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   579038篇
  免费   94012篇
  国内免费   62172篇
电工技术   50942篇
技术理论   53篇
综合类   49698篇
化学工业   87746篇
金属工艺   47039篇
机械仪表   31456篇
建筑科学   42378篇
矿业工程   25212篇
能源动力   18971篇
轻工业   46239篇
水利工程   15007篇
石油天然气   37069篇
武器工业   6924篇
无线电   71665篇
一般工业技术   71998篇
冶金工业   27070篇
原子能技术   6433篇
自动化技术   99322篇
  2024年   4008篇
  2023年   9827篇
  2022年   15180篇
  2021年   20197篇
  2020年   19248篇
  2019年   26041篇
  2018年   28751篇
  2017年   30975篇
  2016年   29836篇
  2015年   32945篇
  2014年   35772篇
  2013年   38847篇
  2012年   40010篇
  2011年   42752篇
  2010年   36513篇
  2009年   31622篇
  2008年   29411篇
  2007年   27324篇
  2006年   26942篇
  2005年   24169篇
  2004年   22401篇
  2003年   18946篇
  2002年   17840篇
  2001年   15650篇
  2000年   14618篇
  1999年   15205篇
  1998年   12179篇
  1997年   10664篇
  1996年   9710篇
  1995年   8713篇
  1994年   7051篇
  1993年   6551篇
  1992年   5574篇
  1991年   4172篇
  1990年   3421篇
  1989年   2958篇
  1988年   2337篇
  1987年   1124篇
  1986年   914篇
  1985年   589篇
  1984年   390篇
  1983年   295篇
  1982年   304篇
  1981年   253篇
  1980年   245篇
  1979年   150篇
  1976年   277篇
  1975年   226篇
  1972年   257篇
  1960年   216篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Multi-valued and universal binary neurons (MVN and UBN) are the neural processing elements with the complex-valued weights and high functionality. It is possible to implement an arbitrary mapping described by partially defined multiple-valued function on the single MVN. An arbitrary mapping described by partially defined or fully defined Boolean function, which can be non-threshold, may be implemented on the single UBN. The quickly converging learning algorithms exist for both types of neurons. Such features of the MVN and UBN may be used for solving the different problems. One of the most successful applications of the MVN and UBN is their usage as basic neurons in the Cellular Neural Networks (CNN). It opens the new effective opportunities in nonlinear image filtering and its applications to noise reduction, edge detection and solving of the super resolution problem. A number of experimental results are presented to illustrate the performance of the proposed algorithms.An erratum to this article can be found at  相似文献   
32.
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ cs and the intergranular transport current densityJ cr are identical if the measurement conditions are similar. A degradation ofJ cs measured in the external field with AC ripple has been observed.  相似文献   
33.
Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples.  相似文献   
34.
35.
This paper presents different approaches which enable a data base management system to obtain a plausible fuzzy estimate for an attribute value of an item for which the information is not explicitly stored in the data base. This can be made either by a kind of analogical reasoning from information about particular items or by means of expert rules which specify the (fuzzy) sets of possible values of the attribute under consideration, for various classes of items. Another kind of expert rules enables the system to compute an estimate from the attribute value of another item provided that, in other respects, this latter item sufficiently resembles the item, the value of which we are interested in; then these expert rules are used either for controlling the analogical reasoning process or for enlarging the scope of application of the first kind of expert rules. The different approaches are discussed in the framework of possibility theory.  相似文献   
36.
We describe an architecture for an optical local area network (LAN) or metropolitan area network (MAN) access. The architecture allows for bandwidth sharing within a wavelength and is robust to both link and node failures. The architecture can be utilized with an arbitrary, link-redundant mesh network (node-redundancy is necessary only to handle all node failures), and assumes neither the use of a star topology nor the ability to embed such a topology within the physical mesh. Reservation of, bandwidth is performed in a centralized fashion at a (replicated) head end node, simplifying the implementation of complex sharing policies relative to implementation on a distributed set of routers. Unlike a router, however, the head end does not take any action on individual packets and, in particular, does not buffer packets. The architecture thus avoids the difficulties of processing packets in the optical domain while allowing for packetized shared access of wavelengths. We describe the route construction scheme and prove its ability to recover from single link and single node failures, outline a flexible medium access protocol and discuss the implications for implementing specific policies, and propose a simple implementation of the recovery protocol in terms of state machines for per-link devices  相似文献   
37.
用硫酸铁铵容量法测定钛精矿中二氧化钛含量   总被引:2,自引:0,他引:2  
样品在过氧化钠熔融、水浸取及盐酸酸化后,在盐酸和硫酸介质中,隔绝空气,用金属铝将钛(Ⅳ)还原至钛(Ⅲ),以硫氰酸盐为指示剂,用硫酸铁铵标准溶液滴定。  相似文献   
38.
首钢外购焦炭质量恶化后的高炉生产实践   总被引:2,自引:0,他引:2  
张思斌  王涛  李颖 《炼铁》2004,23(1):18-21
针对焦炭质量劣化的状况,高炉操作以活跃炉缸为主,从上下部调剂入手,采取疏导煤气、控制合理的实际风速和鼓风动能、缓解焦炭在高温区的粉化等措施,有效地改善了高炉的顺行状况,并逐步恢复高炉指标。  相似文献   
39.
The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management.  相似文献   
40.
Good methods are needed to specify, test, and debug material-handling control logic. This article surveys a number of representative methods for defining and describing control algorithms for programmable material-handling equipment used in flexible manufacturing systems. The methods are evaluated with regard to their suitability for communication between people and as bases for interfaces to automatic program generators. It is concluded that no single method is entirely satisfactory. Three methods (position diagrams, function block diagrams, and operation networks) have potential to be combined into an effective hybrid approach that minimizes the need for the user to switch between various conceptual models.  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