全文获取类型
收费全文 | 4205篇 |
免费 | 476篇 |
国内免费 | 170篇 |
专业分类
化学 | 264篇 |
晶体学 | 2篇 |
力学 | 274篇 |
综合类 | 90篇 |
数学 | 3177篇 |
物理学 | 1044篇 |
出版年
2024年 | 5篇 |
2023年 | 53篇 |
2022年 | 102篇 |
2021年 | 139篇 |
2020年 | 93篇 |
2019年 | 105篇 |
2018年 | 82篇 |
2017年 | 149篇 |
2016年 | 154篇 |
2015年 | 96篇 |
2014年 | 262篇 |
2013年 | 400篇 |
2012年 | 187篇 |
2011年 | 245篇 |
2010年 | 228篇 |
2009年 | 262篇 |
2008年 | 303篇 |
2007年 | 264篇 |
2006年 | 203篇 |
2005年 | 197篇 |
2004年 | 136篇 |
2003年 | 122篇 |
2002年 | 115篇 |
2001年 | 109篇 |
2000年 | 100篇 |
1999年 | 96篇 |
1998年 | 101篇 |
1997年 | 66篇 |
1996年 | 63篇 |
1995年 | 58篇 |
1994年 | 40篇 |
1993年 | 36篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 33篇 |
1989年 | 19篇 |
1988年 | 9篇 |
1987年 | 26篇 |
1986年 | 11篇 |
1985年 | 35篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有4851条查询结果,搜索用时 15 毫秒
201.
Arthur Berg Dimitris N. Politis 《Annals of the Institute of Statistical Mathematics》2009,61(2):477-498
Improved performance in higher-order spectral density estimation is achieved using a general class of infinite-order kernels.
These estimates are asymptotically less biased but with the same order of variance as compared to the classical estimators
with second-order kernels. A simple, data-dependent algorithm for selecting the bandwidth is introduced and is shown to be
consistent with estimating the optimal bandwidth. The combination of the specialized family of kernels with the new bandwidth
selection algorithm yields a considerably improved polyspectral estimator surpassing the performances of existing estimators
using second-order kernels. Bispectral simulations with several standard models are used to demonstrate the enhanced performance
with the proposed methodology. 相似文献
202.
Jean-Daniel Boissonnat Leonidas J. Guibas Steve Y. Oudot 《Discrete and Computational Geometry》2009,42(1):37-70
It is a well-established fact that the witness complex is closely related to the restricted Delaunay triangulation in low
dimensions. Specifically, it has been proved that the witness complex coincides with the restricted Delaunay triangulation
on curves, and is still a subset of it on surfaces, under mild sampling conditions. In this paper, we prove that these results
do not extend to higher-dimensional manifolds, even under strong sampling conditions such as uniform point density. On the
positive side, we show how the sets of witnesses and landmarks can be enriched, so that the nice relations that exist between
restricted Delaunay triangulation and witness complex hold on higher-dimensional manifolds as well. We derive from our structural
results an algorithm that reconstructs manifolds of any arbitrary dimension or co-dimension at different scales. The algorithm
combines a farthest-point refinement scheme with a vertex pumping strategy. It is very simple conceptually, and it does not
require the input point sample to be sparse. Its running time is bounded by c(d)n
2, where n is the size of the input point cloud, and c(d) is a constant depending solely (yet exponentially) on the dimension d of the ambient space. Although this running time makes our reconstruction algorithm rather theoretical, recent work has shown
that a variant of our approach can be made tractable in arbitrary dimensions, by building upon the results of this paper.
This work was done while S.Y. Oudot was a post-doctoral fellow at Stanford University. His email there is no longer valid. 相似文献
203.
本文研究缺失数据下对数线性模型参数的极大似然估计问题.通过Monte-Carlo EM算法去拟合所提出的模型.其中,在期望步中利用Metropolis-Hastings算法产生一个缺失数据的样本,在最大化步中利用Newton-Raphson迭代使似然函数最大化.最后,利用观测数据的Fisher信息得到参数极大似然估计的渐近方差和标准误差. 相似文献
204.
205.
Liang Zhao 《Journal of Differential Equations》2019,266(9):5615-5624
In this paper, let be n-dimensional noncompact metric measure space which satisfies Poincaré inequality with some Ricci curvature condition. We obtain a Liouville theorem for positive weak solutions to weighted p-Lichnerowicz equation where are real constants. 相似文献
206.
This paper mainly concerns a tuple of multiplication operators
defined on the weighted and unweighted multi-variable Bergman
spaces, their joint reducing subspaces and the von Neumann algebra
generated by the orthogonal projections onto these subspaces. It is
found that the weights play an important role in the structures of
lattices of joint reducing subspaces and of associated von Neumann
algebras. Also, a class of special weights is taken into account.
Under a mild condition it is proved that if those multiplication
operators are defined by the same symbols, then the corresponding
von Neumann algebras are $*$-isomorphic to the one defined on the
unweighted Bergman space. 相似文献
207.
研究了条件泛函及其导数的非参数估计,对随机与固定设计的条件泛函,分别利用核估计和非参数加权估计,在核函数及权函数满足一定条件下,证明了估计一致强收敛于待估函数的速度可达到最优。从而进一步推广和发展了Hrdle,etal.(1988)、Severini,etal.(1992)的许多结果。 相似文献
208.
讨论了单位球上D打ichlet型空间砩到μ-Bloch空间艮的加权复合算子的有界性和紧性问题,并给出了 Tψ,φ为有界算子和紧算子的充要条件. 相似文献
209.
本文研究了定时和定数截尾情形CE模型下Weibull分布场合步进应力加速寿命试验的Bayes估计.利用加速系数和加速方程将各种加速应力水平下的尺度参数换算为正常应力水平下的尺度参数,从而获得含正常应力下尺度参数的似然函数.在参数先验的选取时,尺度参数和加速系数分别取共轭先验和无信息先验,当形状参数m<1和m>1时分别取Beta分布和Gamma分布作为其先验.在平方损失下,利用Gibbs抽样和切片抽样给出了该模型参数的Bayes估计.最后,通过Monte Carlo模拟表明该Bayes估计是有效的. 相似文献
210.
首先给出了Jam es-S te in估计优于岭估计的充分条件,随后在P itm an准则下给出了Jam es-S te in估计优于最小二乘估计的简短证明. 相似文献