全文获取类型
收费全文 | 91篇 |
免费 | 1篇 |
专业分类
化学 | 11篇 |
力学 | 32篇 |
数学 | 17篇 |
物理学 | 32篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有92条查询结果,搜索用时 62 毫秒
1.
In this paper, we investigate the feasibility of employing the Hyperspherical Adiabatic (HA) basis set to describe continuum states of the Helium trimer molecule. 相似文献
2.
Prof. Li Chen Genevieve E. Mullen Myriam Le Roch Cody G. Cassity Prof. Nicolas Gouault Prof. Henry Y. Fadamiro Prof. Robert E. Barletta Prof. Richard A. O'Brien Prof. Richard E. Sykora Prof. Alexandra C. Stenson Prof. Kevin N. West Howard E. Horne Jeffrey M. Hendrich Kang Rui Xiang Prof. James H. Davis Jr. 《Angewandte Chemie (International ed. in English)》2014,53(44):11762-11765
The practical utility of ionic liquids (ILs) makes the absence (heretofore) of reported examples from nature quite puzzling, given the facility with which nature produces many other types of exotic but utilitarian substances. In that vein, we report here the identification and characterization of a naturally occurring protic IL. It can be formed during confrontations between the ants S. invicta and N. fulva. After being sprayed with alkaloid‐based S. invicta venom, N. fulva detoxifies by grooming with its own venom, formic acid. The mixture is a viscous liquid manifestly different from either of the constituents. Further, we find that the change results as a consequence of formic acid protonation of the N centers of the S. invicta venom alkaloids. The resulting mixed‐cation ammonium formate milieu has properties consistent with its classification as a protic IL. 相似文献
3.
This short note is a response to the comment on our recently published paper cited in the title. All points raised by the
author of the comment are discussed. It is shown that one of the remarks, concerning eigenflow solutions in the limiting case
of forced convection, does not have a sound physical basis. In fact, it refers to a circumstance, a fluid with a thermal expansion
coefficient greater than that of a perfect gas, of marginal or no interest in the framework of convection in porous media. 相似文献
4.
The use of a continuous wave-high power diode laser for removing surface Co-binder from Co-cemented tungsten carbide (WC-Co (5.8 wt%.)) hardmetal slabs was investigated. Combined scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses were performed in order to study the phase transformations and micro-structural modifications of the WC-Co substrates occurring during and after laser irradiation. The micro-structure of the WC-Co progressively transforms as energy density increased, exhibiting stronger removal of Co and WC grain growth. At very high energy density, local melting of the WC grains with the formation of big agglomerates of interlaced grains is observed, and the crystalline structure of the irradiated substrate shows the presence of a brittle ternary eutectic phase of W, Co and C (often referred to as the η-phase). The latter can be detrimental to the mechanical properties of WC-Co. Therefore, the proper adjustment of the laser processing parameters plays a crucial role in surface treatments of WC-Co substrates prior to post-processing like diamond deposition. 相似文献
5.
The laminar and parallel flow of a Newtonian fluid in a vertical cylindrical duct with circular cross section has been analysed.
Both the viscous dissipation effect and the buoyancy effect have been taken into account. The momentum balance equation and
the energy balance equation have been solved by means of a perturbation method, in the case of a uniform heat flux prescribed
at the wall of the duct. The velocity distribution, the temperature distribution, the Nusselt number and the Fanning friction
factor have been evaluated analytically. Moreover, the velocity and temperature of the fluid have been compared with those
obtained in two special cases: forced convection with viscous dissipation (i.e. negligible buoyancy effect); mixed convection
with negligible effects of viscous dissipation.
Received on 26 June 2000 相似文献
6.
Summary A rigorous deduction of the thermodynamic-equilibrium condition is provided for a homogeneous, uncharged and linear dielectric
fluid contained in an electrostatic field. Contrary to the previous ones, this deduction does not postulate the existence
of a mechanical stress tensor and of a body force density in the polarized fluid. Then, the equilibrium condition is employed
to obtain the mass density distribution of the fluid and to present a correct proof of the well-known formula for the attractive
force between the plates of a plane-parallel capacitor immersed in the fluid. 相似文献
7.
The prediction of the mechanical properties of polyester powder coatings is of paramount importance, as they have to undergo a wide variety of forces and deformations during their service life. Determine the response of polymeric coatings to the actual loading conditions can be, however, very troublesome as their properties are function of the material physical state, rate-dependence and yield and break behaviour. Further, the characterization of soft, contaminated organic surfaces such as polymers can often cause severe problems with reliability and imaging accuracy due to instrumental artefacts.This is therefore the context in which this paper investigates the capability of multiple parameters scratch tests joined with non-contact CLA profilometry and FE-SEM to detect the scratch response of polyester powder coatings for protective and decorative outdoor applications. Scratch tests with blunt contact geometry were used to evaluate the response of polyester coatings baked at different time-temperature programs and, so, at different stages of their curing process. In particular, being such coatings highly non-linear in their response to mechanical stress or strain, the influence from scratch load and speed was carefully taken into account. Analytical evaluations of the experimental results led to good correlations between the extent of the deformed zone after scratch, scratch parameters and curing operational settings. This allows mapping the scratch response of the polyester topcoats to broad ranges of both scratch parameters and curing conditions. 相似文献
8.
9.
The propagation of thermal waves in a solid cylinder which undergoes a change of its boundary temperature is studied by assuming the validity of Cattaneo-Vernotte's constitutive equation for the heat flux. The hyperbolic energy equation, together with its boundary and initial conditions, is written in a dimensionless form and solved analytically by the Laplace transform method. It is shown that, if the boundary temperature undergoes a step change, the temperature field presents singularities. On the other hand, no singularity is present if the temperature change is achieved by a continuous monotonic evolution of the boundary temperature. However, even in this case, the absolute value of the temperature change in internal points of the cylinder can be greater than that prescribed at the boundary. 相似文献
10.
Elisabetta Barletta Sorin Dragomir Howard Jacobowitz 《Complex Analysis and Operator Theory》2017,11(8):1685-1713
The total space \({\mathfrak M} \approx {\mathbb H}_1 \times S^1\) of the canonical circle bundle over the 3-dimensional Heisenberg group \({\mathbb H}_1\) is a space–time with the Lorentzian metric \(F_{\theta _0}\) (Fefferman’s metric) associated to the canonical Tanaka–Webster flat contact form \(\theta _0\) on \({\mathbb H}_1\). The matter and energy content of \(\mathfrak M\) is described by the energy-momentum tensor \({T}_{\mu \nu }\) (the trace-less Ricci tensor of \(F_{\theta _0}\)) as an effect of the non flat nature of Feferman’s metric \(F_{\theta _0}\). We study the gravitational field equations \(R_{\mu \nu } - (1/2) \, R \, g_{\mu \nu } = {T}_{\mu \nu }\) on \({\mathfrak M}\). We consider the first order perturbation \(g = F_{\theta _0} + \epsilon \, h\), \(\epsilon<< 1\), and linearize the field equations about \(F_{\theta _0}\). We determine a Lorentzian metric g on \({\mathfrak M}\) which solves the linearized field equations corresponding to a diagonal perturbation h. 相似文献