全文获取类型
收费全文 | 7717篇 |
免费 | 140篇 |
国内免费 | 3篇 |
专业分类
化学 | 4432篇 |
晶体学 | 164篇 |
力学 | 152篇 |
数学 | 1130篇 |
物理学 | 1982篇 |
出版年
2022年 | 192篇 |
2021年 | 179篇 |
2020年 | 106篇 |
2019年 | 138篇 |
2018年 | 139篇 |
2017年 | 141篇 |
2016年 | 241篇 |
2015年 | 192篇 |
2014年 | 261篇 |
2013年 | 621篇 |
2012年 | 370篇 |
2011年 | 428篇 |
2010年 | 334篇 |
2009年 | 304篇 |
2008年 | 350篇 |
2007年 | 340篇 |
2006年 | 298篇 |
2005年 | 241篇 |
2004年 | 228篇 |
2003年 | 227篇 |
2002年 | 171篇 |
2001年 | 143篇 |
2000年 | 131篇 |
1999年 | 94篇 |
1998年 | 101篇 |
1997年 | 72篇 |
1996年 | 75篇 |
1995年 | 99篇 |
1994年 | 58篇 |
1993年 | 43篇 |
1992年 | 72篇 |
1991年 | 48篇 |
1990年 | 69篇 |
1989年 | 58篇 |
1988年 | 74篇 |
1987年 | 55篇 |
1986年 | 65篇 |
1985年 | 97篇 |
1984年 | 109篇 |
1983年 | 67篇 |
1982年 | 64篇 |
1981年 | 68篇 |
1980年 | 83篇 |
1979年 | 57篇 |
1978年 | 63篇 |
1977年 | 67篇 |
1976年 | 66篇 |
1975年 | 51篇 |
1974年 | 47篇 |
1973年 | 44篇 |
排序方式: 共有7860条查询结果,搜索用时 0 毫秒
991.
T. Radoń 《Surface science》1980,100(2):353-367
Photo field emission currents from clean (013) and clean and barium covered (111) regions of a tungsten tip have been measured in a field emission microscope using two wavelengths of laser radiation and phase-sensitive detection. The photo field emission current-voltage characteristics show various slopes and shoulders. These shoulders are considered as correlated with optical transitions between energy bands of tungsten. The final and initial energies are evaluated from the excitation energy and the known lowering of the barrier maximum. The obtained results are in fairly good agreement with the band structure of tungsten calculated by Christensen and Feuerbacher [1]. Except direct transitions which are prevailing also some indirect transitions were found. The slopes of the photocurrent characteristics are discussed. 相似文献
992.
Ohne Zusammenfassung 相似文献
993.
O-Protonation of secondary enamino ketones in TFA or concentrated mineral acids in various solvents is the kinetically favoured course of reaction leading ultimately to stable 2,5- or 3,4-disubstituted pyridinium salts. The mechanism of formation of the salts involves electrophilic attack by the C-3 carbon atom on C-2 or N-nucleophilic centres of the O-protonated molecule. 相似文献
994.
The properties of central charges in the framework of the massive supersymmetric quantum field theory related to internal symmetries, Lorentz covariance and locality of the fields are investigated. It is shown that in the presence of z central charges the largest semisimple part of the internal symmetry algebra is a direct sum of z compact symplectic group algebras and possibly an additional term representing the unimodular unitary group algebra. Next it is shown that 4j ? N + K, where j is the highest spin value of the underlying fields, N is the number of spinorial charges and K the number of these spinorial charges which are not linked to other spinorial charges by a central charge. It is further demonstrated that, in general, the central charge can not be redefined in such a way that it is at the same time real and preserves the locality principle. The discussion of the obtained results concludes the paper. 相似文献
995.
The surface composition of the AuPd alloy system has been determined by Auger electron spectroscopy. Measurements were performed on polished polycrystalline alloy foils. After cleaning, the intensities of the 71 eV and 2024 eV gold Auger transitions, and the intensity of the 330 eV palladium transition were measured, and then converted to atom concentrations in the surface layer. The surfaces of the annealed samples were found to be significantly enriched in gold with respect to the bulk. This result disagrees with the regular solution theory prediction. After extensive sputtering of the AuPd alloys with 1.5 keV Ar+ ions, a slight surface enrichment with palladium was found, as predicted by the simple theoretical model for sputtering. 相似文献
996.
The authors extended the integral equation for a one-component adsorption isotherm on to n-component adsorption from gaseous mixtures. It appears that the n-component adsorption isotherm on heterogeneous surfaces can be presented as a multiple integral. Two methods were used for evaluation of the surface heterogeneity with regard to a gas mixture. The first method is based on the n-dimensional gaussian energy distribution. The second one concerns the extension of our method for studying adsorption systems of high surface heterogeneity. Two-component adsorption systems have been analyzed in details. 相似文献
997.
M. Chvojka V. Hermoch B. Králiková J. Krása L. Láska K. Mašek J. Musil S. Polák K. Rohlena J. Schmiedberger J. Skála J. Sulek 《Czechoslovak Journal of Physics》1988,38(12):1337-1356
The photodissociation iodine laser system PERUN I is described. The laser generates and amplifies the subnanosecond pulse with the energy about 80 J of the fundamental wavelength 1·315 μm and beam diameter 10 cm. The physical principles of this type of the high power laser are briefly explained and the laser system and its characteristics are described from the physical and technical point of view. Special attention is paid to the realization of such system with the slow optical pumping (≈300 μs). 相似文献
998.
Pawel Kruszyński 《Reports on Mathematical Physics》1975,7(3):395-401
The problem of linearity of probability measures on hyperfinite factors is studied in Part I. Part II contains the extension of Vital-Hahn-Saks, Egoroff and Lusic theorems for probability measures on von Neumann algebras. These problems have immediate connections with properties of physical states on observable algebras in the sense of Mackey. 相似文献
999.
P. Mikusiński 《Acta Mathematica Hungarica》1988,51(3-4):271-281
1000.