全文获取类型
收费全文 | 2164篇 |
免费 | 105篇 |
国内免费 | 16篇 |
专业分类
化学 | 1455篇 |
晶体学 | 6篇 |
力学 | 51篇 |
数学 | 352篇 |
物理学 | 421篇 |
出版年
2024年 | 4篇 |
2023年 | 26篇 |
2022年 | 16篇 |
2021年 | 71篇 |
2020年 | 71篇 |
2019年 | 116篇 |
2018年 | 77篇 |
2017年 | 74篇 |
2016年 | 94篇 |
2015年 | 81篇 |
2014年 | 104篇 |
2013年 | 126篇 |
2012年 | 166篇 |
2011年 | 186篇 |
2010年 | 110篇 |
2009年 | 84篇 |
2008年 | 158篇 |
2007年 | 131篇 |
2006年 | 136篇 |
2005年 | 120篇 |
2004年 | 97篇 |
2003年 | 51篇 |
2002年 | 51篇 |
2001年 | 15篇 |
2000年 | 21篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 22篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有2285条查询结果,搜索用时 31 毫秒
1.
2.
Dmitry I. Bugaenko Alexey A. Volkov Dr. Mikhail V. Livantsov Prof. Dr. Marina A. Yurovskaya Dr. Alexander V. Karchava 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(54):12502-12506
The visible-light-induced arylation of tertiary phosphines with aryl(mesityl)iodonium triflates to produce the quaternary phosphonium salts occurs under mild, metal, and catalyst-free conditions. Photo-excited EDA complexes between diaryliodonium salts and phosphines supposedly enable this transformation, which is difficult to achieve through the traditional ground-state reactions. Demonstrating high functional group tolerance, broad scope, and complete selectivity of the aryl group transfer, the method is particularly compatible with sterically congested phosphines, which are challenging under metal-based catalytic methods. 相似文献
3.
We consider the conformal flow model derived in Bizoń et al. (2017) as a normal form for the conformally invariant cubic wave equation on 𝕊3. We prove that the energy attains a global constrained maximum at a family of particular stationary solutions that we call the ground state family. Using this fact and spectral properties of the linearized flow (which are interesting in their own right due to a supersymmetric structure), we prove nonlinear orbital stability of the ground state family. The main difficulty in the proof is due to the degeneracy of the ground state family as a constrained maximizer of the energy. © 2019 Wiley Periodicals, Inc. 相似文献
4.
5.
6.
Normal halogen dependence of 13C NMR chemical shifts of halogenomethanes revisited at the four‐component relativistic level 下载免费PDF全文
Dmitry O. Samultsev Yury Yu. Rusakov Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2016,54(10):787-792
The ‘Normal Halogen Dependence’ of 13C NMR chemical shifts in the series of halogenomethanes is revisited at the four‐component relativistic level. Calculations of 13C NMR chemical shifts of 70 halogenomethanes have been carried out at the density functional theory (DFT) and MP2 levels with taking into account relativistic effects using the four‐component relativistic theory of Dirac‐Coulomb within the different computational methods (4RPA, 4OPW91) and hybrid computational schemes (MP2 + 4RPA, MP2 + 4OPW91). The most efficient computational protocols are derived for practical purposes. Relativistic shielding effect reaches as much as several hundreds of ppm for heavy halogenomethanes, and to account for this effect in comparison with experiment at the qualitative level, relativistic Dyall's basis sets of triple‐zeta quality or higher are to be used within the framework of the four‐component relativistic theory taking into account solvent effects. Relativistic geometrical optimization (as compared with the non‐relativistic level) is essential for the molecules containing at least two iodines at one carbon atom. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
Aishabibi Kassymbek Prof. Dmitry G. Gusev Dr. Anton Dmitrienko Prof. Melanie Pilkington Prof. Georgii I. Nikonov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(4):e202103455
Reaction of the Ga(I) compound NacNacGa ( 9 ) with the diazo compound N2CHSiMe3 affords the nitrilimine compound NacNacGa(N-NCSiMe3)(CH2SiMe3) ( 10 ). Carrying out this reaction in the presence of pyridine does not lead to C−H activation on the transient alkylidene NacNacGa=CHSiMe3 but generates a metallated diazo species NacNacGa(NHN=CHSiMe3)(CN2SiMe3) ( 13 ) that further rearranges into the isonitrile compound NacNacGa(NHN=CHSiMe3)(N(NC)SiMe3) ( 15 ). Reactions of 10 with the silane H3SiPh and the borane HBcat furnished products of 1,3 addition to the nitrilimine moiety NacNacGa{N(ERn)NCSiMe3}(CH2SiMe3), whereas reaction with the diborane B2cat2 gave the product of formal nitrene insertion into the B−B bond. DFT calculations suggest that the interaction of 9 with N2CHSiMe3 proceeds through intermediate formation of an alkylidene compound that undergoes CH activation with a second molecule of N2CHSiMe3. Insertion into the B−B bond likely proceeds through an initial 1,3-addition of the diborane, followed by boryl migration to the former nitrene center. 相似文献
8.
Bryzgunov M. I. Bubley A. V. Denisov A. P. Goncharov A. D. Parkhomchuk V. V. Panasyuk V. M. Reva V. B. Kremnev N. S. Putmakov A. A. Belikov O. V. Gorchakov K. M. Skorobogatov D. N. Chekavinskiy V. A. Bekhtenev E. A. Zharikov A. A. Karpov G. V. Kondaurov M. N. Gusev I. A. Senkov D. V. 《Physics of Particles and Nuclei Letters》2020,17(4):425-428
Physics of Particles and Nuclei Letters - In order to achieve the design luminosity in the NICA collider, it is planned to equip it with both stochastic and electron cooling. The electron-cooling... 相似文献
9.
10.
Anastasia O. Kolesnikova Dmitry A. Kornilov Aidar T. Gubaidullin Vladimir D. Kiselev 《国际化学动力学杂志》2020,52(5):301-309
The kinetic parameters and enthalpies of the Diels–Alder reactions between cyclopentadiene and 2,3-dicyano-1,4-benzoquinone leading to the formation of two different monoadducts and bisadduct were determined. The stability of adducts is compared. Monoadduct appears to be thermodynamically more stable than the bisadduct. Comparison with the other Diels–Alder reactions studied previously allows us to conclude that the heat effects upon formation of the considered Diels–Alder adducts are the lowest in comparison with all the studied dienophiles. 相似文献