全文获取类型
收费全文 | 12376篇 |
免费 | 1331篇 |
国内免费 | 476篇 |
专业分类
化学 | 5148篇 |
晶体学 | 32篇 |
力学 | 1125篇 |
综合类 | 31篇 |
数学 | 5578篇 |
物理学 | 2269篇 |
出版年
2023年 | 158篇 |
2022年 | 180篇 |
2021年 | 243篇 |
2020年 | 428篇 |
2019年 | 306篇 |
2018年 | 288篇 |
2017年 | 271篇 |
2016年 | 465篇 |
2015年 | 470篇 |
2014年 | 598篇 |
2013年 | 1038篇 |
2012年 | 659篇 |
2011年 | 702篇 |
2010年 | 501篇 |
2009年 | 818篇 |
2008年 | 765篇 |
2007年 | 783篇 |
2006年 | 671篇 |
2005年 | 499篇 |
2004年 | 477篇 |
2003年 | 457篇 |
2002年 | 385篇 |
2001年 | 380篇 |
2000年 | 352篇 |
1999年 | 296篇 |
1998年 | 302篇 |
1997年 | 237篇 |
1996年 | 230篇 |
1995年 | 163篇 |
1994年 | 124篇 |
1993年 | 118篇 |
1992年 | 82篇 |
1991年 | 76篇 |
1990年 | 64篇 |
1989年 | 54篇 |
1988年 | 52篇 |
1987年 | 41篇 |
1986年 | 52篇 |
1985年 | 33篇 |
1984年 | 48篇 |
1983年 | 16篇 |
1982年 | 27篇 |
1981年 | 30篇 |
1980年 | 20篇 |
1979年 | 25篇 |
1978年 | 41篇 |
1977年 | 41篇 |
1976年 | 40篇 |
1975年 | 16篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
In this paper, we formulate the l
p
-norm optimization problem as a conic optimization problem, derive its duality properties (weak duality, zero duality gap, and primal attainment) using standard conic duality and show how it can be solved in polynomial time applying the framework of interior-point algorithms based on self-concordant barriers. 相似文献
42.
In this paper, we use parametric quintic splines to derive some consistency relations which are then used to develop a numerical method for computing the solution of a system of fourth-order boundary-value problems associated with obstacle, unilateral, and contact problems. It is known that a class of variational inequalities related to contact problems in elastostatics can be characterized by a sequence of variational inequations, which are solved using some numerical method. Numerical evidence is presented to show the applicability and superiority of the new method over other collocation, finite difference, and spline methods. 相似文献
43.
David S. Dummit Brett A. Tangedal Paul B. van Wamelen. 《Mathematics of Computation》2004,73(247):1525-1546
Systematic computation of Stark units over nontotally real base fields is carried out for the first time. Since the information provided by Stark's conjecture is significantly less in this situation than the information provided over totally real base fields, new techniques are required. Precomputing Stark units in relative quadratic extensions (where the conjecture is already known to hold) and coupling this information with the Fincke-Pohst algorithm applied to certain quadratic forms leads to a significant reduction in search time for finding Stark units in larger extensions (where the conjecture is still unproven). Stark's conjecture is verified in each case for these Stark units in larger extensions and explicit generating polynomials for abelian extensions over complex cubic base fields, including Hilbert class fields, are obtained from the minimal polynomials of these new Stark units.
44.
Some previous works show that symmetric fixed- and variable-stepsize linear multistep methods for second-order systems which do not have any parasitic root in their first characteristic polynomial give rise to a slow error growth with time when integrating reversible systems. In this paper, we give a technique to construct variable-stepsize symmetric methods from their fixed-stepsize counterparts, in such a way that the former have the same order as the latter. The order and symmetry of the integrators obtained is proved independently of the order of the underlying fixed-stepsize integrators. As this technique looks for efficiency, we concentrate on explicit linear multistep methods, which just make one function evaluation per step, and we offer some numerical comparisons with other one-step adaptive methods which also show a good long-term behaviour.
45.
46.
Jean-Pierre Dedieu Gregorio Malajovich Mike Shub 《Foundations of Computational Mathematics》2005,5(2):145-171
We prove a linear bound on the average total curvature of the
central path of linear programming theory in terms of the number
of independent variables of the primal problem, and independent of
the number of constraints. 相似文献
47.
Numerical schemes for systems with multiple spatio-temporal scales are investigated. The multiscale schemes use asymptotic results for this type of systems which guarantee the existence of an effective dynamics for some suitably defined modes varying slowly on the largest scales. The multiscale schemes are analyzed in general, then illustrated on a specific example of a moderately large deterministic system displaying chaotic behavior due to Lorenz. Issues like consistency, accuracy, and efficiency are discussed in detail. The role of possible hidden slow variables as well as additional effects arising on the diffusive time-scale are also investigated. As a byproduct we obtain a rather complete characterization of the effective dynamics in Lorenz model. 相似文献
48.
S. Al-Homidan 《Journal of Optimization Theory and Applications》2007,135(3):583-598
Given a data matrix, we find its nearest symmetric positive-semidefinite Toeplitz matrix. In this paper, we formulate the
problem as an optimization problem with a quadratic objective function and semidefinite constraints. In particular, instead
of solving the so-called normal equations, our algorithm eliminates the linear feasibility equations from the start to maintain
exact primal and dual feasibility during the course of the algorithm. Subsequently, the search direction is found using an
inexact Gauss-Newton method rather than a Newton method on a symmetrized system and is computed using a diagonal preconditioned
conjugate-gradient-type method. Computational results illustrate the robustness of the algorithm. 相似文献
49.
Asymptotic methods for contact problems are expounded. Some typical integral equations are considered 相似文献
50.
A formulation of an implicit characteristic-flux-averaging method for the unsteady Euler equations with real gas effects is presented. Incorporation of a real gas into a general equation of state is achieved by considering the pressure as a function of density and specific internal energy. The Ricmann solver as well as the flux-split algorithm are modified by introducing the pressure derivatives with respect to density and internal energy. Expressions for calculating the values of the flow variables for a real gas at the cell faces are derived. The Jacobian matrices and the eigenvectors are defined for a general equation of state. The solution of the system of equations is obtained by using a mesh-sequencing method for acceleration of the convergence. Finally, a test case for a simple form of equation of state displays the differences from the corresponding solution for an ideal gas. 相似文献