全文获取类型
收费全文 | 415篇 |
免费 | 18篇 |
专业分类
化学 | 332篇 |
晶体学 | 4篇 |
力学 | 1篇 |
数学 | 41篇 |
物理学 | 55篇 |
出版年
2023年 | 6篇 |
2022年 | 18篇 |
2021年 | 23篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 19篇 |
2015年 | 15篇 |
2014年 | 25篇 |
2013年 | 22篇 |
2012年 | 35篇 |
2011年 | 55篇 |
2010年 | 23篇 |
2009年 | 15篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 17篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有433条查询结果,搜索用时 15 毫秒
61.
Bojan Šarac Janez Cerkovnik Bernard Ancian Guillaume Mériguet Gaëlle M. Roger Serge Durand-Vidal Marija Bešter-Rogač 《Colloid and polymer science》2011,289(14):1597-1607
The complex aggregation processes of dodecyltrimethylammonium chloride (DTAC) have been studied in dilute solutions of sodium
salicylate (NaSal) by isothermal titration calorimetry and electrical conductivity at temperatures between 278.15 K and 318.15 K.
A structural transformation that was dependent on the concentrations of DTAC and NaSal was observed. The micellization process
in dilute solutions of DTAC has been subjected to a detailed thermodynamic analysis and shown to occur at considerably lower
critical micelle concentrations than reported for DTAC in water and NaCl solutions. Gibbs free energy, Δ
mic
G
o, and entropy, Δ
mic
S
o, were deduced by taking into account the degree of micelle ionization, β, estimated from conductivity measurements. From the temperature dependence of the enthalpy of micellization, Δ
mic
H
o, the heat capacities of micellization, Dmic cpo {\Delta_{{{\rm mic} }}}c_p^o were determined and discussed in terms of the removal of large areas of non-polar surface from contact with water upon micellization.
The process is exothermic at all temperatures, indicating, in addition to the hydrophobic effect, the presence of strong interactions
between surfactant and salicylate ions. These were confirmed by 1H NMR spectroscopy and diffusion NMR experiments. Salicylate ions not only interact with the headgroups but also insert further
into the micelle core. At c
NaSal/c
DTAC > 2.5, the structural rearrangements occur even at relatively low concentrations of NaSal. 相似文献
62.
Masković M Dotsikas Y Malenović A Jancić-Stojanović B Ivanović D Medenica M 《Journal of AOAC International》2011,94(3):723-734
This paper describes the development and validation of a microemulsion liquid chromatography (MELC) method for simultaneous determination of perindopril tert-butylamine and its impurities in bulk active substances and the pharmaceutical dosage form of tablets. An appropriate resolution with reasonable retention times was obtained for a microemulsion containing 0.24% (w/v) butyl acetate, 0.30% (w/v) ethyl acetate, 2% (w/v) sodium dodecyl sulfate, 7.75% (w/v) n-butanol, and 20.0 mM potassium dihydrogen phosphate, the pH of which was adjusted to 3.70 with 85% orthophosphoric acid. Separations were performed on a Nucleosil 120-5 butyl modified (C4), 250 x 4 mm, 5 microm particle size silica column at 40 degrees C, with a mobile phase flow rate of 1.25 mL/min. UV detection was performed at 254 nm. The established method was subjected to method validation, and required validation parameters were defined. Robustness testing, an important part of method validation, was performed as well. Since robustness validation can be conducted using different experimental designs, the Plackett-Burman design was applied due to its possibility of testing many factors at the same time. The validated MELC method was found to be suitable for the simultaneous determination of perindopril tert-butylamine and its impurities in pharmaceuticals. 相似文献
63.
The histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) was used to turn on the biosynthesis of EGM-556, a new cyclodepsipeptide of hybrid biosynthetic origin, isolated from the Floridian marine sediment-derived fungus Microascus sp. The absolute configurations of three chiral centers were determined by Marfey's derivatization. EGM-556 represents one of the few examples in which silent biosynthetic genes, encoding a new secondary metabolite, were activated by means of epigenetic manipulation of the fungal metabolome. 相似文献
64.
Marija Miloševi? Miljana Jovanovi? 《Journal of Computational and Applied Mathematics》2011,235(15):4439-4451
The subject of this paper is the analytic approximation method for solving stochastic differential equations with time-dependent delay. Approximate equations are defined on equidistant partitions of the time interval, and their coefficients are Taylor approximations of the coefficients of the initial equation. It will be shown, without making any restrictive assumption for the delay function, that the approximate solutions converge in Lp-norm and with probability 1 to the solution of the initial equation. Also, the rate of the Lp convergence increases when the degrees in the Taylor approximations increase, analogously to what is found in real analysis. At the end, a procedure will be presented which allows the application of this method, with the assumption of continuity of the delay function. 相似文献
65.
Central European Journal of Operations Research - Industry 4.0 (I4.0) implies a group of technologies, organisational concepts and management principles to improve the performance of manufacturing... 相似文献
66.
67.
Darja Jenko Andreja Bencan Barbara Malic Janez Holc Marija Kosec 《Microscopy and microanalysis》2005,11(6):572-580
Using electron microscopy, K0.5Na0.5NbO3 (KNN) ceramics sintered at 1030 degrees C for 8 h and 1100 degrees C for 2 and 24 h was studied. The scanning electron microscopy and X-ray spectrometry revealed that the materials consisted of a matrix phase in which the (Na+K)/Nb ratio corresponded closely to the nominal composition and a small amount of Nb-rich secondary phase. A bimodal microstructure of cube-shaped grains was revealed in the fracture and thermally-etched surfaces of the KNN. In the ceramics sintered at 1100 degrees C, the larger grains (up to 30 mum across), contained angular trapped pores. The transmission electron microscopy analysis revealed that the crystal planes of the grains bordering the intragranular pore faces were of the {100} family with respect to the simple perovskite cell. Ferroelectric domains were observed in the grains of this material. 相似文献
68.
Marija Vilfan Robert Blinc Venceslav Rutar 《Molecular Crystals and Liquid Crystals》2013,570(1-3):271-281
The frequency dispersion of the proton spin-lattice relaxation rates T?1 1 in the ferroelectric smectic phases of DOBAMBC has been determined in the MHz region and analyzed in terms of the order fluctuations, self-diffusion, and rotational contributions to T?1 1. In the smectic C* phase the main rate determining contribution are order fluctuations with a T?1 1 ∝ ν?1/2 L frequency dependence, whereas in the smectic H* phase the translational diffusion, which is slower than in the smectic H* phase, determines the dispersion of T?1 1. 相似文献
69.
Multi body system contains finite number of rigid bodies that are placed on each axis, which do not intersect each other. Derivatives of the linear momentum and angular momentum with respect to time by use mass moment vectors and vector rotators for pole and axis, are determined. A number of theorems are defined. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
70.
Marija argonja Darko Mekterovi Paula
urga Jagoda Ravli‐Gulan Iva Bogdanovi Radovi Gordana
auhar 《X射线光谱测定》2021,50(1):68-79
During metal welding and cutting, large amounts of particulate matter (PM) are produced that might represent a significant health risk for the exposed workers. In the present pilot study, we performed an elemental analysis of fine PM collected in a metal workshop. Also, elemental analysis of the hair and nail samples collected from workers exposed to the workshop dust and control group was done. Concentrations of 15 elements in PM were measured with X‐Ray Fluorescence (XRF) and Particle Induced X‐ray Emission (PIXE), whereas inductively coupled plasma mass spectrometry (ICP‐MS) was used to determine 12 elements in hair and nail samples. Mean 8‐hr concentrations of PM2.5, Fe, and Mn in the vicinity of welders were up to 1803, 860, and 30 μg/m3, respectively, whereas in the nearby city, daily PM2.5 concentrations are on average 11 μg/m3. We found that several elements, especially Fe and Mn, had substantially higher concentrations in hair and nail samples of exposed workers than in the control group, which indicates the accumulation of metals in workers' tissues, although limit values were not exceeded. 相似文献