全文获取类型
收费全文 | 2702篇 |
免费 | 309篇 |
国内免费 | 281篇 |
专业分类
化学 | 181篇 |
晶体学 | 6篇 |
力学 | 145篇 |
综合类 | 67篇 |
数学 | 2549篇 |
物理学 | 344篇 |
出版年
2024年 | 11篇 |
2023年 | 37篇 |
2022年 | 26篇 |
2021年 | 72篇 |
2020年 | 74篇 |
2019年 | 74篇 |
2018年 | 69篇 |
2017年 | 102篇 |
2016年 | 107篇 |
2015年 | 50篇 |
2014年 | 119篇 |
2013年 | 218篇 |
2012年 | 132篇 |
2011年 | 174篇 |
2010年 | 152篇 |
2009年 | 181篇 |
2008年 | 164篇 |
2007年 | 149篇 |
2006年 | 173篇 |
2005年 | 133篇 |
2004年 | 106篇 |
2003年 | 141篇 |
2002年 | 122篇 |
2001年 | 98篇 |
2000年 | 91篇 |
1999年 | 73篇 |
1998年 | 74篇 |
1997年 | 50篇 |
1996年 | 40篇 |
1995年 | 32篇 |
1994年 | 44篇 |
1993年 | 24篇 |
1992年 | 15篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 3篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1936年 | 5篇 |
排序方式: 共有3292条查询结果,搜索用时 78 毫秒
31.
A fifth-order theory for solving the problem of interaction between Stokes waves and exponential profile currents is proposed.
The calculated flow fields are compared with measurements. Then the errors caused by the linear superposition method and approximate
theory are discussed. It is found that the total wavccurrent field consists of pure wave, pure current and interaction components.
The shear current not only directly changes the flow field, but also indirectly does so by changing the wave parameters due
to wave-current interaction. The present theory can predict the wave kinematics on shear currents satisfactorily. The linear
superposition method may give rise to more than 40% loading error in extreme conditions. When the apparent wave period is
used and the Wheeler stretching method is adopted to extrapolate the current, application of the approximate theory is the
best.
Project supported by the Chinese Academy of Sciences. 相似文献
32.
双环网络是计算机互连网络和通讯系统的一类重要拓扑结构.1993年,李乔等人提出一个系统的构造方法,构造出69类0紧优和33类1紧优双环网络的无限族,并提出研究下述问题:求k(k>1)紧优双环网络的无限族.2003年,徐俊明等人给出一个4紧优双环网络的无限族.本文首先证明从每一个具体的0紧优双环网络出发,都可以构造若干0紧优双环网络无限族;结合同余方程组理论和数论中的素数理论,给出若干求一般k(k≥0)紧优双环网络无限族(包括非单位步长双环网络无限族)的方法. 相似文献
33.
对于有限Abel群G,t(G)定义为其直接因子的个数,在[5]中,E.Kratzel对于和式得到一渐近公式,对应余项为△_1(x).本文利用E.Fouvry和H .Iwaniec的方法,得到了关于△_1(x)的一个新的估计,改进了H.Menzer等人的结果. 相似文献
34.
Martin Weese 《Mathematical Logic Quarterly》1992,38(1):325-326
35.
In this paper, we study the existence, uniqueness, and the global exponential stability of the periodic solution and equilibrium of hybrid bidirectional associative memory neural networks with discrete delays. By ingeniously importing real parameters di > 0 (i = 1,2, …, n) which can be adjusted, making use of the Lyapunov functional method and some analysis techniques, some new sufficient conditions are established. Our results generalize and improve the related results in [9]. These conditions can be used both to design globally exponentially stable and periodical oscillatory hybrid bidirectional associative neural networks with discrete delays, and to enlarge the area of designing neural networks. Our work has important significance in related theory and its application. 相似文献
36.
37.
In survival or reliability studies, the mean residual life or life expectancy is an important characteristic of the model. Whereas the failure rate can be expressed quite simply in terms of the mean residual life and its derivative, the inverse problem—namely that of expressing the mean residual life in terms of the failure rate—typically involves an integral of a complicated expression. In this paper, we obtain simple expressions for the mean residual life in terms of the failure rate for certain classes of distributions which subsume many of the standard cases. Several results in the literature can be obtained using our approach. Additionally, we develop an expansion for the mean residual life in terms of Gaussian probability functions for a broad class of ultimately increasing failure rate distributions. Some examples are provided to illustrate the procedure. 相似文献
38.
H. Petersson 《Acta Mathematica Hungarica》2003,100(1-2):69-81
The PDE-preserving operators O on the space of nuclearly entire functions of bounded type HNb(E) on a Banach space E are characterized. An operator is PDE-preserving when it preserves homogenous solutions to homogeneous convolution equations.
We establish a one to one correspondence between O and a set Σ of sequences of entire functionals, i.e. exponential type functions. In this way, algebraic structures on Σ,
such as ring structures, can be carried over to O and vice versa. In particular, it follows that O is a non-commutative ring (algebra) with unity with respect to composition and the convolution operators form a commutative
subring (subalgebra). We discuss range and kernel properties, for the operators in O, and characterize the projectors (onto polynomial spaces) in O by determining the corresponding elements in Σ.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
39.
Xinghua Wang 《计算数学(英文版)》2003,(2)
The convergence problem of the family of Euler-Halley methods is considered under the Lipschitz condition with the L-average, and a united convergence theory with its applications is presented. 相似文献
40.
Guido Consonni Piero Veronese Eduardo Gutirrez-Pea 《Journal of multivariate analysis》2004,88(2):335-364
Reference analysis is one of the most successful general methods to derive noninformative prior distributions. In practice, however, reference priors are often difficult to obtain. Recently developed theory for conditionally reducible natural exponential families identifies an attractive reparameterization which allows one, among other things, to construct an enriched conjugate prior. In this paper, under the assumption that the variance function is simple quadratic, the order-invariant group reference prior for the above parameter is found. Furthermore, group reference priors for the mean- and natural parameter of the families are obtained. A brief discussion of the frequentist coverage properties is also presented. The theory is illustrated for the multinomial and negative-multinomial family. Posterior computations are especially straightforward due to the fact that the resulting reference distributions belong to the corresponding enriched conjugate family. A substantive application of the theory relates to the construction of reference priors for the Bayesian analysis of two-way contingency tables with respect to two alternative parameterizations. 相似文献