全文获取类型
收费全文 | 8635篇 |
免费 | 198篇 |
国内免费 | 4篇 |
专业分类
化学 | 4930篇 |
晶体学 | 188篇 |
力学 | 177篇 |
数学 | 1385篇 |
物理学 | 2157篇 |
出版年
2022年 | 96篇 |
2021年 | 147篇 |
2020年 | 117篇 |
2019年 | 164篇 |
2018年 | 146篇 |
2017年 | 151篇 |
2016年 | 270篇 |
2015年 | 217篇 |
2014年 | 286篇 |
2013年 | 642篇 |
2012年 | 421篇 |
2011年 | 479篇 |
2010年 | 379篇 |
2009年 | 347篇 |
2008年 | 419篇 |
2007年 | 405篇 |
2006年 | 343篇 |
2005年 | 308篇 |
2004年 | 268篇 |
2003年 | 288篇 |
2002年 | 217篇 |
2001年 | 179篇 |
2000年 | 167篇 |
1999年 | 125篇 |
1998年 | 126篇 |
1997年 | 100篇 |
1996年 | 93篇 |
1995年 | 121篇 |
1994年 | 71篇 |
1993年 | 59篇 |
1992年 | 82篇 |
1991年 | 52篇 |
1990年 | 79篇 |
1989年 | 69篇 |
1988年 | 70篇 |
1987年 | 65篇 |
1986年 | 70篇 |
1985年 | 108篇 |
1984年 | 122篇 |
1983年 | 74篇 |
1982年 | 73篇 |
1981年 | 80篇 |
1980年 | 88篇 |
1979年 | 62篇 |
1978年 | 65篇 |
1977年 | 75篇 |
1976年 | 71篇 |
1975年 | 60篇 |
1974年 | 51篇 |
1973年 | 45篇 |
排序方式: 共有8837条查询结果,搜索用时 125 毫秒
1.
Gürbüzbalaban Mert Ruszczyński Andrzej Zhu Landi 《Journal of Optimization Theory and Applications》2022,194(3):1014-1041
Journal of Optimization Theory and Applications - We consider a distributionally robust formulation of stochastic optimization problems arising in statistical learning, where robustness is with... 相似文献
2.
3.
4.
Lithium Insertion Mechanism in Iron-Based Oxyfluorides with Anionic Vacancies Probed by PDF Analysis
Dr. Damien Dambournet Dr. Karena W Chapman Dr. Mathieu Duttine Dr. Olaf Borkiewicz Dr. Peter J Chupas Dr. Henri Groult 《ChemistryOpen》2015,4(4):443-447
The mechanism of lithium insertion that occurs in an iron oxyfluoride sample with a hexagonal–tungsten–bronze (HTB)-type structure was investigated by the pair distribution function. This study reveals that upon lithiation, the HTB framework collapses to yield disordered rutile and rock salt phases followed by a conversion reaction of the fluoride phase toward lithium fluoride and nanometer-sized metallic iron. The occurrence of anionic vacancies in the pristine framework was shown to strongly impact the electrochemical activity, that is, the reversible capacity scales with the content of anionic vacancies. Similar to FeOF-type electrodes, upon de-lithiation, a disordered rutile phase forms, showing that the anionic chemistry dictates the atomic arrangement of the re-oxidized phase. Finally, it was shown that the nanoscaling and structural rearrangement induced by the conversion reaction allow the in situ formation of new electrode materials with enhanced electrochemical properties. 相似文献
5.
Russian Chemical Bulletin - The discovery and studies of chemistry of dichlorocarbene and other electron deficient carbenes are discussed. 相似文献
6.
Karolina Kula Agnieszka Kcka-Zych Agnieszka apczuk-Krygier Zbigniew Wzorek Anna K. Nowak Radomir Jasiski 《Molecules (Basel, Switzerland)》2021,26(5)
The present paper is a continuation of comprehensive study regarding to synthesis and properties of pyrazoles and their derivatives. In its framework an experimental and theoretical studies of thermal decomposition of the 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline were performed. It was found, that the decompositions of the mentioned pyrazoline system in the solution and at the melted state proceed via completely different molecular mechanisms. These mechanisms have been explained in the framework of the Molecular Electron Density Theory (MEDT) with the computational level of B3LYP/6-31G(d). A Bonding Evolution Theory (BET) examination of dehydrochlorination of the 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline permits elucidation of the molecular mechanism. It was found, that on the contrary for most known HCl extrusion processes in solution, this reaction is realised via single-step mechanism. 相似文献
7.
Radomir Jasiski 《Journal of heterocyclic chemistry》2015,52(1):185-192
The analysis of electrophilicity indexes and the results of potential energy surface (PES) simulations for the reaction pathways proved that the [2 + 3] cycloadditions of nitroallylic systems with nitrones should be considered nonpolar reactions. Our simulations proved that the reactions always proceed via a one‐step mechanism through a prereaction complex. Although the symmetry of respective transition states is quite varied, their polarity is low and does not change when a polar medium is introduced to the reaction environment. When the polarity of the reaction medium increases, the kinetic pathway preference does not change. The regiochemistry of the cycloadditions tested may, however, be controlled to some extent by steric effects. 相似文献
8.
9.
Space-time directional Lyapunov exponents are introduced. They describe the maximal velocity of propagation to the right or to the left of fronts of perturbations in a frame moving with a given velocity. The continuity of these exponents as function of the velocity and an inequality relating them to the directional entropy is proved. 相似文献
10.
Olaf Hansen 《Mathematical Methods in the Applied Sciences》2002,25(12):1075-1090
In this article we study the radiosity operator along an edge between two adjacent half‐planes. First we show that the radiosity operator is invertible in a whole scale of anisotropic Sobolev spaces. In the absence of any shadows we are able to derive regularity properties of the solution, which depend only on the angle between the half‐planes, the reflectivity coefficients and the right‐hand side. This work can be considered as a supplement to the article of Rathsfeld (Mathematical Methods in the Applied Sciences 1999; 22 : 217–241). Copyright © 2002 John Wiley & Sons, Ltd. 相似文献