全文获取类型
收费全文 | 19681篇 |
免费 | 757篇 |
国内免费 | 1044篇 |
专业分类
化学 | 2281篇 |
晶体学 | 41篇 |
力学 | 418篇 |
综合类 | 93篇 |
数学 | 4782篇 |
物理学 | 2036篇 |
综合类 | 11831篇 |
出版年
2024年 | 24篇 |
2023年 | 131篇 |
2022年 | 167篇 |
2021年 | 195篇 |
2020年 | 228篇 |
2019年 | 278篇 |
2018年 | 241篇 |
2017年 | 345篇 |
2016年 | 323篇 |
2015年 | 410篇 |
2014年 | 946篇 |
2013年 | 1100篇 |
2012年 | 1025篇 |
2011年 | 1203篇 |
2010年 | 1118篇 |
2009年 | 1352篇 |
2008年 | 1319篇 |
2007年 | 1341篇 |
2006年 | 1247篇 |
2005年 | 1097篇 |
2004年 | 925篇 |
2003年 | 827篇 |
2002年 | 754篇 |
2001年 | 679篇 |
2000年 | 586篇 |
1999年 | 478篇 |
1998年 | 421篇 |
1997年 | 372篇 |
1996年 | 299篇 |
1995年 | 255篇 |
1994年 | 236篇 |
1993年 | 202篇 |
1992年 | 186篇 |
1991年 | 133篇 |
1990年 | 124篇 |
1989年 | 158篇 |
1988年 | 133篇 |
1987年 | 77篇 |
1986年 | 51篇 |
1985年 | 64篇 |
1984年 | 54篇 |
1983年 | 24篇 |
1982年 | 52篇 |
1981年 | 59篇 |
1980年 | 70篇 |
1979年 | 55篇 |
1978年 | 28篇 |
1977年 | 29篇 |
1976年 | 22篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
161.
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
162.
We study a system of quasilinear equations describing one-dimensional flow of a viscous compressible heat-conducting medium with a nonmonotone state function and mass force. The large-time behavior of solutions is considered for arbitrarily large initial data. In spite of possible nonuniqueness and discontinuity of the stationary solution, we prove L2-stabilization for the stress and heat flux as t → ∞ along with corresponding global energy estimates for them. The new method of proof utilizes a combination of energy type equalities for the stress and heat flux. Consequently, H1-stabilization of the velocity and temperature along with global estimates for their derivatives are valid as well. 相似文献
163.
164.
刘文献 《科技情报开发与经济》2007,17(6):186-187
分析了地方性科技期刊陷入困境的主要原因,并有针对性地提出了一些促进科技期刊发展的对策和建议。 相似文献
165.
森林资源调查方法存在的问题及对策 总被引:1,自引:0,他引:1
辛胜利 《科技情报开发与经济》2007,17(17):265-266
对临汾市历年来森林资源调查方法存在的问题进行了分析,提出了完善森林资源调查的对策。 相似文献
166.
陈定璜 《渝西学院学报(自然科学版)》2007,(4):70-72
“程伟案件”将当前法院在执行款的执行制度上存在的问题暴露无遗,引发了社会各界对法院执行款管理问题的再度关注.本文从不同角度就人民法院执行款管理中存在的问题进行剖析并提出了相应的对策性建议. 相似文献
167.
给出模糊半群上的模糊同余的概念,并进一步研究它的一些基本代数性质。同时研究带有模糊半群上的模糊同余扩张性质(FCEPF)的半群类,得到一个半群有模糊半群上的模糊同余扩张性质、有模糊同余扩张性质(FCEP)、有同余扩张性质(CEP)三个条件是等价的。 相似文献
168.
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
169.
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
170.
A linear inequality system with infinitely many constraints is polynomial (analytical) if its index set is a compact interval
of the real line and all its coefficients are polynomial (analytical, respectively) functions of the index on this interval.
This paper provides an example of analytical system whose solution set cannot be the solution set of any polynomial system.
Research supported by DGES of Spain and FEDER of UE, Grant BFM2002-04114-C02-01.
Research supported by CONACyT of Mexico, Grant 130036.
Research partially supported by CONACyT of Mexico, Grant 44003. 相似文献