全文获取类型
收费全文 | 1208篇 |
免费 | 41篇 |
国内免费 | 8篇 |
专业分类
化学 | 621篇 |
晶体学 | 8篇 |
力学 | 17篇 |
数学 | 156篇 |
物理学 | 455篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 17篇 |
2020年 | 27篇 |
2019年 | 28篇 |
2018年 | 28篇 |
2017年 | 28篇 |
2016年 | 42篇 |
2015年 | 26篇 |
2014年 | 44篇 |
2013年 | 59篇 |
2012年 | 69篇 |
2011年 | 103篇 |
2010年 | 65篇 |
2009年 | 45篇 |
2008年 | 73篇 |
2007年 | 75篇 |
2006年 | 91篇 |
2005年 | 68篇 |
2004年 | 72篇 |
2003年 | 62篇 |
2002年 | 32篇 |
2001年 | 21篇 |
2000年 | 8篇 |
1999年 | 16篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 2篇 |
1991年 | 11篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有1257条查询结果,搜索用时 156 毫秒
1.
Optics and Spectroscopy - Optical investigations of crystals of solid solutions NdxGd1 – xCr3(BO3)4, 0.01 ≤ x ≤ 1, have been performed. Absorption spectra in the... 相似文献
2.
Novikov V. S. Kuznetsov S. M. Kuzmin V. V. Prokhorov K. A. Sagitova E. A. Darvin M. E. Lademann J. Ustynyuk L. Yu. Nikolaeva G. Yu. 《Doklady Physics》2021,66(9):257-263
Doklady Physics - The dependence of Raman spectra of the molecules containing polyene chains on the conjugation length, structure of side and end groups, and isomer type is analyzed theoretically. 相似文献
3.
Butvina V. G. Kuzmin A. V. Spivak A. V. Safonov O. G. Lazarenko V. A. Dorovatovskii P. V. 《Crystallography Reports》2022,67(7):1114-1121
Crystallography Reports - The structure of a potassium compound with the chemical formula K0.90Ti5.16Cr2.94Fe2.54Mg0.87Al0.22Mn0.30O19 has been investigated by single-crystal X-ray diffraction... 相似文献
4.
Physics of Atomic Nuclei - A two-stage method is proposed for controlling the regulators in the fuel burnup process during a single operating period. At the first stage, the coefficient of the heat... 相似文献
5.
Alex van der Ham Thomas Hansen Dr. Gerrit Lodder Dr. Jeroen D. C. Codée Dr. Trevor A. Hamlin Dr. Dmitri V. Filippov 《Chemphyschem》2019,20(16):2103-2109
Lithium ion selective crown ethers have been the subject of much research for a multitude of applications. Current research is aimed at structurally rigidifying crown ethers, as restructuring of the crown ether ring upon ion binding is energetically unfavorable. In this work, the lithium ion binding ability of the relatively rigid 8-crown-4 was investigated both computationally by density functional theory calculations and experimentally by 1H and 7Li NMR spectroscopy. Although both computational and experimental results showed 8-crown-4 to bind lithium ion, this binding was found to be weak compared to larger crown ethers. The computational analysis revealed that the complexation is driven by enthalpy rather than entropy, illustrating that rigidity is only of nominal importance. To elucidate the origin of the favorable interaction of lithium ion with crown ethers, activation strain analyses and energy decomposition analyses were performed pointing to the favorable interaction being mainly electrostatic in nature. 8-crown-4 presents the smallest crown ether reported to date capable of binding lithium ion, possessing two distinct conformations from which it is able to do so. 相似文献
6.
It is known that under resonance conditions, a group of strongly interacting bosonic atoms, trapped in a double-well potential, mimics a single particle, performing Rabi oscillations between the wells. By implication, all atoms need to tunnel at roughly the same time, even though the Bose–Hubbard Hamiltonian accounts only for one-atom-at-a-time transfers. The mechanism of this collective behavior is analyzed, the Rabi frequencies in the process are evaluated, and the limitation of this simple picture is discussed. In particular, it is shown that the small rapid oscillations superimposed on the slow Rabi cycle result from splitting the transferred cluster at the sudden onset of tunnelling, and disappear if tunnelling is turned on gradually. 相似文献
7.
We establish an analogue of the Ikehara theorem for positive non-increasing functions convergent to zero. In particular, this provides a complete proof of the results formulated in Diekmann & Kaper (1978) [5] and Carr & Chmaj (2004) [1], which are widely used nowadays to prove the uniqueness of traveling waves for various reaction–diffusion equations. 相似文献
8.
Shinkar’ E. V. Smolyaninov I. V. Kuzmin V. V. Berberova N. T. 《Russian Journal of General Chemistry》2019,89(4):689-696
Russian Journal of General Chemistry - A novel and efficient method for the synthesis of biologically active organic di-, tri- and tetrasulfides has been proposed. Different methods of redox... 相似文献
9.
Dr. Stefan van der Vorm Thomas Hansen Dr. Erwin R. van Rijssel Rolf Dekkers Jerre M. Madern Prof. Dr. Herman S. Overkleeft Dr. Dmitri V. Filippov Prof. Dr. Gijsbert A. van der Marel Dr. Jeroen D. C. Codée 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(29):7149-7157
The 3D shape of glycosyl oxocarbenium ions determines their stability and reactivity and the stereochemical course of SN1 reactions taking place on these reactive intermediates is dictated by the conformation of these species. The nature and configuration of functional groups on the carbohydrate ring affect the stability of glycosyl oxocarbenium ions and control the overall shape of the cations. We herein map the stereoelectronic substituent effects of the C2-azide, C2-fluoride and C4-carboxylic acid ester on the stability and reactivity of the complete suite of diastereoisomeric furanoses by using a combined computational and experimental approach. Surprisingly, all furanosyl donors studied react in a highly stereoselective manner to provide the 1,2-cis products, except for the reactions in the xylose series. The 1,2-cis selectivity for the ribo-, arabino- and lyxo-configured furanosides can be traced back to the lowest-energy 3E or E3 conformers of the intermediate oxocarbenium ions. The lack of selectivity for the xylosyl donors is related to the occurrence of oxocarbenium ions adopting other conformations. 相似文献
10.
Dmitri V. Konarev Aleksey V. Kuzmin Salavat S. Khasanov Alexander F. Shestakov Akihiro Otsuka Hideki Yamochi Hiroshi Kitagawa Rimma N. Lyubovskaya 《化学:亚洲杂志》2020,15(17):2689-2695
Two salts of the aromatic hydrocarbon decacyclene, {cryptand[2.2.2](Cs+)} (decacyclene.?) ( 1 ) and {Bu3MeP+}(decacyclene.?) ( 2 ), were obtained. In both salts, decacyclene.? radical anions formed channels occupied by cations. However, corrugated hexagonal decacyclene.? layers could be outlined in the crystal structure of 1 with several side‐by‐side C???C approaches. The decacyclene.? radical anions showed strong distortion in both salts, deviating from the C3 symmetry owing to the repulsion of closely arranged hydrogen atoms and the Jahn‐Teller effect. Radical anions showed intense unusually low energy absorption in the IR‐range, with maxima at 4800 and 6000 cm?1. According to the carculations, these bands can originate from the SOMO‐LUMO+1 and SOMO‐LUMO+2 transitions, respectively. Radical anions exhibited a S=1/2 spin state, with an effective magnetic moment of 1.72 μB at 300 K. The decacyclene.? spin antiferromagnetically coupled with a Weiss temperature of ?11 K. Spin ordering was not observed down to 1.9 K owing to spin frustration in the hexagonal decacyclene.? layers. 相似文献