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   33277篇
  免费   3615篇
  国内免费   2667篇
电工技术   3073篇
技术理论   7篇
综合类   4357篇
化学工业   1981篇
金属工艺   1030篇
机械仪表   1403篇
建筑科学   9079篇
矿业工程   837篇
能源动力   930篇
轻工业   977篇
水利工程   537篇
石油天然气   1988篇
武器工业   299篇
无线电   3094篇
一般工业技术   2505篇
冶金工业   778篇
原子能技术   347篇
自动化技术   6337篇
  2024年   155篇
  2023年   462篇
  2022年   883篇
  2021年   962篇
  2020年   977篇
  2019年   885篇
  2018年   837篇
  2017年   1016篇
  2016年   1187篇
  2015年   1283篇
  2014年   2217篇
  2013年   2026篇
  2012年   2483篇
  2011年   2723篇
  2010年   2250篇
  2009年   2271篇
  2008年   2193篇
  2007年   2404篇
  2006年   2140篇
  2005年   1742篇
  2004年   1455篇
  2003年   1131篇
  2002年   978篇
  2001年   823篇
  2000年   726篇
  1999年   610篇
  1998年   440篇
  1997年   373篇
  1996年   318篇
  1995年   302篇
  1994年   246篇
  1993年   207篇
  1992年   190篇
  1991年   113篇
  1990年   104篇
  1989年   94篇
  1988年   79篇
  1987年   46篇
  1986年   50篇
  1985年   27篇
  1984年   19篇
  1983年   14篇
  1982年   19篇
  1981年   23篇
  1980年   12篇
  1979年   10篇
  1978年   7篇
  1977年   6篇
  1976年   6篇
  1959年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
一种非线性和时滞系统自适应控制方法   总被引:3,自引:0,他引:3  
杨智  贾立  李尔国 《信息与控制》2001,30(2):143-148
提出一种新的基于高斯基函数(GPFN-G aussian potential function networks)网络的内模控制算法,并对高斯基函数网络内部模 型和内模控制器的建立进行了深入分析.仿真及实时控制结果表明该算法是有效的,具有很 好的自适应性和鲁棒性,可以应用于具有时滞和非线性时变系统中.  相似文献   
73.
Pei‐Chi Wu 《Software》2001,31(12):1125-1130
ISO 10646 Universal Character Set (UCS) is a 31‐bit coding architecture that covers symbols in most of the world's written languages. Identifiers in programming languages are usually defined by using alphanumeric characters of ASCII, which represent mainly English words. An approach for working around this deficiency is to encode multilingual identifiers into the alphanumeric range of ASCII. For case‐sensitive languages, an encoding that utilizes [0–9][A–Z][a–z] can be more space‐efficient for multilingual identifiers. This paper proposes a base62 transformation format of ISO 10646 called UTF‐62. The resulting string of UTF‐62 is within a [0–9][A–Z][a–z] range, a total of 62 base characters. UTF‐62 also preserves the lexicographic sorting order of UCS‐4. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
74.
The parallelism attained by the use of Field Programmable Gate Arrays (FPGAs) has shown remarkable potential for accelerating control systems applications. This comes at a time when well established methods based on inherited serial Central Processor Units (CPUs) cannot guarantee solutions for the increasing execution speed demands. However, the transition from serial to parallel architectures represents a tremendous challenge due to overwhelming numbers of unexplored options and conflicting factors. The work presented achieves a parallelisation characterisation for generic MIMO systems using stand-alone FPGA implementations. The main contribution is that a very fine subset of possible serial/parallel implementations is obtained. This is used to achieve a flexible trade-off between cost and performance. Automatic optimisation of latency, occupied FPGA area and execution speed is attained and justified in respect to most of the feasible scenarios.  相似文献   
75.
《国际计算机数学杂志》2012,89(8):1366-1374
In this study we are concerned with the local convergence of a Newton-type method introduced by us [I.K. Argyros and D. Chen, On the midpoint iterative method for solving nonlinear equations in Banach spaces, Appl. Math. Lett. 5 (1992), pp. 7–9.] for approximating a solution of a nonlinear equation in a Banach space setting. This method has also been studied by Homeier [H.H.H. Homeier, A modified Newton method for rootfinding with cubic convergence, J. Comput. Appl. Math. 157 (2003), pp. 227–230.] and Özban [A.Y. Özban, Some new variants of Newton's method, Appl. Math. Lett. 17 (2004), pp. 677–682.] in real or complex space. The benefits of using this method over other methods using the same information have been explained in [I.K. Argyros, Computational theory of iterative methods, in Studies in Computational Mathematics, Vol. 15, C.K. Chui and L. Wuytack, eds., Elsevier Science Inc., New York, USA, 2007.; I.K. Argyros and D. Chen, On the midpoint iterative method for solving nonlinear equations in Banach spaces, Appl. Math. Lett. 5 (1992), pp. 7–9.; H.H.H. Homeier, A modified Newton method for rootfinding with cubic convergence, J. Comput. Appl. Math. 157 (2003), pp. 227–230.; A.Y. Özban, Some new variants of Newton's method, Appl. Math. Lett. 17 (2004), pp. 677–682.]. Here, we give the convergence radii for this method under a type of weak Lipschitz conditions proven to be fruitful by Wang in the case of Newton's method [X. Wang, Convergence of Newton's method and inverse function in Banach space, Math. Comput. 68 (1999), pp. 169–186 and X. Wang, Convergence of Newton's method and uniqueness of the solution of equations in Banach space, IMA J. Numer. Anal. 20 (2000), pp. 123–134.]. Numerical examples are also provided.  相似文献   
76.
Vanishing point detection algorithms based on 2D histogramming techniques have been employed in a variety of computer vision systems. Previous algorithms achieved some good results but still failed to maintain a balanced performance in both accuracy and time. Recent research (Li et al., 2010) shows that, vanishing point detection could be converted to a 1D histogram search problem, which largely accelerates the procedure. In this paper, we further improve this idea and propose a complete scheme for vanishing point detection from images of the so called “Manhattan world”. We test our algorithm and some commonly used vanishing point detection methods on public database YorkUrbanDB and our own implemented database PKUCampusDB. Our algorithm shows significant performance improvements.  相似文献   
77.
爱伦·坡的《阿芒提拉多的酒桶》是一部充满哥特色彩的短篇小说。该小说采用谋杀者蒙特利瑟自述的形式,讲述50年前他对弗图那多的谋杀,呈现了阴森酒窖里性格扭曲的蒙特利瑟活埋弗图那多的恐怖画面。借助当代文学批评理论中的空间话语研究该短篇小说中的哥特书写,从建筑场景、人物并置和叙事特征方面分析小说哥特空间的构建,进一步突出故事的哥特主题——恐怖、扭曲和死亡。  相似文献   
78.
以能量守恒原理为主线,在各向同性前提下,对Taylor剪胀方程、Cam-clay剪胀方程、修正Cam-clay剪胀方程、Rowe剪胀方程和扩展的Rowe剪胀方程等进行了较全面的综述.论证了剪胀方程和塑性势函数之间的相互转化关系.指出了Lade-Kim塑性势函数和Nova塑性势函数的缺陷之处,即这两个塑性势函数均没有合理耦合临界状态这一概念.  相似文献   
79.
从段落向量空间模型、特征词权重等多个侧面分析比较了已有的文本结构分析算法,提出了优化的AP-CAPSA算法;给出了算法性能的评价准则,并在不同的语料集合上进行了测试。实验表明该方法能够更有效地反映文本的结构,为中文自动摘要系统奠定了重要的理论基础。  相似文献   
80.
In a pot culture experiment, the effect of gypsum (50% of soil requirement), pyrites (equivalent to gypsum), farmyard manure (0.5 g per 100g soil) and Zn (10mg Zn kg–1 soil) on Zn equilibria in Ghabdan and Langrian series of sodic soils was studied. The equilibrium soil solutions collected anaerobically after 1, 14, 28, 42, 56, 70 and 84 days of submergence were analysed for pH, EC, HCO3 and Zn. Submergence markedly decreased soil solution pH and Zn up to 14 days and thereafter, the former slightly increased and the latter continued to decrease. Addition of amendments decreased soil solution pH in the order gypsum, pyrites and farmyard manure (FYM) and increased Zn concentration in the order FYM, gypsum and pyrites. The values of Zn potential (pZn + 2pOH) were within the range of pKsp for Zn(OH)2-Zn2+ (aq) from 16 to 84 days of submergence in Ghabdan soil and from 9 to 42 days of submergence in Langrian soil, where later it shifted to ZnCO3-Zn2+ (aq) system. Addition of FYM, pyrites and gypsum shortened the period of predominant existence of Zn(OH)2-Zn2+ (aq) system to 40, 30 and 12 days in Ghabdan soil and 30, 20 and 6 days in Langrian soil respectively. After these periods the system was saturated with respect to ZnCO3-Zn2+ (aq) except gypsum treatment where Zn-soil (unknown solid phases) -Zn2+ (aq) system controlled the solubility of Zn after 38 and 28 days of submergence of Ghabdan and Langrian soil respectively.  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