全文获取类型
收费全文 | 784篇 |
免费 | 36篇 |
专业分类
化学 | 651篇 |
晶体学 | 4篇 |
力学 | 17篇 |
数学 | 69篇 |
物理学 | 79篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 32篇 |
2021年 | 51篇 |
2020年 | 30篇 |
2019年 | 57篇 |
2018年 | 37篇 |
2017年 | 34篇 |
2016年 | 38篇 |
2015年 | 37篇 |
2014年 | 24篇 |
2013年 | 55篇 |
2012年 | 61篇 |
2011年 | 56篇 |
2010年 | 47篇 |
2009年 | 30篇 |
2008年 | 51篇 |
2007年 | 31篇 |
2006年 | 37篇 |
2005年 | 30篇 |
2004年 | 12篇 |
2003年 | 19篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有820条查询结果,搜索用时 318 毫秒
81.
Efim Pelinovsky Tatiana Talipova Ira Didenkulova Ekaterina Didenkulova 《Studies in Applied Mathematics》2019,142(4):513-527
Long wave propagation in a two‐layer fluid with variable depth is studied for specific bottom configurations, which allow waves to propagate over large distances. Such configurations are found within the linear shallow‐water theory and determined by a family of solutions of the second‐order ordinary differential equation (ODE) with three arbitrary constants. These solutions can be used to approximate the true bottom bathymetry. All such solutions represent smooth bottom profiles between two different singular points. The first singular point corresponds to the point where the two‐layer flow transforms into a uniform one. In the vicinity of this point nonlinear shallow‐water theory is used and the wave breaking criterion, which corresponds to the gradient catastrophe is found. The second bifurcation point corresponds to an infinite increase in water depth, which contradicts the shallow‐water assumption. This point is eliminated by matching the “nonreflecting” bottom profile with a flat bottom. The wave transformation at the matching point is described by the second‐order Fredholm equation and its approximated solution is then obtained. The results extend the theory of internal waves in inhomogeneous stratified fluids actively developed by Prof. Roger Grimshaw, to the new solutions types. 相似文献
82.
Larisa Popova Olga Ivanchenko Evgeniia Pochkaeva Sergey Klotchenko Marina Plotnikova Angelica Tsyrulnikova Ekaterina Aronova 《Molecules (Basel, Switzerland)》2021,26(13)
The increased complexity due to the emergence and rapid spread of new viral infections prompts researchers to search for potential antiviral and protective agents for mucous membranes among various natural objects, for example, plant raw materials, their individual components, as well as the products of their chemical modification. Due to their structure, resin acids are valuable raw materials of natural origin to synthesize various bioactive substances. Therefore, the purpose of this study was to confirm the possibility of using resin acid derivatives for the drug design. As a result, we studied the cytotoxicity and biological activity of resin acid derivatives. It was shown that a slight decrease in the viral load in the supernatants was observed upon stimulation of cells (II) compared with the control. When using PASS-online modeling (Prediction of Activity Spectra for Substances), the prediction of the biological activity spectrum showed that compound (I) is capable of exhibiting antiviral activity against the influenza virus. The use of the SWISS-ADME webserver to reveal the drug-like properties of compounds did not directly indicate the presence of antiviral activity. These results indicate the potential of resin acid derivatives as a starting point for extensive research in the study of biological activity. 相似文献
83.
Andrew M. Edmonds Mushtaq A. Sobhan Varun K. A. Sreenivasan Ekaterina A. Grebenik James R. Rabeau Ewa M. Goldys Andrei V. Zvyagin 《Particle & Particle Systems Characterization》2013,30(6):506-513
Bioprobes based on fluorescent ruby nanoparticles, which are suitable for ultrasensitive imaging, are reported. A stable aqueous/buffer colloid, permitting facile conjugation to proteins, is produced by femtosecond laser ablation of ruby and the nanoparticles (mean size 17 nm) are photostable, with long lifetime (1–4 ms) 694 nm emission. With time‐gating complete (>20 dB) suppression of cell autofluorescence and suppression of exogenous fluorophores is observed. Nanoparticles are imaged in as‐grown cells and those immunolabeled with quantum dots. Immunoassay binding to target biomolecules is also demonstrated. 相似文献
84.
Ekaterina A. Shilova Valery P. Perevalov Corinne Moustrou 《Tetrahedron letters》2007,48(23):4127-4130
A convenient new synthetic route to p-aminophenylaminobenzo- and naphthopyrans was developed via palladium-catalyzed C-N coupling. It was demonstrated that novel targeted aminoderivatives reveal photochromic properties. The structure of intermediate p-nitrophenylaminochromenes was confirmed by X-ray crystallographic analysis. 相似文献
85.
Functionalization of the diaminodibenzocrown ethers with 2H-[1]benzopyrane and 3H-naphtho[2,1-b]pyrane units by Buchwald-Hartwig C-N coupling was developed. It is demonstrated that the novel molecule possesses photochromic properties that can be modified by the complex formation process. 相似文献
86.
Yuliya A. Volkova Ekaterina M. Budynina Tamara S. Kuznetsova Nikolai S. Zefirov 《Tetrahedron》2008,64(16):3548-3553
A novel approach to acyclic alkyldinitronitronates using nucleophilic opening of epoxides with the trinitromethyl anion is presented. The scope and limitations of this synthetic procedure are presented. A series of highly functionalized 3,3-dinitroisoxazolidines were synthesized as mixtures of diastereomers. 相似文献
87.
Ekaterina V. Matveeva 《Tetrahedron letters》2008,49(42):6129-6133
Water as a solvent significantly accelerates the addition of various amines to diethyl vinylphosphonate to yield β-aminophosphonates without any catalyst compared to known procedures for such aza-Michael reactions. The products are obtained in quantitative yields and high purity over short reaction times. Using a reactant ratio (vinylphosphonate/amine) of 2:1 resulted in double phosphorylation of primary amines. 相似文献
88.
89.
Bogdan Kurtev Ekaterina Simova Maya Victorova Nikolina Berova Stefanka Christoskova 《Monatshefte für Chemie / Chemical Monthly》1981,112(5):669-673
Diphenylhalonium salts were used in stereospecific N-phenylation of racemic and optically active 3-amino-2,3-diphenyl-1-propanols leading to 3-anilino-2,3-diphenyl-1-propanols. The absolute configurations of the latter and of genetically related compounds were established.
Stereochemische Korrelation von diastereomeren 3-Amino- mit 3-Arylaminosäuren bzw. ihrer Derivate durch stereospezifische N-Phenylierung mit DiphenylhaloniumsalzenKurze Mitteilung
Zusammenfassung Durch stereospezifische N-Phenylierung mit Hilfe von Diphenylhaloniumsalzen werden racemische sowie optische aktive 3-Amino-2,3-diphenyl-1-propanole in die entsprechenden 3-Anilino-2,3-diphenyl-1-propanole übergeführt. Auf Grund dieser Umwandlung wird die absolute Konfiguration der Aminoalkohole und davon abgeleiteter Derivate ermittelt.相似文献
90.