全文获取类型
收费全文 | 187篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 151篇 |
晶体学 | 1篇 |
数学 | 27篇 |
物理学 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 27篇 |
2012年 | 9篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 2篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1969年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有193条查询结果,搜索用时 15 毫秒
121.
Abstract By applying a continuous distribution function instead of the mole fractions, mass fractions, etc. of individual components, continuous thermodynamics permits a drastic reduction of the computational expense for calculating phase equilibria in complex multi-component systems such as petroleum fractions, shale oils, polymer solutions, and polymer mixtures. In this paper, continuous thermodynamics is applied to compatibility in mixtures of two polymers. If, e.g., the cloud-point curve is known, the shadow curve, the spinodal, the critical mixing point, and other interesting quantities may easily be calculated. Some examples are given to illustrate the method. 相似文献
122.
Based on an improved calculation of activity coefficients, continuous thermodynamics using a generalized divariate Stockmayer distribution is applied to the liquid-liquid equilibrium of random copolymer solutions. The effects of the chemical polydispersity on the cloud-point curve, the shadow curve, the spinodal, and the critical point are discussed. The theory can account for the occurrence of three-phase equilibria as well as for the phase separation in pure copolymers. 相似文献
123.
Margit T. Rätzsch Christian Wohlfarth Dieter Browarzik Horst Kehlen 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1497-1523
Continuous thermodynamics is applied to the liquid‐liquid equilibrium in random copolymer blends. Two copolymers are mixed, each consisting of two different monomer units. Hence, up to four monomer units may be present in the system. Both copolymers are characterized by divariate distribution functions with respect to molecular weight (chain length) and chemical composition. The basic relations necessary for phase equilibrium calculations are derived. The influences of both polydispersities and of the different parameters included in the model for the excess Gibbs free energy are discussed by calculating cloud‐point curves and shadow curves. Applications to practical systems are given. 相似文献
124.
The paper describes a method for the separation of 18 nucleotides, nucleosides and nucleobases by isocratic solvent-generated ion-pair chromatography in 55 min. It has been developed for pharmacodynamic monitoring of mycophenolic acid, the active metabolite of the immunosuppressant mycophenolate mofetil. The method was applied for the detection of mycophenolic acid-induced changes in inosine 5′-monophosphate dehydrogenase (IMPDH) activity in the lysate of human peripheral blood mononuclear cells. 相似文献
125.
126.
Semisynthetic murine prion protein equipped with a GPI anchor mimic incorporates into cellular membranes 总被引:1,自引:0,他引:1
Olschewski D Seidel R Miesbauer M Rambold AS Oesterhelt D Winklhofer KF Tatzelt J Engelhard M Becker CF 《Chemistry & biology》2007,14(9):994-1006
Conversion of cellular prion protein (PrP(C)) into the pathological conformer (PrP(Sc)) has been studied extensively by using recombinantly expressed PrP (rPrP). However, due to inherent difficulties of expressing and purifying posttranslationally modified rPrP variants, only a limited amount of data is available for membrane-associated PrP and its behavior in vitro and in vivo. Here, we present an alternative route to access lipidated mouse rPrP (rPrP(Palm)) via two semisynthetic strategies. These rPrP variants studied by a variety of in vitro methods exhibited a high affinity for liposomes and a lower tendency for aggregation than rPrP. In vivo studies demonstrated that double-lipidated rPrP is efficiently taken up into the membranes of mouse neuronal and human epithelial kidney cells. These latter results enable experiments on the cellular level to elucidate the mechanism and site of PrP-PrP(Sc) conversion. 相似文献
127.
Maliarik M Nagle JK Ilyukhin A Murashova E Mink J Skripkin M Glaser J Kovacs M Horváth A 《Inorganic chemistry》2007,46(11):4642-4653
The new crystalline compounds Tl2Ni(CN)4 and Tl2Pd(CN)4 were synthesized by several procedures. The structures of the compounds were determined by single-crystal X-ray diffraction. The compounds are isostructural with the previously reported platinum analogue, Tl2Pt(CN)4. A new synthetic route to the latter compound is also suggested. In contrast to the usual infinite columnar stacking of [M(CN)4]2- ions with short intrachain M-M separations, characteristic of salts of tetracyanometalates of NiII, PdII, and PtII, the structure of the thallium compounds is noncolumnar with the two TlI ions occupying axial vertices of a distorted pseudo-octahedron of the transition metal, [MTl2C4]. The Tl-M distances in the compounds are 3.0560(6), 3.1733(7), and 3.140(1) A for NiII, PdII, and PtII, respectively. The short Tl-Ni distance in Tl2Ni(CN)4 is the first example of metal-metal bonding between these two metals. The strength of the metal-metal bonds in this series of compounds was assessed by means of vibrational spectroscopy. Rigorous calculations, performed on the molecules in D4h point group symmetry, provide force constants for the Tl-M stretching vibration constants of 146.2, 139.6, and 156.2 N/m for the NiII, PdII, and PtII compounds, respectively, showing the strongest metal-metal bonding in the case of the Tl-Pt compound. Amsterdam density-functional calculations for isolated Tl2M(CN)4 molecules give Tl-M geometry-optimized distances of 2.67, 2.80, and 2.84 A for M = NiII, PdII, and PtII, respectively. These distances are all substantially shorter than the experimental values, most likely because of intermolecular Tl-N interactions in the solid compounds. Time-dependent density-functional theory calculations reveal a low-energy, allowed transition in all three compounds that involves excitation from an a1g orbital of mixed Tl 6pz-M ndz2 character to an a2u orbital of dominant Tl 6pz character. 相似文献
128.
Margit Pap 《Journal of Fourier Analysis and Applications》2011,17(5):755-776
In signal processing and system identification for
H2(\BbbT)H^{2}(\Bbb{T}) and
H2(\BbbD)H^{2}(\Bbb{D}) the traditional trigonometric bases and trigonometric Fourier transform are replaced by the more efficient rational orthogonal
bases like the discrete Laguerre, Kautz and Malmquist-Takenaka systems and the associated transforms. These bases are constructed
from rational Blaschke functions, which form a group with respect to function composition that is isomorphic to the Blaschke
group, respectively to the hyperbolic matrix group. Consequently, the background theory uses tools from non-commutative harmonic
analysis over groups and the generalization of Fourier transform uses concepts from the theory of the voice transform. The
successful application of rational orthogonal bases needs a priori knowledge of the poles of the transfer function that may
cause a drawback of the method. In this paper we give a set of poles and using them we will generate a multiresolution in
H2(\BbbT)H^{2}(\Bbb{T}) and
H2(\BbbD)H^{2}(\Bbb{D}). The construction is an analogy with the discrete affine wavelets, and in fact is the discretization of the continuous voice
transform generated by a representation of the Blaschke group over the space
H2(\BbbT)H^{2}(\Bbb{T}). The constructed discretization scheme gives opportunity of practical realization of hyperbolic wavelet representation of
signals belonging to
H2(\BbbT)H^{2}(\Bbb{T}) and
H2(\BbbD)H^{2}(\Bbb{D}) if we can measure their values on a given set of points inside the unit circle or on the unit circle. Convergence properties
of the hyperbolic wavelet representation will be studied. 相似文献
129.
Harry Schäfer Margit Gruner Gisbert Großmann Karl Gewald 《Monatshefte für Chemie / Chemical Monthly》1991,122(11):959-966
Summary The title compounds were synthesized by reaction of nitroketene aminals with -chlorovinylcarbonyl compounds. The chloromethylene malononitriles1 react with nitromethylenimidazolin (2 a) and -benzimidazoles2 b to yield the 8-nitro-2,3-dihydroimidazo[1,2-a]pyridines3 and the 4-nitropyrido[1,2-a]-benzimidazoles6, both containing an amino group. Analogously, from the special 3-chloro-2-propeniminium salt7 and2 a the imidazopyridine derivative9 was formed. The 3-aryl-3-chloro-2-propeniminium salts10 were converted into the nitro-dihydroimidazo[1,2-a]pyridines11 and the pyrido[1,2-a]benzimidazole12 containing the aryl group by reaction with2 a and2 b, respectively. The structures were investigated by 2-dimensional1H/13C-NMR-spectroscopy. 相似文献
130.
Keita Nomoto Daniel Hiller Sebastian Gutsch Anna V. Ceguerra Andrew Breen Margit Zacharias Gavin Conibeer Ivan Perez‐Wurfl Simon P. Ringer 《固体物理学:研究快报》2017,11(1)
Doping of silicon nanocrystals is essential to control their electronic and optical properties. The incorporation of an impurity into a silicon nanovolume is a nontrivial task due to the self‐purification effect. Here, a systematic atom probe tomography study of the phosphorus distribution and incorporation in size‐controlled silicon nanocrystals embedded in silicon dioxide is presented. Qualitatively, it turns out that the phosphorus distribution in the system follows a universal, nanocrystal‐size independent trend: phosphorus‐enrichment at the interface with a substantial phosphorus‐incorporation in the silicon nanocrystal as small as 2 nm in diameter. This clearly contradicts strict self‐purification. These observations are explained by the bulk‐solubility and ‐segregation behaviour, kinetic effects related to the diffusion lengths, and nanoscale interface strain. The quantitative determination of the amount of phosphorus atoms per quantum dot enables a systematic understanding of phosphorus‐induced effects on optical and electronic properties of silicon nanovolumes. 相似文献