全文获取类型
收费全文 | 4742篇 |
免费 | 147篇 |
国内免费 | 214篇 |
专业分类
化学 | 768篇 |
晶体学 | 3篇 |
力学 | 249篇 |
综合类 | 11篇 |
数学 | 3219篇 |
物理学 | 853篇 |
出版年
2023年 | 59篇 |
2022年 | 67篇 |
2021年 | 77篇 |
2020年 | 70篇 |
2019年 | 95篇 |
2018年 | 76篇 |
2017年 | 86篇 |
2016年 | 78篇 |
2015年 | 86篇 |
2014年 | 164篇 |
2013年 | 390篇 |
2012年 | 227篇 |
2011年 | 250篇 |
2010年 | 244篇 |
2009年 | 345篇 |
2008年 | 360篇 |
2007年 | 361篇 |
2006年 | 231篇 |
2005年 | 170篇 |
2004年 | 179篇 |
2003年 | 153篇 |
2002年 | 146篇 |
2001年 | 89篇 |
2000年 | 85篇 |
1999年 | 66篇 |
1998年 | 87篇 |
1997年 | 84篇 |
1996年 | 106篇 |
1995年 | 75篇 |
1994年 | 90篇 |
1993年 | 64篇 |
1992年 | 58篇 |
1991年 | 31篇 |
1990年 | 35篇 |
1989年 | 25篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 29篇 |
1985年 | 36篇 |
1984年 | 28篇 |
1983年 | 11篇 |
1982年 | 43篇 |
1981年 | 19篇 |
1980年 | 22篇 |
1979年 | 25篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1973年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有5103条查询结果,搜索用时 15 毫秒
21.
C. Bogani M. G. Gasparo A. Papini 《Journal of Optimization Theory and Applications》2007,134(1):47-59
We propose a pattern search method to solve a classical nonsmooth optimization problem. In a deep analogy with pattern search
methods for linear constrained optimization, the set of search directions at each iteration is defined in such a way that
it conforms to the local geometry of the set of points of nondifferentiability near the current iterate. This is crucial to
ensure convergence. The approach presented here can be extended to wider classes of nonsmooth optimization problems. Numerical
experiments seem to be encouraging.
This work was supported by M.U.R.S.T., Rome, Italy. 相似文献
22.
Markus Hegland Jochen Garcke Vivien Challis 《Linear algebra and its applications》2007,420(2-3):249-275
The combination technique has repeatedly been shown to be an effective tool for the approximation with sparse grid spaces. Little is known about the reasons of this effectiveness and in some cases the combination technique can even break down. It is known, however, that the combination technique produces an exact result in the case of a projection into a sparse grid space if the involved partial projections commute.
The performance of the combination technique is analysed using a projection framework and the C/S decomposition. Error bounds are given in terms of angles between the spanning subspaces or the projections onto these subspaces. Based on this analysis modified combination coefficients are derived which are optimal in a certain sense and which can substantially extend the applicability and performance of the combination technique. 相似文献
23.
This paper considers the general synchronization dynamics of coupled Van der Pol–Duffing oscillators. The linear and nonlinear stability analysis on the synchronization process is derived through the Whittaker method and the Floquet theory in addition to the multiple time scales method. A stability map displaying different dynamical states of the system is performed. Numerical simulation is carried out to support and to complement the accuracy of the analytical treatment. 相似文献
24.
设{u_k}_k≥0为一个线性递归序列.序列{u_k(mod q)}_(k≥0)是周期的,很多人都对其周期有过研究.本文应用二次数域中理想的理论,较完全地刻面了二次线性递归序列模q的周期长度,所获结果加强并推广了Engstrom及Wall的结论. 相似文献
25.
26.
Carsten Franz 《Proceedings of the American Mathematical Society》2006,134(8):2437-2446
A method to approximate the eigenvalues of linear operators depending on an unknown distribution is introduced and applied to weighted sums of squared normally distributed random variables. This area of application includes the approximation of the asymptotic null distribution of certain degenerated U- and V-statistics.
27.
V. A. KHATSKEVICH V.A. SENDEROV 《数学学报(英文版)》2006,22(6):1687-1694
The operator sets, which are the subject of this paper, have been studied in many papers where, under different restrictions on the generating operators, convexity, compactness in the weak operator topology, and nonemptiness were proved for sets of different classes under study. Then the results obtained were used in these papers to solve several applied problems. Namely, they played the key role in establishing the dichotomy of nonautonomous dynamical systems, with either continuous or discrete time. In the present paper, we generalize and sharpen the already known criteria and obtain several new criteria for convexity, compactness, and nonemptiness of several special operator sets. Then, using the assertions obtained, we construct examples of sets of the form under study which are nonconvex, noncompact in the weak operator topology, as well as empty, and are generated by "smooth" operators of a special class. The existence problem for such sets remained open until the authors of this paper announced some of its results. 相似文献
28.
Several techniques for experimental determination of floating point precision in practical computations are examined, and applied to linear algebra algorithms. These techniques are simple enough to be directly applicable to existing production codes, requiring a very limited amount of software on many machines, and yet they yield interesting information on the numerical precision of a computation. Our choice of linear algebra algorithms includes a direct solver (namely the MA32 program from the Harwell Library) and several variants of preconditioned conjugate gradients (the methods DIAG, INV, MINV and POL of Reference 1). The results may be of interest as method selection criteria, and thus complement Mflop performance data available from several sources. 相似文献
29.
有序分组资料的线性趋势检验主要用于检验几个二项总体反应率的线性趋势;在医学与生物学中最典型的用途是研究剂量和反应的关系. 如果用Z检验来代替通常在本检验中所用的卡方检验,就可容易地导出本检验的确切概率计算方法,和其他2×C有序列联表有着相同的形式.本文给出了该检验的确切概率计算方法. 相似文献
30.
本文讨论了在带有截断情况的线性回归模型中 ,响应变量均值的估计问题 .将经验似然的方法应用到带有截断情况的回归模型中 ,在估计响应变量的均值时构造了调整的经验似然统计量 ,证明了在一定的条件下 ,该统计量渐近服从 χ2 分布 ,给出了均值的置信区间 ,并与正态下得到的结果进行了比较 ,模拟的结果说明了经验似然的优良性 . 相似文献