全文获取类型
收费全文 | 4764篇 |
免费 | 183篇 |
国内免费 | 319篇 |
专业分类
化学 | 400篇 |
晶体学 | 1篇 |
力学 | 167篇 |
综合类 | 31篇 |
数学 | 3711篇 |
物理学 | 956篇 |
出版年
2024年 | 7篇 |
2023年 | 37篇 |
2022年 | 81篇 |
2021年 | 54篇 |
2020年 | 98篇 |
2019年 | 115篇 |
2018年 | 126篇 |
2017年 | 97篇 |
2016年 | 104篇 |
2015年 | 78篇 |
2014年 | 219篇 |
2013年 | 371篇 |
2012年 | 169篇 |
2011年 | 252篇 |
2010年 | 209篇 |
2009年 | 315篇 |
2008年 | 394篇 |
2007年 | 308篇 |
2006年 | 247篇 |
2005年 | 210篇 |
2004年 | 159篇 |
2003年 | 174篇 |
2002年 | 143篇 |
2001年 | 121篇 |
2000年 | 120篇 |
1999年 | 115篇 |
1998年 | 122篇 |
1997年 | 102篇 |
1996年 | 95篇 |
1995年 | 61篇 |
1994年 | 52篇 |
1993年 | 50篇 |
1992年 | 49篇 |
1991年 | 35篇 |
1990年 | 28篇 |
1989年 | 42篇 |
1988年 | 35篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 37篇 |
1984年 | 37篇 |
1983年 | 13篇 |
1982年 | 25篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1979年 | 22篇 |
1978年 | 16篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1973年 | 3篇 |
排序方式: 共有5266条查询结果,搜索用时 15 毫秒
41.
K. Gowri Navada 《Proceedings Mathematical Sciences》1995,105(3):281-285
We give an estimate for the number of elements in the intersection of topological Sidon sets inR
n with compact convex subsets and deduce a necessary and sufficient conditions for an orbit of a linear transformation ofR
n to be a topological Sidon set. 相似文献
42.
Pure adaptive search in global optimization 总被引:10,自引:0,他引:10
Pure adaptive seach iteratively constructs a sequence of interior points uniformly distributed within the corresponding sequence of nested improving regions of the feasible space. That is, at any iteration, the next point in the sequence is uniformly distributed over the region of feasible space containing all points that are strictly superior in value to the previous points in the sequence. The complexity of this algorithm is measured by the expected number of iterations required to achieve a given accuracy of solution. We show that for global mathematical programs satisfying the Lipschitz condition, its complexity increases at mostlinearly in the dimension of the problem.This work was supported in part by NATO grant 0119/89. 相似文献
43.
A new collectively fixed point theorem for a family of set-valued mappings defined on product spaces of non-compact topological spaces without linear structure is proved and some special cases are also discussed. As applications, some non-empty intersection theorems of sets with convex sections and equilibrium existence theorem of abstract economies are obtained under much weaker assumptions. Our results includes a number of known results as many special cases. 相似文献
44.
Three-dimensional (3-D) ZnO random-wall nanostructures and one-dimensional (1-D) ZnO nanorods were prepared on silicon substrates by a simple solid-vapour phase thermal sublimation technique. Optical pumped random lasing has been observed in the ZnO random-wall arrays with a threshold intensity of 0.38 MW/cm2 in the emission wavelength from 380 to 395 nm. The optical gain was attributed to the closed-loop scattering and light amplification of the ZnO random-wall. The experimental result suggests that the morphology of nanostructure is the key factor to effect random lasing. 相似文献
45.
We introduce a generalized notion of semiring and prove that all known properties that semirings have according to the old definition are preserved. 相似文献
46.
Some non-singlet quasi-instabilities (QIs) cases that arise in the calculation of NMR-J parameters are analyzed within response theory. The relationship between ‘very close to zero’ eigenvalues of the principal propagator and the rate of convergency for specific coupling pathways is shown by a power series implemented to calculate the principal propagator matrix. A natural criterion for the analysis of the stability problem emerges from that series. This is more general and accurate compared with previous proposals. Its relationship with π-type molecular orbitals is given. We present an alternative scheme to minimize the effects of non-singlet QIs in such a way that the NMR-J parameters become close to the best theoretical calculations for H2CX (X=CH2, NH and O). 相似文献
47.
Joël Benoist 《Journal of Global Optimization》2003,25(3):321-335
In finite dimensional Euclidean space, we prove the contractibility of the efficient frontier of simply shaded sets. This work extends the result of Peleg [7], which confirms the contractibility of the efficient frontier in the convex case. 相似文献
48.
Noninferior Nash Strategies for Multi-Team Systems 总被引:1,自引:0,他引:1
This paper is concerned with the optimization of systems that are controlled by several teams of decision makers. The decision makers within each team cooperate for the benefit of their team. On the other hand, the teams compete among themselves in order to achieve an objective that relates to the overall performance of the system. An approach that merges concepts from team theory and game theory for dealing with such systems and a solution called the noninferior Nash strategy are introduced. This multi-team solution provides a new framework for analyzing hierarchically controlled systems so as to address complicated coordination problems among the decision makers. The properties of the noninferior Nash solution in static multi-team systems are investigated and necessary conditions for its existence are derived. Analytical expressions for the noninferior Nash strategies are derived for a class of linear-quadratic static multi-team games. In order to deal with the issue of nonuniqueness of the solution, the concept of a noninferior Nash strategy with a team leader is introduced. Several examples are presented to illustrate the results. 相似文献
49.
Michel Vasquez 《Journal of Heuristics》2004,10(4):407-413
For the Queens_n
2 graph coloring problems no chromatic numbers are available for n > 9 except where n is not a multiple of 2 or 3. In this paper we propose an exact algorithm that takes advantage of the particular structure of these graphs. The algorithm works on the independent sets of the graph rather than on the vertices to be colored. It combines branch and bound, for independent set assignment, with a clique based filtering procedure. A first experimentation of this approach provided the coloring number values ranging for n = 10 to n = 14. 相似文献
50.
M. A. Noor 《Journal of Optimization Theory and Applications》2004,121(2):385-395
In this paper, we suggest and analyze some iterative methods for solving nonconvex variational inequalities using the auxiliary principle technique, the convergence of which requires either only pseudomonotonicity or partially relaxed strong monotonicity. Our proofs of convergence are very simple. As special cases, we obtain earlier results for solving general variational inequalities involving convex sets. 相似文献