全文获取类型
收费全文 | 474篇 |
免费 | 17篇 |
国内免费 | 7篇 |
专业分类
化学 | 12篇 |
力学 | 84篇 |
数学 | 269篇 |
物理学 | 133篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 17篇 |
2016年 | 21篇 |
2015年 | 9篇 |
2014年 | 24篇 |
2013年 | 25篇 |
2012年 | 36篇 |
2011年 | 29篇 |
2010年 | 29篇 |
2009年 | 32篇 |
2008年 | 39篇 |
2007年 | 32篇 |
2006年 | 17篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 12篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有498条查询结果,搜索用时 31 毫秒
21.
We establish the boundedness and continuity of parametric Marcinkiewicz integrals associated to homogeneous compound mappings on Triebel-Lizorkin spaces and Besov spaces. Here the integral kernels are provided with some rather weak size conditions on the unit sphere and in the radial direction. Some known results are naturally improved and extended to the rough case. 相似文献
22.
Joseph Akeyo Omolo 《Pramana》2008,71(6):1311-1320
The quantum dynamics of a two-mode non-resonant parametric down-conversion process is studied by recasting the time evolution
equations for the basic operators in an equivalent spin equation form with simpler exact solutions for a pump field with harmonic
time dependence. Expectation values of suitable operators for studying important features such as squeezing and quantum revivals
are presented in simple forms.
相似文献
23.
The dynamical behavior of the Φ6-Van der Pol system subjected to both external and parametric excitation is investigated. The effect of parametric excitation
amplitude on the routes to chaos is studied by numerical analysis. It is found that the probability of chaos happening increases
along with the parametric excitation amplitude increases while the external excitation amplitude fixed. Based on the invariance
principle of differential equations, the system is lead to desirable periodic orbit or chaotic state (synchronization) with
different control techniques. Numerical simulations are provided to validate the proposed method. 相似文献
24.
The paper considers the application of the method of direct separation of motions to the investigation of distributed systems.
An approach is proposed which allows one to apply the method directly to the initial equation of motion and to satisfy all
boundary conditions, arising for both slow and fast components of motion. The methodology is demonstrated by means of a classical
problem concerning the so-called Indian magic rope trick (Blekhman et al. in Selected topics in vibrational mechanics, vol.
11, pp. 139–149, [2004]; Champneys and Fraser in Proc. R. Soc. Lond. A 456:553–570, [2000]; in SIAM J. Appl. Math. 65(1):267–298, [2004]; Fraser and Champneys in Proc. R. Soc. Lond. A 458:1353–1373, [2002]; Galan et al. in J. Sound Vib. 280:359–377, [2005]), in which a wire with an unstable upper vertical position is stabilized due to vertical vibration of its bottom support
point. The wire is modeled as a heavy Bernoulli–Euler beam with a vertically vibrating lower end. As a result of the treatment,
an explicit formula is obtained for the vibrational correction to the critical flexural stiffness of the nonexcited system. 相似文献
25.
26.
27.
Infinite-dimensional parameter-dependent optimization problems of the form ‘minJ(u;p) subject to g(u)?0’ are studied, where u is sought in an L∞ function space, J is a quadratic objective functional, and g represents pointwise linear constraints. This setting covers in particular control constrained optimal control problems. Sensitivities with respect to the parameter p of both, optimal solutions of the original problem, and of its approximation by the classical primal-dual interior point approach are considered. The convergence of the latter to the former is shown as the homotopy parameter μ goes to zero, and error bounds in various Lq norms are derived. Several numerical examples illustrate the results. 相似文献
28.
This work assumes that the small area quantities of interest follow a Fay–Herriot model with spatially correlated random area
effects. Under this model, parametric and nonparametric bootstrap procedures are proposed for estimating the mean squared
error of the empirical best linear unbiased predictor (EBLUP). A simulation study based on the Italian Agriculture Census
2000 compares bootstrap and analytical estimates of the MSE and studies their robustness to non-normality. Results indicate
lower bias for the non-parametric bootstrap under specific departures from normality.
相似文献
29.
三I算法是一种新的模糊推理方法,是传统的模糊推理方法的修改和补充. 三I表达式取最小值时的最优解算法(即对偶三I算法)是三I算法思想的延伸和完善.本文针对蕴涵算子族Ip,讨论了FMP和FMT问题的对偶三I算法,给出了相应的计算公式,从而也进一步促进了对三I算法的研究. 相似文献
30.
Jesús A. De Loera Edward D. Kim Shmuel Onn Francisco Santos 《Journal of Combinatorial Theory, Series A》2009,116(8):1306-1325
This paper discusses properties of the graphs of 2-way and 3-way transportation polytopes, in particular, their possible numbers of vertices and their diameters. Our main results include a quadratic bound on the diameter of axial 3-way transportation polytopes and a catalogue of non-degenerate transportation polytopes of small sizes. The catalogue disproves five conjectures about these polyhedra stated in the monograph by Yemelichev et al. (1984). It also allowed us to discover some new results. For example, we prove that the number of vertices of an m×n transportation polytope is a multiple of the greatest common divisor of m and n. 相似文献