全文获取类型
收费全文 | 17487篇 |
免费 | 1872篇 |
国内免费 | 1403篇 |
专业分类
化学 | 2486篇 |
晶体学 | 60篇 |
力学 | 1623篇 |
综合类 | 545篇 |
数学 | 11097篇 |
物理学 | 4951篇 |
出版年
2024年 | 21篇 |
2023年 | 129篇 |
2022年 | 227篇 |
2021年 | 289篇 |
2020年 | 338篇 |
2019年 | 342篇 |
2018年 | 393篇 |
2017年 | 479篇 |
2016年 | 532篇 |
2015年 | 367篇 |
2014年 | 668篇 |
2013年 | 1191篇 |
2012年 | 765篇 |
2011年 | 1031篇 |
2010年 | 1012篇 |
2009年 | 1235篇 |
2008年 | 1252篇 |
2007年 | 1230篇 |
2006年 | 1180篇 |
2005年 | 932篇 |
2004年 | 831篇 |
2003年 | 770篇 |
2002年 | 732篇 |
2001年 | 610篇 |
2000年 | 568篇 |
1999年 | 500篇 |
1998年 | 433篇 |
1997年 | 375篇 |
1996年 | 334篇 |
1995年 | 287篇 |
1994年 | 213篇 |
1993年 | 189篇 |
1992年 | 181篇 |
1991年 | 122篇 |
1990年 | 130篇 |
1989年 | 103篇 |
1988年 | 81篇 |
1987年 | 73篇 |
1986年 | 49篇 |
1985年 | 70篇 |
1984年 | 64篇 |
1983年 | 36篇 |
1982年 | 70篇 |
1981年 | 42篇 |
1980年 | 44篇 |
1979年 | 63篇 |
1978年 | 43篇 |
1977年 | 40篇 |
1974年 | 26篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
912.
Digital image correlation (DIC) has received a widespread research and application in experimental mechanics. In DIC, the performance of subpixel registration algorithm (e.g., Newton-Raphson method, quasi-Newton method) relies heavily on the initial guess of deformation. In the case of small inter-frame deformation, the initial guess could be found by simple search scheme, the coarse-fine search for instance. While for large inter-frame deformation, it is difficult for simple search scheme to robustly estimate displacement parameters and deformation parameters simultaneously with low computational cost. In this paper, we proposed three improving strategies, i.e. Q-stage evolutionary strategy (T), parameter control strategy (C) and space expanding strategy (E), and then combined them into three population-based intelligent algorithms (PIAs), i.e. genetic algorithm (GA), differential evolution (DE) and particle swarm optimization (PSO), and finally derived eighteen different algorithms to calculate the initial guess for qN. The eighteen algorithms were compared in three sets of experiments including large rigid body translation, finite uniaxial strain and large rigid body rotation, and the results showed the effectiveness of proposed improving strategies. Among all compared algorithms, DE-TCE is the best which is robust, convenient and efficient for large inter-frame deformation measurement. 相似文献
913.
914.
Igor Leite Freire 《Journal of Mathematical Analysis and Applications》2010,367(2):716-9473
Using the scalar curvature of the product manifold S2×R and the complete group classification of nonlinear Poisson equation on (pseudo) Riemannian manifolds, we extend the previous results on symmetry analysis of homogeneous wave equation obtained by H. Azad and M.T. Mustafa [H. Azad, M.T. Mustafa, Symmetry analysis of wave equation on sphere, J. Math. Anal. Appl. 333 (2007) 1180-1188] to nonlinear Klein-Gordon equations on the two-dimensional sphere. 相似文献
915.
Ján Jakubík 《Czechoslovak Mathematical Journal》2008,58(1):183-202
In the present paper we deal with generalized MV-algebras (GMV-algebras, in short) in the sense of Galatos and Tsinakis. According to a result of the mentioned authors, GMV-algebras can be obtained by a truncation construction from lattice ordered groups. We investigate direct summands and retract
mappings of GMV-algebras. The relations between GMV-algebras and lattice ordered groups are essential for this investigation.
Supported by VEGA Agency grant 1/2002/05.
This work has been partially supported by the Slovak Academy of Sciences via the project Center of Excellence-Physics of Information,
grant I/2/2005. 相似文献
916.
定义了一般线性模型参数的最小二乘估计(LS估计)与BLU估计的一种新的相对效率,给出了当设计矩阵满秩,协方差阵非负定时这种相对效率的下界,最后讨论了其与广义相关系数(zρ3)之间的关系. 相似文献
917.
The directed flow of protons is studied in the quark-gluon string model as a function of the impact parameter for S+S and Pb+Pb reactions at 160 AGeV/c. A significant reduction of the directed flow in midrapidity range, which can lead to the development of the antiflow, is found due to the absorption of early emitted particles by massive spectators (shadowing effect). This effect can mimic the formation of the quark-gluon plasma (QGP). However, in the absorption scenario the antiflow is stronger for the system of light colliding nuclei than for the heavy ones, while in the case of the plasma creation the effect should be opposite. 相似文献
918.
Jan Kühr 《Czechoslovak Mathematical Journal》2008,58(2):395-415
We deal with unbounded dually residuated lattices that generalize pseudo MV-algebras in such a way that every principal order-ideal is a pseudo MV-algebra. We describe the connections of these generalized pseudo MV-algebras to generalized pseudo effect algebras, which allows us to represent every generalized pseudo MV-algebra A by means of the positive cone of a suitable ℓ-group G
A
. We prove that the lattice of all (normal) ideals of A and the lattice of all (normal) convex ℓ-subgroups of G
A
are isomorphic. We also introduce the concept of Archimedeanness and show that every Archimedean generalized pseudo MV-algebra is commutative.
Supported by the Research and Development Council of the Czech Govenrment via the project MSM6198959214. 相似文献
919.
920.
In the present paper we answer two questions raised by Barbilian in 1960. First, we study how far can the hypothesis of Barbilian’s
metrization procedure can be relaxed. Then, we prove that Barbilian’s metrization procedure in the plane generates either
Riemannian metrics or Lagrance generalized metrics not reducible to Finslerian or Langrangian metrics. 相似文献