全文获取类型
收费全文 | 109046篇 |
免费 | 7819篇 |
国内免费 | 9477篇 |
专业分类
化学 | 64325篇 |
晶体学 | 1826篇 |
力学 | 6351篇 |
综合类 | 705篇 |
数学 | 13637篇 |
物理学 | 39498篇 |
出版年
2023年 | 814篇 |
2022年 | 1608篇 |
2021年 | 2298篇 |
2020年 | 2675篇 |
2019年 | 2870篇 |
2018年 | 3187篇 |
2017年 | 3353篇 |
2016年 | 3808篇 |
2015年 | 2892篇 |
2014年 | 4139篇 |
2013年 | 5867篇 |
2012年 | 5948篇 |
2011年 | 6417篇 |
2010年 | 5366篇 |
2009年 | 5423篇 |
2008年 | 5709篇 |
2007年 | 5338篇 |
2006年 | 4953篇 |
2005年 | 4293篇 |
2004年 | 3771篇 |
2003年 | 3231篇 |
2002年 | 3324篇 |
2001年 | 3059篇 |
2000年 | 2624篇 |
1999年 | 1920篇 |
1998年 | 1715篇 |
1997年 | 1458篇 |
1996年 | 1394篇 |
1995年 | 1174篇 |
1994年 | 1270篇 |
1993年 | 1215篇 |
1992年 | 1144篇 |
1991年 | 1178篇 |
1990年 | 1188篇 |
1989年 | 1104篇 |
1988年 | 970篇 |
1987年 | 963篇 |
1986年 | 908篇 |
1985年 | 931篇 |
1984年 | 929篇 |
1983年 | 835篇 |
1982年 | 814篇 |
1979年 | 803篇 |
1978年 | 815篇 |
1977年 | 806篇 |
1976年 | 919篇 |
1975年 | 812篇 |
1974年 | 841篇 |
1973年 | 846篇 |
1972年 | 751篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Complexes of Co(II) and Zn(II) with three-membered structures containing 1,3-indanedione, 1,3,4-thiadiazole, and pyridine moieties were obtained. 相似文献
992.
We investigate the scattering problem for a relativistic electron with spin in a Coulomb field in the framework of pseudoclassical mechanics. We obtain an analytic expression for the scattering angle and limiting estimates for the scattering parameters for the spinless and nonrelativistic cases. For small angles, the pseudoclassical model under consideration leads to the well-known quantum-mechanical Mott formula. 相似文献
993.
Ginzburg B. M. Smirnov A. S. Filatov S. K. Shibaev L. A. Melenevskaya E. Yu. Novoselova A. V. Shepelevskii A. A. 《Russian Journal of Applied Chemistry》2003,76(3):457-459
The structure of aggregates of fullerene C6
0 introduced into films of radical polymethyl methacrylate in the stage of solution preparation was studied by wide-angle X-ray diffraction. 相似文献
994.
995.
Structural properties of the condensate in two-dimensional mesoscopic systems of strongly correlated excitons 总被引:1,自引:0,他引:1
A two-dimensional mesoscopic Bose system of dipoles in a 2D trap is considered using computer simulation by the quantum path-integral Monte Carlo method. The model describes a rarefied system of spatially indirect excitons in a confining potential. Bose condensation in the system and its superfluid and structural properties are studied over a wide range of interparticle spatial correlations, from an almost ideal Bose gas to the regime of a strongly correlated system. It is found that, at strong interparticle spatial correlations, particles in the condensate form a crystal-like structure. In this case, the spatial correlations of particles in the condensate are less pronounced than the correlations of noncondensed particles. The effect of recurrent crystallization is observed in the regime of strong interparticle correlations. 相似文献
996.
Methods for accelerometer unit calibration are usually based on sufficiently strict requirements on the knowledge of the gravity orientation with respect to the unit (of the order of fractions of an arc minute). But it is not always possible to know the orientation with such high accuracy. In the present paper, we consider an approach to accelerometer unit calibration for whose implementation it suffices to have rough angular information (of the order of tens of arc minutes). We use a guaranteeing approach to calculate optimal schemes calibration experiments and propose an iterative scheme of calibration. 相似文献
997.
A. I. Kolesnikov I. A. Kaplunov I. V. Talyzin S. A. Tret’yakov O. V. Gritsunova E. Yu. Vorontsova 《Crystallography Reports》2008,53(7):1144-1149
A computer simulation and measurements of the light transmittance of germanium and paratellurite crystals of different thickness
were used to show that, at scattering probabilities of photons comparable to their absorption probabilities, the standard
methods for calculating light extinction coefficients on the basis of the Bouguer law lead to rough errors in estimation of
the optical quality of a material. 相似文献
998.
Retractable structures which alter their geometries according to practical requirements are widely used in roof structures of stadiums for their versatility. A retractable structure based on threefold-symmetric Bricard linkages and rotating rings of tetrahedra is proposed and developed in this paper. By replacing each link of a threefold-symmetric Bricard linkage with a tetrahedron, a retractable structure is obtained which can repeatedly open and close by rotating the tetrahedra. The geometric relationship between the retractable structure and the threefold-symmetric Bricard linkage is derived and ranges of main geometric parameters are determined to ensure a continuous and smooth movement in the deployment of the structure. Then the relative displacement of the support and the open rate of the structure, two main parameters concerned in practical applications, are investigated. Preferred ranges of main geometric parameters are proposed and a physical model is manufactured to verify them. A discussion on some possible improvements and modifications of the structure is also presented. 相似文献
999.
Z. R. Khasanova M. Yu. Vozhdaeva N. N. Kabal’nova E. A. Kantor 《Russian Journal of Applied Chemistry》2007,80(7):1105-1110
Products of the reaction of 1,2,4-trimethylbenzene with chlorine dioxide in aqueous solution were studied. A scheme of 1,2,4-trimethylbenzene transformations was suggested. The influence exerted on the number of the reaction products by the ClO2 dosage and time of its contact with the substrate was examined. 相似文献
1000.