全文获取类型
收费全文 | 75362篇 |
免费 | 6120篇 |
国内免费 | 5126篇 |
专业分类
化学 | 28142篇 |
晶体学 | 499篇 |
力学 | 10660篇 |
综合类 | 758篇 |
数学 | 22031篇 |
物理学 | 24518篇 |
出版年
2024年 | 127篇 |
2023年 | 741篇 |
2022年 | 1477篇 |
2021年 | 1547篇 |
2020年 | 1920篇 |
2019年 | 1743篇 |
2018年 | 1600篇 |
2017年 | 1863篇 |
2016年 | 2220篇 |
2015年 | 1890篇 |
2014年 | 2926篇 |
2013年 | 5048篇 |
2012年 | 3234篇 |
2011年 | 3594篇 |
2010年 | 2881篇 |
2009年 | 4300篇 |
2008年 | 4421篇 |
2007年 | 4957篇 |
2006年 | 4266篇 |
2005年 | 3503篇 |
2004年 | 3056篇 |
2003年 | 3317篇 |
2002年 | 3573篇 |
2001年 | 2814篇 |
2000年 | 2687篇 |
1999年 | 2379篇 |
1998年 | 2293篇 |
1997年 | 1520篇 |
1996年 | 1404篇 |
1995年 | 1207篇 |
1994年 | 1127篇 |
1993年 | 861篇 |
1992年 | 935篇 |
1991年 | 671篇 |
1990年 | 617篇 |
1989年 | 451篇 |
1988年 | 389篇 |
1987年 | 372篇 |
1986年 | 339篇 |
1985年 | 307篇 |
1984年 | 317篇 |
1983年 | 180篇 |
1982年 | 242篇 |
1981年 | 224篇 |
1980年 | 148篇 |
1979年 | 191篇 |
1978年 | 175篇 |
1977年 | 168篇 |
1976年 | 119篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Mingxin Wang 《Journal of Mathematical Analysis and Applications》2002,274(1):424-436
This paper deals with positive solutions of degenerate and quasilinear parabolic systems not in divergence form: ut=up(Δu+av), vt=vq(Δv+bu), with null Dirichlet boundary conditions and positive initial conditions, where p, q, a and b are all positive constants. The local existence and uniqueness of classical solution are proved. Moreover, it will be proved that all solutions exist globally if and only if ab?λ12, where λ1 is the first eigenvalue of −Δ in Ω with homogeneous Dirichlet boundary condition. 相似文献
113.
Patrick Dehornoy 《Algebra Universalis》2002,48(2):223-248
We solve the word problem of the identity x(yz) = (xy)(yz) by investigating a certain group describing the geometry of that identity. We also construct a concrete realization of the
one-generated free algebra relative to the above identity.
Received March 23, 2001; accepted in final form July 6, 2002. 相似文献
114.
115.
A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity. 相似文献
116.
A. Khrennikov 《Annalen der Physik》2003,12(10):575-585
We study the probabilistic consequences of the choice of the basic number field in the quantum formalism. We demonstrate that by choosing a number field for a linear space representation of quantum model it is possible to describe various interference phenomena. We analyse interference of probabilistic alternatives induced by real, complex, hyperbolic (Clifford) and p‐adic representations. 相似文献
117.
平行机半在线排序问题研究(Ⅰ) 总被引:15,自引:1,他引:14
对半在线平行机排序问题的研究进展作了详细综述和进一步探讨。文章给出半在线排序问题的背景、定义、分类和求解。介绍它们定义和在不同机器环境和目标函数下半在线排序问题分类,以及第一类半在线模型的近似算法的设计及其竞争比分析。 相似文献
118.
We establish the existence and stability of multidimensional transonic shocks for the Euler equations for steady potential compressible fluids. The Euler equations, consisting of the conservation law of mass and the Bernoulli law for the velocity, can be written as a second-order, nonlinear equation of mixed elliptic-hyperbolic type for the velocity potential. The transonic shock problem can be formulated into the following free boundary problem: The free boundary is the location of the transonic shock which divides the two regions of smooth flow, and the equation is hyperbolic in the upstream region where the smooth perturbed flow is supersonic. We develop a nonlinear approach to deal with such a free boundary problem in order to solve the transonic shock problem. Our results indicate that there exists a unique solution of the free boundary problem such that the equation is always elliptic in the downstream region and the free boundary is smooth, provided that the hyperbolic phase is close to a uniform flow. We prove that the free boundary is stable under the steady perturbation of the hyperbolic phase. We also establish the existence and stability of multidimensional transonic shocks near spherical or circular transonic shocks.
119.
The effect of the amount of desorbed water on the mechanical properties of composites based on low-density polyethylene and linen yarn production waste (LW) is analyzed by statistical methods. It is shown that the amount of absorbed water decreases during the desorption process at room temperature both for specimens modified and unmodified with diphenylmethane diisocyanate (DIC.) The most sensitive to the action of water is the elastic modulus, which decreases considerably under the effect of water and is fully restored in the desorption process. The tensile strain also increases with the amount of absorbed water. It is found that the elastic modulus of the unmodified composite correlates linearly with the amount of desorbed water. Between the amount of desorbed water and the tensile strain, as well the specific work of deformation, a negative linear correlation is revealed. After water desorption, all strength and deformation characteristics of both the modified and unmodified composites are fully recovered.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 515–524, July–August, 2005. 相似文献
120.
By further generalizing the skew-symmetric triangular splitting iteration method studied by Krukier, Chikina and Belokon (Applied Numerical Mathematics, 41 (2002), pp. 89–105), in this paper, we present a new iteration scheme, called the modified skew-Hermitian triangular splitting iteration method, for solving the strongly non-Hermitian systems of linear equations with positive definite coefficient matrices. We discuss the convergence property and the optimal parameters of this new method in depth. Moreover, when it is applied to precondition the Krylov subspace methods like GMRES, the preconditioning property of the modified skew-Hermitian triangular splitting iteration is analyzed in detail. Numerical results show that, as both solver and preconditioner, the modified skew-Hermitian triangular splitting iteration method is very effective for solving large sparse positive definite systems of linear equations of strong skew-Hermitian parts. 相似文献