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   17962篇
  免费   1425篇
  国内免费   1094篇
电工技术   1593篇
综合类   2143篇
化学工业   897篇
金属工艺   466篇
机械仪表   1237篇
建筑科学   492篇
矿业工程   279篇
能源动力   488篇
轻工业   183篇
水利工程   380篇
石油天然气   204篇
武器工业   137篇
无线电   1169篇
一般工业技术   1445篇
冶金工业   224篇
原子能技术   50篇
自动化技术   9094篇
  2024年   36篇
  2023年   149篇
  2022年   235篇
  2021年   299篇
  2020年   387篇
  2019年   442篇
  2018年   350篇
  2017年   523篇
  2016年   558篇
  2015年   639篇
  2014年   972篇
  2013年   1367篇
  2012年   1030篇
  2011年   1142篇
  2010年   890篇
  2009年   1013篇
  2008年   1094篇
  2007年   1168篇
  2006年   1034篇
  2005年   898篇
  2004年   765篇
  2003年   688篇
  2002年   631篇
  2001年   541篇
  2000年   473篇
  1999年   420篇
  1998年   333篇
  1997年   349篇
  1996年   300篇
  1995年   255篇
  1994年   262篇
  1993年   190篇
  1992年   177篇
  1991年   148篇
  1990年   104篇
  1989年   98篇
  1988年   95篇
  1987年   54篇
  1986年   56篇
  1985年   41篇
  1984年   53篇
  1983年   32篇
  1982年   36篇
  1981年   23篇
  1980年   23篇
  1979年   29篇
  1978年   11篇
  1977年   23篇
  1976年   17篇
  1975年   12篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
This paper is an introduction to rule-based programming in Maude. We illustrate in particular the use of operator attributes to structure the state of a system, and the difference between equations and rules. We use well-known mathematical games and puzzles for our examples illustrating the expressive power of Maude.  相似文献   
52.
The paper is devoted to the first order delayed linear system with relay output controlled by the proportional-integral (PI) regulator. The deterministic system exhibits stable oscillations, and, since the system itself is stable, it can be suitable to switch off the controller if there are no disturbances during a long time interval. In the present work, the random disturbances are modelled by a Poisson stream of impulses, and the goal is to determine the instants of switching on (off) of the PI controller. After several assumptions and quantization of the time axis, we construct the new optimal control problem which is successfully solved with the help of the dynamic programming approach.  相似文献   
53.
In this work, we study dynamic provisioning of multicast sessions in a wavelength-routed sparse splitting capable WDM network with an arbitrary mesh topology where the network consists of nodes with full, partial, or no wavelength conversion capabilities and a node can be a tap-and-continue (TaC) node or a splitting and delivery (SaD) node. The objectives are to minimize the network resources in terms of wavelength-links used by each session and to reduce the multicast session blocking probability. The problem is to route the multicast session from each source to the members of every multicast session, and to assign an appropriate wavelength to each link used by the session. We propose an efficient online algorithm for dynamic multicast session provisioning. To evaluate the proposed algorithm, we apply the integer linear programming (ILP) optimization tool on a per multicast session basis to solve off-line the optimal routing and wavelength assignment given a multicast session and the current network topology as well as its residual network resource information. We formulate the per session multicast routing and wavelength assignment problem as an ILP. With this ILP formulation, the multicast session blocking probability or success probability can then be estimated based on solving a series of ILPs off-line. We have evaluated the effectiveness of the proposed online algorithm via simulation in terms of session blocking probability and network resources used by a session. Simulation results indicate that our proposed computationally efficient online algorithm performs well even when a fraction of the nodes are SaD nodes.  相似文献   
54.
55.
To satisfy public demands for environmental values, forest companies are facing the prospect of a reduction in wood supply and increases in costs. Some Canadian provincial governments have proposed intensifying silviculture in special zones dedicated to timber production as the means for pushing out the forest possibility frontiers. In this paper, we compare the traditional two‐zone land allocation framework which includes ecological reserves and integrated forest management zones with the triad — a three‐zone scheme which adds a zone dedicated to intensive timber production. We compare the solutions of the mixed‐integer linear programs formulated under both land‐allocation frameworks. We explore through sensitivity analysis the conditions under which the triad regime can offset the impact on timber production from increased environmental demands. We show that under the realistic conditions characteristic to Coastal British Columbia, higher environmental demands may be satisfied under the triad regime without increasing the financial burdens on the industry or reducing its wood supply. This occurs, however, only if regulatory constraints in timber production zone are flexible.  相似文献   
56.
57.
The embedding of a small but expressive language of multidimensional functional programming in a well known and widely used language of object‐oriented programming leads to the combination of two radically different programming models. In this paper, we formally define the syntax and semantics of GLU?, which can be thought of as the multidimensional core of Lucid and GLU, and we describe its implementation as a language embedded in C++. With the aid of a few examples, we argue that the marriage of the two programming models is not only compatible and natural, but also that it produces a new and interesting hybrid language. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
58.
MSP-G320240DBCW-211N大规模点阵式LCD与PIC单片机接口技术   总被引:5,自引:2,他引:3  
赵立生  杜安  张伟 《液晶与显示》2004,19(6):478-482
介绍了大规模点阵式液晶显示器MSP-G320240DBCW-211N的特点及其与PIC18F6620单片机的接口技术,提出了应用过程中可能遇到的问题和解决方法.给出相关的C程序设计并在研制的智能光电检测仪器上得以成功地应用。  相似文献   
59.
This paper evaluates different forms of rank-based selection that are used with genetic algorithms and genetic programming. Many types of rank based selection have exactly the same expected value in terms of the sampling rate allocated to each member of the population. However, the variance associated with that sampling rate can vary depending on how selection is implemented. We examine two forms of tournament selection and compare these to linear rank-based selection using an explicit formula. Because selective pressure has a direct impact on population diversity, we also examine the interaction between selective pressure and different mutation strategies.  相似文献   
60.
This paper presents an application of genetic programming (GP) to optimally select and fuse conventional features (C-features) for the detection of epileptic waveforms within intracranial electroencephalogram (IEEG) recordings that precede seizures, known as seizure precursors. Evidence suggests that seizure precursors may localize regions important to seizure generation on the IEEG and epilepsy treatment. However, current methods to detect epileptic precursors lack a sound approach to automatically select and combine C-features that best distinguish epileptic events from background, relying on visual review predominantly. This work suggests GP as an optimal alternative to create a single feature after evaluating the performance of a binary detector that uses: (1) genetically programmed features; (2) features selected via GP; (3) forward sequentially selected features; and (4) visually selected features. Results demonstrate that a detector with a genetically programmed feature outperforms the other three approaches, achieving over 78.5% positive predictive value, 83.5% sensitivity, and 93% specificity at the 95% level of confidence.  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