全文获取类型
收费全文 | 1122篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 612篇 |
晶体学 | 12篇 |
力学 | 81篇 |
数学 | 121篇 |
物理学 | 317篇 |
出版年
2022年 | 14篇 |
2020年 | 15篇 |
2019年 | 18篇 |
2018年 | 14篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 10篇 |
2014年 | 35篇 |
2013年 | 85篇 |
2012年 | 69篇 |
2011年 | 75篇 |
2010年 | 45篇 |
2009年 | 30篇 |
2008年 | 40篇 |
2007年 | 34篇 |
2006年 | 32篇 |
2005年 | 32篇 |
2004年 | 26篇 |
2003年 | 37篇 |
2002年 | 30篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 23篇 |
1996年 | 16篇 |
1995年 | 21篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 11篇 |
1974年 | 10篇 |
1973年 | 13篇 |
1941年 | 11篇 |
1936年 | 9篇 |
排序方式: 共有1143条查询结果,搜索用时 15 毫秒
101.
M. V. Rama Krishna 《Journal of computational chemistry》1990,11(5):629-635
An analytical procedure is presented for the determination of the proper dissociation configurations of a molecule. We illustrate this procedure by determining the proper dissociation configurations of many electronic states of the first-row diatomic molecules and ozone. Finally, a few simple guidelines are provided to help in the identification of the important configurations needed for proper dissociation of a molecule. 相似文献
102.
103.
Summary The protonation constants of several metal extractants, especially hydroxamic acids have been determined by a solvent extraction method. The influence of the acidity on the solubility and the distribution ratio has been studied. A plot correlates the protonation behaviour of these metal extractants with the Hammett Acidity Function, Ho. The protonation constant is useful to explain the acid catalysed hydrolysis rate of these metal extractants and to determine the extraction coefficients of their metal chelates. 相似文献
104.
105.
Generalizing earlier results of [1], we analyze here the spherically symmetric gravitational collapse of a matter cloud with a general form of matter for the formation of a naked singularity. It is shown that this is related basically to the choice of initial data to the Einstein field equations, and would therefore occur in generic situations from regular initial data within the general context considered here, subject to the matter satisfying the weak energy condition. The condition on initial data which leads to the formation of black hole is also characterized. 相似文献
106.
Rama T. Lingham S. Sivaganesan 《Annals of the Institute of Statistical Mathematics》1997,49(4):693-710
Conventional Bayes factors for hypotheses testing cannot typically accommodate the use of standard noninformative priors, as such priors are defined only up to arbitrary constants which affect the values of the Bayes factors. To circumvent this problem, Berger and Pericchi (1996, J. Amer. Statist. Assoc., 19, 109-122) introduced a new criterion called the Intrinsic Bayes Factor (IBF). In this paper, we use their methodology to test several hypotheses regarding the shape parameter of the power law process. Assuming that we have data from the process according to the failure-truncation sampling scheme, we derive the arithmetic and geometric IBF's using the reference priors. We deduce a set of intrinsic priors that correspond to these IBF's, as the observed number of failures tends to infinity. We then use these results to analyze an actual data set on the failures of an aircraft generator. 相似文献
107.
Some recent developments in boundary layer instabilities and transition are reviewed. Background disturbance levels determine
the instability mechanism that ultimately leads to turbulence. At low noise levels, the traditional Tollmien-Schlichting route
is followed, while at high levels, a ‘by-pass’ route is more likely. Our recent work shows that spot birth is related to the
pattern of secondary instability in either route. 相似文献
108.
Free convection flow from an isothermal horizontal circular cylinder immersed in a fluid with viscosity proportional to an inverse linear function of temperature is studied. The governing boundary layer equations are transformed into a non-dimensional form and the resulting nonlinear system of partial differential equations is reduced to local non-similarity equations which are solved numerically by a very efficient implicit finite difference method together with Keller box scheme. Numerical results are presented by velocity and viscosity profiles of the fluid as well as heat transfer characteristics, namely the local heat transfer rate and the local skin-friction coefficients for a wide range of viscosity parameter (= 0.0, 0.5, 1.0, 2.0, 3.0,4.0) and the Prandtl number Pr (= 1.0, 7.0, 10.0, 15.0, 20.0, 30.0). 相似文献
109.
K.?Sanjeev RaoEmail author Rajeswari?Seshadri Rama?Govindarajan 《Theoretical and Computational Fluid Dynamics》2004,17(4):233-248
A new minimal composite theory that extends the approach of Govindarajan and Narasimha [1] is proposed here for 2D non-parallel compressible boundary-layer stability subject to 3D disturbances. The mean profiles are obtained from Hortons analysis, which provides a good approximation for a large range of Prandtl numbers at non-zero pressure gradients. In the lowest order, all effects of order lower than O(R-2/3) anywhere in the boundary-layer are included, R being the local boundary-layer Reynolds number; the resulting non-parallel formulation yields a set of four ordinary differential equations, as compared to the five coupled equations of classical parallel flow theory of Mack [2]. The largest effect on stability of flow non-parallelism is found to be due to the wall-normal advection of velocity and temperature disturbance quantities by the mean flow. The present theory shows that the bulk viscosity, invariably included in compressible stability theories, is irrelevant at the lowest order. In comparison with the full [O(R-1)] non-parallel theory, the present theory is marginally better than the parallel flow theory. PACS 03.50.De, 04.20-q, 42.65-k 相似文献
110.
An analysis is presented to investigate the effect of radiation on mixed convection from a horizontal flat plate in a saturated porous medium. Both a hot surface facing upward and a cold surface facing downward are considered in the analysis. The conservation equations that govern the problem are reduced to a system of nonlinear ordinary different equations. The important parameters of this problem are the radiation parameter R, the buoyancy parameter B, and the freestream to wall temperature ratio T ∞/T w for the case of a hot surface or the wall to freestream to wall temperature T w /T ∞ for the case of a cold surface. 相似文献