全文获取类型
收费全文 | 700619篇 |
免费 | 5384篇 |
国内免费 | 2004篇 |
专业分类
化学 | 340378篇 |
晶体学 | 9892篇 |
力学 | 38259篇 |
综合类 | 27篇 |
数学 | 112897篇 |
物理学 | 206554篇 |
出版年
2021年 | 5837篇 |
2020年 | 6292篇 |
2019年 | 7184篇 |
2018年 | 19338篇 |
2017年 | 19187篇 |
2016年 | 19159篇 |
2015年 | 8036篇 |
2014年 | 12585篇 |
2013年 | 28177篇 |
2012年 | 25016篇 |
2011年 | 35227篇 |
2010年 | 24521篇 |
2009年 | 24902篇 |
2008年 | 30279篇 |
2007年 | 31968篇 |
2006年 | 22064篇 |
2005年 | 20693篇 |
2004年 | 19676篇 |
2003年 | 18318篇 |
2002年 | 17255篇 |
2001年 | 17705篇 |
2000年 | 13714篇 |
1999年 | 10559篇 |
1998年 | 9128篇 |
1997年 | 9010篇 |
1996年 | 8512篇 |
1995年 | 7579篇 |
1994年 | 7624篇 |
1993年 | 7363篇 |
1992年 | 7880篇 |
1991年 | 8281篇 |
1990年 | 7991篇 |
1989年 | 7913篇 |
1988年 | 7709篇 |
1987年 | 7441篇 |
1986年 | 7166篇 |
1985年 | 9153篇 |
1984年 | 9570篇 |
1983年 | 7995篇 |
1982年 | 8231篇 |
1981年 | 7791篇 |
1980年 | 7370篇 |
1979年 | 8002篇 |
1978年 | 8221篇 |
1977年 | 8185篇 |
1976年 | 8160篇 |
1975年 | 7795篇 |
1974年 | 7584篇 |
1973年 | 7957篇 |
1972年 | 5853篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
L. E. Payne G. A. Philippin V. Proytcheva 《Mathematical Methods in the Applied Sciences》2007,30(15):1885-1898
In this paper, we investigate the continuous dependence on the geometry and the initial time for solutions u( x , t) of a class of nonlinear parabolic initial‐boundary value problems. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
942.
A nonlocal difference scheme for the heat conduction equation with a real parameter γ > 1 or γ < 0 in the boundary condition is considered. Thus, the analysis of this problem is generalized to all real values of the parameter in the boundary condition. The spectrum of the spatial operator of the scheme is studied. The results obtained are used to formulate a stability criterion for the difference scheme. The case γ = ?1 proves to be special, because the system of eigenfunctions of the operator does not form a basis in the space of grid functions. 相似文献
943.
D.L. Skuratov Yu.L. Ratis I.A. Selezneva J. Pérez P. Fernández de Córdoba J.F. Urchueguía 《Applied Mathematical Modelling》2007
This paper deals with modelling the workpiece temperature field produced during the grinding process. The proposed model is given in terms of a two-dimensional boundary-value problem where the interdependence among the grinding wheel, the workpiece and the coolant is described by two variable functions in the boundary condition. An explicit integral form solution is constructed using the Laplace and Fourier transforms and the Green’s function method. 相似文献
944.
Wilson A. Cañas-Marín Julián D. Ortiz-Arango Uriel E. Guerrero-Aconcha Claudia P. Soto-Tavera 《Fluid Phase Equilibria》2007
The ability of Soave–Redlich–Kwong cubic equation of state (SRK EoS) to predict densities and thermodynamic derivative properties such as thermal expansivity, isothermal compressibility, calorific capacity, and Joule–Thompson coefficients, for two gas condensates over a wide range of pressures (up to 110 MPa) was studied. The predictions of the EoS were compared to Monte Carlo simulation data obtained by Lagache et al. [M.H. Lagache, P. Ungerer, A. Boutin, Fluid Phase Equilibr. 220 (2004) 221]. Two completely different alpha functions for the SRK EoS attractive term were used and their respective effects on the predictions of such properties were analyzed. Also, two different forms of the crossed terms of the attractive parameter, aij, and three expressions of the crossed terms of the repulsive parameter, bij, were combined in different ways, and predictions were carried out. Little sensitivity of the properties on the chosen alpha function, except for the calorific capacities, was found in the systems studied. The most commonly used combination rules to model phase behavior of reservoir fluids, i.e. geometric and arithmetic forms of aij and bij, respectively, predicted very deficient results for these fluids at extreme conditions, specially for density calculations. 相似文献
945.
946.
The treatment of tertiary esters with triphenylphosphine and iodine under mild conditions gives the most stable alkene in good yield. Formates, acetates and trifluoroacetates were studied. 相似文献
947.
Khaled A. Aamer Gregory N. Tew 《Journal of polymer science. Part A, Polymer chemistry》2007,45(6):1109-1121
Supramolecular block‐random copolymers containing [Ir(terpy)2]3+ in the side chain were synthesized via postfunctionalization of a P(S‐b‐ACterpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐ACterpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007 相似文献
948.
Roderich Tumulka 《Foundations of Physics》2007,37(2):186-197
In a recent paper Conway and Kochen, Found. Phys. 36, 2006, claim to have established that theories of the Ghirardi-Rimini-Weber
(RW) type, i.e., of spontaneous wave function collapse, cannot be made relativistic. On the other hand, relativistic GRW-type
theories have already been presented, in my recent paper, J. Stat. Phys. 125, 2006, and by Dowker and Henson, J. Stat. Phys.
115, 2004. Here, I elucidate why these are not excluded by the arguments of Conway and Kochen.
相似文献
949.
Formulas that include the contribution from dipole-distributed anomalous masses represented as layers distributed in height relative to the reference ellipsoid to the gravitational field in the quadratic approximation have been derived. The relationships between the expansion coefficients of some function and its square in terms of spherical functions have been established. The contribution from the relief masses and the density jump at the Mohorovicic discontinuity is used to illustrate the results. 相似文献
950.
In this paper we describe the design and manufacture of an axial-torsion test specimen, and provide relationships needed when
conducting stress-strain characterization experiments with the specimen. The specimen is a short hollow cylinder of rubber
bonded between two steel mounting rings, in which simultaneous axial and shear strains are produced via independently controlled
axial and twist displacements. We present calculations for the strain-displacement and stress-load relationships, and strain
energy density. These relationships have been established and validated via a combination of analytical and experimental techniques,
and finite element analysis. We have investigated the extent and effects of strain and stress field non-uniformity in the
test specimen. The specimen design is sufficiently simple that a closed-form expression for the strain-displacement relationship
has been successfully developed. 相似文献