全文获取类型
收费全文 | 325篇 |
免费 | 26篇 |
国内免费 | 1篇 |
专业分类
化学 | 284篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 36篇 |
物理学 | 26篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 25篇 |
2012年 | 33篇 |
2011年 | 30篇 |
2010年 | 18篇 |
2009年 | 19篇 |
2008年 | 14篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 23篇 |
2004年 | 17篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1981年 | 4篇 |
1972年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有352条查询结果,搜索用时 15 毫秒
101.
The successful separation of the disaccharide lactose from a complex mixture of human milk oligosaccharides (HMOS) with the continuous chromatography of simulated moving bed (SMB) technique is described. Since lactose is the main carbohydrate in human milk with well-known functions for the infant, it is necessary to separate it from the rest of the oligosaccharides to divide them into less complex fractions and analyse their partial unknown functions. For separation of lactose from HMOS two different stationary phases (size-exclusion gel as well as ion-exchange gel) were used. As the main result, it is shown that a size-exclusion gel with the particle size of 50-100 microm and porosity of 50 A was the preferred stationary phase for our separation process with almost complete lactose separation and stable conditions. 相似文献
102.
Dramićanin T Dramićanin MD Jokanović V Nikolić-Vukosavljević D Dimitrijević B 《Photochemistry and photobiology》2005,81(6):1554-1558
Specimens of malignant and normal female human breast tissues were analyzed after surgery by means of synchronous luminescence spectroscopy. Measurements were performed in the ranges of excitation wavelengths from 330 to 650 nm and synchronous wavelengths from 30 to 120 nm to obtain ordinary and first derivative three-dimensional total synchronous luminescence spectra (3d-TSLS) of each specimen. Arithmetic mean of these spectra has been calculated for normal and malignant specimens and analyzed to establish criteria for tissue differentiation. Spectral domain volumes (volumes below luminescence intensity surface) and mean spectral slopes have been calculated and also analyzed as tissue discrimination criteria. The obtained results are discussed in view of the possible relevance of synchronous luminescence spectroscopy in discrimination between normal and malignant breast tissue. 相似文献
103.
Vaclav Pitthard Martina Griesser Sabine Stanek Tatjana Bayerova 《Macromolecular Symposia》2006,238(1):37-45
Within the Kunsthistorisches Museum (KHM), Vienna, three off-line GC-MS analytical procedures for the identification of natural organic media have been refined, tested, and validated for the use in investigating original, historic works of art. The analysis of a sample from a Greek terracotta statue suggested that the white ground layer of the polychromy, still partly present today, contained a gum-based binding medium. Furthermore, a procedure for the simultaneous analysis of oils, waxes and resins was applied to the identification of the composition of the varnish layer from the 16th century painting “Lucretia” by Jacopo Negretti (1480–1528). In addition, in a collaboration with the Department for Conservation and Restoration, University of Applied Arts, Vienna, a series of samples from paintings on wooden panels from the Buddhist temple complex in Nako, Himachal Pradesh, India, was investigated for the presence of proteinaceous binding media. 相似文献
104.
Elke Debroye Prof. Sophie Laurent Prof. Luce Vander Elst Prof. Robert N. Muller Prof. Tatjana N. Parac‐Vogt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(47):16019-16028
Six diethylene triamine pentaacetic acid (DTPA) bisamide derivatives functionalized with p‐toluidine (DTPA‐BTolA), 6‐aminocoumarin (DTPA‐BCoumA), 1‐naphthalene methylamine (DTPA‐BNaphA), 4‐ethynylaniline (DTPA‐BEthA), p‐dodecylaniline (DTPA‐BC12PheA) and p‐tetradecyl‐aniline (DTPA‐BC14PheA) were coordinated to dysprosium(III) and the magnetic and optical properties of the complexes were examined in detail. The complexes consisting of amphiphilic ligands (DTPA‐BC12PheA and DTPA‐BC14PheA) were further assembled into mixed micelles. Upon excitation into the ligand levels, the complexes display characteristic DyIII emission with quantum yields of 0.3–0.5 % despite the presence of one water molecule in the first coordination sphere. A deeper insight into the energy‐transfer processes has been obtained by studying the photophysical properties of the corresponding GdIII complexes. Since the luminescence quenching effect is decreased by the intervention of non‐ionic surfactant, quantum yields up to 1 % are obtained for the micelles. The transverse relaxivity r2 per DyIII ion at 500 MHz and 310 K reaches a maximum value of 27.4 s?1 mM ?1 for Dy‐DTPA‐BEthA and 36.0 s?1 mM ?1 for the Dy‐DTPA‐BC12PheA assemblies compared with a value of 0.8 s?1 mM ?1 for Dy‐DTPA. The efficient T2 relaxation, especially at high magnetic field strengths, is sustained by the high magnetic moment of the dysprosium ion, the coordination of water molecules with slow water exchange kinetics and long rotational correlation times. These findings open the way to the further development of bimodal optical and magnetic resonance imaging probes starting from single lanthanide compounds. 相似文献
105.
Stefan Badza Tatjana Jevremovic 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(1):427-431
The main motivation in studying different types of rice was to determine how processing of rice affects its mineral composition, and to compare how it affects rice dietary intake. Specifically the estimated difference in between the brown and white rice produced in Japan and California are studied. These various rice samples were analyzed using neutron activation analysis technique available at the Utah Nuclear Engineering Program (UNEP). Samples were prepared using novel technique developed at UNEP and submitted for short and long irradiation. The detected elements were As, Br, Cl, Cd, Mn, Na, K. The concentrations of Mn, K and Na are significantly higher in the brown then in the white rice, while As, Br and Cl have more homogeneous presence and therefore smaller difference in concentration. Elemental concentration was compared with The Institute of Medicine (IOM) in the United States values of recommended dietary allowance and Food and Drug Administration (FDA) limits for harmful elements. From these measurements, only the concentration of Mn in rice satisfies daily needs in the range set as defined by IOM. The concentrations of potentially harmful elements are lower than FDA limits. 相似文献
106.
Oksana V. Dudka Vjacheslav A. Ksenofontov Alexei A. Mazilov Tatjana I. Mazilova Evgenij V. Sadanov 《辐射效应与固体损伤》2016,171(7-8):606-614
Using low-temperature field ion microscope techniques, we studied at the atomic level the elementary events of radiation-induced surface diffusion of tungsten adatoms on the ideally pristine surface. The experiments on surface-damage formation and adatom displacements have been performed in situ with a source of neutral helium atoms with an energy of 5?keV. It was demonstrated that the low-energy He atomic bombardment at grazing incidence was able to induce a substantial surface mobility of adatoms. Most of the radiation-induced adatom displacements were oriented along the direction of irradiation. The long impact-induced jumps of adatoms, spanning more than a nearest-neighbor distance, were revealed. Performed molecular dynamics simulations reproduce the general experimental trends and conclusions. 相似文献
107.
108.
109.
Sergiy Kotrechko Oleksandr Ovsjannikov Tatjana Mazilova Igor Mikhailovskij Evgenij Sadanov 《哲学杂志》2013,93(12):930-943
AbstractExperimental value of strength of nano-sized crystal under uniform triaxial (hydrostatic) tension was obtained for the first time. Strength was measured by in situ high-field mechanical testing of tungsten defect-free nano-sized specimen carried out inside a field-ion microscope. At temperature 77 K, this strength is 28 ± 3 GPa. Based on the MD simulation findings, it is ascertained that under these conditions the instability of an entire nano-sized specimen (global instability) is initiated by the Bain transition within a local region of the specimen. The model of ‘fluctuation-induced Bain transition’ is offered. Within the framework of the model proposed, it is exhibited that possibility of realisation of such local Bain transition under global hydrostatic tension is due to the fluctuation of local tensile stresses. In general, it is shown that fluctuation-induced Bain transition governs the level of the strength of nano-sized bcc crystals under hydrostatic tension. 相似文献
110.
Tatjana Gric Liudmila Nickelson Romanas Martavicius 《Applied Physics A: Materials Science & Processing》2014,115(2):575-580
Here we present the analyses of the open (without a metal screen) ridged and photonic waveguide structures by means of the electrodynamical rigorous method of the Singular Integral Equations (SIE). The waveguides are made of a lossy silicon carbide (SiC) material. We have discovered peculiarities of the dispersion characteristics. We have found the numerical solutions to the complex wave equations. The dispersion characteristics of both waveguide structures are numerically analyzed and compared with each other. It was found that the losses of modes propagating in the waveguide structure with air openings (channels) are smaller than the losses in the waveguide structure without air openings. We came to the conclusion that it is possible to optimize the dispersion characteristics by adding openings of different shapes and sizes into the waveguide structures. 相似文献