全文获取类型
收费全文 | 610535篇 |
免费 | 4642篇 |
国内免费 | 1479篇 |
专业分类
化学 | 307138篇 |
晶体学 | 8731篇 |
力学 | 31529篇 |
综合类 | 24篇 |
数学 | 81703篇 |
物理学 | 187531篇 |
出版年
2021年 | 5644篇 |
2020年 | 6102篇 |
2019年 | 6969篇 |
2018年 | 9450篇 |
2017年 | 9603篇 |
2016年 | 13049篇 |
2015年 | 6945篇 |
2014年 | 11783篇 |
2013年 | 26607篇 |
2012年 | 20658篇 |
2011年 | 24662篇 |
2010年 | 18655篇 |
2009年 | 18655篇 |
2008年 | 23401篇 |
2007年 | 23185篇 |
2006年 | 21059篇 |
2005年 | 18802篇 |
2004年 | 17629篇 |
2003年 | 15899篇 |
2002年 | 15886篇 |
2001年 | 17105篇 |
2000年 | 13141篇 |
1999年 | 10150篇 |
1998年 | 8844篇 |
1997年 | 8664篇 |
1996年 | 8057篇 |
1995年 | 7291篇 |
1994年 | 7249篇 |
1993年 | 7056篇 |
1992年 | 7433篇 |
1991年 | 8031篇 |
1990年 | 7659篇 |
1989年 | 7626篇 |
1988年 | 7392篇 |
1987年 | 7205篇 |
1986年 | 6887篇 |
1985年 | 8798篇 |
1984年 | 9109篇 |
1983年 | 7716篇 |
1982年 | 8001篇 |
1981年 | 7511篇 |
1980年 | 7073篇 |
1979年 | 7733篇 |
1978年 | 8044篇 |
1977年 | 7970篇 |
1976年 | 7958篇 |
1975年 | 7636篇 |
1974年 | 7429篇 |
1973年 | 7785篇 |
1972年 | 5805篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
The Li oxides species formed on Li over-deposited V2O5 thin film surfaces have been studied by using X-ray and UV induced photoelectron spectroscopy (XPS and UPS). The photoelectron spectroscopic data show that the Li over-deposited V2O5 system itself is not stable. Further chemical decomposition reactions are taken place even under UHV conditions and lead to form Li2O and Li2O2 compounds on the surface. The formation of Li2O2 causes to arise an emission line at about 11.3 eV in the valence band spectra. 相似文献
943.
Computability and computational complexity were first considered over the fields of real and complex numbers and generalized to arbitrary algebraic systems. This article approaches the theory of computational complexity over an arbitrary algebraic system by taking computability over the list extension for a computational model of it. We study the resultant polynomial complexity classes and mention some NP-complete problems. 相似文献
944.
We consider some types of packet discretization for continuous spectra in quantum scattering problems. As we previously showed, this discretization leads to a convenient finite-dimensional (i.e., matrix) approximation for integral operators in the scattering theory and allows reducing the solution of singular integral equations connected with the scattering theory to some suitable purely algebraic equations on an analytic basis. All singularities are explicitly singled out. Our primary emphasis is on realizing the method practically. 相似文献
945.
We use the Jacobi method to construct various integrable systems, such as the Stäckel systems and Toda chains, related to various root systems. We find canonical transformations that relate integrals of motion for the generalized open Toda chains of types B
n, C
n, and D
n. 相似文献
946.
R A Forder 《The Journal of the Operational Research Society》2004,55(4):319-332
The paper presents a survey of operational research (OR) as it is currently used in the UK Ministry of Defence (MoD). After a short historical introduction summarising developments since 1945, it identifies the impact which the end of the Cold War has had on defence operational analysis (OA), as the discipline is generally called within MoD, in terms of the problems studied, the technical challenges presented and the techniques employed. The factors, both external and internal, that have led to the MoD maintaining and indeed expanding its OA activity against a background of falling defence budgets are discussed in the context of previously reported research on the survival and success of OR groups. 相似文献
947.
This paper develops a theory for the global solution of nonconvex optimization problems with parameter-embedded linear dynamic systems. A quite general problem formulation is introduced and a solution is shown to exists. A convexity theory for integrals is then developed to construct convex relaxations for utilization in a branch-and-bound framework to calculate a global minimum. Interval analysis is employed to generate bounds on the state variables implied by the bounds on the embedded parameters. These bounds, along with basic integration theory, are used to prove convergence of the branch-and-bound algorithm to the global minimum of the optimization problem. The implementation of the algorithm is then considered and several numerical case studies are examined thoroughly 相似文献
948.
Azuelos G. Benslama K. Costanzo D. Couture G. Garcia J.E. Hinchliffe I. Kanaya N. Lechowski M. Mehdiyev R. Polesello G. Ros E. Rousseau D. 《The European Physical Journal C - Particles and Fields》2004,39(2):13-24
The European Physical Journal C - We discuss possible searches for the new particles predicted by Little Higgs Models at the LHC. By using a simulation of the ATLAS detector, we demonstrate how the... 相似文献
949.
AbbasA. Zaman 《Particle & Particle Systems Characterization》2003,20(5):342-350
Effects of a low molecular weight physically adsorbed polyethylene oxide (PEO) and the range of the electrostatic repulsion on the rheological behavior of silica dispersions (as a model system) has been investigated. Particular attention is given to the evolution of the rheological behavior with increasing the polymer concentration in the system and also effectiveness of the polymer as a dispersant under extreme conditions (high ionic strength). Results indicate that at small separation distances and low polymer coverage, the polymer chains are long enough to adsorb on the surface of two particles simultaneously causing bridging flocculation in the system and hence increasing the viscosity and linear viscoelastic functions of the dispersion. A significant increase was observed in the viscosity of the dispersion at salt concentrations high enough to eliminate electrostatics between the particles. Under these conditions,the viscosity of the system increased significantly when PEO was added to the dispersion showing that at high electrolyte concentrations, a neutral polymer such as PEO is not able to stabilize the system. 相似文献
950.