全文获取类型
收费全文 | 693篇 |
免费 | 39篇 |
国内免费 | 30篇 |
专业分类
化学 | 32篇 |
力学 | 15篇 |
综合类 | 1篇 |
数学 | 184篇 |
物理学 | 213篇 |
无线电 | 317篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 12篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 21篇 |
2014年 | 52篇 |
2013年 | 47篇 |
2012年 | 31篇 |
2011年 | 50篇 |
2010年 | 29篇 |
2009年 | 53篇 |
2008年 | 45篇 |
2007年 | 56篇 |
2006年 | 47篇 |
2005年 | 24篇 |
2004年 | 23篇 |
2003年 | 20篇 |
2002年 | 29篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 17篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 3篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1985年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有762条查询结果,搜索用时 31 毫秒
1.
By leveraging the secret data coding using the remainder storage based exploiting modification direction (RSBEMD), and the pixel change operation recording based on multi-segment left and right histogram shifting, a novel reversible data hiding (RHD) scheme is proposed in this paper. The secret data are first encoded by some specific pixel change operations to the pixels in groups. After that, multi-segment left and right histogram shifting based on threshold manipulation is implemented for recording the pixel change operations. Furthermore, a multiple embedding policy based on chess board prediction (CBP) and threshold manipulation is put forward, and the threshold can be adjusted to achieve adaptive data hiding. Experimental results and analysis show that it is reversible and can achieve good performance in capacity and imperceptibility compared with the existing methods. 相似文献
2.
3.
NMOS器件两次沟道注入杂质分布和阈电压计算 总被引:1,自引:1,他引:0
分别考虑了深浅两次沟道区注入杂质在氧化扩散过程中对表面浓度的贡献。对两次注入杂质的扩散分别提取了扩散系数的氧化增强系数、氧化衰减系数和有效杂地系数,给出了表面浓度与工艺参数之间的模拟关系式,以峰值浓度为强反型条件计算了开启电压,文章还给出了开启电压、氧化条件、不同注入组合之间的关系式。 相似文献
4.
5.
6.
This paper presents an analysis of a portfolio model which can be used to assist a property-liability insurance company in determining the optimal composition of the insurance and investment portfolios. By introducing insurer's threshold risk and relaxing some non-realistic assumptions made in traditional chance constraint insurance and investment portfolio models, we propose a method for an insurer to maximize his return threshold for a given threshold risk level. This proposed model can be used to optimize the composition of underwriting and investment portfolios regarding the insurer's threshold risk level, as well as to generate the efficient frontier by adjusting insurer's threshold risk levels. A numerical example is given based on the industry's aggregated data for a sixteen year period. 相似文献
7.
In this paper we consider the (t, n)-threshold visual secret sharing scheme (VSSS) in which black pixels in a secret black-white images is reproduced perfectly
as black pixels when we stack arbitrary t shares. This paper provides a new characterization of the (t, n)-threshold visual secret sharing scheme with such a property (hereafter, we call such a VSSS the (t, n)-PBVSSS for short). We use an algebraic method to characterize basis matrices of the (t, n)-PBVSSS in a certain class of matrices. We show that the set of all homogeneous polynomials each element of which yields
basis matrices of the (t, n)-PBVSSS becomes a set of lattice points in an (n−t+1)-dimensional linear space. In addition, we prove that the optimal basis matrices in the sense of maximizing the relative
difference among all the basis matrices in the class coincides with the basis matrices given by Blundo, Bonis and De Santis
[3] for all n≥ t ≥ 2. 相似文献
8.
Alexandru V. Asimit 《Insurance: Mathematics and Economics》2007,41(1):53-61
This paper exploits a stochastic representation of bivariate elliptical distributions in order to obtain asymptotic results which are determined by the tail behavior of the generator. Under certain specified assumptions, we present the limiting distribution of componentwise maxima, the limiting upper copula, and a bivariate version of the classical peaks over threshold result. 相似文献
9.
10.