全文获取类型
收费全文 | 145篇 |
免费 | 10篇 |
国内免费 | 9篇 |
专业分类
化学 | 55篇 |
力学 | 8篇 |
综合类 | 3篇 |
数学 | 43篇 |
物理学 | 55篇 |
出版年
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 34篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 1篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有164条查询结果,搜索用时 46 毫秒
131.
J. MEDINA YU. G. GUREVICH G. N. LOGVINOV P. RODRÍGUEZ G. GONZÁLEZ DE LA CRUZ 《Molecular physics》2013,111(19):3133-3138
The problem of the effective thermal diffusivity of two-layer systems is investigated using the photoacoustic spectroscopy. The experimental results are examined in terms of the effective thermal parameters of the composite system determined from a homogeneous material that produces the same physical response under an external perturbation in the detector device. It is shown that the effective thermal conductivity is not symmetric under exchange of the two layers of the composite, i.e. the effective thermal parameters depend upon which layer is illuminated in the photoacoustic experiments. Particular emphasis is given to the characterization of the interface thermal conductivity between the layer system. 相似文献
132.
This paper investigates the random buffeting excitation forces that apply to tubes in two-phase cross-flows. The spectral magnitude of these forces is studied with the help of a database that includes most of the available experimental data on direct or indirect force measurements. Different fluid mixtures, namely steam–water, air–water and various types of Freon, as well as different thermohydraulic or geometrical situations are included in the database. Using a formalism similar in principle to that used successfully in the modelling of buffeting in single-phase flows, the scaling of the data is undertaken. While dynamic pressure, viscosity or surface tension are found not to be relevant parameters, gravity forces allow us to define appropriate dimensionless spectra for all cases. The meaning of these parameters as well as the effects of flow regimes or fluid mixtures are discussed. Finally, an upper bound on the magnitude of these forces, which is of practical applicability, is proposed. 相似文献
133.
M DE SANCTIS 《Pramana》2013,81(3):467-483
Hypothetical superheavy fourth-generation fermions with a very small coupling with the rest of the Standard Model can give rise to long enough lived bound states. The production and the detection of these bound states would be experimentally feasible at the LHC. Extending, in the present study, the analysis of other authors, a semirelativistic wave equation is solved using an accurate numerical method to determine the binding energies of these possible superheavy fermion-bound states. The interaction given by the Yukawa potential of the Higgs boson exchange is considered; the corresponding relativistic corrections are calculated by means of a model based on the covariance properties of the Hamiltonian. We study the effects given by the Coulomb force. Moreover, we calculate the contributions given by the Coulombic and confining terms of the strong interaction in the case of superheavy quark bound states. The results of the model are critically analysed. 相似文献
134.
New low molar mass liquid crystalline vitrifying materials have been synthesized and tested for application in optical films. The molecules were based on spiro compounds derived from pentaerythritol and mesogenic groups derived from cyanobiphenylyl moieties. The resulting materials showed glass transition temperatures as high as 85 degrees C and nematic to isotropic phase transition temperatures up to 222 degrees C. Crystallization from the melt was strongly suppressed. Well-aligned, solid, birefringent layers were obtained from the materials by spincoating. Uniaxially oriented layers with an optic axis tilted with respect to the substrate were obtained by spincoating the liquid crystals on pretilt amplification layers. When an anisotropic dye was incorporated in the liquid crystals, polarizers with a tilted absorption axis were obtained. In addition, the compounds were found to be suitable as hosts for photo-induced reorientation of photo-isomerizable dyes. 相似文献
135.
In this article, we analyze the decisional power index, the so called Hoede-Bakker index. This index takes the preferences of the players into account, as well as the social structure in which players may influence each other. We investigate the properties of the Hoede-Bakker index. We adapt some postulates for power indices and voting power paradoxes for the Hoede-Bakker set up. We investigate whether this decisional power index displays the adapted voting power paradoxes and whether it satisfies the adapted postulates for power indices. 相似文献
136.
137.
Suranjan DE 《Annals of Operations Research》1988,12(1):109-134
This paper reports the development of a computer-based system for production scheduling in a dedicated FMS. The system is based on the state-operator framework commonly used in artificial intelligence. Such a system consists of three components: (i) a knowledge base of states, which describes both the current task domain situation and the goal to be achieved; (ii) a set of operators that are used to manipulate the knowledge base; and (iii) a control strategy to decide which operators to apply next and to resolve conflicts. Some of the interesting features of the scheduling system include: (i) the ability to detect resource conflicts; (ii) the ability to determine alternate routes for a given part in the event of a resource conflict; and (iii) the ability to amend plans if an alternate route is found. These features allow the system to take advantage of the flexible routing for parts that an FMS allows. The system has been implemented using the XLISP programming language. Implementation considerations are discussed. A small but comprehensive example is presented. Further research directions are suggested. 相似文献
138.
139.
This paper presents a robust control algorithm for plants involvingboth internal (i.e. in the state) and external (i.e. in theoutput or input) known point delays. Several stabilizing controllerstructures are given and analysed for the case of perfectlymodelled plants with known parameters. The parametrized partsof two of the controller structures involve delays, while thoseof the two remaining controllers are delay-free. However, auxiliarycompensating signals which weight the plant input and outputintegrals are incorporated in all the controller structuresfor stabilization and model matching purposes. 相似文献
140.
The nonlinear nonlocal system of the equilibrium equations ofan elastic ring under the action of an external two-dimensionaluniformly subsonic potential barotropic steady-state gas flowis considered. The configurations of the elastic ring are identifiedby a pair of functions (, ). The simple curve represents theshape of the ring and the real-valued function identifies theorientation of the material sections of the ring. The pressurefield on the ring depends nonlocally on , and on two parametersU and P which represent the pressure and the velocity at infinity.The system is shown to be equivalent to a fixed-point problem,which is then treated with continuation methods. It is shownthat the solution branch ensuing from certain equilibrium states((0, 0), 0, P0) in the solution-parameter space of ((0, 0),0, P0) either approaches the boundary of the admissible ((,), U,p)'s in a well-defined sense, or is unbounded, or is homotopicallynontrivial in the sense that there exists a continuous map from the branch to a two-dimensional sphere which is not homotopicin the sphere to a constant, while restricted to the branchminus ((0, 0), 0, P0) is homotopic to a constant in the sphere.Furthermore, by fixing the pressure parameter at P0 and by consideringthe one-parameter problem in ((, ), U), the following holds.Every hyperplane in the solution-parameter space of the ((,), U)'s which contains the equilibrium state ((0, 0), 0) anddoes not include a welldetermined one-dimensional subspace intersectsthe solution branch above at a point different from ((0, 0),0). 相似文献