全文获取类型
收费全文 | 34832篇 |
免费 | 5112篇 |
国内免费 | 2176篇 |
专业分类
化学 | 2953篇 |
晶体学 | 62篇 |
力学 | 5299篇 |
综合类 | 421篇 |
数学 | 19997篇 |
物理学 | 13388篇 |
出版年
2024年 | 59篇 |
2023年 | 338篇 |
2022年 | 397篇 |
2021年 | 565篇 |
2020年 | 1029篇 |
2019年 | 957篇 |
2018年 | 935篇 |
2017年 | 915篇 |
2016年 | 1031篇 |
2015年 | 859篇 |
2014年 | 1635篇 |
2013年 | 2851篇 |
2012年 | 1783篇 |
2011年 | 2196篇 |
2010年 | 2017篇 |
2009年 | 2202篇 |
2008年 | 2352篇 |
2007年 | 2334篇 |
2006年 | 2019篇 |
2005年 | 2005篇 |
2004年 | 1716篇 |
2003年 | 1634篇 |
2002年 | 1397篇 |
2001年 | 1144篇 |
2000年 | 1051篇 |
1999年 | 978篇 |
1998年 | 913篇 |
1997年 | 745篇 |
1996年 | 592篇 |
1995年 | 517篇 |
1994年 | 426篇 |
1993年 | 326篇 |
1992年 | 296篇 |
1991年 | 308篇 |
1990年 | 239篇 |
1989年 | 165篇 |
1988年 | 158篇 |
1987年 | 143篇 |
1986年 | 121篇 |
1985年 | 116篇 |
1984年 | 105篇 |
1983年 | 53篇 |
1982年 | 102篇 |
1981年 | 87篇 |
1980年 | 60篇 |
1979年 | 64篇 |
1978年 | 38篇 |
1977年 | 33篇 |
1976年 | 24篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
31.
Nobuaki Obata 《Acta Appl Math》1997,47(1):49-77
A general theory of operators on Boson Fock space is discussed in terms of the white noise distribution theory on Gaussian space (white noise calculus). An integral kernel operator is generalized from two aspects: (i) The use of an operator-valued distribution as an integral kernel leads us to the Fubini type theorem which allows an iterated integration in an integral kernel operator. As an application a white noise approach to quantum stochastic integrals is discussed and a quantum Hitsuda–Skorokhod integral is introduced. (ii) The use of pointwise derivatives of annihilation and creation operators assures the partial integration in an integral kernel operator. In particular, the particle flux density becomes a distribution with values in continuous operators on white noise functions and yields a representation of a Lie algebra of vector fields by means of such operators. 相似文献
32.
关于一类二次哈密尔顿系统在二次扰动下的极限环个数问题 总被引:2,自引:0,他引:2
本文研究了一类具有两个鞍点和一个中心的通用二次哈密尔顿向量场在二次扰动下的三参数开折,证明极限环的最小上界为2。 相似文献
33.
许明浩 《武汉大学学报(理学版)》1996,(1)
讨论如下Hilbert空间中的半线性随机发展方程的Cauchy问题 dy(t)=[Ay(t) f(t,y(t))]dt G(t,y(t))dw(t) y(O)=V_u的适度解的存在唯一性,在更一般的条件下,得到了该问题的适度解的存在唯一性。 相似文献
34.
本文给出了混合型多项式Hammerstein积分方程正解的迭代求法,并将所得结果应用到二阶非线性常微分方程的边值问题 相似文献
35.
施国勇 《宁波大学学报(理工版)》1998,(2)
提出了一个线性双向联想存储器的模型,一组有限个向量对由一线性算子建立起双向联想关系,此线性算于是一个网络的联结权重矩阵。该权矩阵由最小二乘法决定。由权矩阵的解导出一特殊类型的Lyapunov矩阵方程.本文提供了这种Lyapunov矩阵方程的解。 相似文献
36.
Summary This paper is concerned with the problem of developing numerical integration algorithms for differential equations that, when
viewed as equations in some Euclidean space, naturally evolve on some embedded submanifold. It is desired to construct algorithms
whose iterates also evolve on the same manifold. These algorithms can therefore be viewed as integrating ordinary differential
equations on manifolds. The basic method “decouples” the computation of flows on the submanifold from the numerical integration
process. It is shown that two classes of single-step and multistep algorithms can be posed and analyzed theoretically, using
the concept of “freezing” the coefficients of differential operators obtained from the defining vector field. Explicit third-order
algorithms are derived, with additional equations augmenting those of their classical counterparts, obtained from “obstructions”
defined by nonvanishing Lie brackets. 相似文献
37.
38.
Second-order random wave solutions for interfacial internal waves in N-layer density-stratified fluid 下载免费PDF全文
This paper studies the random internal wave equations describing the density interface displacements and the velocity potentials of N-layer stratified fluid contained between two rigid walls at the top and bottom. The density interface displacements and the velocity potentials were solved to the second-order by an expansion approach used by Longuet-Higgins (1963) and Dean (1979) in the study of random surface waves and by Song (2004) in the study of second- order random wave solutions for internal waves in a two-layer fluid. The obtained results indicate that the first-order solutions are a linear superposition of many wave components with different amplitudes, wave numbers and frequencies, and that the amplitudes of first-order wave components with the same wave numbers and frequencies between the adjacent density interfaces are modulated by each other. They also show that the second-order solutions consist of two parts: the first one is the first-order solutions, and the second one is the solutions of the second-order asymptotic equations, which describe the second-order nonlinear modification and the second-order wave-wave interactions not only among the wave components on same density interfaces but also among the wave components between the adjacent density interfaces. Both the first-order and second-order solutions depend on the density and depth of each layer. It is also deduced that the results of the present work include those derived by Song (2004) for second-order random wave solutions for internal waves in a two-layer fluid as a particular case. 相似文献
39.
40.
Lin Surong 《Annals of Differential Equations》2006,22(4):517-523
The singularly perturbed boundary value problem for nonlinear higher order ordinary differential equation involving two small parameters has been considered. Under appropriate assumptions, for the three cases:ε/μ2→0(μ→0),μ2/ε→0 (ε→0) andε=μ2, the uniformly valid asymptotic solution is obtained by using the expansion method of two small parameters and the theory of differential inequality. 相似文献