全文获取类型
收费全文 | 893篇 |
免费 | 37篇 |
国内免费 | 52篇 |
专业分类
化学 | 249篇 |
晶体学 | 2篇 |
力学 | 20篇 |
综合类 | 3篇 |
数学 | 571篇 |
物理学 | 137篇 |
出版年
2023年 | 6篇 |
2022年 | 15篇 |
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 20篇 |
2017年 | 17篇 |
2016年 | 26篇 |
2015年 | 15篇 |
2014年 | 32篇 |
2013年 | 56篇 |
2012年 | 18篇 |
2011年 | 39篇 |
2010年 | 32篇 |
2009年 | 45篇 |
2008年 | 65篇 |
2007年 | 70篇 |
2006年 | 43篇 |
2005年 | 61篇 |
2004年 | 42篇 |
2003年 | 38篇 |
2002年 | 41篇 |
2001年 | 28篇 |
2000年 | 29篇 |
1999年 | 31篇 |
1998年 | 20篇 |
1997年 | 22篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有982条查询结果,搜索用时 193 毫秒
81.
Summary Rf values of twenty therapeutic sulfonamides have been estimated in seven solvent systems. Based on these data a simple identification scheme was developed demanding only three solvent systems for complete separation.Quantification of corresponding fluorescamine derivatives at nanogram level was performed by the use of an TLC-scanner configured online with a microcomputer. Mathematical treatment of standard curves using the computer program Curve Fitter are discussed. Validity and reproducibility of results are compared with data obtained by HPLC and show good correlation. 相似文献
82.
M. Van Barel E. Van Camp N. Mastronardi 《Numerical Linear Algebra with Applications》2005,12(10):981-1000
Very recently, an algorithm, which reduces any symmetric matrix into a semiseparable one of semi‐ separability rank 1 by similar orthogonality transformations, has been proposed by Vandebril, Van Barel and Mastronardi. Partial execution of this algorithm computes a semiseparable matrix whose eigenvalues are the Ritz‐values obtained by the Lanczos' process applied to the original matrix. Also a kind of nested subspace iteration is performed at each step. In this paper, we generalize the above results and propose an algorithm to reduce any symmetric matrix into a similar block‐semiseparable one of semiseparability rank k, with k ∈ ?, by orthogonal similarity transformations. Also in this case partial execution of the algorithm computes a block‐semiseparable matrix whose eigenvalues are the Ritz‐values obtained by the block‐Lanczos' process with k starting vectors, applied to the original matrix. Subspace iteration is performed at each step as well. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
83.
Takashi Aoki Yasuhiro Kombu Yasuo Ohno 《Proceedings of the American Mathematical Society》2008,136(2):387-395
A generating function for specified sums of multiple zeta values is defined and a differential equation that characterizes this function is given. As applications, some relations for multiple zeta values over the field of rational numbers are discussed.
84.
Behnoush Maherani Olivier Wattraint 《Journal of Dispersion Science and Technology》2017,38(11):1633-1639
Liposomes play an important role in medical and pharmaceutical science as, nanoscale drug carriers. One of the most important features is their size and size distribution, influencing both their bio-distribution and their targeting efficiency to tumors and also therapeutic activity of liposomal antitumor drugs. In this study, the effect of preparation method and molecular interaction on size and shape of liposome was studied. The size and shape characterization of liposomes was performed by asymmetrical flow field-flow fractionation coupled online with multi-angle light scattering (AF4-MALS). The size distributions obtained by AF4-MALS were compared to mean particle sizes and size distribution measured with other standard method such as Photon Correlation Spectroscopy (PCS). Furthermore, the effect of molecular interaction (hydrophilic and hydrophobic model drugs) on liposomal structure was assessed. 相似文献
85.
86.
《Applied Mathematical Modelling》2014,38(5-6):1698-1709
We consider Bayesian estimation of the stress–strength reliability based on record values. The estimators are derived under the squared error loss function in the one parameter as well as two-parameter exponential distributions. The Bayes estimators are derived, in some cases in closed form, and their performance is investigated in terms of their bias and mean squared errors and compared with the maximum likelihood estimators. An illustrative example is given. 相似文献
87.
主要研究差分方程a_1(z)f(x+1)+a_0(z)f(z)=F(z)的一个有穷级超越亚纯解f(z)与亚纯函数g(z)分担0,1,∞CM时的唯一性问题(其中a_(z),a0(z),F(z)为非零多项式,且满足a_1(z)+a_0(z)■0),得到f(x)≡g(z),或f(z)+g(z)≡f(z)g(z),或存在一个多项式β(z)=az+b_0和一个常数a_0满足e~(a_0)≠e~(b_0),使得f(z)=(1-e~(β(x)))/(e~(β(x))(e~(a_o-b_0)-1))与g(z)=(1-e~(β(x)))/(1-e~(b_o-a_0)),其中a(≠0),b_0为常数. 相似文献
88.
Xingzhi Zhan 《Linear and Multilinear Algebra》2013,61(2):191-194
We pose some problems on the Hadamard product and singular values of matrices. 相似文献
89.
Juan M. Gracia Inmaculadade Hoyos Franscisco E. Velasco 《Linear and Multilinear Algebra》1999,46(1):25-49
We give safety neighbourhoods for the necessary conditions in the change of the Jordan canonical form of a matrix under small perturbations. We also obtain the minimum distance from an n × n complex matrix which has less than k nonconstant invariant factors (2≤ k≤ n) to the set of matrices which have more or equal to k. When k= 2, we get in particular the distance from a nonderogatory matrix to the set of derogatory matrices. 相似文献
90.
This work establishes a strong uniqueness property for a class of planar locally integrable vector fields. A result on pointwise convergence to the boundary value is also proved for bounded solutions.Dedicated to Constantine Dafermos on his 60th birthdayWork supported in part by CNPq, FINEP, FAPESP and a Research Incentive Fund grant of Temple University. 相似文献