全文获取类型
收费全文 | 6011篇 |
免费 | 204篇 |
国内免费 | 32篇 |
专业分类
化学 | 4145篇 |
晶体学 | 19篇 |
力学 | 209篇 |
数学 | 1029篇 |
物理学 | 845篇 |
出版年
2022年 | 33篇 |
2021年 | 59篇 |
2020年 | 65篇 |
2019年 | 80篇 |
2018年 | 85篇 |
2017年 | 79篇 |
2016年 | 152篇 |
2015年 | 141篇 |
2014年 | 169篇 |
2013年 | 257篇 |
2012年 | 326篇 |
2011年 | 367篇 |
2010年 | 233篇 |
2009年 | 231篇 |
2008年 | 330篇 |
2007年 | 324篇 |
2006年 | 332篇 |
2005年 | 302篇 |
2004年 | 262篇 |
2003年 | 241篇 |
2002年 | 285篇 |
2001年 | 106篇 |
2000年 | 102篇 |
1999年 | 56篇 |
1998年 | 58篇 |
1997年 | 65篇 |
1996年 | 76篇 |
1995年 | 53篇 |
1994年 | 64篇 |
1993年 | 52篇 |
1992年 | 49篇 |
1991年 | 57篇 |
1990年 | 48篇 |
1989年 | 44篇 |
1988年 | 39篇 |
1987年 | 44篇 |
1986年 | 39篇 |
1985年 | 84篇 |
1984年 | 83篇 |
1983年 | 51篇 |
1982年 | 86篇 |
1981年 | 56篇 |
1980年 | 77篇 |
1979年 | 56篇 |
1978年 | 74篇 |
1977年 | 56篇 |
1976年 | 56篇 |
1975年 | 42篇 |
1974年 | 44篇 |
1973年 | 33篇 |
排序方式: 共有6247条查询结果,搜索用时 0 毫秒
21.
22.
Tran Quang Minh Léon Christiaens Pierre Grandclaudon Alain Lablache-Combier 《Tetrahedron》1977,33(17):2225-2229
Photoirradiated in presence of acetophenone, benzo[b]selenophene and its 3-methyl derivative add to dimethyl acetylenedicarboxylate. In each ease, the primary reaction product is unstable and has not been isolated. Photoexeited in its triplet state (the energy of which is in the neighbourhood of 69 ) benzo[b]selenophene and its 2- and 3-methyl, 2,3 dimethyl, 3 acetoxy and 2-methyl-3-acetoxy derivatives add to 1,2 dichloroethylene leading to cyclobutanes. Neither cyclo-addition occurs in absence of photosensitiser. Single-crystal X-ray analysis gave the structures of the two adducts of 3-acetoxybenzo[b]selenophene with trans-1,2-dichloroethylene. In both compounds the chlorine atoms are trans. 相似文献
23.
24.
25.
To obtain the intrinsic acidity constant of a carboxylic ion-exchanger, we propose a method of graphical double extrapolation. The results for an ion-exchanger made of polyvinyl alcohol grafted with acrylic acid are close to those published for the corresponding linear polyacid. 相似文献
26.
Manijeh Mohraz Wang Jian-qi Edgar Heilbronner Pierre Vogel Olivier Pilet 《Helvetica chimica acta》1980,63(3):568-570
The photoelectron spectrum of the title compound is reported and assigned by correlation with the photoelectron spectra of related molecules. 相似文献
27.
Pierre Laszlo 《Angewandte Chemie (International ed. in English)》1978,17(4):254-266
With the availability of Fourier transform spectrometers, 23Na-NMR spectroscopy has become an important tool. It affords direct insight into solvation and ion pairing phenomena, both in organic and in bio-inorganic systems. Monitoring the chemical shifts and linewidths of 23Na signals gives access to binding constants, reorientational correlation times and the microdynamics of the sodium coordination shell. The binding of other cations can also be studied by 23Na-NMR spectroscopy, in competition experiments. 相似文献
28.
Claude Balny Jennifer Canva Pierre Douzou Jean Bourdon 《Photochemistry and photobiology》1969,10(6):375-382
Abstract— Chemiluminescence and photochemiluminescence of systems generating excited (singlet) molecular oxygen has been studied at low temperature in fluid media. A possible interpretation is proposed: that dimers of singlet oxygen are directly or indirectly responsible for the observed emission, the species [1 δg +1 σg+ ] predominating. Energy transfer to a fluorescent molecule is possible only when conditions of spectral overlap, required for transfer by inductive resonance, are fulfilled. Evidence is also presented for the formation of a transient complex between oxygen and a sensitiser or acceptor molecule [S…O2 ], which is the precursor of singlet oxygen in these systems. However, other possible mechanisms cannot be excluded. 相似文献
29.
Crystals of Li0.33 MoO3 (blue), Rb0.23MoO3 (blue) and Cs0.31MoO3 (red) were grown by electrolysis from MoO3M2MoO4 melts (M =alkali metal) with composition 70–77 mole% MoO3. Melts richer in M2MoO4 produced MoO2 only. Correlation is made between bronze formation and the coordination of Mo in the melt and in the equilibrium solid phase M2Mo4O13. Li0.33MoO3 and Cs0.31MoO3 are semiconductors with high-temperature-range activation energies 0.16 and 0.12 eV. Rb0.23MoO3 has an electrical behavior similar to that of blue KxMoO3 with a semiconductor-metal transition at (170 ± 5) K. ESR spectra observed in Li0.33MoO3 and Rb0.23MoO3 single crystals at 4.2 K show extensive delocalization of the 4d1 electron associated with Mo(V) centers. Attempts to grow molybdenum bronzes containing Ca or Y were unsuccessful. 相似文献
30.
André Begouen-Demeaux Gérard Villers Pierre Gibart 《Journal of solid state chemistry》1975,15(2):178-180
The system FeCrTe was investigated around the composition FeCr2Te4. FeCr2Te4 is a metastable compound. Single crystals with Fe0·93Cr1·76Te4 composition were grown by vapor transport or the Bridgman method. These crystals are metallic and anisotropic ferromagnets. 相似文献