全文获取类型
收费全文 | 16216篇 |
免费 | 2079篇 |
国内免费 | 872篇 |
专业分类
化学 | 1232篇 |
晶体学 | 144篇 |
力学 | 2765篇 |
综合类 | 200篇 |
数学 | 10456篇 |
物理学 | 4370篇 |
出版年
2024年 | 28篇 |
2023年 | 139篇 |
2022年 | 217篇 |
2021年 | 227篇 |
2020年 | 363篇 |
2019年 | 338篇 |
2018年 | 312篇 |
2017年 | 442篇 |
2016年 | 466篇 |
2015年 | 350篇 |
2014年 | 604篇 |
2013年 | 1229篇 |
2012年 | 729篇 |
2011年 | 759篇 |
2010年 | 703篇 |
2009年 | 884篇 |
2008年 | 971篇 |
2007年 | 1081篇 |
2006年 | 927篇 |
2005年 | 922篇 |
2004年 | 758篇 |
2003年 | 812篇 |
2002年 | 714篇 |
2001年 | 627篇 |
2000年 | 598篇 |
1999年 | 529篇 |
1998年 | 482篇 |
1997年 | 430篇 |
1996年 | 301篇 |
1995年 | 252篇 |
1994年 | 220篇 |
1993年 | 226篇 |
1992年 | 176篇 |
1991年 | 135篇 |
1990年 | 126篇 |
1989年 | 81篇 |
1988年 | 96篇 |
1987年 | 92篇 |
1986年 | 88篇 |
1985年 | 98篇 |
1984年 | 92篇 |
1983年 | 48篇 |
1982年 | 65篇 |
1981年 | 75篇 |
1980年 | 64篇 |
1979年 | 65篇 |
1978年 | 68篇 |
1977年 | 55篇 |
1976年 | 53篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
For vector quasivariational inequalities involving multifunctions in topological vector spaces, an existence result is obtained without a monotonicity assumption and with a convergence assumption weaker than semicontinuity. A new type of quasivariational inequality is proposed. Applications to quasicomplementarity problems and traffic network equilibria are considered. In particular, definitions of weak and strong Wardrop equilibria are introduced for the case of multivalued cost functions. 相似文献
62.
Patrick Guidotti 《Mathematische Nachrichten》2004,272(1):32-45
We consider elliptic and parabolic problems in unbounded domains. We give general existence and regularity results in Besov spaces and semi‐explicit representation formulas via operator‐valued fundamental solutions which turn out to be a powerful tool to derive a series of qualitative results about the solutions. We give a sample of possible applications including asymptotic behavior in the large, singular perturbations, exact boundary conditions on artificial boundaries and validity of maximum principles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
63.
We present a new approach to the a posteriori error analysis of stable Galerkin approximations of reaction–convection–diffusion problems. It relies upon a non-standard variational formulation of the exact problem, based on the anisotropic wavelet decomposition of the equation residual into convection-dominated scales and diffusion-dominated scales. The associated norm, which is stronger than the standard energy norm, provides a robust (i.e., uniform in the convection limit) control over the streamline derivative of the solution. We propose an upper estimator and a lower estimator of the error, in this norm, between the exact solution and any finite dimensional approximation of it. We investigate the behaviour of such estimators, both theoretically and through numerical experiments. As an output of our analysis, we find that the lower estimator is quantitatively accurate and robust. 相似文献
64.
Sufficient conditions are established for the asymptotic behavior of solutionsof nonlinear delay differential equations x′(t)+sum from i=1 to m(pi(t)x(t-т_i))=F(t,x_t),t≥0where 0<т_1<т_2<…<т_m≤r,pi∈C([0,∞)),i=1,2,…,m,F∈C([0,∞)×C_0,R).C_0=C([-r,0],R)equipped with the sup norm ||·|| forsome r>0. A new result is established, some known results are improved. 相似文献
65.
Zhu Yongliang; Pagilla Prabhakar R. 《IMA Journal of Mathematical Control and Information》2005,22(2):181-186
We derive some useful and easily computable necessary conditionsfor the existence of a positive semi-definite solution to thealgebraic Ricatti equation (ARE). A motivating example is givento highlight the usefulness of the conditions for controllerand observer designs for nonlinear systems. Further, an upperbound on the trace of the solution to the ARE is also derived. 相似文献
66.
We consider a splitting finite-difference scheme for an initial-boundary value problem for a two-dimensional nonlinear evolutionary
equation. The problem is split into nonlinear and linear parts. The linear part is also split into locally one-dimensional
equations. We prove the convergence and stability of the scheme in L
2 and C norms.
Printed in Lietuvos Matematikos Rinkinys, Vol. 45, No. 3, pp. 413–434, July–September, 2005. 相似文献
67.
An all-optical fiber nonlinear Fabry-Perot resonator is proposed. The steady-state model for describing this resonator is developed. The transmission and refection bistabilities are shown numerically. Our results show that the bistability in this system is similar to that in a normal nonlinear Fabry-Perot etalon, except that the characteristics of the bistability can be changed not only by the cavity length but also by the phase shifts of the fiber loop mirrors. 相似文献
68.
Matrix extensions and eigenvalue completions, the generic case 总被引:2,自引:0,他引:2
William Helton Joachim Rosenthal Xiaochang Wang 《Transactions of the American Mathematical Society》1997,349(8):3401-3408
In this paper we provide new necessary and sufficient conditions for the so-called eigenvalue completion problem.
69.
报道了KDP晶体中的三倍频产生的实验研究,计算了比较了直接三倍频过程和级联过程对KDP晶体三阶有效非线性系数的贡献,并探讨了KDP作为非线性晶体材料三阶非线性系数测量基准的可行性。 相似文献
70.
Song Jiang 《Mathematische Nachrichten》1998,190(1):169-183
We consider initial boundary value problems for the equations of the one-dimensional motion of a viscous, heat-conducting gas with density-dependent viscosity that decreases (to zero) with decreasing density. We prove that if the viscosity does not decrease to zero too rapidly, then smooth solutions exist globally in time. 相似文献