全文获取类型
收费全文 | 205637篇 |
免费 | 23286篇 |
国内免费 | 15523篇 |
专业分类
化学 | 128640篇 |
晶体学 | 2541篇 |
力学 | 12781篇 |
综合类 | 992篇 |
数学 | 24943篇 |
物理学 | 74549篇 |
出版年
2023年 | 2648篇 |
2022年 | 3509篇 |
2021年 | 5394篇 |
2020年 | 6395篇 |
2019年 | 6452篇 |
2018年 | 6254篇 |
2017年 | 6044篇 |
2016年 | 8535篇 |
2015年 | 7148篇 |
2014年 | 9336篇 |
2013年 | 12759篇 |
2012年 | 14632篇 |
2011年 | 15497篇 |
2010年 | 11114篇 |
2009年 | 10757篇 |
2008年 | 11448篇 |
2007年 | 10503篇 |
2006年 | 9680篇 |
2005年 | 8384篇 |
2004年 | 6774篇 |
2003年 | 5707篇 |
2002年 | 5672篇 |
2001年 | 4843篇 |
2000年 | 4044篇 |
1999年 | 3879篇 |
1998年 | 3484篇 |
1997年 | 3184篇 |
1996年 | 3296篇 |
1995年 | 2701篇 |
1994年 | 2715篇 |
1993年 | 2330篇 |
1992年 | 2201篇 |
1991年 | 2140篇 |
1990年 | 1946篇 |
1989年 | 1633篇 |
1988年 | 1403篇 |
1987年 | 1325篇 |
1986年 | 1267篇 |
1985年 | 1255篇 |
1984年 | 1163篇 |
1983年 | 981篇 |
1982年 | 946篇 |
1981年 | 813篇 |
1979年 | 848篇 |
1978年 | 844篇 |
1977年 | 833篇 |
1976年 | 953篇 |
1975年 | 845篇 |
1974年 | 886篇 |
1973年 | 875篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
Xiaowei Sun Zijiang Liu Qifeng Chen Chengwei Wang 《Journal of Physics and Chemistry of Solids》2007,68(2):249-255
Molecular dynamics (MD) method is used to investigate the behavior of the pressure-volume-temperature (P-V-T) relationship, lattice constant and thermal expansivity for ZnO with rock-salt structure at high pressures and temperatures. The interionic potential is taken to be the sum of pair-wise additive Coulomb, van der Waals attraction, and repulsive interactions. The isothermal and isobaric properties are discussed from the corresponding P-V-T relationship, and it is shown that the MD simulation is successful in reproducing the measured volumes of ZnO over a wide range of temperature and pressure. Meanwhile, the equations of state parameters including lattice constant, linear thermal expansion coefficient, and isothermal bulk modulus are calculated and compared with the available experimental data and the latest theoretical results. At an extended pressure and temperature range, P-V-T relationship, lattice constant, and linear thermal expansion coefficient have been predicted. The structural and thermodynamic properties of ZnO with rock-salt structure are summarized in the pressure 0-100 GPa ranges and the temperature up to 3100 K. 相似文献
992.
L. G. Smirnova Yu. B. Grunin S. V. Krasil'nikova M. A. Zaverkina D. R. Bakieva E. V. Smirnov 《Colloid Journal》2003,65(6):778-781
The pulsed NMR, isopiestic and pycnometric methods are applied to investigate the physicochemical properties of softwood [GOST (State Standard) 9571-89] and hardwood [GOST 28172-89] celluloses, as well as flax cellulose [GOST 10330-76, 9394-76], both in the initial state and subjected to chemical treatment. Possible changes occurring in the supramolecular structure of a polymer are analyzed. The structural and sorption characteristics of the investigated samples are calculated. Their water absorption capacities are determined. 相似文献
993.
A novel heath monitoring system of the rocket based on fiber optic Bragg gratings is brought forward, its component units and working principle are also described. 相似文献
994.
995.
The paper considers the problem of constructing an efficient automatic procedure for reducing the block size in the block conjugate gradient method insuring that the resulting rate of convergence is comparable with that of the block conjugate gradient method with constant block size. The numerical results provided show that, independently of the type of distribution of the smallest eigenvalues of the preconditioned matrix, the procedure suggested always leads to a decrease of the arithmetic costs with respect to those of the block method with constant block size. Bibliography: 8 titles. 相似文献
996.
M. Yu. Kulikov 《Radiophysics and Quantum Electronics》2004,47(9):662-673
On the example of the effect of an atmospheric wave with given amplitude on the density oscillations of minor gas constituents near the mesopause (at heights 80–90 km, we consider the influence of the quasi-resonant periodic spatial transport on a distributed system responding subharmonically to a periodic external action (diurnal sunlight variations). Numerical modeling revealed the formation of a coherent horizontal distribution of the dynamical variables (i.e., the concentrations of small constituents). Application of this effect to the mesopause conditions is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 47, No. 9, pp. 739–752, September, 2004. 相似文献
997.
Single-crystalline layered lithium manganese oxide nanorods were prepared via a low-temperature molten salt synthesis method. The material was investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS). 相似文献
998.
A. Yu. Kolesov E. F. Mishchenko N. Kh. Rozov 《Proceedings of the Steklov Institute of Mathematics》2007,256(1):206-222
The well-known sine-Gordon equation, supplemented with small damping and small quasiperiodic external force, is studied under the zero Dirichlet boundary conditions at the endpoints of a finite interval. The main assumption is that all frequencies of the external force are in 1:1 resonance with certain eigenfrequencies of the unperturbed equation; i.e., the socalled fundamental multifrequency resonance is observed. It is shown that in this case, by an appropriate choice of the parameters of the external force, one can make it so that the boundary value problem has a stable invariant torus of any finite dimension that bifurcates from zero on any preassigned finite set of spatial modes. It is also shown (by numerical analysis) that in a number of cases the above-mentioned torus coexists with a chaotic attractor. 相似文献
999.
G. I. Petrashen V. V. Reshetnikov Yu. A. Surkov 《Journal of Mathematical Sciences》2007,142(6):2645-2654
A nonstationary problem concerning the propagation of low-frequency waves for a model that consists of a packet of elastic
layers lying on an elastic half-space is considered, and exact mathematical solutions in the form of repeated integrals are
constructed in three basic forms. It is proved that these solutions satisfy initial conditions. The representation of solutions
as a superposition of multiple waves is treated. Bibliography: 6 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 332, 2006, pp. 220–239. 相似文献
1000.
O. Yu. Ivanova 《Journal of Mathematical Sciences》2007,147(5):7088-7097
A complete two-dimensional local field K of mixed characteristic with finite second residue field is considered. The existence
of a completely ramified extension L of K such that L is a standard field is assumed. It is proved that the rank of the quotient
U(1)K
2
top
K/TK, where TK is the closure of the torsion subgroup, is equal to the degree of the constant subfield of K over ℚp. I. B. Zhukov constructed a set of generators of this quotient in the case where K is a standard field. In this paper, two
natural generalizations of this set are considered, and it is proved that one of them generates the entire group and the other
generates its subgroup of finite index. Bibliography: 5 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 343, 2007, pp. 206–221. 相似文献