全文获取类型
收费全文 | 653918篇 |
免费 | 6196篇 |
国内免费 | 1757篇 |
专业分类
化学 | 332951篇 |
晶体学 | 9657篇 |
力学 | 32343篇 |
综合类 | 22篇 |
数学 | 85456篇 |
物理学 | 201442篇 |
出版年
2021年 | 5809篇 |
2020年 | 6360篇 |
2019年 | 7196篇 |
2018年 | 9594篇 |
2017年 | 9676篇 |
2016年 | 13551篇 |
2015年 | 7591篇 |
2014年 | 12444篇 |
2013年 | 29258篇 |
2012年 | 22666篇 |
2011年 | 27081篇 |
2010年 | 19854篇 |
2009年 | 19649篇 |
2008年 | 25385篇 |
2007年 | 25353篇 |
2006年 | 23221篇 |
2005年 | 20806篇 |
2004年 | 19443篇 |
2003年 | 17481篇 |
2002年 | 17221篇 |
2001年 | 18481篇 |
2000年 | 14389篇 |
1999年 | 11138篇 |
1998年 | 9515篇 |
1997年 | 9370篇 |
1996年 | 8770篇 |
1995年 | 7978篇 |
1994年 | 7854篇 |
1993年 | 7588篇 |
1992年 | 8151篇 |
1991年 | 8573篇 |
1990年 | 8224篇 |
1989年 | 8009篇 |
1988年 | 7912篇 |
1987年 | 7718篇 |
1986年 | 7338篇 |
1985年 | 9367篇 |
1984年 | 9963篇 |
1983年 | 8324篇 |
1982年 | 8714篇 |
1981年 | 8312篇 |
1980年 | 7876篇 |
1979年 | 8346篇 |
1978年 | 8700篇 |
1977年 | 8555篇 |
1976年 | 8582篇 |
1975年 | 8150篇 |
1974年 | 7981篇 |
1973年 | 8371篇 |
1972年 | 5961篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
991.
Paulo D. Cordaro 《Advances in Mathematics》2004,184(1):89-118
Taking as a start point the recent article of Meziani [7], we present several results concerning the normalization of a class of complex vector fields in the plane which degenerate along a real curve. We mainly deal with operators with finite regularity and analyze both the local situation as well as the case of normalization near a circle. Some related questions (e.g., on semi-global solvability and on the normalization of a class of generalized Mizohata operators) are also discussed. 相似文献
992.
Blokhina S. V. Bykova V. V. Sharapova A. V. Ol'khovich M. V. Trostin A. N. 《Russian Journal of General Chemistry》2003,73(2):257-259
The sorption properties of stationary phases based on nematic p-substituted azoxybenzenes were studied. Correlations were revealed between the structural selectivity of mesogens, chemical nature of terminal substituents, capability for dispersion interactions and polarity of the sorbents, temperature gradient of the retention indices, and thermodynamic parameters of solution of xylene isomers in the sorbents. 相似文献
993.
Amorphization of Al32Ge68 at normal pressure, starting from the thermobarically quenched high-pressure crystalline metallic γ-phase, was studied in a slow heating run by performing NMR field-sweep experiments. In the temperature interval from 77 to 300 K the 27Al central line exhibits a continuous broadening and a positive frequency shift. Close to 300 K rather abrupt changes were observed, where the shift changed its sign, and the line width jumped to its highest value. The discontinuous course of the phase changes indicates that the amorphization process proceeds via a sequence of intermediate metastable states, which can be ‘overheated’ in a slow heating run and consequently transform in an explosion-like manner to the final amorphous state at a well-defined temperature. The frequency shift could be decomposed into the negative second-order quadrupolar shift and the positive Knight shift. The change of the shift sign from positive to negative at 300 K reflects the vanishing tendency of the Knight shift upon heating and is compatible with the conduction-electron localization upon structure amorphization. 相似文献
994.
A group representation of radiation propagation in an anisotropic medium is developed. The system of wave equations for electromagnetic potentials, obtained from the Maxwell equations with account for the constitutive equations, has been factorized. It is shown that the linear differential operator of the factorized system is orthogonal in transparent crystals and unitary in gyrotropic ones and is represented through the momentum operator. On the basis of the commutation relations for the components of this operator, the eigenvalue problem has been solved and the expression for the change in the radiant energy in the crystal in the form of spherical waves has been obtained. The dependences of the ray and phase velocities and the polarization vectors of waves on the birefringence anisotropy and gyrotropy as well as on the angular momentum, displacement current, and bound charge determining them have been analyzed. It has been established that in the general case of gyrotropic crystals where the nonreciprocity phenomenon takes place and in magnetoelectrics Maxwell equations are represented in a form similar to the Dirac equations and the electromagnetic radiation is correctly described by means of bispinors and is quantized as fermions. 相似文献
995.
996.
A tomographic reconstruction method based on Monte Carlo random searching guided by the information contained in the projections
of radiographed objects is presented. In order to solve the optimization problem, a multiscale algorithm is proposed to reduce
computation. The reconstruction is performed in a coarse-to-fine multigrid scale that initializes each resolution level with
the reconstruction of the previous coarser level, which substantially improves the performance. The method was applied to
a real case reconstructing the internal structure of a small metallic object with internal components, showing excellent results. 相似文献
997.
Ya. I. Kurys’ N. S. Netyaga V. G. Koshechko V. D. Pokhodenko 《Theoretical and Experimental Chemistry》2007,43(5):334-342
A guest-host nanocomposite based on electroconducting polyaniline doped with 12-phosphotungstic acid and V2O5 as well as its bifunctional analog containing not more than 5 mass% nanosized platinum were obtained. A study was carried
out on the structure of these nanocomposites, their redox characteristics, and electrocatalytic activity in the reduction
of oxygen. These nanocomposites were found to display catalytic properties in the electrochemical reduction of oxygen, while
the presence of even a slight amount of nanosized platinum in the bifunctional composite leads to a significant increase in
its electrocatalytic activity.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 307–314, September–October, 2007. 相似文献
998.
The influence of the well width fluctuations on the dependence of the binding energy of excitonic complexes in quantum wells is studied by using the path-integral Monte-Carlo technique. The results are compared with available experimental data and a good agreement is found.Postdoctoral researcher of FWO-Vlaanderen 相似文献
999.
Th. Münzel A. Wynter Blyth Kützing Ch. Girard 《Analytical and bioanalytical chemistry》1882,21(1):436-438
1000.
A. Lehmann 《Analytical and bioanalytical chemistry》1882,21(1):414-415