全文获取类型
收费全文 | 344378篇 |
免费 | 1809篇 |
国内免费 | 424篇 |
专业分类
化学 | 160781篇 |
晶体学 | 5284篇 |
力学 | 19189篇 |
综合类 | 3篇 |
数学 | 47787篇 |
物理学 | 113567篇 |
出版年
2021年 | 3471篇 |
2020年 | 3788篇 |
2019年 | 4621篇 |
2018年 | 6811篇 |
2017年 | 7026篇 |
2016年 | 8839篇 |
2015年 | 4063篇 |
2014年 | 7661篇 |
2013年 | 14071篇 |
2012年 | 11761篇 |
2011年 | 13630篇 |
2010年 | 11304篇 |
2009年 | 11477篇 |
2008年 | 13110篇 |
2007年 | 12808篇 |
2006年 | 11598篇 |
2005年 | 10006篇 |
2004年 | 9631篇 |
2003年 | 8984篇 |
2002年 | 9203篇 |
2001年 | 9039篇 |
2000年 | 7073篇 |
1999年 | 5295篇 |
1998年 | 5013篇 |
1997年 | 4799篇 |
1996年 | 4306篇 |
1995年 | 3824篇 |
1994年 | 3881篇 |
1993年 | 3885篇 |
1992年 | 3950篇 |
1991年 | 4394篇 |
1990年 | 4311篇 |
1989年 | 4353篇 |
1988年 | 4058篇 |
1987年 | 4072篇 |
1986年 | 3803篇 |
1985年 | 4435篇 |
1984年 | 4750篇 |
1983年 | 4051篇 |
1982年 | 4273篇 |
1981年 | 3902篇 |
1980年 | 3628篇 |
1979年 | 4128篇 |
1978年 | 4315篇 |
1977年 | 4501篇 |
1976年 | 4468篇 |
1975年 | 4211篇 |
1974年 | 4076篇 |
1973年 | 4237篇 |
1972年 | 3546篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
V. Ya. Popkova L. E. Vinogradova L. A. Leites V. K. Osmanov 《Russian Chemical Bulletin》1991,40(10):2075-2078
The reaction of ammonia with 2-chloroperfluoro-1-cyclohexene-1-thiocyanate leads to 2-amino-7-iminoperfluoro-4,5,6-trihydrobenzo-1,3-thiazole (II) due to intramolecular heterocyclization in the Thorpe reaction with the concurrent exoiminization. Analysis of the IR spectra of (II) in CCl4 and in the solid phase indicated that molecules of (II) in the crystal form hydrogen-bonded centrosymmetric dimers (D), which are in equilibrium with free molecules of (II) in solution.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2366–2370, October, 1991.The authors express their gratitude to D. I. Zagorevskii for taking the mass spectrum of (II) and to L. S. German for a useful discussion of this work. 相似文献
994.
995.
It is shown how, with the help of approximate integral manifolds, to solve the reduction problem in stability theory in the nonsingular critical case. A generalization of the first fundamental Lyapunov-Malkin theorem in critical cases is obtained.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 10, pp. 1324–1329, October, 1991. 相似文献
996.
J. Kircher M. Cardona M. Alouani S. Gopalan O. Jepsen O. K. Andersen
E. Kaldis
J. Karpinski S. Rusieki 《Physica C: Superconductivity and its Applications》1992,200(3-4):413-417We report results of ellipsometric measurements of the dielectric tensor of YBa2Cu4O8 as well as calculations employing density functional theory in the local density approximation (LDA). For the computation of the one-electron eigenvalues and states the linear-muffin-tin-orbital method (LMTO) was used. Measured and calculated results show good agreement. In particular, the calculation predicts different band structures for YBa2Cu3O7 and YBa2Cu4O8 in the vicinity of the Fermi energy which lead to significant differences in the optical spectra. One such difference is a region of small ε2 in the near infrared which is a fingerprint of the high (relative to the top of the highest fully occupied band) Fermi energy as compared to the situation in YBa2Cu3O7. Our experimental results confirm the theoretical findings. 相似文献
997.
998.
H. Glatzel R. Schneider T. Fauster V. Dose 《Zeitschrift für Physik B Condensed Matter》1992,88(1):53-61
Inverse photoemission spectra were taken for thin epitaxial iron films on Cu(100). For a film thickness of eight monolayers the observed electronic states are characteristic for a fcc(100) surface. Thed-bands of iron show a ferromagnetic exchange splitting of 1.1 eV, considerably smaller than the bulk value of 1.8 eV, which we observe for film thicknesses above 18 monolayers. 相似文献
999.
1000.
Auguet C. Martorell F. Moll F. Torra V: 《Journal of Thermal Analysis and Calorimetry》2002,70(1):277-290
The miniaturized calorimetric devices furnish a reduced working flat surface and permits measurements with extremely low-mass
quantities. The experimental sensitivity shows relevant position dependence with x-y surface coordinates and with z-distance. The device identification is realized via a 2-D model based in Fourier general equation.
Using the Marquardt method the experimental flat surface device can be identified and the fitted parameters used to simulate
the behavior of the experimental system. From the model, the effects of several dissipation configurations can be evaluated.
Also, via the RC-analogy, a way to 3-D experimental devices is roughly described.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献