全文获取类型
收费全文 | 14605篇 |
免费 | 1413篇 |
国内免费 | 1439篇 |
专业分类
化学 | 3552篇 |
晶体学 | 226篇 |
力学 | 1910篇 |
综合类 | 238篇 |
数学 | 9101篇 |
物理学 | 2430篇 |
出版年
2024年 | 34篇 |
2023年 | 145篇 |
2022年 | 170篇 |
2021年 | 241篇 |
2020年 | 367篇 |
2019年 | 333篇 |
2018年 | 315篇 |
2017年 | 380篇 |
2016年 | 418篇 |
2015年 | 313篇 |
2014年 | 592篇 |
2013年 | 1023篇 |
2012年 | 749篇 |
2011年 | 868篇 |
2010年 | 854篇 |
2009年 | 925篇 |
2008年 | 1004篇 |
2007年 | 1066篇 |
2006年 | 876篇 |
2005年 | 807篇 |
2004年 | 730篇 |
2003年 | 766篇 |
2002年 | 640篇 |
2001年 | 509篇 |
2000年 | 472篇 |
1999年 | 421篇 |
1998年 | 378篇 |
1997年 | 311篇 |
1996年 | 266篇 |
1995年 | 235篇 |
1994年 | 196篇 |
1993年 | 137篇 |
1992年 | 133篇 |
1991年 | 107篇 |
1990年 | 91篇 |
1989年 | 67篇 |
1988年 | 67篇 |
1987年 | 52篇 |
1986年 | 57篇 |
1985年 | 59篇 |
1984年 | 47篇 |
1983年 | 24篇 |
1982年 | 55篇 |
1981年 | 42篇 |
1980年 | 30篇 |
1979年 | 23篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
This paper presents a nonlinear dual transformation method and general complementary energy principle for solving large deformation theory of elastoplasticity governed by nonsmooth constitutive laws. It is shown that by using this method and principle, the nonconvex and nonsmooth total potential energy is dual to a smooth complementary energy functional, and fully nonlinear equilibrium equations in finite deformation problems can be converted into certain tensor equations. The algebraic relation between the first and the second Piola–Kirchhoff stresses are revealed. A closed form solution for general three-dimensional large deformation boundary value problems is obtained. The properties of this general solution are clarified by a triality extremum principle. This triality theory reveals an important phenomenon in nonconvex variational problems. Applications are illustrated by nonlinear, nonsmooth equilibrium problems in Hencky's plasticity, 3D cylindrical structures and post buckling analysis of elastoplastic bar with jumping and hardening effects. The idea and methods presented in this paper can be used and generalized to solve many nonlinear boundary value problems in finite deformation theory.Sommario. Il lavoro presenta un metodo di trasformazione duale nonlineare ed un principio generale di energia complementare per la soluzione di problemi di teoria elastoplastica in grandi deformazioni governati da leggi costitutive con discontinuità. Si mostra come, usando il metodo ed il principio proposti, l' energia potenziale totale discontinua e nonconvessa duale di un funzionale energia complementare continuo, e le equazioni di equilibrio nonlineare in problemi di deformazione finita, possano essere convertite in equazioni tensoriali. Vengono mostrate le relazioni algebriche fra il primo ed il secondo tensore delle tensioni di Piola–Kirchhoff. Si ottiene una soluzione in forma chiusa per problemi al contorno generali tridimensionali in grandi deformazioni. Le proprietà di tale soluzione generale vengono chiarite per mezzo di un principio estremale di trialità. La eoria della trialità evidenzia un fenomeno importante in problemi variazionali nonconvessi. Vengono presentate applicazioni a problemi di equilibrio nonlineare con discontinuità in situazioni di plasticità alla Hencky, strutture cilindriche in 3D, e nell'analisi postcritica di una barra elastoplastica con effetti hardening e di jumping. L'idea ed i metodi presentati in questo lavoro possono essere usati e generalizzati per risolvere molti problemi al contorno nonlineari nella teoria delle deformazioni finite. 相似文献
993.
考虑了有界区域上一类非线性退化波动方程的初边值问题.通过改进Vitillaro,Li和Tsai的方法,建立了非正的初始能量以及正的初始能量下解的爆破结果.同时,还给出了解的生命跨度估计. 相似文献
994.
Fuyi Li Yanbiao Zhang Yuhua Li 《Journal of Mathematical Analysis and Applications》2008,344(1):417-428
In this paper, we consider the fourth-order Neumann boundary value problem u(4)(t)−2u″(t)+u(t)=f(t,u(t)) for all t∈[0,1] and subject to u′(0)=u′(1)=u?(0)=u?(1)=0. Using the fixed point index and the critical group, we establish the existence theorem of solutions that guarantees the problem has at least one positive solution and two sign-changing solutions under certain conditions. 相似文献
995.
L. T. Ashchepkov 《Computational Mathematics and Mathematical Physics》2008,48(4):531-538
Criteria for symmetry and boundedness are found for the combined solution set of a system of linear algebraic equations with interval coefficients. It is shown that the problem of the best inner interval estimation of a symmetric solution set can be exactly solved by linear programming methods. 相似文献
996.
A simple and direct method is described to construct the soliton-like solution for the general KdV equation with external force. Crucial to the method is the assumption that the solution chosen is a special truncated expansion. 相似文献
997.
A test problem generator, by means of neural networks nonlinear function approximation capability, is given in this paper which provides test problems, with many predetermined local minima and a global minimum, to evaluate nonlinear programming algorithms that are designed to solve the problem globally. 相似文献
998.
In this paper, we study Levitin–Polyak type well-posedness for generalized quasivariational inequality problems with explicit constraints. Four types of Levitin–Polyak well-posedness will be introduced. Various criteria and characterizations will be derived for these types of Levitin–Polyak well-posedness. 相似文献
999.
一类二阶奇异微分方程正解的存在唯一性 总被引:2,自引:1,他引:1
利用上下解方法,不动点理论研究奇异微分方程u" f(t,u)=0,t∈(0,1)在边界条件au(0)-βu'(0)=0,γu(1) δu'(1)=0下C[0,1]正解和C1[0,1]正解的存在性与唯一性.其中非线性项f(t,u)关于u是减的,仅满足较弱的要求. 相似文献
1000.
In this note we provide a characterization of a subclass of bargaining problems for which the Nash solution has the property
of disagreement point monotonicity. While the original d-monotonicity axiom and its stronger notion, strong d-monotonicity, were introduced and discussed by Thomson (J Econ Theory, 42: 50–58, 1987), this paper introduces local strong
d-monotonicity and derives a necessary and sufficient condition for the Nash solution to be locally strongly d-monotonic. This characterization is given by using the sensitivity matrix of the Nash bargaining solution w.r.t. the disagreement
point d. Moverover, we present a sufficient condition for the Nash solution to be strong d-monotonic. 相似文献