全文获取类型
收费全文 | 9445篇 |
免费 | 78篇 |
国内免费 | 9篇 |
专业分类
教育 | 6490篇 |
科学研究 | 1173篇 |
各国文化 | 59篇 |
体育 | 664篇 |
综合类 | 4篇 |
文化理论 | 60篇 |
信息传播 | 1082篇 |
出版年
2022年 | 59篇 |
2021年 | 104篇 |
2020年 | 135篇 |
2019年 | 185篇 |
2018年 | 309篇 |
2017年 | 281篇 |
2016年 | 282篇 |
2015年 | 168篇 |
2014年 | 283篇 |
2013年 | 1603篇 |
2012年 | 224篇 |
2011年 | 253篇 |
2010年 | 222篇 |
2009年 | 199篇 |
2008年 | 247篇 |
2007年 | 214篇 |
2006年 | 181篇 |
2005年 | 165篇 |
2004年 | 187篇 |
2003年 | 141篇 |
2002年 | 148篇 |
2001年 | 214篇 |
2000年 | 211篇 |
1999年 | 188篇 |
1998年 | 105篇 |
1997年 | 138篇 |
1996年 | 125篇 |
1995年 | 88篇 |
1994年 | 111篇 |
1993年 | 90篇 |
1992年 | 178篇 |
1991年 | 144篇 |
1990年 | 125篇 |
1989年 | 164篇 |
1988年 | 138篇 |
1987年 | 114篇 |
1986年 | 112篇 |
1985年 | 117篇 |
1984年 | 90篇 |
1983年 | 106篇 |
1982年 | 75篇 |
1981年 | 80篇 |
1980年 | 71篇 |
1979年 | 116篇 |
1978年 | 76篇 |
1977年 | 72篇 |
1976年 | 64篇 |
1975年 | 58篇 |
1974年 | 70篇 |
1973年 | 66篇 |
排序方式: 共有9532条查询结果,搜索用时 31 毫秒
41.
K. C. Soh 《Psychology in the schools》1973,10(3):316-320
42.
43.
Starting from the notion of h-type indices for infinite sequences we investigate if these indices satisfy natural inequalities related to the arithmetic, the geometric and the harmonic mean. If f denotes an h-type index, such as the h- or the g-index, then we investigate inequalities such as min(f(X),f(Y)) ≤ f((X?+?Y)/2) ≤ max(f(X), f(Y)). We further investigate if: f(min(X,Y)) = min(f(X),f(Y)) and if f(max(X,Y)) = max(f(X),f(Y)). It is shown that the h-index satisfies all the equalities and inequalities we investigate but the g-index does not always, while it is always possible to find a counterexample involving the R-index. This shows that the h-index enjoys a number of interesting mathematical properties as an operator in the partially ordered positive cone (R+)∞ of all infinite sequences with non-negative real values.In a second part we consider decreasing vectors X and Y with components at most at distance d. Denoting by D the constant sequence (d,d,d, …) and by Y-D the vector (max(yr-d), 0)r, we prove that under certain natural conditions, the double inequality h(Y-D) ≤ h(X) ≤ h(Y?+?D) holds. 相似文献
44.
Ronald Rousseau 《情报学报》2006,25(5):580-586
网络信息检索中,逻辑运算符AND连接检索词的顺序很大程度上会影响检索效率.论文首先分析、介绍了the Staceys测度方法在改善AND检索效率中发挥的作用,并在此基础上提出简化了的测度算法,最后通过实例说明其实现步骤. 相似文献
45.
The graph-theoretic field model— II. application of multi-terminal representations to field problems
This paper is a sequel to a paper entitled “The Graph-Theoretic Field Model—I: Modelling and Formulations” (1). Herein, the Theory of Multi-Terminal Representations is applied to the Graph-Theoretic Field Model to provide mathematical models of finite elements. The element models are obtained solely from the algebraic building blocks of the Graph-Theoretic Field Model, without recourse to any functional mathematics. The theory of Multi-Terminal Representations is developed for both linear and non-linear problems. Examples of the application of the theory to one- and two-dimensional field problems are presented from heat conduction and electrostatics. 相似文献
46.
K.B. Datta 《Journal of The Franklin Institute》1980,309(2):103-123
47.
48.
The Graph-Theoretical Field Model provides a unifying approach for developing numerical models of field and continuum problems. The methodology examines the field problem from the first stages of conceptualization without recourse to the governing differential equations of the field problem; this is accomplished by deriving discrete statements of the physical laws which govern the field behaviour. There are generally three laws, and these are modelled by the “cutset equations”, the “circuit equations”, and the “terminal equations”. In order to establish these three sets of equations it is expedient first to spatially discretize the field in a manner similar to the finite difference method and then to associate a linear graph (denoted as the field graph) with the spatial discretization. The concept of “through” and “across” variables, which underlies the cutset and circuit equations respectively, enables one to define the graph in an unambiguous manner such that each “edge” of the graph identifies a pair of complementary variables. From a knowledge of the constitutive properties and the boundary conditions of the field it is possible to associate terminal equations with sets of edges. Since the resulting sets of equations represent the field equations, these equations provide the basis for a complete (but approximate) solution to the field or continuum problem. In fact, this system approach uses a two part model: one for the components and another for the interconnection pattern of the components which renders the formulation procedures totally independent of the solution procedure.This paper presents the theoretical basis of the model and several graph-theoretic formulations for steady-state problems. Examples from heat conduction and small- deformation elasticity are included. 相似文献
49.
50.
This paper introduces a polynomial operator called the DT-polynomial as a novel approach to network flow problems. The class of networks dealt with is time-varying in the sense that the capacity, cost, and travel-time of each edge may vary in discrete time. The Dt-polynomial is a polynomial in two operators, D (delay) and T (time), which is used for describing the time-varying transmission characteristics. The paper starts with the mathematics involving the DT-polynomials. A new shortest arrival route algorithm is presented, and its computational complexity is found to be favorable in comparison with others such as Dijkstra's method and the potential method derived from Ford-Fulkerson's technique. Furthermore, a dynamic flow problem is formulated and analyzed in terms of DT-polynomials, and a latest-departure earliest-arrival schedule is given. Finally, a modified DT-polynomial is applied to digital filter networks. 相似文献