全文获取类型
收费全文 | 553篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
化学 | 358篇 |
晶体学 | 3篇 |
力学 | 4篇 |
数学 | 115篇 |
物理学 | 95篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 17篇 |
2016年 | 24篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 28篇 |
2012年 | 39篇 |
2011年 | 53篇 |
2010年 | 28篇 |
2009年 | 34篇 |
2008年 | 30篇 |
2007年 | 43篇 |
2006年 | 37篇 |
2005年 | 22篇 |
2004年 | 18篇 |
2003年 | 11篇 |
2002年 | 28篇 |
2001年 | 13篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
排序方式: 共有575条查询结果,搜索用时 0 毫秒
61.
Mauricio Arias Javier Concepción Irma Crivelli Alvaro Delgadillo Ramiro Díaz Angélica Francois Francisco Gajardo Rosa López Ana María Leiva Bárbara Loeb 《Chemical physics》2006
Different strategies to improve the excited state properties of polypyridinic complexes by varying ligand structure and molecular geometry are described. Bidentate and tetradentate ligands based on fragments as dipyrido[3,2-a:2′,3′-c]phenazine, dppz, and pyrazino[2,3-f][1,10]-phenanthroline, ppl, have been used. Quinonic residues were fused to these basic units to improve acceptor properties. Photophysical studies were performed in order to test theoretical predictions. 相似文献
62.
Mauricio Gomes Constantino Valdemar Lacerda Júnior Gil Valdo Jos Da Silva 《Journal of heterocyclic chemistry》2003,40(2):369-371
A new and efficient 2‐step synthesis of 3‐hydroxychromone is described. Commercially available chromone is converted to the corresponding epoxide which is rearranged with niobium pentachloride to 3‐hydroxychromone in 61% overall yield. 相似文献
63.
Gil V. J. da Silva Mauricio G. Constantino Cláudio F. Tormena R. Thomas Williamson Brian L. Marquez 《Magnetic resonance in chemistry : MRC》2007,45(3):282-282
The original article to which this Erratum refers was published in Magnetic Resonance in volume 45 issue 1. 相似文献
64.
65.
Jarod Alper Tristram Bogart Mauricio Velasco 《Foundations of Computational Mathematics》2017,17(3):829-836
We prove that the determinantal complexity of a hypersurface of degree \(d > 2\) is bounded below by one more than the codimension of the singular locus, provided that this codimension is at least 5. As a result, we obtain that the determinantal complexity of the \(3 \times 3\) permanent is 7. We also prove that for \(n> 3\), there is no nonsingular hypersurface in \({\mathbb {P}}^n\) of degree d that has an expression as a determinant of a \(d \times d\) matrix of linear forms, while on the other hand for \(n \le 3\), a general determinantal expression is nonsingular. Finally, we answer a question of Ressayre by showing that the determinantal complexity of the unique (singular) cubic surface containing a single line is 5. 相似文献
66.
Mauricio ROMO 《数学年刊B辑(英文版)》2017,38(4):937-962
The author reviews some recent developments in Chern-Simons theory on a hyperbolic 3-manifold M with complex gauge group G.The author focuses on the case of G =SL(N,C) and M being a knot complement:M =S3 \ k.The main result presented in this note is the cluster partition function,a computational tool that uses cluster algebra techniques to evaluate the Chern-Simons path integral for G =SL(N,C).He also reviews various applications and open questions regarding the cluster partition function and some of its relation with string theory. 相似文献
67.
We introduce a family of braided Hopf algebras that (in characteristic zero) generalizes the rank 1 Hopf algebras introduced by Krop and Radford and we study its cleft extensions. 相似文献
68.
Mario Llano-RestrepoAuthor Vitae Y. Mauricio Muñoz-MuñozAuthor Vitae 《Fluid Phase Equilibria》2011,307(1):45-57
Due to the economics of the ethylene market and the subsidized production of fermentation-based ethanol in some countries, use of the ethylene hydration process to make ethanol has been steadily declining. The economics of this process might improve by combining the reaction and separation in a reactive distillation column, whose conceptual design requires a study of the combined chemical and phase equilibrium (CPE) of the reacting system. In this work, the Peng-Robinson-Stryjek-Vera equation of state was combined with the UNIQUAC activity coefficient model through the Wong-Sandler (WS) mixing rules in order to correlate the available experimental data for the vapor-liquid equilibria (VLE) of the ethylene-water, ethylene-ethanol, and ethanol-water binary systems at 200 °C. The interaction energies of the UNIQUAC model and the binary interaction coefficient of the WS mixing rules were used as the fitting parameters. From the optimum values of these parameters, both the VLE and the combined CPE of the ethylene-water-ethanol ternary system were predicted at 200 °C and various pressures. At this temperature, the catalytic activity of a H-pentasil zeolite has already been reported to exhibit a maximum for ethylene hydration, and also the experimentally measured two-phase region of the ternary system is sufficiently wide. By means of the reactive flash method, the chemical equilibrium compositions of the liquid and vapor phases were determined for several pressures, and the equilibrium conversion and the vapor fraction were calculated as functions of the ethylene to water feed mole ratio. It turns out that the vapor-liquid mixed-phase hydration of ethylene achieves equilibrium conversions much higher than those computed for a vapor-phase reaction that would hypothetically occur at the same conditions of pressure and feed mole ratio. It was found that the reactive phase diagram of the ternary system exhibits a critical point at 200 °C and 155 atm. 相似文献
69.
Zahra Shariatinia Mauricio F. Erben Carlos O. Della Védova Majid Abdous Saman Azodi 《Structural chemistry》2011,22(6):1347-1352
Intermolecular interactions between α-, β-glucose, and methacrylic acid (MAA) have been investigated. Twenty-two possible
conformations have been optimized at the DFT(B3LYP) level of theory with the 6-31G(d) basis set. The geometrical parameters
for the most stable configurations of hydrogen bonding sites in the optimized systems have been determined. The binding energies
ΔE
bind have been calculated at the MP2/6-311++G(d,p) level of approximation taking into account the basis set superposition error
(BSSE) and the zero-point vibrational energies corrections. Results indicate that the most stabilized complexes form hydrogen
bonds either through carboxylic and hemiacetal oxygen atoms acting as proton acceptors. Both, α- and β-anomers are studied
in the pyranose six-membered ring. In all complexes, the nuclear quadrupole coupling constants (χ) for 17O nuclei were obtained about 10.0 MHz, while for the 2H atoms they vary from ≈200.0 to ≈350.0 kHz. 相似文献
70.
Leopoldo Eduardo Cárdenas-Barrón Hui-Ming Wee Mauricio F. Blos 《Mathematical and Computer Modelling》2011,53(5-6):991-997
In the past, economic order quantity (EOQ) and economic production quantity (EPQ) were treated independently from the viewpoints of the buyer or the vendor. In most cases, the optimal solution for one player was non-optimal to the other player. In today’s competitive markets, close cooperation between the vendor and the buyer is necessary to reduce the joint inventory cost and the response time of the vendor–buyer system. The successful experiences of National Semiconductor, Wal-Mart, and Procter and Gamble have demonstrated that integrating the supply chain has significantly influenced the company’s performance and market share (Simchi-Levi et al. (2000) [1]). Recently, Yang et al. (2007) [2] presented an inventory model to determine the economic lot size for both the vendor and buyer, and the number of deliveries in an integrated two stage supply chain. In this paper, we present an alternative approach to determine the global optimal inventory policy for the vendor–buyer integrated system using arithmetic–geometric inequality. 相似文献