首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   83112篇
  免费   7195篇
  国内免费   8629篇
化学   29554篇
晶体学   446篇
力学   8003篇
综合类   1524篇
数学   29442篇
物理学   29967篇
  2024年   127篇
  2023年   678篇
  2022年   1450篇
  2021年   1608篇
  2020年   1625篇
  2019年   1936篇
  2018年   1596篇
  2017年   1987篇
  2016年   2213篇
  2015年   2017篇
  2014年   3045篇
  2013年   5335篇
  2012年   3448篇
  2011年   3988篇
  2010年   3584篇
  2009年   4830篇
  2008年   5295篇
  2007年   5486篇
  2006年   5144篇
  2005年   4344篇
  2004年   3907篇
  2003年   3917篇
  2002年   3548篇
  2001年   3042篇
  2000年   2962篇
  1999年   2630篇
  1998年   2435篇
  1997年   2034篇
  1996年   1814篇
  1995年   1597篇
  1994年   1435篇
  1993年   1235篇
  1992年   1216篇
  1991年   936篇
  1990年   759篇
  1989年   687篇
  1988年   598篇
  1987年   464篇
  1986年   387篇
  1985年   457篇
  1984年   451篇
  1983年   218篇
  1982年   372篇
  1981年   416篇
  1980年   311篇
  1979年   317篇
  1978年   233篇
  1977年   214篇
  1976年   160篇
  1974年   122篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
In this paper, we consider questions related to the structure of inverse matrices of linear bounded operators acting in infinite-dimensional complex Banach spaces. We obtain specific estimates of elements of inverse matrices for bounded operators whose matrices have a special structure. Matrices are introduced as special operator-valued functions on an index set. The matrix structure is described by the behavior of the given function on elements of a special partition of the index set. The method used for deriving the estimates is based on an analysis of Fourier series of strongly continuous periodic functions.  相似文献   
142.
抓好数学建模竞赛 推动数学教学改革   总被引:5,自引:0,他引:5  
本文通过近几年组织数学建模教学和指导学生参加竞赛的实践 ,探索抓好数学建模竞赛 ,促进数学教学改革 ,推动数学素质教育 ,提高人才培养质量的途径、措施和方法  相似文献   
143.
We extract some properties of Mahlo’s operation and show that some other very natural operations share these properties. The weakly compact sets form a similar hierarchy as the stationary sets. The height of this hierarchy is a large cardinal property connected to saturation properties of the weakly compact ideal.  相似文献   
144.
This paper gives a p-adic analogue of the Mackey theory, which relates representations of a group of type G - H × t A to systems of imprimitivity.  相似文献   
145.
牛顿弦截法预估校正迭代格式的收敛阶   总被引:2,自引:0,他引:2  
研究如下形式的牛顿弦截法的预估校正(P.C.)格式:P(预估):~xk+1=xk-(xk-xk-1)f(xk)f(xk)-f(xk-1)C(校正):xk+1=xk-(~xk+1-xk)f(xk)f~(xk+1)-f(xk)证明了它的收敛阶为2.618.  相似文献   
146.
Maxim Perelstein 《Pramana》2006,67(5):813-820
Little Higgs models are an interesting extension of the Standard Model at the TeV scale. They provide a simple and attractive mechanism of electroweak symmetry breaking. We review one of the simplest models of this class, the Littlest Higgs model, and its extension with T parity. The model with T parity satisfies precision electroweak constraints without fine-tuning, contains an attractive dark matter candidate, and leads to interesting phenomenology at the Large Hadron Collider (LHC).  相似文献   
147.
In [W.-C. Kuo, C.C.A. Labuschagne, B.A. Watson, Discrete-time stochastic processes on Riesz spaces, Indag. Math. (N.S.) 15 (3) (2004) 435-451], we introduced the concepts of conditional expectations, martingales and stopping times on Riesz spaces. Here we formulate and prove order theoretic analogues of the Birkhoff, Hopf and Wiener ergodic theorems and the Strong Law of Large Numbers on Riesz spaces (vector lattices).  相似文献   
148.
Differential inequality method, bounding function method and topological degree are applied to obtain the existence criterions of at least one solution for the general fourth-order differential equations under nonlinear boundary conditions, and many existing results are complemented.  相似文献   
149.
We consider the problem of scheduling orders for multiple different product types in an environment with m dedicated machines in parallel. The objective is to minimize the total weighted completion time. Each product type is produced by one and only one of the m dedicated machines; that is, each machine is dedicated to a specific product type. Each order has a weight and may also have a release date. Each order asks for certain amounts of various different product types. The different products for an order can be produced concurrently. Preemptions are not allowed. Even when all orders are available at time 0, the problem has been shown to be strongly NP-hard for any fixed number (?2) of machines. This paper focuses on the design and analysis of efficient heuristics for the case without release dates. Occasionally, however, we extend our results to the case with release dates. The heuristics considered include some that have already been proposed in the literature as well as several new ones. They include various static and dynamic priority rules as well as two more sophisticated LP-based algorithms. We analyze the performance bounds of the priority rules and of the algorithms and present also an in-depth comparative analysis of the various rules and algorithms. The conclusions from this empirical analysis provide insights into the trade-offs with regard to solution quality, speed, and memory space.  相似文献   
150.
狭缝式高速摄影机胶片的计算机判读   总被引:3,自引:1,他引:2  
根据狭缝摄影机胶片的成象原理,运用数字图象处理技术,对狭缝式高速摄影机胶片判读工作的计算机化进行研究.应用结果表明,该技术先进实用,极大地提高了判读的精度和效率,将是这种胶片判读技术的发展方向.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号