全文获取类型
收费全文 | 3550篇 |
免费 | 484篇 |
国内免费 | 136篇 |
专业分类
化学 | 323篇 |
晶体学 | 1篇 |
力学 | 255篇 |
综合类 | 54篇 |
数学 | 1739篇 |
物理学 | 561篇 |
无线电 | 1237篇 |
出版年
2024年 | 10篇 |
2023年 | 54篇 |
2022年 | 77篇 |
2021年 | 104篇 |
2020年 | 105篇 |
2019年 | 90篇 |
2018年 | 91篇 |
2017年 | 117篇 |
2016年 | 161篇 |
2015年 | 129篇 |
2014年 | 254篇 |
2013年 | 264篇 |
2012年 | 226篇 |
2011年 | 218篇 |
2010年 | 173篇 |
2009年 | 158篇 |
2008年 | 206篇 |
2007年 | 198篇 |
2006年 | 184篇 |
2005年 | 163篇 |
2004年 | 153篇 |
2003年 | 119篇 |
2002年 | 113篇 |
2001年 | 118篇 |
2000年 | 95篇 |
1999年 | 76篇 |
1998年 | 74篇 |
1997年 | 70篇 |
1996年 | 39篇 |
1995年 | 37篇 |
1994年 | 36篇 |
1993年 | 41篇 |
1992年 | 26篇 |
1991年 | 22篇 |
1990年 | 26篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 4篇 |
1985年 | 28篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1973年 | 4篇 |
1957年 | 1篇 |
排序方式: 共有4170条查询结果,搜索用时 15 毫秒
1.
Thalia Tsiaka Panagiotis Zoumpoulakis Vassilia J. Sinanoglou Constantinos Makris Georgios A. Heropoulos Antony C. Calokerinos 《Analytica chimica acta》2015
High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE. 相似文献
2.
Reducing the complexity of distance measurement methods for circular turbo codes that use structured interleavers
下载免费PDF全文
![点击此处可从《International Journal of Communication Systems》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Youssouf Ould‐Cheikh‐Mouhamedou 《International Journal of Communication Systems》2015,28(9):1572-1579
The knowledge of turbo code's minimum Hamming distance (dmin) and its corresponding codeword multiplicity (Amin) is of a great importance because the error correction capability of a code is strongly tied to the values of dmin and Amin. Unfortunately, the computational complexity associated with the search for dmin and Amin can be very high, especially for a turbo code that has high dmin value. This paper introduces some useful properties of turbo codes that use structured interleavers together with circular encoding. These properties allow for a significant reduction of search space and thus reduce significantly the computational complexity associated with the determination of dmin and Amin values. © 2014 The Authors. International Journal of Communication Systems published by John Wiley & Sons, Ltd. 相似文献
3.
In this paper, we study the existence of the uniformly minimum risk equivariant (UMRE) estimators of parameters in a class
of normal linear models, which include the normal variance components model, the growth curve model, the extended growth curve
model, and the seemingly unrelated regression equations model, and so on. The necessary and sufficient conditions are given
for the existence of UMRE estimators of the estimable linear functions of regression coefficients, the covariance matrixV and (trV)α, where α > 0 is known, in the models under an affine group of transformations for quadratic losses and matrix losses, respectively.
Under the (extended) growth curve model and the seemingly unrelated regression equations model, the conclusions given in literature
for estimating regression coefficients can be derived by applying the general results in this paper, and the sufficient conditions
for non-existence of UMRE estimators ofV and tr(V) are expanded to be necessary and sufficient conditions. In addition, the necessary and sufficient conditions that there
exist UMRE estimators of parameters in the variance components model are obtained for the first time. 相似文献
4.
Lubomír Kubáček 《Applications of Mathematics》2006,51(6):565-582
Some remarks to problems of point and interval estimation, testing and problems of outliers are presented in the case of multivariate
regression model.
This work was supported by the Council of Czech Government J14/98:153100011. 相似文献
5.
关于AOR迭代法的研究 总被引:5,自引:0,他引:5
陈恒新 《应用数学与计算数学学报》2002,16(1):40-46
本文论证了严格对角占优矩阵之AOR法的误差估计式中的误差估计常数hγ,ω(0≤γ≤ω0)的最小值是h1,1. 相似文献
6.
7.
图G称为K1,n-free图,如果它不含K1,n作为其导出子图.对K1,n-free图具有给定性质的[a,b]-因子涉及到最小度条件进行了研究,得到一个充分条件. 相似文献
8.
9.
1 IntroductionThestickingpointofassociationrulealgorithmsdependsoneffectivelyfindingallcorrelationpatternsthatsatisfyvaluerequirementinthemagnanimityofdata.Butthealgorithmsalsobringanegativeef fect:thenumberofassociationrulesisverylarge.Alsoinformation… 相似文献
10.
By using the quasi-Lyapunov function, some sufficient conditions of global exponential stability for impulsive systems are established, which is the basis for the following discussion. Then, by employing Riccati inequality and Hamilton-Jacobi inequality approach, some sufficient conditions of robust exponential stability for uncertain linear/nonlinear impulsive systems are derived, respectively. Finally, some examples are given to illustrate the applications of the theory. 相似文献