全文获取类型
收费全文 | 304篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 242篇 |
力学 | 6篇 |
数学 | 35篇 |
物理学 | 37篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 12篇 |
2013年 | 18篇 |
2012年 | 18篇 |
2011年 | 24篇 |
2010年 | 16篇 |
2009年 | 20篇 |
2008年 | 12篇 |
2007年 | 23篇 |
2006年 | 16篇 |
2005年 | 14篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1967年 | 1篇 |
1966年 | 2篇 |
排序方式: 共有320条查询结果,搜索用时 390 毫秒
91.
Marcella S. R. Martins Myriam R. B. S. Delgado Ricardo Lüders Roberto Santana Richard A. Gonçalves Carolina P. de Almeida 《Journal of Heuristics》2018,24(1):25-47
Nowadays, a number of metaheuristics have been developed for efficiently solving multi-objective optimization problems. Estimation of distribution algorithms are a special class of metaheuristic that intensively apply probabilistic modeling and, as well as local search methods, are widely used to make the search more efficient. In this paper, we apply a Hybrid Multi-objective Bayesian Estimation of Distribution Algorithm (HMOBEDA) in multi and many objective scenarios by modeling the joint probability of decision variables, objectives, and the configuration parameters of an embedded local search (LS). We analyze the benefits of the online configuration of LS parameters by comparing the proposed approach with LS off-line versions using instances of the multi-objective knapsack problem with two to five and eight objectives. HMOBEDA is also compared with five advanced evolutionary methods using the same instances. Results show that HMOBEDA outperforms the other approaches including those with off-line configuration. HMOBEDA not only provides the best value for hypervolume indicator and IGD metric in most of the cases, but it also computes a very diverse solutions set close to the estimated Pareto front. 相似文献
92.
Marc Van den Bulcke Antoon Lievens Elodie Barbau-Piednoir Guillaume MbongoloMbella Nancy Roosens Myriam Sneyers Amaya Leunda Casi 《Analytical and bioanalytical chemistry》2010,396(6):2113-2123
The detection of genetically modified (GM) materials in food and feed products is a complex multi-step analytical process invoking screening, identification, and often quantification of the genetically modified organisms (GMO) present in a sample. “Combinatory qPCR SYBR®Green screening” (CoSYPS) is a matrix-based approach for determining the presence of GM plant materials in products. The CoSYPS decision-support system (DSS) interprets the analytical results of SYBR®GREEN qPCR analysis based on four values: the C t- and T m values and the LOD and LOQ for each method. A theoretical explanation of the different concepts applied in CoSYPS analysis is given (GMO Universe, “Prime number tracing”, matrix/combinatory approach) and documented using the RoundUp Ready soy GTS40-3-2 as an example. By applying a limited set of SYBR®GREEN qPCR methods and through application of a newly developed “prime number”-based algorithm, the nature of subsets of corresponding GMO in a sample can be determined. Together, these analyses provide guidance for semi-quantitative estimation of GMO presence in a food and feed product. 相似文献
93.
Ayat Abbood Claire Smadja Myriam Taverna Christine Herrenknecht 《Journal of chromatography. A》2010,1217(4):450-458
Separation of twelve enkephalins was investigated on a quaternary ammonium-embedded stationary phase (Stability BS-C23). Variation of buffer pH of the mobile phase highlighted the complex relationship between repulsive/attractive electrostatic interactions and the reversed-phase partitioning mechanism. The effect of three different anions employed as additives (phosphate, chloride and perchlorate) was examined at various concentrations and two pH values (acidic and neutral). At pH 2.5, an increase in the anion eluent concentration resulted in a higher retention factors of positively charged enkephalins. This effect was more pronounced when perchlorate ions were added to the mobile phase rather than phosphate and chloride ions, due to chaotropic and ion-pairing effects. In contrast, at pH 7.5, retention factors of negatively charged enkephalins decreased when these salts were added, due to an anion-exchange mechanism. Perchlorate caused a sharper decrease than chloride and phosphate anions did. The results presented here provide insight into the possible adjustment of retention and separation of peptides on a mixed-mode stationary phase (BS-C23) by a careful control of the buffer pH, the nature and concentration of anions, added to the buffer, and organic modifier content. 相似文献
94.
95.
Myriam E. Rodriguez Virginia E. Diz Josefina Awruch Lelia E. Dicelio 《Photochemistry and photobiology》2010,86(3):513-519
The photophysical properties of lipophilic phthalocyanines encapsulated into a polymer and two different gels were studied in order to predict their photosensitizing efficacy in vivo. Photophysical techniques for solid phase were adapted for light dispersing samples. Gel formulation of two tetrasubstituted phthalocyanines, tetra-t-butylphthalocyaninato zinc(II) ( 1 ), tetrakis(1,1-dimethyl-2-phthalimido)ethylphtalocyaninatozinc(II) ( 2 ) and two octasubstituted phthalocyanines, 2,3,9,10,16,17,23,24-octakis(decyloxy)phthalocyaninatozinc(II) ( 3 ) and 2,3,9,10,16,17,23,24-octakis[(N,N-dimethylamino)ethylsulfanyl]phthalocyaninatozinc(II) ( 4 ) were investigated for their possible use in photodynamic therapy for topical purposes. Supporting the fact that gel formulation improves the photophysical properties of phthalocyanines, singlet molecular oxygen quantum yield (ΦΔ) values for 1 – 4 zinc(II) phthalocyaninates in Lutrol® F 127-Cremophor® RH 40 were 0.60, 0.60, 0.20 and 0.26, respectively. Permeation studies showed that no release of phthalocyanines occurs, thus indicating there should be no risk of generalized skin photosensitivity in areas other than the dye-deposition site. 相似文献
96.
Myriam Ounaies 《Analysis Mathematica》2003,29(1):59-74
We study interpolating discrete varieties for weighted spaces Ap(Cn) of entire functions such that supzC
n|f(z)|exp(-B p(z))< for some B>0. We give a necessary and sufficient condition for a finite union of interpolating discrete varieties to be itself interpolating. Then we use L2 techniques for ∂ to give a sufficient geometric interpolating condition. 相似文献
97.
We prove three theorems. First, Lovászs theorem about
minimal imperfect clutters, including also Padbergs
corollaries. Second, Lehmans result on minimal nonideal
clutters. Third, a common generalization of these two. The
endeavor of working out a common denominator for Lovászs and
Lehmans theorems leads, besides the common generalization, to a
better understanding and simple polyhedral proofs of
both.* Visiting of the French Ministry of Research and
Technology, laboratoire LEIBNIZ, Grenoble, November 1995—April
1996. 相似文献
98.
99.
Simon T. Ingate Jos L. Marco Myriam Witvrouw Cristophe Pannecouque Erik De Clercq 《Tetrahedron》1997,53(52):17795-17814
The synthesis, and anti HIV-1 activity, of new derivatives of 4-amino-1,2-oxathiole 2,2-dioxide (3, 5, 6 and 9) and 4-amino-2,3-dihydroisothiazole 1,1-dioxide (14), a new heterocyclic ring system, is described. 相似文献
100.
Balaban TS Goddard R Linke-Schaetzel M Lehn JM 《Journal of the American Chemical Society》2003,125(14):4233-4239
The 2-aminopyrimidin-5-yl ligand is revealed to be a promising candidate for the construction of supramolecular porphyrin arrays with broad absorption bands for efficient light-harvesting. 10-Mono- and 10,20-di(2-aminopyrimidin-5-yl) derivatives of 5,15-bis(3,5-di-tert-butylphenyl)porphyrin have been synthesized in high yield. Their Zn(II) salts show variable concentration and temperature-dependent UV/vis spectra in solution, consistent with supramolecular aggregation. Whereas the FAB mass spectra of the monosubsituted derivative in toluene suggest the formation of a tetramer at high concentrations and low temperatures (estimated association free enthalpy Delta H = 220 +/- 10 kJ/mol), the larger splitting of the Sorret band (ca. 40 nm) in the variable temperature UV/vis spectra of the disubstituted bis(3,5-di-tert-butylphenyl)porphyrin is indicative of yet higher aggregates involving both 2-aminopyrimidin-5-yl groups. The tetrameric nature of the monosubsituted derivative is confirmed by X-ray analysis, which reveals that two of the 2-aminopyrimidin-5-yl groups are encapsulated by the aggregate and consequently are prevented from undergoing hydrogen bonding. NMR studies show there is no exchange of the 2-aminopyrimidin-5-yl groups, so the tetramer is rigid, which is confirmed by molecular modeling calculations. The tetramer formation is governed by pi-pi interactions, metal coordination, and hydrogen bonding. The di(2-aminopyrimidin-5-yl) derivative forms strongly scattering solutions, which upon standing form green flocculate precipitates, reminiscent of shaken suspensions of bacteriochlorophyll c. 相似文献