全文获取类型
收费全文 | 12224篇 |
免费 | 1386篇 |
国内免费 | 765篇 |
专业分类
化学 | 1600篇 |
晶体学 | 27篇 |
力学 | 766篇 |
综合类 | 144篇 |
数学 | 9874篇 |
物理学 | 1964篇 |
出版年
2024年 | 16篇 |
2023年 | 107篇 |
2022年 | 206篇 |
2021年 | 278篇 |
2020年 | 370篇 |
2019年 | 378篇 |
2018年 | 355篇 |
2017年 | 356篇 |
2016年 | 398篇 |
2015年 | 308篇 |
2014年 | 592篇 |
2013年 | 1119篇 |
2012年 | 625篇 |
2011年 | 655篇 |
2010年 | 598篇 |
2009年 | 739篇 |
2008年 | 695篇 |
2007年 | 802篇 |
2006年 | 710篇 |
2005年 | 583篇 |
2004年 | 537篇 |
2003年 | 503篇 |
2002年 | 482篇 |
2001年 | 376篇 |
2000年 | 388篇 |
1999年 | 346篇 |
1998年 | 293篇 |
1997年 | 283篇 |
1996年 | 189篇 |
1995年 | 140篇 |
1994年 | 119篇 |
1993年 | 78篇 |
1992年 | 103篇 |
1991年 | 54篇 |
1990年 | 55篇 |
1989年 | 39篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 38篇 |
1985年 | 54篇 |
1984年 | 61篇 |
1983年 | 30篇 |
1982年 | 51篇 |
1981年 | 40篇 |
1980年 | 39篇 |
1979年 | 38篇 |
1978年 | 18篇 |
1977年 | 25篇 |
1976年 | 24篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Philip T. Keenan 《Numerical Algorithms》1994,7(2):269-293
We describe a new family of discrete spaces suitable for use with mixed methods on certain quadrilateral and hexahedral meshes. The new spaces are natural in the sense of differential geometry, so all the usual mixed method theory, including the hybrid formulation, carries over to these new elements with proofs unchanged. Because transforming general quadrilaterals into squares introduces nonlinearity and because mixed methods involve the divergence operator, the new spaces are more complicated than either the corresponding Raviart-Thomas spaces for rectangles or corresponding finite element spaces for quadrilaterals. The new spaces are also limited to meshes obtained from a rectangular mesh through the application of a single global bilinear transformation. Despite this limitation, the new elements may be useful in certain topologically regular problems, where initially rectangular grids are deformed to match features of the physical region. They also illustrate the difficulties introduced into the theory of mixed methods by nonlinear transformations. 相似文献
102.
103.
We consider a spatially distributed hybrid system consisting of a convection/reaction system in which the reaction switches discontinuously in time between modes, independently at each spatial point on reaching “switching thresholds”. The model involves a novel formulation for evolution of the free boundary between the modal regions. 相似文献
104.
Chein-Shan Liu 《Journal of Mathematical Analysis and Applications》2007,331(1):547-566
In this paper we study a circular differential equation under a discontinuous periodic input, developing a quadratic differential equations system on S1 and a linear differential equations system in the Minkowski space M3. The symmetry groups of these two systems are, respectively, PSOo(2,1) and SOo(2,1). The Poincaré circle map is constructed exactly, and a critical value αc of the parameter is identified. Depending on α of the input amplitude the equation may exhibit periodic, subharmonic or quasiperiodic motions. When α varies from α>αc to α<αc, there undergoes an inverse tangent bifurcation; consequently, the resultant Poincaré circle map offers one route to the quasiperiodicity via a type I intermittency. In the parameter range of α<αc the orbit generated by the Poincaré circle map is either m-periodic or quasiperiodic when n/m is a rational or an irrational number. 相似文献
105.
本针对P0函数互补问题,给出了一种微方程方法,并且证明了P0函数互补问题的解是微分方程系统的渐进稳定平衡点。在适当的假设条件下,证明了所给出的算法具有二次收敛速度。几个数值例子表明了该算法的有效性。 相似文献
106.
基于模糊方法的多人合作对策的研究 总被引:2,自引:0,他引:2
多人合作对策模型中联盟的收入和总体的收入常常出现相互矛盾的情况 ,此时核是空集 .由于不存在核 ,无法用 Nash-Harsanyi谈判模型求解 .采用模糊数学方法 ,调整模型中线性约束的右端系数 ,使核在一定程度上是非空集合 ,得到模糊意义下的 Nash平衡解 .该方法一定程度上解决了各联盟收入与总体收入的矛盾 .最后通过一个算例说明该方法的可行性 . 相似文献
107.
研究一类脉冲时滞抛物型偏微分方程组解的振动性,利用一阶脉冲时滞微分不等式获得了该类方程组在两类不同边值条件下所有解振动的若干充分条件.所得结果充分反映了脉冲和时滞在振动中的影响作用. 相似文献
108.
M. Benchohra 《Journal of Mathematical Analysis and Applications》2003,286(1):307-325
In this paper, we shall establish sufficient conditions for the existence of integral solutions for some nondensely defined evolution impulsive differential inclusions in Banach spaces with nonlocal conditions. 相似文献
109.
We continue to investigate strongly and weakly Lie remarkable equations, which we defined in a recent paper. We consider some
relevant algebras of vector fields on ℝk (such as the isometric, affine, projective, or conformal algebras) and characterize strongly Lie remarkable equations admitted
by the considered Lie algebras.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 151, No. 3, pp. 486–494, June, 2007. 相似文献
110.
Andreas Rößler 《BIT Numerical Mathematics》2006,46(1):97-110
A general class of stochastic Runge–Kutta methods for Itô stochastic differential equation systems w.r.t. a one-dimensional Wiener process is introduced. The colored rooted tree analysis is applied to derive conditions for the coefficients of the stochastic Runge–Kutta method assuring convergence in the weak sense with a prescribed order. Some coefficients for new stochastic Runge–Kutta schemes of order two are calculated explicitly and a simulation study reveals their good performance. 相似文献