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   342908篇
  免费   25777篇
  国内免费   12596篇
电工技术   18525篇
技术理论   56篇
综合类   20319篇
化学工业   63140篇
金属工艺   18701篇
机械仪表   21259篇
建筑科学   26086篇
矿业工程   11008篇
能源动力   9797篇
轻工业   19079篇
水利工程   5279篇
石油天然气   23002篇
武器工业   2609篇
无线电   36719篇
一般工业技术   41439篇
冶金工业   18416篇
原子能技术   3238篇
自动化技术   42609篇
  2024年   1304篇
  2023年   5720篇
  2022年   9148篇
  2021年   13099篇
  2020年   10394篇
  2019年   8455篇
  2018年   9634篇
  2017年   10686篇
  2016年   9754篇
  2015年   12788篇
  2014年   16468篇
  2013年   19955篇
  2012年   20547篇
  2011年   22721篇
  2010年   19794篇
  2009年   19001篇
  2008年   18228篇
  2007年   17606篇
  2006年   18409篇
  2005年   16282篇
  2004年   10535篇
  2003年   9279篇
  2002年   8296篇
  2001年   7561篇
  2000年   8040篇
  1999年   9739篇
  1998年   8219篇
  1997年   6817篇
  1996年   6433篇
  1995年   5433篇
  1994年   4445篇
  1993年   3219篇
  1992年   2583篇
  1991年   2034篇
  1990年   1591篇
  1989年   1322篇
  1988年   1095篇
  1987年   772篇
  1986年   638篇
  1985年   427篇
  1984年   324篇
  1983年   309篇
  1982年   270篇
  1981年   232篇
  1980年   213篇
  1979年   133篇
  1977年   99篇
  1976年   104篇
  1973年   144篇
  1972年   89篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Laguerre Functional Model has many advantages such as good approximation capability for the variances of system time‐delay, order and other structural parameters, low computational complexity, and the facility of online parameter identification, etc., so this model is suitable for complex industrial process control. A series of successful applications have been gained in linear and non‐linear predictive control fields by the control algorithm based on Laguerre Functional Model, however, former researchers have not systemically brought forward the theoretical analyses of the stability, robustness, and steady‐state performance of this algorithm, which are the keys to guarantee the feasibility of the control algorithm fundamentally. Aimed at this problem, we introduce the principles of the Incremental Mode Linear Laguerre Predictive Control (IMLLPC) algorithm, and then systemically propose the theoretical analyses and proofs of the stability and robustness of the algorithm, in addition, we also put forward the steady‐state performance analysis. At last, the control performances of this algorithm on two different physical industrial plants are presented in detail, and a number of experimental results validate the feasibility and superiority of IMLLPC algorithm. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
92.
STUDYONRESIDUESOF~(14)C-FENITROTHIONINMODELRICE-FISHECOSYSTEMANDFIELDRICE-FISHECOSYSTEMZhangZhongliang(张仲良);WangHuaxin(王化新);G?..  相似文献   
93.
用于重离子核反应实验测量的纵向电场气体电离室   总被引:1,自引:0,他引:1  
本文报道了一种新型的大动态范围,多叠层探测器系统组件之一的纵向电场气体电离室的构造,性能和在中能得离子核反应实验中的应用。  相似文献   
94.
The manufacturing message specification (MMS) is the ISO standard communication protocol specific to manufacturing. To analyze MMS design and performance, service unit automats are introduced to represent individual MMS services, while service connection Petri Nets (PNs) are constructed from these automats to describe MMS service connections and processes. This approach makes MMS protocol specification and analysis possible in terms of well-developed concepts and methods in PN theory. It leads to a distributed and hierarchical model of MMS software system by integrating service connection PNs. A generalized stochastic PN for MMS performance evaluation is obtained by incorporating service parameters and time factors into the model. A technique based on T-invariants is used to simplify the performance analysis  相似文献   
95.
We consider the problem of turbo multiuser detection for synchronous and asynchronous code-division multiple-access (CDMA) in the presence of unknown users. Turbo multiuser detectors, as previously developed, typically require knowledge of the signature waveforms of all of the users in the system and ignore users whose signature sequences are unknown, e.g., users outside the cell. We develop turbo multiuser detection for CDMA uplink systems and other environments in which the receiver has knowledge of the signature waveforms of only K˘⩽ K users. Subspace techniques are used to estimate the interference from the unknown-users and the interference estimate is subtracted from the received signal. We see that the new receiver significantly outperforms the conventional turbo multiuser receiver for moderate and high signal-to-noise ratios. It is also seen that the traditional turbo receiver provides little gain through iteration when unknown users are present  相似文献   
96.
97.
98.
Two new methods are proposed to implement the exclusive-OR and exclusive-NOR functions on the transistor level. The first method uses non-complementary signal inputs and the least number of transistors. The other one improves the performance of the prior method but two more transistors are utilized. Both of them have been fully simulated by HSPICE on a SUN SPARC 2 workstation  相似文献   
99.
A two-dimensional numerical simulation including a new interface state generation model has been developed to study the performance variation of a LDD MOSFET after a dc voltage stress. The spatial distribution of hot carrier induced interface states is calculated with a breaking silicon-hydrogen bond model. Mobility degradation and reduction of conduction charge due to interface traps are considered. A 0.6 μm LDD MOSFET was fabricated. The drain current degradation and the substrate current variation after a stress were characterized to compare the simulation. A reduction of the substrate current at Vg ≃0.5 Vd in a stressed device was observed from both the measurement and the simulation. Our study reveals that the reduction is attributed to a distance between a maximum channel electric field and generated interface states  相似文献   
100.
Motivated by field data which showed a large number of link changeovers and incidences of link oscillations between in-service and out-of-service states in common channel signalling (CCS) networks, a number of analyses of the link error monitoring procedures in the SS7 protocol were performed by the authors. This paper summarizes the results obtained thus far and include the following: (a) results of an exact analysis of the performance of the error monitoring procedures under both random and bursty errors; (b) a demonstration that there exists a range of error rates within which the error monitoring procedures of SS7 may induce frequent changeovers and changebacks; (c) an analysis of the performance of the SS7 level-2 transmission protocol to determine the tolerable error rates within which the delay requirements can be met; (d) a demonstration that the tolerable error rate depends strongly on various link and traffic characteristics, thereby implying that a single set of error monitor parameters will not work well in all situations; and (e) some recommendations on a customizable/adaptable scheme of error monitoring with a discussion on their implementability. These issues may be particularly relevant in the presence of anticipated increases in SS7 traffic due to widespread deployment of advanced intelligent network (AIN) and personal communications service (PCS) as well as for developing procedures for high-speed SS7 links currently under consideration by standards bodies  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