全文获取类型
收费全文 | 74篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 50篇 |
力学 | 1篇 |
数学 | 2篇 |
物理学 | 26篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 11篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2007年 | 1篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1986年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1963年 | 2篇 |
1962年 | 2篇 |
1958年 | 1篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有79条查询结果,搜索用时 31 毫秒
1.
Development of a 100 MeV CW proton LINAC has been planned at CAT. This LINAC will be needing CW rf power in the frequency
ranges of 350 MHz and 700 MHz for its RFQ and DTL/CCDTL/SFDTL structures respectively. The power to the accelerating structures
will be produced by either 1 MW CW or 250 kW CW klystrons/inductive output tubes (HOM IOTs). The power needed by respective
feed points in the structure is max. 250 kW which will be powered by splitting the power from 1 MW klystron/klystrode into
four channels by using a wave-guide system. In case of using 250 kW tubes the power to the structures will be provided directly
from each tube. Two types of wave-guide transmission system have been considered, viz, WR 2300 for 350 MHz rf needs and WR
1500 for 700 MHz rf needs. The typical wave-guide system has been designed using the 1 MW CW klystron followed by wave-guide
filter, dual directional coupler, high-power circulator, three 3 dB magic TEE power dividers to split the main channel into
four equal channels of 250 kW each. Each individual channel has dual directional couplers, flexible wave-guide sections and
high power ceramic vacuum window. The circulator and each power divider is terminated into the isolated ports by high power
CW loads. Out of the four channels three channels have phase shifters. Present paper describes the technological aspects and
design specifications-considerations for these stringent requirements. 相似文献
2.
D. Purushottam 《Fresenius' Journal of Analytical Chemistry》1962,188(6):425-428
Summary A simple and rapid field Chromatographic method for the determination of thorium in ppm quantities in rocks, soils and low grade ores using paper strip chromatography is described. An aliquot of an hydrochloric acid solution of the sample is taken on a special paper (Chromatographic paper of C.R.L./l grade) and the paper is then placed into a beaker containing the solvent mixture consisting of methyl alcohol, acetone, 2-thenoyl trifluoroacetone and hydrochloric acid in the ratio 12 ml6 ml0.04 g2 ml (13) respectively.A saturated alcoholic solution of alizarin atph 2.8-2.4 is used as developing reagent.This method is applicable to samples containing from 0.2 ppm to 1000 ppm of thorium.
Zusammenfassung Eine einfache und schnell durchführbare Feldmethode zur papierchromatographischen Bestimmung von ppm-Mengen Thorium in Gesteinen, Böden und Erzen niederen Gehaltes wird beschrieben. Hierbei wird ein Anteil der salzsauren Probelösung auf ein Spezialpapier (C.R.L./ 1 grade) aufgebracht und dieses in einem Becherglas mit einem Gemisch aus Methanol, Aceton, 2-Thenoxyltrifluoraceton und Salzsäure (12 ml 6 ml0,04 g2 ml [13]) chromatographiert. Zur Entwicklung dient eine gesättigte alkoholische Alizarinlösung (ph 2,8-2,4). 0,2–1000 ppm Thorium können nach diesen Verfahren bestimmt werden.相似文献
3.
Landa Purushottam Unnikrishnan V. B. Dattatraya Gautam Rawale Mansi Gujrati Surya Dev Mishra Sajeev T. K. Neelesh C. Reddy Srinivasa Rao Adusumalli Ram Kumar Mishra Vishal Rai 《Chemical science》2020,11(48):13137
Analytically pure proteins are indispensable for diverse applications, including therapeutics. Here, we report a methodology where a single amino acid, glycine, enables metal-free protein purification. This robust platform is enabled by a Gly-tag resin for site-specific capture, enrichment, and release through chemically triggered C–C bond dissociation by resonance-assisted electron density polarization.Gly-tag resin precisely captures and releases a protein with one glycine at the N-terminus. The user-friendly protocol delivers analytically pure protein free of metal contaminants. 相似文献
4.
Spectroscopic studies on the mode of interaction of an anticancer drug with bovine serum albumin 总被引:3,自引:0,他引:3
The mechanism of interaction of vinblastin sulphate (VBS) with bovine serum albumin (BSA) has been reported. Association constant for VBS-BSA binding was found to be 3.146+/-0.06 x 10(4) M(-1). Stern-Volmer analysis of fluorescence quenching data showed that the fraction of fluorophore (protein) accessible to the quencher (drug) was close to unity indicating thereby that both tryptophan residues of BSA are involved in drug-protein interaction. The rate constant for quenching, greater than 10(10) M(-1) S(-1), indicated that the drug-binding site is in close proximity to tryptophan residues of BSA. Binding studies in the presence of an hydrophobic probe, 8-anilino-1-naphthalein-sulphonic acid, sodium salt (ANS) indicated that there is hydrophobic interaction between VBS and probe and they do not share common sites in BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of VBS to BSA involves predominant hydrophobic forces. The effects of some additives and paracetamol on binding of VBS-BSA have also been investigated. The CD spectrum of BSA in presence of VBS shows that the binding of VBS leads to change in the helicity of BSA. 相似文献
5.
Binita Ghosh Purushottam Chakraborty 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(3):518-524
Although electronics technologies have made great advances in device speed, optical devices can function in the time domain
inaccessible to electronics. In the time domain less than 1 ps, optical devices have no competition. Photonic or optical devices
are designed to switch and process light signals without converting them to electronic form. The major advantages that these
devices offer are speed and preservation of bandwidth. The switching is accomplished through changes in refractive index of
the material that are proportional to the light intensity. The third-order optical susceptibility, χ(3), known as the optical Kerr susceptibility which is related to the non-linear part of the total refractive index, is the nonlinearity
which provides this particular feature. Future opportunities in photonic switching and information processing will depend
critically on the development of improved photonic materials with enhanced Kerr susceptibilities, as these materials are still
in a relatively early stage of development. Different glass systems are now under investigation to increase their nonlinearity
by introducing a variety of modifiers into the glass-network. Ion implantation is an attractive method for inducing colloid
formation at a high local concentration unattainable by the melt-glass fabrication process and for confining the non-linearities
to specific patterned regions in a variety of host matrices. Recent works on metal-ion implanted colloid generation in bulk
fused silica glasses have shown that these nanocluster-glass composites under favourable circumstances have significant enhancement
of χ(3) with picosecond to femtosecond temporal responses. 相似文献
6.
Thermochemistry of gas-phase ion-water clusters together with estimates of the hydration free energy of the clusters and the water ligands are used to calculate the hydration free energy of the ion. Often the hydration calculations use a continuum model of the solvent. The primitive quasichemical approximation to the quasichemical theory provides a transparent framework to anchor such efforts. Here we evaluate the approximations inherent in the primitive quasichemical approach and elucidate the different roles of the bulk medium. We find that the bulk medium can stabilize configurations of the cluster that are usually not observed in the gas phase, while also simultaneously lowering the excess chemical potential of the ion. This effect is more pronounced for soft ions. Since the coordination number that minimizes the excess chemical potential of the ion is identified as the optimal or most probable coordination number, for such soft ions the optimum cluster size and the hydration thermodynamics obtained with and without account of the bulk medium on the ion-water clustering reaction can be different. The ideas presented in this work are expected to be relevant to experimental studies that translate thermochemistry of ion-water clusters to the thermodynamics of the hydrated ion and to evolving theoretical approaches that combine high-level calculations on clusters with coarse-grained models of the medium. 相似文献
7.
Enzyme from Daucus carota root catalyzed Henry reaction of substituted benzaldehydes and nitromethane in phosphate buffer of pH 7 at 28?°C to afford β-nitroalcohols in excellent yields (up to 94%). 相似文献
8.
Dr. Sourav Sarkar Anushree Shil Suman Maity Dr. Yun Lim Jung Dr. Mingchong Dai Prof. Atanu Acharya Prof. Kyo Han Ahn 《Angewandte Chemie (International ed. in English)》2023,62(43):e202311168
Aryl alcohol-type or phenolic fluorophores offer diverse opportunities for developing bioimaging agents and fluorescence probes. Due to the inherently acidic hydroxyl functionality, phenolic fluorophores provide pH-dependent emission signals. Therefore, except for developing pH probes, the pH-dependent nature of phenolic fluorophores should be considered in bioimaging applications but has been neglected. Here we show that a simple structural remedy converts conventional phenolic fluorophores into pH-resistant derivatives, which also offer “medium-resistant” emission properties. The structural modification involves a single-step introduction of a hydrogen-bonding acceptor such as morpholine nearby the phenolic hydroxyl group, which also leads to emission bathochromic shift, increased Stokes shift, enhanced photo-stability and stronger emission for several dyes. The strategy greatly expands the current fluorophores’ repertoire for reliable bioimaging applications, as demonstrated here with ratiometric imaging of cells and tissues. 相似文献
9.
Anushree Das Emily A. Lao Anna D. Gudmundsdottir 《Photochemistry and photobiology》2016,92(3):388-398
Photolysis of ester 1 in argon‐saturated methanol and acetonitrile does not produce any product, whereas irradiation of 1 in oxygen‐saturated methanol yields peroxide 2 . Laser flash photolysis studies demonstrate that 1 undergoes intramolecular H atom abstraction to form biradical 3 (λ max ~ 340 nm), which intersystem crosses to form photoenols Z ‐ 4 and E ‐ 4 (λ max ~ 380 nm). Photoenols 4 decay by regenerating ester 1 . With the aid of density functional theory calculations, it was concluded the photoenol E ‐ 4 does not undergo spontaneous lactonization or electrocyclic ring closure because the transition state barriers for these reactions are too large to compete with reketonization of E ‐ 4 to form 1 . 相似文献
10.
Effect of high‐energy light‐ion irradiation on SI‐GaAs and GaAs:Cr as observed by Raman spectroscopy
Shramana Mishra D. Kabiraj Anushree Roy Subhasis Ghosh 《Journal of Raman spectroscopy : JRS》2012,43(2):344-350
The structural evolutions of high‐energy (50 MeV) lithium ion (Li3+) irradiated undoped semi‐insulating GaAs (SI‐GaAs) and chromium‐doped SI‐GaAs (GaAs:Cr) were investigated by Raman measurements. It is shown that high‐energy Li3+ irradiation causes amorphization beyond a fluence of 3 × 1013 ions/cm2 in undoped SI‐GaAs. Interestingly, the same fluence of ions does not seem to affect the crystallinity in GaAs:Cr appreciably. The effect of ion irradiation on the change in lattice ordering and anharmonicity of the phonon modes of undoped SI‐GaAs and GaAs:Cr is also compared. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献