全文获取类型
收费全文 | 318篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 124篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 56篇 |
物理学 | 137篇 |
出版年
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 11篇 |
2011年 | 12篇 |
2010年 | 11篇 |
2009年 | 4篇 |
2008年 | 9篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 22篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1968年 | 2篇 |
1965年 | 3篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1956年 | 1篇 |
1952年 | 1篇 |
1942年 | 1篇 |
1935年 | 1篇 |
1934年 | 1篇 |
1927年 | 1篇 |
1924年 | 2篇 |
排序方式: 共有322条查询结果,搜索用时 15 毫秒
1.
Sunanda Banerjee Rohini M Godbole Sreerup Raychaudhuri Ben Allanach Sunanda Banerjee Satyaki Bhattacharyya Debajyoti Choudhury Siba Prasad Das Anindya Datta Rohini M Godbole Monoranjan Guchait Sabine Kraml Gobinda Majumdar David Miller Margarete Mühlleitner Nobuchika Okada Maxim Perelstein Santosh K Rai Sreerup Raychaudhuri Saurabh D Rindani DP Roy K Sridhar Rishikesh Vaidya D Zeppenfeld 《Pramana》2006,67(4):617-637
This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology
(WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these
problems by the subgroups formed during the workshop is included in this report. 相似文献
2.
A system for display of magnetic resonance (MR) spectroscopic imaging (SI) data is described which provides for efficient review and analysis of the multidimensional spectroscopic and spatial data format of this technique. Features include the rapid display of spectra from selected image voxels, formation of spectroscopic images, spectral and image data processing operations, methods for correlating spectroscopic image data with high resolution 1H MR images, and hardcopy facilities. Examples are shown for 31P and 1H spectroscopic imaging studies obtained in human and rat brain. 相似文献
3.
Summary For the numerical solution of non-stiff semi-explicit differentialalgebraic equations (DAEs) of index 1 half-explicit Runge-Kutta methods (HERK) are considered that combine an explicit Runge-Kutta method for the differential part with a simplified Newton method for the (approximate) solution of the algebraic part of the DAE. Two principles for the choice of the initial guesses and the number of Newton steps at each stage are given that allow to construct HERK of the same order as the underlying explicit Runge-Kutta method. Numerical tests illustrate the efficiency of these methods. 相似文献
4.
5.
6.
7.
8.
Khenkin AM Weiner L Wang Y Neumann R 《Journal of the American Chemical Society》2001,123(35):8531-8542
The mechanism of aerobic oxidation of aromatic and alkyl aromatic compounds using anthracene and xanthene, respectively, as a model compound was investigated using a phosphovanadomolybdate polyoxometalate, H(5)PV(2)Mo(10)O(40), as catalyst under mild, liquid-phase conditions. The polyoxometalate is a soluble analogue of insoluble mixed-metal oxides often used for high-temperature gas-phase heterogeneous oxidation which proceed by a Mars-van Krevelen mechanism. The general purpose of the present investigation was to prove that a Mars-van Krevelen mechanism is possible also in liquid-phase, homogeneous oxidation reactions. First, the oxygen transfer from H(5)PV(2)Mo(10)O(40) to the hydrocarbons was studied using various techniques to show that commonly observed liquid-phase oxidation mechanisms, autoxidation, and oxidative nucleophilic substitution were not occurring in this case. Techniques used included (a) use of (18)O-labeled molecular oxygen, polyoxometalate, and water; (b) carrying out reactions under anaerobic conditions; (c) performing the reaction with an alternative nucleophile (acetate) or under anhydrous conditions; and (d) determination of the reaction stoichiometry. All of the experiments pointed against autoxidation and oxidative nucleophilic substitution and toward a Mars-van Krevelen mechanism. Second, the mode of activation of the hydrocarbon was determined to be by electron transfer, as opposed to hydrogen atom transfer from the hydrocarbon to the polyoxometalate. Kinetic studies showed that an outer-sphere electron transfer was probable with formation of a donor-acceptor complex. Further studies enabled the isolation and observation of intermediates by ESR and NMR spectroscopy. For anthracene, the immediate result of electron transfer, that is formation of an anthracene radical cation and reduced polyoxometalate, was observed by ESR spectroscopy. The ESR spectrum, together with kinetics experiments, including kinetic isotope experiments and (1)H NMR, support a Mars-van Krevelen mechanism in which the rate-determining step is the oxygen-transfer reaction between the polyoxometalate and the intermediate radical cation. Anthraquinone is the only observable reaction product. For xanthene, the radical cation could not be observed. Instead, the initial radical cation undergoes fast additional proton and electron transfer (or hydrogen atom transfer) to yield a stable benzylic cation observable by (1)H NMR. Again, kinetics experiments support the notion of an oxygen-transfer rate-determining step between the xanthenyl cation and the polyoxometalate, with formation of xanthen-9-one as the only product. Schemes summarizing the proposed reaction mechanisms are presented. 相似文献
9.
H. Weiner H.-J. Lunk J. Fuchs B. Ziemer R. Stsser C. Pietzsch P. Reich 《无机化学与普通化学杂志》1991,594(1):191-201
Synthesis and Structure Studies of Ba2H[α-FeO4W12O36] · 26 H2O The heteropolyanion compound Ba2H[α-FeO4W12O36] · 26 H2O (I) crystallizes in the tetragonal space group P4 n2 with the lattice parameters a = 12.398(6), c = 18.721(6) Å; Z = 2; Dx = 4.128 g · cm?3. The structure was solved on a twinned crystal from 1029 observed reflections and refined to an index R of 7.6%. The calculations were done by means of a modified ORFLS-programme by Eitel and Bärnighausen. The heteropolyanion [α-FeO4W12O36]5? has the well known α-Keggin structure. The average distance of the four central oxygen atoms to the FeIII position (0, 0, 0) is 1.84 Å. The angles ? O? Fe? O are 112.3° (4X) and 103.9 (2X), respectively, which leads to an disphenoidal distortion of the FeO4 tetrahedron. The powder and single crystal ESR spectra of I show the anisotropy of the FeIII fine structure transition 1/2 ? ?1/2. The Mößbauer spectra confirm the tetragonal distortion of the central FeO4 tetrahedron (quadrupole splitting Δ ≈ 0.50 mm · s?1). 相似文献
10.
Rahimipour S Litichever-Coslovsky N Alaluf M Freeman D Ehrenberg B Weiner L Mazur Y Fridkin M Koch Y 《Photochemistry and photobiology》2005,81(2):250-258
A combination of light, oxygen and a photosensitizer is used to induce death of cancer cells by photodynamic therapy. In this study, we have synthesized several new methyl helianthrone derivatives and compared their phototoxicity with that of hypericin. In contrast to hypericin, methyl helianthrones are soluble in aqueous solutions and have a broad range of light absorbance, which allows the use of polychromatic light. Structural modifications of methyl helianthrone demonstrated that substitution of hydrogen atoms of methyl helianthrone at Positions 2 and 5 with Br atoms or methylation of its phenolic hydroxyls, significantly increases the corresponding singlet oxygen quantum yield and their phototoxicity toward alphaT3-1, M2R and LNCaP cells. The phototoxicity of some of these compounds was similar to that of hypericin. Methyl helianthrones, like hypericin, accumulated mainly in the perinuclear region as evident by confocal microscopy. Irradiation of cells pretreated with methyl helianthrone derivatives generates intracellular reactive oxygen species and lipid free radicals, as shown by a fluorescentic probe and electron paramagnetic resonance methods, respectively. The phototoxicity of these methyl helianthrones as well as their ability to oxidize membrane lipids were significantly decreased on addition of specific Type-II inhibitors, suggesting the involvement of singlet oxygen as the main oxidant. 相似文献