全文获取类型
收费全文 | 246篇 |
免费 | 3篇 |
专业分类
化学 | 103篇 |
晶体学 | 1篇 |
力学 | 8篇 |
数学 | 35篇 |
物理学 | 43篇 |
无线电 | 59篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2015年 | 1篇 |
2014年 | 9篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 10篇 |
2010年 | 11篇 |
2009年 | 5篇 |
2008年 | 17篇 |
2007年 | 10篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 16篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有249条查询结果,搜索用时 234 毫秒
71.
Mario Farina 《Journal of inclusion phenomena and macrocyclic chemistry》1992,14(2):101-111
The phase relationships in binary systems forming a crystalline addition compound are obtained by means of classical thermodynamic arguments for the case in which both components are volatile. This approach can be applied to inclusion compounds and to other low-stability addition compounds existing only in the solid phase. The results are consistent with those already known for clathrates containing a volatile guest and a non-volatile host, and for symmetric systems, such as racemic compounds. The temperature range in which the adduct undergoes a congruent sublimation depends on the ratio of the vapor pressures of the two components. A relation has been found to exist between the properties of the pure components, the melting behavior and the enthalpy of formation of the adduct. 相似文献
72.
Juan J. Perez Marta Filizola Maria Caritenì‐Farina 《Journal of mathematical chemistry》1998,23(1-2):229-238
The only results available at present about the structural features of G‐protein coupled receptors are the low resolution
electron projection maps obtained from microscopy studies carried out on two‐dimensional crystals of rhodopsin. These studies
support previous suggestions that these integral proteins are constituted by seven transmembrane domains. The low resolution
electron density map of rhodopsin can be used to extract information about helix relative positions and tilt. This information,
together with a reliable procedure to assess the residues involved in each of the transmembrane regions, can be used to construct
a model of rhodopsin at atomic resolution. We have developed an algorithm that can be used to generate such a model in a completely
automated fashion. The steps involved are: (i) locate the centers of the helices according to the low resolution electron
density map; (ii) compute the tilt of each helix based on the elliptical shape observed by each helix in the map; (iii) define
a local coordinate system for each of the helices; (iv) bring them together in an antiparallel orientation; (v) rotate each
helix through the helical axis in such a way that its hydrophobic moment points in the same direction as the bisector formed
between three consecutive helices in the bundle; (vi) rotate each helix through an axis perpendicular to the helical one to
assign a proper tilt; (vii) translate each of the helix to its center deduced from the projection map. A major advantage of
the procedure presented is its generality and consequently can be used to obtain a model of any G‐protein coupled receptor
with the only assumption that the shape of the bundle is the same as found in rhodopsin. This avoids uncertainties found in
other procedures that construct models of G‐protein coupled receptors based on sequence homology using rhodopsin as template.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
73.
A high-performance liquid chromatographic method was studied to optimize the separation of FCE 23762, a new antitumour agent, from both synthetic impurities and degradation products having very similar molecular structures. The main problems faced in the analytical method development using the most common reversed-phase columns available arose from the presence of analytical peaks with poor symmetry, a long analysis time and the separation between FCE 23762 and its R-isomer, which was often unsuitable for the correct determination of the drug substance. The use of a new stationary phase, Zorbax Rx-C8, together with a suitable mobile phase resulted in a good separation between the diastereomers, with satisfactory peak symmetry and run time. The method permitted the study of the stability of the drug substance in formulations for clinical trials. 相似文献
74.
Alessandra Farina Stefano Valdo Meille Maria Teresa Messina Pierangelo Metrangolo Giuseppe Resnati Giuseppe Vecchio 《Angewandte Chemie (International ed. in English)》1999,38(16):2433-2436
Halogen bonds , attractive intermolecular interactions between perfluoroalkyl bromides and bromide ions, are present in cocrystals of (−)-sparteinium hydrobromide ( 1 ) and (S)-1,2-dibromohexafluoropropane ( 2 ; shown schematically), and result in enantiopure and infinite supramolecular helices. The perfluorocarbon–hydrocarbon self-assembly allows the resolution of racemic 2 . 相似文献
75.
Farina Erica Gastaldi Dario Baino Francesco Vernè Enrica Massera Jonathan Orlygsson Gissur Vena Pasquale 《Acta Mechanica Sinica》2021,37(2):292-306
Acta Mechanica Sinica - In this study, the mechanical properties of glass scaffolds manufactured by robocasting are investigated through micro computed tomography ( $$\mu -CT$$ ) based finite... 相似文献
76.
M. V. Cougo-Pinto C. Farina A. J. Seguí-Santonja 《Letters in Mathematical Physics》1994,31(4):309-313
We apply a method recently proposed by Schwinger to the massive scalar field to calculate the Casimir effect. The method is applied with two different regularization schemes: Schwinger's original one by means of Poisson formula and another one by means of analytical continuation. 相似文献
77.
The Casimir energy of a massive Dirac field at finite temperature and confined between two parallel infinite plates is computed using a method proposed by Schwinger. The boundary conditions are those of zero current through the plates, as inspired by quark confinement in the MIT bag model for hadrons. We use Schwinger's original regularization by a cutoff in proper-time. We comment on the analytical continuation method of regularization, which allows the employment of Epstein function techniques, and on the different possible expressions for the final answer. 相似文献
78.
Alberto Farina 《Comptes Rendus Mathematique》2005,341(7):415-418
In this Note we study solutions, possibly unbounded and sign-changing, of the equation on unbounded domains of with and . We prove some Liouville-type results and a classification theorem for solutions belonging to one of the following classes: stable solutions, finite Morse index solutions and solutions which are stable outside a compact set. We also extend, to smooth coercive epigraphs, the well-known results of Gidas and Spruck concerning non-negative solutions of the considered equation. To cite this article: A. Farina, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献
79.
Noninvasive estimation of motor unit conduction velocity distribution using linear electrode arrays 总被引:2,自引:0,他引:2
Determining the conduction velocity of motor unit action potentials is one of the most important problems in surface electromyography. The estimate of one average conduction velocity value depends on a variety of uncontrollable factors. More meaningful information is obtained from the estimation of the distribution of the different delays in the myoelectric signals. A solution to the problem is the separation and characterization of the individual components propagating at different velocities. A technique, based on surface electrode array recording, is proposed to estimate motor unit conduction velocity distribution. The method consists in the identification of the single action potentials in the time scale domain (with the continuous wavelet transform) and in the estimation of their conduction velocities based on the beamforming algorithm. The performances of the technique have been evaluated using simulated and real myoelectric signals. The results demonstrate that the technique is accurate and reliable. The method may be useful for the diagnosis of neuromuscular disorders, for the monitoring of muscle fatigue and for noninvasive investigation of individual motor units. 相似文献
80.
We discuss the transient and steady state behaviour of the self-pulsing instability of a bistable system using the dressed mode approach of Benza and Lugiato. This formalism, in a suitable limit, is shown to afford an exact adiabatic elimination of the atomic modes, and to lead to explicit and manageable equations of motion describing the evolution of the transmitted radiation. In steady state, the self-pulsing solutions display first and second order phase transition-type behavior. A higher bifurcation of the Hopf type, where the self-pulsing becomes unstable, is also identified, and the accompanying unstable limit cycle is displayed by integrating the equations of motion backward in time. 相似文献