全文获取类型
收费全文 | 780篇 |
免费 | 32篇 |
国内免费 | 1篇 |
专业分类
化学 | 701篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 43篇 |
物理学 | 65篇 |
出版年
2021年 | 10篇 |
2020年 | 14篇 |
2019年 | 13篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 21篇 |
2015年 | 20篇 |
2014年 | 18篇 |
2013年 | 36篇 |
2012年 | 32篇 |
2011年 | 48篇 |
2010年 | 16篇 |
2009年 | 28篇 |
2008年 | 46篇 |
2007年 | 35篇 |
2006年 | 38篇 |
2005年 | 28篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 16篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 20篇 |
1994年 | 15篇 |
1993年 | 13篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 7篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1978年 | 12篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1943年 | 3篇 |
1930年 | 4篇 |
排序方式: 共有813条查询结果,搜索用时 15 毫秒
51.
Hermann Staudinger V. Grignardt G. Dupont R. Loquin A. Guillaumin Ch. Courtot F. S. Kipping J. Doeuvre und P. Baud 《Fresenius' Journal of Analytical Chemistry》1939,117(1-2):72-73
Ohne Zusammenfassung 相似文献
52.
53.
Calculations on negatively charged planar Cu
n
O
m
clusters are reported. Starting from a self-consistent field calculation within a good Gaussian-type orbital basis set, correlations are included by using the Local Ansatz. A charge analysis reveals that the Cu 3d occupation is 9.5, in close agreement with Local Spin Density calculations. The electrons in the formal ((CuO2)2–)
n
entities are delocalized between Cu and O sites and strongly correlated. Our findings do not agree with the assumption of localized Cu2+ spins which lead to thet-J model. Spin correlations indicate strong short-range antiferromagnetic order even when additional electrons are removed. For them, there is no difference between O and Cu sites. 相似文献
54.
Wolfgang Petz Diego M. Andrada Markus Hermann Gernot Frenking Bernhard Neumüller 《无机化学与普通化学杂志》2017,643(16):1096-1099
The formation and X‐ray structure analysis of the PtIV complex [(CH2C{PPh2C6H4}2)PtI2] is reported. The molecule possesses the orthometalated ligand (PPh3)2C→CH2, which serves via its C2 fragment as an unprecedented four‐electron σ donor. 相似文献
55.
56.
Wolfgang Holzer Angelika Ebner Karin Schalle Gyselle Batezila Gernot A. Eller 《Journal of fluorine chemistry》2010,131(10):1013-1024
A straightforward, two-step synthesis of fluoro substituted chromeno[2,3-c]pyrazol- and [1]benzothieno[2′,3′:5,6]pyrano[2,3-c]pyrazol-4(1H)-ones, respectively, is presented. Hence, treatment of 1-substituted or 1,3-disubstituted 2-pyrazolin-5-ones with fluoro substituted 2-fluorobenzoyl chlorides or 3-chloro-6-fluoro-1-benzothiophene-2-carbonyl chloride using calcium hydroxide in refluxing 1,4-dioxane gave the corresponding 4-aroylpyrazol-5-ols, which were cyclized into the fused ring systems. 5-Fluorochromeno[2,3-c]pyrazol-4(1H)-one was obtained upon treatment of the 1-(4-methoxybenzyl) protected congener with trifluoroacetic acid. Treatment of 5-fluorochromeno[2,3-c]pyrazol-4(1H)-ones with methylhydrazine afforded novel tetracyclic ring systems such as 2-methyl-7-phenyl-2,7-dihydropyrazolo[4′,3′:5,6]pyrano[4,3,2-cd]indazole. Detailed NMR spectroscopic investigations (1H, 13C, 15N, 19F) with the obtained compounds were undertaken. 相似文献
57.
Wang Y Fernández I Duvall M Wu JI Li Q Frenking G Schleyer PR 《The Journal of organic chemistry》2010,75(23):8252-8257
Quantitative evaluations of the aromaticity (antiaromaticity) of neutral exocyclic substituted cyclopropenes (HC)(2)C=X (X = BH to InH (group 13), CH(2) to SnH(2) (group 14), NH to SbH (group 15), O to Te (group 16)) by their computed extra cyclic resonance energies (ECRE, via the block-localized wave function method) and by their aromatic stabilization energies (ASEs, via energy decomposition analyses) correlate satisfactorily (R(2) = 0.974). Electronegative X-based substituents increase the aromaticity of the cyclopropene rings, whereas electropositive substituents have the opposite effect. For example, (HC)(2)C=O is the most aromatic (ECRE = 10.3 kcal/mol), and (HC)(2)C=InH is the most antiaromatic (ECRE = -15.0 kcal/mol). The most refined dissected nucleus-independent chemical shift magnetic aromaticity index, NICS(0)(πzz), also agrees with both energetic indexes (R(2) = 0.968, for ECRE; R(2) = 0.974, for ASE), as do anisotropy of the induced current density plots. 相似文献
58.
Valerie Huemer Gernot A. Eller Wolfgang Holzer 《Magnetic resonance in chemistry : MRC》2010,48(6):476-482
Various [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐thiones were synthesized in high yields by treatment of the corresponding [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐ones with Lawesson's reagent. Detailed NMR spectroscopic studies were undertaken of the title compounds. Complete and unambiguous assignment of chemical shifts (1H, 13C, 15N) and coupling constants (1H,1H; 13C,1H) was achieved by the combined application of various one‐ and two‐dimensional (1D and 2D) NMR spectroscopic techniques. Unequivocal mapping of most 13C,1H spin coupling constants is accomplished by 2D (δ, J) long‐range INEPT spectra with selective excitation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
59.
60.