全文获取类型
收费全文 | 653篇 |
免费 | 10篇 |
国内免费 | 3篇 |
专业分类
化学 | 217篇 |
晶体学 | 1篇 |
力学 | 11篇 |
数学 | 109篇 |
物理学 | 286篇 |
综合类 | 42篇 |
出版年
2019年 | 7篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 15篇 |
2012年 | 14篇 |
2011年 | 31篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 32篇 |
2007年 | 21篇 |
2006年 | 25篇 |
2005年 | 27篇 |
2004年 | 24篇 |
2003年 | 23篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 18篇 |
1999年 | 17篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 8篇 |
1974年 | 15篇 |
1973年 | 13篇 |
1972年 | 4篇 |
1971年 | 10篇 |
1969年 | 4篇 |
1928年 | 4篇 |
排序方式: 共有666条查询结果,搜索用时 31 毫秒
101.
It is shown that all spherically symmetric distributions of prematter in the framework of general relativity are static. These results provide a justification for the models of elementary particles proposed previously. 相似文献
102.
The molecular conformation problem is discussed, and a concave quadratic global minimization approach for solving it is described. This approach is based on a quadratic assignment formulation of a discrete approximation to the original problem. 相似文献
103.
We have measured the temperature dependence of the low frequency Raman spectrum of ammonium nitrate in its solid phases IV, II and I and also in its melt. Librational modes are observed in phases IV and II but disappear in both phase I and the melt. Our results indicate that the NO3 group is almost freely rotating in the solid phase I. 相似文献
104.
105.
Nathan Rosen 《General Relativity and Gravitation》1973,4(6):435-447
A bi-metric theory of gravitation is proposed, satisfying the covariance and equivalence principles. It is based on a simple form of Lagrangian and has a simpler mathematical structure than that of the general theory of relativity. The theory agrees with general relativity up to the accuracy of the observations made up to now. The static spherically symmetric solution of the present field equations does not involve any 'black hole'. 相似文献
106.
Let μ be the measure onI′ (? d ) corresponding to the Gaussian process with mean zero and covariance (f,(?Δ+1)?1 g) onI (? d ). It is proven that the set $$( - \Delta _{d - 1} + 1)^{d/4 - \tfrac{1}{2} + \alpha } (1 + x^2 )^{d/4} [\log (2 + x^2 )]^\beta L^2 (\mathbb{R}^d )$$ has μ measure one if α>0 and β>1/2 and μ measure zero if α>0 and β<1/2; here Δ d?1 is the Laplacian in anyd?1 dimensions whend>1 and Δ0=Δ. 相似文献
107.
We explore the possibility of using neutral weak interactions to see whether neutrinos may flip their helicity. Experiments ranging from low-energy neutrino-nucleus scattering to high-energy inclusive reactions are discussed as tests for the presence of helicity-flipping scalar, pseudoscalar and tensor interactions. 相似文献
108.
I.G Rosen 《Journal of Differential Equations》1981,40(3):377-449
A discrete approximation framework for initial-value problems involving certain classes of linear functional differential equations (FDE) of the retarded type is constructed. An equivalence between the FDE and abstract evolution equations (AEE) in an appropriately chosen Hilbert space is established. This equivalence is then employed in the development of discrete approximation schemes in which the infinite-dimensional AEE is replaced by a finite-dimensional system of difference equations. Convergence and rates of convergence are demonstrated via the properties of rational functions with operator arguments and both classical and recent results from linear semigroup theory. Two examples of families of approximation schemes which are included in the general framework and which may be implemented directly on high-speed computing machines are developed. A numerical study of examples which illustrates the application and feasibility of the approximation techniques in a variety of problems together with a summary and analysis of the numerical results are also included. 相似文献
109.
Einstein's principle of general relativity is a dynamical-group approach in that all dynamics is implied by the invariance and no force is introduced (as an external, symmetry-breaking factor). In this spirit we take a Poincaré-invariant free wave equation and, deforming the Poincaré group to the de Sitter group, obtain interaction. This illustrates our algebraic approach to gauge invariance, whereby the (generalized) Maxwell tensor of the Yang-Mills field appears as structure constants of the homogeneous algebra obtained as a deformation of an inhomogeneous one, with interaction appearing via the same tensor, which plays a role corresponding to the curvature tensor in Einstein's general relativity. 相似文献
110.
G. Rosen 《Physics letters. A》1973,45(3):263-264
It is shown that within the manifold of exact solutions a system of reaction-diffusion equations admits only travelling waves with planar symmetry. A derivation of the generic form of approximate (asymptotic) cylindrical and spiral travelling periodic wave solutions is given. If an exact solution homogeneous in space and periodic in time is admitted by the system of reaction-diffusion equations, then travelling periodic spiral waves are admissble as approximate solutions. This is the theoretical explanation for the travelling periodic waves of chemical activity observed in recent experiments. 相似文献