全文获取类型
收费全文 | 4702篇 |
免费 | 407篇 |
国内免费 | 477篇 |
专业分类
化学 | 17篇 |
力学 | 164篇 |
综合类 | 125篇 |
数学 | 4978篇 |
物理学 | 302篇 |
出版年
2024年 | 7篇 |
2023年 | 50篇 |
2022年 | 62篇 |
2021年 | 92篇 |
2020年 | 118篇 |
2019年 | 122篇 |
2018年 | 121篇 |
2017年 | 145篇 |
2016年 | 154篇 |
2015年 | 96篇 |
2014年 | 242篇 |
2013年 | 377篇 |
2012年 | 230篇 |
2011年 | 312篇 |
2010年 | 276篇 |
2009年 | 349篇 |
2008年 | 381篇 |
2007年 | 319篇 |
2006年 | 302篇 |
2005年 | 261篇 |
2004年 | 188篇 |
2003年 | 181篇 |
2002年 | 198篇 |
2001年 | 136篇 |
2000年 | 146篇 |
1999年 | 138篇 |
1998年 | 119篇 |
1997年 | 93篇 |
1996年 | 68篇 |
1995年 | 50篇 |
1994年 | 36篇 |
1993年 | 33篇 |
1992年 | 25篇 |
1991年 | 22篇 |
1990年 | 17篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 7篇 |
1936年 | 5篇 |
排序方式: 共有5586条查询结果,搜索用时 31 毫秒
991.
孙文兵 《浙江大学学报(理学版)》2017,44(5):531-537
建立了一个关于Riemann-Liouville分数次积分的恒等式,利用此恒等式,得到了一些函数为可微且s-凸映射的关于分数次积分的新Hermite-Hadamard型积分不等式,并且对于可微的s-凹函数也得到一些新的结果.文中的新结果推广了部分已有研究的结论.最后给出了一个应用实例. 相似文献
992.
Free-matrix-based time-dependent discontinuous Lyapunov functional for synchronization of delayed neural networks with sampled-data control 下载免费PDF全文
This paper is concerned with the synchronization of delayed neural networks via sampled-data control. A new technique, namely, the free-matrix-based time-dependent discontinuous Lyapunov functional approach, is adopted in constructing the Lyapunov functional, which takes advantage of the sampling characteristic of sawtooth input delay. Based on this discontinuous Lyapunov functional, some less conservative synchronization criteria are established to ensure that the slave system is synchronous with the master system. The desired sampled-data controller can be obtained through the use of the linear matrix inequality(LMI) technique. Finally, two numerical examples are provided to demonstrate the effectiveness and the improvements of the proposed methods. 相似文献
993.
Cell function is based on many dynamically complex networks of interacting biochemical reactions. Enzymes may increase the rate of only those reactions that are thermodynamically consistent. In this paper we specifically treat the contraction of smooth muscle cells from the continuum thermodynamics point of view by considering them as an open system where matter passes through the cell membrane. We systematically set up a well-known four-state kinetic model for the cross-bridge interaction of actin and myosin in smooth muscle, where the transition between each state is driven by forward and reverse reactions. Chemical, mechanical and energy balance laws are provided in local forms, while energy balance is also formulated in the more convenient temperature form. We derive the local (non-negative) production of entropy from which we deduce the reduced entropy inequality and the constitutive equations for the first Piola–Kirchhoff stress tensor, the heat flux, the ion and molecular flux and the entropy. One example for smooth muscle contraction is analyzed in more detail in order to provide orientation within the established general thermodynamic framework. In particular the stress evolution, heat generation, muscle shorting rate and a condition for muscle cooling are derived. 相似文献
994.
Two-Level Defect-Correction Method for Steady Navier-Stokes Problem with Friction Boundary Conditions 下载免费PDF全文
In this paper, we present two-level defect-correction finite element method
for steady Navier-Stokes equations at high Reynolds number with the friction boundary
conditions, which results in a variational inequality problem of the second kind.
Based on Taylor-Hood element, we solve a variational inequality problem of Navier-Stokes
type on the coarse mesh and solve a variational inequality problem of Navier-Stokes
type corresponding to Newton linearization on the fine mesh. The error estimates
for the velocity in the $H^1$ norm and the pressure in the $L^2$ norm are derived.
Finally, the numerical results are provided to confirm our theoretical analysis. 相似文献
995.
Yujiao Li & Tingsong Du 《数学研究》2016,49(1):82-92
Using an integral identity for a once differentiable mapping, this paper establishes
Hadamard's integral inequalities for $s$-convex and $s$-concave mappings. In
particular, our results improve and extend some known ones in the literature. Finally,
these inequalities are applied to special means. 相似文献
996.
《International Journal of Solids and Structures》2014,51(3-4):886-893
The inclined crack problems are considered for a thin strip and a strip with finite thickness in a perpendicular magnetic field. The critical current density is assumed to be a constant. The crack orientation is varied and the effect of crack on the magnetic field distribution is neglected. Based on the analytical results and variational inequality, the field and current distributions are computed for both thin strip and strip with finite thickness cases, respectively. Then, the stress intensity factors at the crack tip are determined using the finite element method for magnetic field loads. The numerical results are presented for different inclined crack angles, magnetization processes and geometry parameters of the strip. The results show that the fracture behavior of the strip with finite thickness is more complicated than that of the thin strip. With the numerical results, we can predict the largest possibility of cracking as the strip is in an external field. 相似文献
997.
In this paper we give three characterizations of VMO(Rn) space, which are of John-Nirenberg type, Uchiyama-type and Miyachi-type, respectively. 相似文献
998.
We give a conjecture on the lower bound of the ADM mass M by using the null energy condition. The conjecture includes a Penrose-like inequality $3M\geqslant \kappa { \mathcal A }/(4\pi )+\sqrt{{ \mathcal A }/4\pi }$ and the Penrose inequality $2M\geqslant \sqrt{{ \mathcal A }/4\pi }$ with ${ \mathcal A }$ the event horizon area and κ the surface gravity. Both the conjecture in the static spherically symmetric case and the Penrose inequality for a dynamical spacetime with spherical symmetry are proved by imposing the null energy condition. We then generalize the conjecture to a general dynamical spacetime. Our results raise a new challenge for the famous unsettled question in general relativity: in what general case can the null energy condition replace other energy conditions to ensure the Penrose inequality? 相似文献
999.
首先考察了概率密度演化理论中的点演化和群演化与概率空间剖分的关系. 继而,讨论了点集筛选的基本准则. 在此基础上推广了点集偏差的概念,对非均匀、非正态的一般多维分布,提出了广义F 偏差(GF 偏差)的概念,避免了偏差计算的NP 难解问题. 探索了GF 偏差与EF 偏差的关系. 以GF 偏差最小化为准则,建议了概率空间最优剖分与点集重整的新策略. 结果表明,上述方法能够处理包含多达数10 个随机变量的结构动力响应概率密度演化分析问题. 最后,指出了需要进一步研究的问题. 相似文献
1000.
《Optimization》2012,61(6):873-885
Many problems to appear in signal processing have been formulated as the variational inequality problem over the fixed point set of a nonexpansive mapping. In particular, convex optimization problems over the fixed point set are discussed, and operators which are considered to the problems satisfy the monotonicity. Hence, the uniqueness of the solution of the problem is not always guaranteed. In this article, we present the variational inequality problem for a monotone, hemicontinuous operator over the fixed point set of a firmly nonexpansive mapping. The main aim of the article is to solve the proposed problem by using an iterative algorithm. To this goal, we present a new iterative algorithm for the proposed problem and its convergence analysis. Numerical examples for the proposed algorithm for convex optimization problems over the fixed point set are provided in the final section. 相似文献