derivatization with MPA and NMR studies. 相似文献
549.
Daniel Josiane S. P. Cruz Jonas C. Catelani Tiago A. Garcia Jerusa S. Trevisan Marcello G. 《Journal of Thermal Analysis and Calorimetry》2021,143(4):3127-3135
Journal of Thermal Analysis and Calorimetry - This study aims to characterize erythromycin (ERY) estolate by thermogravimetry analysis and differential scanning calorimetry. For such a purpose,... 相似文献
550.