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   7688篇
  免费   336篇
  国内免费   71篇
化学   5479篇
晶体学   82篇
力学   324篇
综合类   1篇
数学   934篇
物理学   1275篇
  2024年   23篇
  2023年   82篇
  2022年   629篇
  2021年   456篇
  2020年   324篇
  2019年   315篇
  2018年   288篇
  2017年   234篇
  2016年   388篇
  2015年   216篇
  2014年   281篇
  2013年   640篇
  2012年   444篇
  2011年   458篇
  2010年   285篇
  2009年   246篇
  2008年   317篇
  2007年   314篇
  2006年   258篇
  2005年   214篇
  2004年   199篇
  2003年   179篇
  2002年   181篇
  2001年   87篇
  2000年   61篇
  1999年   59篇
  1998年   43篇
  1997年   31篇
  1996年   54篇
  1995年   39篇
  1994年   43篇
  1993年   41篇
  1992年   50篇
  1991年   47篇
  1990年   35篇
  1989年   49篇
  1988年   44篇
  1987年   31篇
  1986年   41篇
  1985年   36篇
  1984年   43篇
  1983年   36篇
  1982年   28篇
  1981年   21篇
  1980年   32篇
  1979年   27篇
  1978年   31篇
  1977年   20篇
  1976年   18篇
  1975年   16篇
排序方式: 共有8095条查询结果,搜索用时 31 毫秒
951.
In this paper we study an inverse problem for a degenerate differential equation on a Banach space. A projection method will be used to reduce the problem to a regular abstract inverse problem. To this end some conditions on the operators are assumed to avoid the calculations of some inverses of the involved operators.  相似文献   
952.
We define non-pluripolar products of an arbitrary number of closed positive (1, 1)-currents on a compact Kähler manifold X. Given a big (1, 1)-cohomology class α on X (i.e. a class that can be represented by a strictly positive current) and a positive measure μ on X of total mass equal to the volume of α and putting no mass on pluripolar sets, we show that μ can be written in a unique way as the top-degree self-intersection in the non-pluripolar sense of a closed positive current in α. We then extend Kolodziedj’s approach to sup-norm estimates to show that the solution has minimal singularities in the sense of Demailly if μ has L 1+ε -density with respect to Lebesgue measure. If μ is smooth and positive everywhere, we prove that T is smooth on the ample locus of α provided α is nef. Using a fixed point theorem, we finally explain how to construct singular Kähler–Einstein volume forms with minimal singularities on varieties of general type.  相似文献   
953.
954.
Planning horizon is a key issue in production planning. Different from previous approaches based on Markov Decision Processes, we study the planning horizon of capacity planning problems within the framework of stochastic programming. We first consider an infinite horizon stochastic capacity planning model involving a single resource, linear cost structure, and discrete distributions for general stochastic cost and demand data (non-Markovian and non-stationary). We give sufficient conditions for the existence of an optimal solution. Furthermore, we study the monotonicity property of the finite horizon approximation of the original problem. We show that, the optimal objective value and solution of the finite horizon approximation problem will converge to the optimal objective value and solution of the infinite horizon problem, when the time horizon goes to infinity. These convergence results, together with the integrality of decision variables, imply the existence of a planning horizon. We also develop a useful formula to calculate an upper bound on the planning horizon. Then by decomposition, we show the existence of a planning horizon for a class of very general stochastic capacity planning problems, which have complicated decision structure.  相似文献   
955.
In this note, we prove the global well posedness and the local energy decay for semilinear wave equation with small data.  相似文献   
956.
A metrical common fixed point theorem for a pair of self mappings due to Sastry and Murthy (K.P.R. Sastry, I.S.R. Krishna Murthy, A common fixed points of two partially commuting tangential selfmaps on a metric space, J. Math. Anal. Appl. 250 (2000) 731734.) [8] is extended to symmetric spaces which in turn generalises a fixed point theorem due to Pant (R.P. Pant, Common fixed points of Lipschitz type mapping pairs, J. Math. Anal. Appl. 248 (1999) 280283.) [11] besides deriving some related results. Some illustrative examples to highlight the realised improvements are also furnished.  相似文献   
957.
Hybrid compounds of macrosphelides and epothilones, both of which are natural macrolides having a 16-membered skeleton, were designed and synthesized using a ring-closing metathesis (RCM) strategy. Some of these hybrids were found to exhibit notable apoptosis-inducing activity against human lymphoma cells with higher potency than parent natural macrosphelides, and to be a promising lead compound for development of a new antitumor agent.  相似文献   
958.
This work presents the results of applying an advanced fault detection and isolation technique to centrifugal compressor; this advanced technique uses physics models of the centrifugal compressor with a fuzzy modeling and control solution method. The fuzzy fault detection and isolation has become an issue of primary importance in modern process engineering automation as it provides the prerequisites for the task of fault detection. In this work, we present an application of this approach in fault detection and isolation of surge in compression system. The ability to detect the surge is essential to improve reliability and security of the gas compressor plants. We describe and illustrate an alternative implementation to the compression systems supervision task using the basic principles of fuzzy fault detection and isolation associated with fuzzy modeling approach. In this supervision task, the residual generation is obtained from the real input-output data process and the residual evaluation is based on fuzzy logic method. The results of this application are very encouraging with relatively low levels of false alarms and obtaining a good limitation of surge in natural gas pipeline compressors.  相似文献   
959.
960.
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