全文获取类型
收费全文 | 5606篇 |
免费 | 770篇 |
国内免费 | 623篇 |
专业分类
化学 | 1944篇 |
晶体学 | 84篇 |
力学 | 787篇 |
综合类 | 97篇 |
数学 | 1372篇 |
物理学 | 2715篇 |
出版年
2024年 | 13篇 |
2023年 | 53篇 |
2022年 | 88篇 |
2021年 | 130篇 |
2020年 | 115篇 |
2019年 | 112篇 |
2018年 | 99篇 |
2017年 | 161篇 |
2016年 | 217篇 |
2015年 | 164篇 |
2014年 | 278篇 |
2013年 | 433篇 |
2012年 | 312篇 |
2011年 | 398篇 |
2010年 | 347篇 |
2009年 | 370篇 |
2008年 | 374篇 |
2007年 | 417篇 |
2006年 | 341篇 |
2005年 | 342篇 |
2004年 | 265篇 |
2003年 | 253篇 |
2002年 | 238篇 |
2001年 | 175篇 |
2000年 | 170篇 |
1999年 | 152篇 |
1998年 | 120篇 |
1997年 | 115篇 |
1996年 | 88篇 |
1995年 | 88篇 |
1994年 | 91篇 |
1993年 | 79篇 |
1992年 | 54篇 |
1991年 | 54篇 |
1990年 | 38篇 |
1989年 | 31篇 |
1988年 | 29篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 29篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 12篇 |
1974年 | 4篇 |
排序方式: 共有6999条查询结果,搜索用时 31 毫秒
891.
W.J. Walker 《Applicable analysis》2013,92(1-2):167-177
The Arithmetic Fourier Transform is an algorithm for the computation of Fourier coefficients. In this paper it is extended to the computation of double Fourier coefficients by a repeated sum. We discuss the relevance of the repeated sum algorithm to signal processing by neurons in the visual pathway. 相似文献
892.
893.
Let (R, 𝔪) be a Cohen–Macaulay local ring of dimension d > 0, I an 𝔪-primary ideal of R and K an ideal containing I. When depth G(I) ≥ d ? 1 and r(I | K) < ∞, we present a lower bound on the second fiber coefficient of the fiber cones, and also provide a characterization, in terms of f 2(I, K), of the condition depth F K (I) ≥ d ? 1. 相似文献
894.
895.
船摇数据实时滤波与预报的时序法 总被引:2,自引:1,他引:2
作为船摇数据建立一个时序时域模型-长自回归模型,在此模型基础上给出了船摇数据的实时滤波和预报的方法,并从均方误差、预报误差、残差序列的相关性、拟合方差、仿真计算等多方面考察了滤波及预报效果。AR(p)模型的系数估计采用最小二乘递推方法,用较少的运算量和存贮量,得到了较高的估值精度。该方法是一种非常值得推荐的船摇数据实时处理方法。 相似文献
896.
Fabian Scheipl Ana-Maria Staicu Sonja Greven 《Journal of computational and graphical statistics》2013,22(2):477-501
We propose an extensive framework for additive regression models for correlated functional responses, allowing for multiple partially nested or crossed functional random effects with flexible correlation structures for, for example, spatial, temporal, or longitudinal functional data. Additionally, our framework includes linear and nonlinear effects of functional and scalar covariates that may vary smoothly over the index of the functional response. It accommodates densely or sparsely observed functional responses and predictors which may be observed with additional error and includes both spline-based and functional principal component-based terms. Estimation and inference in this framework is based on standard additive mixed models, allowing us to take advantage of established methods and robust, flexible algorithms. We provide easy-to-use open source software in the pffr() function for the R package refund. Simulations show that the proposed method recovers relevant effects reliably, handles small sample sizes well, and also scales to larger datasets. Applications with spatially and longitudinally observed functional data demonstrate the flexibility in modeling and interpretability of results of our approach. 相似文献
897.
《Journal of computational and graphical statistics》2013,22(3):694-716
We introduce a nonparametric nonlinear time series model. The novel idea is to fit a model via penalization, where the penalty term is an unbiased estimator of the integrated Hessian of the underlying function. The underlying model assumption is very general: it has Hessian almost everywhere in its domain. Numerical experiments demonstrate that our model has better predictive power: if the underlying model complies with an existing parametric/semiparametric form (e.g., a threshold autoregressive model (TAR), an additive autoregressive model (AAR), or a functional coefficient autoregressive model (FAR)), our model performs comparably; if the underlying model does not comply with any preexisting form, our model outperforms in nearly all simulations. We name our model a Hessian regularized nonlinear model for time series (HRM). We conjecture on theoretical properties and use simulations to verify. Our method can be viewed as a way to generalize splines to high dimensions (when the number of variates is more than three), under which an analogous analytical derivation cannot work due to the curse of dimensionality. Supplemental materials are provided, and will help readers reproduce all results in the article. 相似文献
898.
S. M. Ould Aly 《Applied Mathematical Finance》2013,20(1):84-107
AbstractIn this article, we propose an arbitrage-free modelling framework for the joint dynamics of forward variance along with the underlying index, which can be seen as a combination of the two approaches proposed by Bergomi. The difference between our modelling framework and the Bergomi (2008. Smile dynamics III. Risk, October, 90–96) models is mainly the ability to compute the prices of VIX futures and options by using semi-analytic formulas. Also, we can express the sensitivities of the prices of VIX futures and options with respect to the model parameters, which enables us to propose an efficient and easy calibration to the VIX futures and options. The calibrated model allows to Delta-hedge VIX options by trading in VIX futures, the corresponding hedge ratios can be computed analytically. 相似文献
899.
In the present paper, we give an investigation on the learning rate of l2-coefficient regularized classification with strong loss and the data dependent kernel functional spaces. The results show that the learning rate is influenced by the strong convexity. 相似文献
900.
Angsuman Das 《代数通讯》2013,41(11):4724-4731
In this paper, the authors introduce a graph structure, called subspace inclusion graph ?n(𝕍) on a finite dimensional vector space 𝕍 where the vertex set is the collection of nontrivial proper subspaces of a vector space and two vertices are adjacent if one is contained in other. The diameter, girth, clique number, and chromatic number of ?n(𝕍) are studied. It is shown that two subspace inclusion graphs are isomorphic if and only if the base vector spaces are isomorphic. Finally, some properties of subspace inclusion graph are studied when the base field is finite. 相似文献