全文获取类型
收费全文 | 27358篇 |
免费 | 1745篇 |
国内免费 | 2163篇 |
专业分类
化学 | 13621篇 |
晶体学 | 131篇 |
力学 | 167篇 |
综合类 | 239篇 |
数学 | 2854篇 |
物理学 | 3285篇 |
综合类 | 10969篇 |
出版年
2024年 | 24篇 |
2023年 | 139篇 |
2022年 | 322篇 |
2021年 | 257篇 |
2020年 | 299篇 |
2019年 | 356篇 |
2018年 | 305篇 |
2017年 | 446篇 |
2016年 | 483篇 |
2015年 | 785篇 |
2014年 | 1435篇 |
2013年 | 1805篇 |
2012年 | 1633篇 |
2011年 | 1414篇 |
2010年 | 1270篇 |
2009年 | 1623篇 |
2008年 | 1655篇 |
2007年 | 2012篇 |
2006年 | 1747篇 |
2005年 | 1714篇 |
2004年 | 1351篇 |
2003年 | 1204篇 |
2002年 | 891篇 |
2001年 | 764篇 |
2000年 | 1693篇 |
1999年 | 1303篇 |
1998年 | 1110篇 |
1997年 | 514篇 |
1996年 | 463篇 |
1995年 | 369篇 |
1994年 | 370篇 |
1993年 | 286篇 |
1992年 | 253篇 |
1991年 | 182篇 |
1990年 | 139篇 |
1989年 | 118篇 |
1988年 | 93篇 |
1987年 | 65篇 |
1986年 | 46篇 |
1985年 | 58篇 |
1984年 | 40篇 |
1983年 | 21篇 |
1982年 | 33篇 |
1981年 | 41篇 |
1980年 | 27篇 |
1979年 | 19篇 |
1978年 | 24篇 |
1977年 | 19篇 |
1976年 | 12篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
In this paper we propose a general integration scheme for a Multi-Criteria Decision Making model of the Multi-Attribute Utility
Theory in Constraint Programming. We introduce the Choquet integral as a general aggregation function for multi-criteria optimization
problems and define the Choquet global constraint that propagates this function during the Branch-and-Bound search. Finally the benefits of the propagation
of the Choquet constraint are evaluated on the examination timetabling problem. 相似文献
72.
73.
We introduce the time-consistency concept that is inspired by the so-called “principle of optimality” of dynamic programming
and demonstrate – via an example – that the conditional value-at-risk (CVaR) need not be time-consistent in a multi-stage
case. Then, we give the formulation of the target-percentile risk measure which is time-consistent and hence more suitable
in the multi-stage investment context. Finally, we also generalize the value-at-risk and CVaR to multi-stage risk measures
based on the theory and structure of the target-percentile risk measure. 相似文献
74.
V. N. Sorokoumov S. N. Morozkina I. A. Balova 《Chemistry of Heterocyclic Compounds》2006,42(5):615-624
An investigation of the reaction of 1-lithio-1,3-diynes, generated in situ, with nitriles has been carried out. In the case
of aromatic nitriles 1-arylalk-1-ene-3,5-diynylamines are formed, which undergo dimerization and cyclization on isolation,
giving 3-(alka-1,3-diynyl)-4-(alk-2-ynyl)-2,6-diarylpyridines. The effect of the nature of the substituent in the benzonitrile
molecule on the selectivity of the reaction and the yield of the products has been determined. A scheme is proposed for the
conversions and the structures of the intermediates have been established.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 701–710, May, 2006. 相似文献
75.
Augustine O. Esogbue Qiang Song Donovan Young 《Mathematical Methods of Operations Research》2006,63(3):525-542
In this paper the problem of verifying the Pareto-optimality of a given solution to a dynamic multiple-criterion decision (DMCD) problem is investigated. For this purpose, some new conditions are derived for Pareto-optimality of DMCD problems. In the literature, Pareto-optimality is characterized by means of Euler-Lagrangian differential equations. There exist problems in production and inventory control to which these conditions cannot be applied directly (Song 1997). Thus, it is necessary to explore new conditions for Pareto-optimality of DMCD problems. With some mild assumptions on the objective functionals, we develop necessary and/or sufficient conditions for Pareto-optimality in the sprit of optimization theory. Both linear and non-linear cases are considered. 相似文献
76.
对ALICE实验光子谱仪的触发选判机制进行了模拟研究, 内容包括: 1) 对光子谱仪的能量重建性能进行了研究, 通过计算机模拟检验光子谱仪探测器对大横动量范围的入射粒子的能量重建性能; 2) 对光子谱仪探测器的事件触发效率进行了研究, 通过计算机模拟分析触发阈值的选取并计算触发效率; 3) 对光子谱仪探测器的事件触发频率进行了研究, 通过计算机模拟对p-p和Pb-Pb两种碰撞模式下的触发频率分别进行了估算和讨论. 相似文献
77.
Jian Ming ZHAN Bijan DAVVAZ K. P. SHUM 《数学学报(英文版)》2007,23(8):1345-1356
We describe the relationship between the fuzzy sets and the algebraic hyperstructures. In fact, this paper is a continuation of the ideas presented by Davvaz in (Fuzzy Sets Syst., 117: 477- 484, 2001) and Bhakat and Das in (Fuzzy Sets Syst., 80: 359-368, 1996). The concept of the quasicoincidence of a fuzzy interval value with an interval-valued fuzzy set is introduced and this is a natural generalization of the quasi-coincidence of a fuzzy point in fuzzy sets. By using this new idea, the concept of interval-valued (α,β)-fuzzy sub-hypermodules of a hypermodule is defined. This newly defined interval-valued (α,β)-fuzzy sub-hypermodule is a We shall study such fuzzy sub-hypermodules and sub-hypermodules of a hypermodule. generalization of the usual fuzzy sub-hypermodule. consider the implication-based interval-valued fuzzy 相似文献
78.
Jan P. Boroński 《Topology and its Applications》2007,154(18):3156-3166
A set (or a collection of sets) contained in the Euclidean space Rm is symmetric if it is invariant under the antipodal map. Given a symmetric unicoherent polyhedron X (like an n-dimensional cube or a sphere) and an odd real function f defined on vertices of a certain symmetric triangulation of X, we algorithmically construct a connected symmetric separator of X by choosing a subcollection of the triangulation. Each element of the subcollection contains the vertices v and u such that f(v)f(u)?0. 相似文献
79.
在《达罗卫夫人》和《到灯塔去》两部小说中,伍尔夫探讨了现代人有效的生存状态,与他人的社会交往的同时,主要人物都不忘回归自我,任意识随意流淌,展现完全真实的内在自我,在自我宣泄和与他人交流中达到平衡的生存状态。 相似文献
80.
We study the existence and the continuity properties of the boundary values on the real axis of the resolvent of a self-adjoint operator H in the framework of the conjugate operator method initiated by Mourre. We allow the conjugate operator A to be the generator of a C0-semigroup (finer estimates require A to be maximal symmetric) and we consider situations where the first commutator [H,iA] is not comparable to H. The applications include the spectral theory of zero mass quantum field models. 相似文献