全文获取类型
收费全文 | 289篇 |
免费 | 2篇 |
国内免费 | 4篇 |
专业分类
化学 | 200篇 |
晶体学 | 3篇 |
力学 | 14篇 |
数学 | 35篇 |
物理学 | 43篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 11篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 20篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 11篇 |
2008年 | 15篇 |
2007年 | 23篇 |
2006年 | 14篇 |
2005年 | 22篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有295条查询结果,搜索用时 15 毫秒
101.
Arroyo ST Martin-Romo JC Garcia AH Martín JA 《The journal of physical chemistry. A》2007,111(51):13515-13520
Molecular dynamics simulations of aqueous solutions at infinite dilution of the reaction of water with ethene: H2O + CH2CH2 --> CH3CH2OH were performed using Lennard-Jones 12-6-1 potentials to describe the solute-solvent interactions, and TIP3P to describe the water-water interactions. The Morokuma decomposition scheme of ab initio interaction energies at the SCF level and the dispersion component at the MP2 level were used to reproduce the molecular parameters of the solute-water interaction potentials. The results show that the functions that use the EX-PL-DIS-ES interaction model to describe the solvation of the reactant, transition state, and product systems lead to good values of the reaction (Delta G) and acceptable values of the activation (Delta G#) free energy as compared with those from using AMBER-derived parameters, using the available theoretical and experimental data as referents. 相似文献
102.
Igor A. Sedov Timur I. Magsumov Erin Hart Ashley M. Ramirez Sarah Cheeran Maribel Barrera Melissa Y. Horton Anisha Wadawadigi Olivia Zha Xin Y. Tong William E. AcreeJr. Michael H. Abraham 《Journal of solution chemistry》2017,46(12):2249-2267
A gas chromatographic headspace analysis method was used to experimentally determine gas-to-liquid partition coefficients and infinite dilution activity coefficients for 29 liquid organic solutes dissolved in triethylene glycol at 298.15 K. Solubilities were also determined at 298.15 K for 23 crystalline nonelectrolyte organic compounds in triethylene glycol based on spectroscopic absorbance measurements. The experimental results of the headspace chromatographic and spectroscopic solubility measurements were converted to gas-to-triethylene glycol and water-to-triethylene glycol partition coefficients, and molar solubility ratios using standard thermodynamic relationships. Expressions were derived for solute transfer into triethylene glycol by combining our measured experimental values with published literature data. Mathematical correlations based on the Abraham model describe the observed partition coefficient and solubility data to within 0.16 log10 units (or less). 相似文献
103.
Liliana Maribel Perez-Perez Lorena Armenta-Villegas Hisila Santacruz-Ortega Melesio Gutiérrez-Lomelí José Antonio Aguilar Francisco Javier Reynoso-Marin Miguel Angel Robles-García Ramón Enrique Robles-Zepeda Saúl Ruiz-Cruz Carmen Lizette Del-Toro-Sánchez 《Chemical Papers》2017,71(7):1331-1342
Antioxidant activity is a property of Anemopsis californica essential oil (ACO). However, ACO possesses volatile compounds that provide strong flavors and that are susceptible to degradation, complicating its application. An alternative is its encapsulation in a β-cyclodextrin (β-CD) matrix. Therefore, the characterization of β-CD–ACO inclusion complexes as an antioxidant prolonged-release system was the objective of this work. The ACO yield was 8.26 mg/g of dry sample. Elemicin (EL) (68.9%) and methyleugenol (ME) (11.7%) comprised the majority compounds identified by gas chromatography (GC). The β-CD–ACO inclusion complex, with a 90:10 ratio based on the precipitation technique, exhibited best percentage of recovery, greater ACO retention, and major antioxidant capacity determined by DPPH [2,2-diphenyl-1-picrylhydrazyl] and ABTS [2,2′-azino-bis-(3 ethylbenzothiazoline-6-sulfonic acid)] assays. Antioxidant activity was maintained during encapsulation. Free β-CD and β-CD:ACO presented the hysteresis phenomenon according to water sorption isotherms. A prolonged-release system was studied using different relative humidities (0, 33, 66, 96 and 100%). EL demonstrated 93.75% of release in highest relative humidity, while ME released completely. These results suggest application of the β-CD–ACO complex in systems in which it can be passively released and in controlled form, as in active food or drug packaging. 相似文献
104.
105.
Enantiomerically pure syn-1,2-diaryl-1,2-sulfanylamine derivatives can be obtained in a completely stereoselective manner by reaction of the benzylcarbanion Li-(S)-1 with N-phenyl (or PMP)-arylidene aldimines and further desulfinylation with t-BuLi. Theoretical studies at the DFT (mPW1PW91) level with the CPCM model, by using the Gaussian09 program, provide a good explanation for the stereochemical results. 相似文献
106.
S. Tolosa Arroyo A. Hidalgo García M. Moreno Alvero J. A. Sansón Martín 《Structural chemistry》2011,22(4):909-915
A procedure previously described by us is used for the theoretical study of chemical reactions in solution by means of molecular
dynamics simulation, with solute–solvent interaction potentials LJ (12-6-1) derived from ab initio quantum calculations. We
apply the procedure to the case of the neutral hydrolysis of methyl formate, HCOOCH3 + 3H2O → HCOOH + CH3OH + 2H2O in aqueous solution, via concerted and stepwise water-assisted mechanisms. We use the solvent as reaction coordinate, and
the free-energy curves for the calculation of the activation energies. The theoretical calculation for the thermodynamics
of this hydrolysis reaction in aqueous solution, assisted by three water molecules, is in agreement with the available experimental
information. In particular our study gives values of ΔG
≠ = 28.88 and 28.17 kcal/mol for the concerted and stepwise mechanisms, close to the experimental activation barrier of 28.8 kcal/mol,
and a significant improvement over the values of 48.05 and 45.66 kcal/mol found in another similar study using the PCM model. 相似文献
107.
Boyer AE Gallegos-Candela M Lins RC Kuklenyik Z Woolfitt A Moura H Kalb S Quinn CP Barr JR 《Molecules (Basel, Switzerland)》2011,16(3):2391-2413
Matrix-assisted laser-desorption time-of-flight (MALDI-TOF) mass spectrometry (MS) is a valuable high-throughput tool for peptide analysis. Liquid chromatography electrospray ionization (LC-ESI) tandem-MS provides sensitive and specific quantification of small molecules and peptides. The high analytic power of MS coupled with high-specificity substrates is ideally suited for detection and quantification of bacterial enzymatic activities. As specific examples of the MS applications in disease diagnosis and select agent detection, we describe recent advances in the analyses of two high profile protein toxin groups, the Bacillus anthracis toxins and the Clostridium botulinum neurotoxins. The two binary toxins produced by B. anthracis consist of protective antigen (PA) which combines with lethal factor (LF) and edema factor (EF), forming lethal toxin and edema toxin respectively. LF is a zinc-dependent endoprotease which hydrolyzes specific proteins involved in inflammation and immunity. EF is an adenylyl cyclase which converts ATP to cyclic-AMP. Toxin-specific enzyme activity for a strategically designed substrate, amplifies reaction products which are detected by MALDI-TOF-MS and LC-ESI-MS/MS. Pre-concentration/purification with toxin specific monoclonal antibodies provides additional specificity. These combined technologies have achieved high specificity, ultrasensitive detection and quantification of the anthrax toxins. We also describe potential applications to diseases of high public health impact, including Clostridium difficile glucosylating toxins and the Bordetella pertussis adenylyl cyclase. 相似文献
108.
109.
Biot C Castro W Botté CY Navarro M 《Dalton transactions (Cambridge, England : 2003)》2012,41(21):6335-6349
Despite recent encouraging advances against the disease, malaria remains a major public health problem affecting almost half a billion people and killing almost a million per annum. Due to a short arsenal of efficient antimalarial agents and the frequent appearance of resistance to the drugs in current use, which consequently reduce our means to treat patients, there is a very urgent and continuous need to develop new compounds. This perspective outlines a unique strategy for that purpose through the development of metal-based antimalarial agents. The examples presented here illustrate an attractive alternative to classical drugs. 相似文献
110.
In the study of Ring Theory, several concepts of dimension have appeared; among others we can find the Krull dimension, the Gabriel dimension and the Goldie dimension. These concepts have provided many interesting constructions. In a general context, these concepts are diffe nt, although there are some relations among them. 相似文献