全文获取类型
收费全文 | 285篇 |
免费 | 5篇 |
国内免费 | 5篇 |
专业分类
化学 | 94篇 |
力学 | 1篇 |
数学 | 179篇 |
物理学 | 21篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 2篇 |
2013年 | 13篇 |
2012年 | 10篇 |
2011年 | 23篇 |
2010年 | 18篇 |
2009年 | 14篇 |
2008年 | 13篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1938年 | 1篇 |
1935年 | 1篇 |
1921年 | 1篇 |
排序方式: 共有295条查询结果,搜索用时 616 毫秒
91.
Zoltán Boros 《Results in Mathematics》1994,26(3-4):225-228
The construction of a specific multiadditive function leads to a structure theorem on the set of vectors with algebraically dependent components. A counterexample in the theory of quadratic functions is also obtained. 相似文献
92.
We present a rational version of the classical Landen transformation for elliptic integrals. This is employed to obtain explicit closed-form expressions for a large class of integrals of even rational functions and to develop an algorithm for numerical integration of these functions.
93.
It is shown that for fixed 1 r s < d and > 0, if X PG(d, q) contains (1 + )qs points, then the number of r-flats spanned by X is at least c()q(r+1)(s+1−r), i.e. a positive fraction of the number of r-flats in PG(s + 1,q). 相似文献
94.
The residual-free bubble method (RFB) is a parameter-free stable finite element method that has been successfully applied to a wide range of boundary-value problems exhibiting multiple-scale behaviour. If some local features of the solution are known a priori, the approximation properties of the RFB finite element space can be improved by enriching it on selected edges of the partition by edge-bubbles that are supported on pairs of neighbouring elements. Motivated by this idea, we define and analyse an enhanced residual-free bubble method for the solution of convection-dominated convection-diffusion problems in 2-D. Our a priori analysis highlights the limitations of the RFB method and the improved global approximation properties of the new method. The theoretical results are supported by detailed numerical experiments. 相似文献
95.
The IR, 1H and 13C NMR spectra of six esters of 1-aryl-4-methyl-3- and 5-pyrazolecarboxylic acids are reported. On the basis of their spectra the 3- or 5-position of the substituent in such structural isomeric pairs can be established without recourse to the spectrum of the other member of the pair. The spectral data also give information on the conformation, which depends on the relative position and size of the hetero ring substituents. 相似文献
96.
Endre Szemerédi 《Foundations of Computational Mathematics》2016,16(6):1737-1749
We discuss results obtained jointly with Van Vu on the length of arithmetic progressions in \(\ell \)-fold sumsets of the form and where \(\mathcal {A}\) is a set of integers. Applications are also discussed.
相似文献
$$\begin{aligned} \ell \mathcal {A}=\{a_1+\dots +a_\ell ~|~a_i\in \mathcal {A}\} \end{aligned}$$
$$\begin{aligned} \ell \mathcal {A}=\{a_1+\dots +a_\ell ~|~a_i\in \mathcal {A}\text { all distinct}\}, \end{aligned}$$
97.
Rasheed Rashed Taleb Mansoor Hadeel S. Abdullah Thamer Adnan Juzsakova Tatjana Al-Jammal Noor Salman Ali Dawood Al-Shaikhly Rasha R. Le Phuoc Cuog Domokos Endre Abdulla Thaer A. 《Journal of Thermal Analysis and Calorimetry》2021,145(2):297-307
Journal of Thermal Analysis and Calorimetry - This paper deals with an advanced colorimetric method used to determine the catalase mimetic activity of V2O5 nanoparticles by measuring the decrease... 相似文献
98.
Dr. Eszter Boros Dr. Raja Srinivas Dr. Hee-Kyung Kim Prof. Arnold M. Raitsimring Dr. Andrei V. Astashkin Dr. Oleg G. Poluektov Dr. Jens Niklas Dr. Andrew D. Horning Prof. Bruce Tidor Prof. Peter Caravan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(20):5695-5698
Aqua ligands can undergo rapid internal rotation about the M−O bond. For magnetic resonance contrast agents, this rotation results in diminished relaxivity. Herein, we show that an intramolecular hydrogen bond to the aqua ligand can reduce this internal rotation and increase relaxivity. Molecular modeling was used to design a series of four Gd complexes capable of forming an intramolecular H-bond to the coordinated water ligand, and these complexes had anomalously high relaxivities compared to similar complexes lacking a H-bond acceptor. Molecular dynamics simulations supported the formation of a stable intramolecular H-bond, while alternative hypotheses that could explain the higher relaxivity were systematically ruled out. Intramolecular H-bonding represents a useful strategy to limit internal water rotational motion and increase relaxivity of Gd complexes. 相似文献
99.
Endre Boros Yves Crama Peter L. Hammer Toshihide Ibaraki Alexander Kogan Kazuhisa Makino 《Annals of Operations Research》2011,188(1):33-61
Learning from examples is a frequently arising challenge, with a large number of algorithms proposed in the classification,
data mining and machine learning literature. The evaluation of the quality of such algorithms is frequently carried out ex post, on an experimental basis: their performance is measured either by cross validation on benchmark data sets, or by clinical
trials. Few of these approaches evaluate the learning process ex ante, on its own merits. In this paper, we discuss a property of rule-based classifiers which we call “justifiability”, and which
focuses on the type of information extracted from the given training set in order to classify new observations. We investigate
some interesting mathematical properties of justifiable classifiers. In particular, we establish the existence of justifiable
classifiers, and we show that several well-known learning approaches, such as decision trees or nearest neighbor based methods,
automatically provide justifiable classifiers. We also identify maximal subsets of observations which must be classified in
the same way by every justifiable classifiers. Finally, we illustrate by a numerical example that using classifiers based
on “most justifiable” rules does not seem to lead to overfitting, even though it involves an element of optimization. 相似文献
100.
We study the path behaviour of general random walks, and that of their local times, on the 2-dimensional comb lattice C2 that is obtained from Z2 by removing all horizontal edges off the x-axis. We prove strong approximation results for such random walks and also for their local times. Concentrating mainly on the latter, we establish strong and weak limit theorems, including Strassen-type laws of the iterated logarithm, Hirsch-type laws, and weak convergence results in terms of functional convergence in distribution. 相似文献