全文获取类型
收费全文 | 1484篇 |
免费 | 86篇 |
国内免费 | 32篇 |
专业分类
化学 | 66篇 |
晶体学 | 1篇 |
力学 | 137篇 |
综合类 | 11篇 |
数学 | 1229篇 |
物理学 | 158篇 |
出版年
2023年 | 16篇 |
2022年 | 16篇 |
2021年 | 24篇 |
2020年 | 23篇 |
2019年 | 23篇 |
2018年 | 21篇 |
2017年 | 31篇 |
2016年 | 30篇 |
2015年 | 36篇 |
2014年 | 62篇 |
2013年 | 99篇 |
2012年 | 82篇 |
2011年 | 51篇 |
2010年 | 50篇 |
2009年 | 76篇 |
2008年 | 83篇 |
2007年 | 98篇 |
2006年 | 87篇 |
2005年 | 58篇 |
2004年 | 57篇 |
2003年 | 52篇 |
2002年 | 52篇 |
2001年 | 46篇 |
2000年 | 34篇 |
1999年 | 47篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 25篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1973年 | 1篇 |
排序方式: 共有1602条查询结果,搜索用时 31 毫秒
191.
192.
Ning Ju 《Journal of Differential Equations》2006,226(1):54-79
We study the two-dimensional quasi-geostrophic equations (2D QG) in Sobolev spaces. We first prove a new analytic condition for global regularity which is both sufficient and necessary. We then prove several new results on the geometric constraints on the 2D QG active scalar which suppress the development of singularity from the nonlinear stretching mechanism. We focus mainly on the case with critical dissipation. Our results are also relevant to the inviscid case. 相似文献
193.
Cristina Pignotti 《Journal of Mathematical Analysis and Applications》2005,305(1):197-218
In this paper we give semiconcavity results for the value function of some constrained optimal control problems with infinite horizon in a half-space. In particular, we assume that the control space is the l1-ball or the l∞-ball in Rn. 相似文献
194.
Brockwell A. Polak E. Evans R. Ralph D. 《Journal of Optimization Theory and Applications》2003,116(3):485-516
Moving-horizon control is a type of sampled-data feedback control in which the control over each sampling interval is determined by the solution of an open-loop optimal control problem. We develop a dual-sampling-rate moving-horizon control scheme for a class of linear, continuous-time plants with strict input saturation constraints in the presence of plant uncertainty and input disturbances. Our control scheme has two components: a slow-sampling moving-horizon controller for a nominal plant and a fast-sampling state-feedback controller whose function is to force the actual plant to emulate the nominal plant. The design of the moving-horizon controller takes into account the nonnegligible computation time required to compute the optimal control trajectory.We prove the local stability of the resulting feedback system and illustrate its performance with simulations. In these simulations, our dual-sampling-rate controller exhibits performance that is considerably superior to its single-sampling-rate moving-horizon controller counterpart. 相似文献
196.
Anton STEFANESCU 《数学学报(英文版)》2007,23(4):677-684
The paper produces new versions of the minimax theorem based on original conditions. Moreover, we investigate not only the sufficiency, but also the necessity of such conditions. The proofs are very simple and preclude any topological technique. 相似文献
197.
最后S.Liu[2]和笔[4]得到了两个Hermite矩阵的Khatri-Rao乘积的一些不等式。我们以两种方式来推广这些结果。首先,将结论推广到任意有限个Hermite矩阵的Khatri-Rao乘积;其次,给出了相应不等式的等式成立的充分必要条件。 相似文献
198.
Marcus Ritt Alysson M. Costa Sergio Mergen Viviane M. Orengo 《European Journal of Operational Research》2009
We introduce a problem called maximum common characters in blocks (MCCB), which arises in applications of approximate string comparison, particularly in the unification of possibly erroneous textual data coming from different sources. We show that this problem is NP-complete, but can nevertheless be solved satisfactorily using integer linear programming for instances of practical interest. Two integer linear formulations are proposed and compared in terms of their linear relaxations. We also compare the results of the approximate matching with other known measures such as the Levenshtein (edit) distance. 相似文献
199.
L. Ferreira-Mendonça V. L. R. Lopes J. M. Martínez 《Computational Optimization and Applications》2008,40(3):373-388
Optimality (or KKT) systems arise as primal-dual stationarity conditions for constrained optimization problems. Under suitable
constraint qualifications, local minimizers satisfy KKT equations but, unfortunately, many other stationary points (including,
perhaps, maximizers) may solve these nonlinear systems too. For this reason, nonlinear-programming solvers make strong use
of the minimization structure and the naive use of nonlinear-system solvers in optimization may lead to spurious solutions.
Nevertheless, in the basin of attraction of a minimizer, nonlinear-system solvers may be quite efficient. In this paper quasi-Newton
methods for solving nonlinear systems are used as accelerators of nonlinear-programming (augmented Lagrangian) algorithms,
with equality constraints. A periodically-restarted memoryless symmetric rank-one (SR1) correction method is introduced for
that purpose. Convergence results are given and numerical experiments that confirm that the acceleration is effective are
presented.
This work was supported by FAPESP, CNPq, PRONEX-Optimization (CNPq / FAPERJ), FAEPEX, UNICAMP. 相似文献
200.
Augmented Lagrangian methods for large-scale optimization usually require efficient algorithms for minimization with box constraints.
On the other hand, active-set box-constraint methods employ unconstrained optimization algorithms for minimization inside
the faces of the box. Several approaches may be employed for computing internal search directions in the large-scale case.
In this paper a minimal-memory quasi-Newton approach with secant preconditioners is proposed, taking into account the structure
of Augmented Lagrangians that come from the popular Powell–Hestenes–Rockafellar scheme. A combined algorithm, that uses the
quasi-Newton formula or a truncated-Newton procedure, depending on the presence of active constraints in the penalty-Lagrangian
function, is also suggested. Numerical experiments using the Cute collection are presented. 相似文献