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   908373篇
  免费   132561篇
  国内免费   92856篇
电工技术   83715篇
技术理论   9篇
综合类   93570篇
化学工业   116001篇
金属工艺   71229篇
机械仪表   58302篇
建筑科学   65209篇
矿业工程   40968篇
能源动力   24897篇
轻工业   90689篇
水利工程   30018篇
石油天然气   40078篇
武器工业   12887篇
无线电   103074篇
一般工业技术   98246篇
冶金工业   40694篇
原子能技术   15958篇
自动化技术   148246篇
  2024年   6483篇
  2023年   15090篇
  2022年   31335篇
  2021年   39889篇
  2020年   32477篇
  2019年   31173篇
  2018年   33902篇
  2017年   38854篇
  2016年   36119篇
  2015年   46234篇
  2014年   53954篇
  2013年   61404篇
  2012年   72300篇
  2011年   72775篇
  2010年   68780篇
  2009年   64381篇
  2008年   64062篇
  2007年   62119篇
  2006年   53847篇
  2005年   44317篇
  2004年   35779篇
  2003年   25808篇
  2002年   24228篇
  2001年   22043篇
  2000年   18596篇
  1999年   10969篇
  1998年   7096篇
  1997年   6071篇
  1996年   5594篇
  1995年   5336篇
  1994年   4437篇
  1993年   4062篇
  1992年   3968篇
  1991年   3080篇
  1990年   2699篇
  1989年   2561篇
  1988年   2034篇
  1987年   1261篇
  1986年   1121篇
  1985年   981篇
  1984年   900篇
  1983年   818篇
  1982年   855篇
  1981年   900篇
  1980年   898篇
  1979年   909篇
  1978年   873篇
  1976年   974篇
  1975年   915篇
  1972年   934篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
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   
43.
44.
45.
张宏利 《辽宁化工》2002,31(11):481-484
C12H26,C13H28,C14H30等正构烷烃是重要的化工原料,可通过液蜡精馏得到。文章对液蜡精馏的工艺设计进行探讨,对影响工艺的参数进行了比较,寻找出精馏工艺的较佳方案,并通过了生产实践的检验。  相似文献   
46.
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   
47.
Structures and compositions of the monomers guanidine acrylate and guanidine methacrylate, their homopolymers, and copolymers with diallyldimethylammonium chloride enriched in acrylate comonomer units were determined. It was shown that ampholytic copolymers, owing to their ionic nature, contained comonomeric guanidine acrylate or methacrylate units and diallyldimethylammonium chloride units, as well as the acrylate comonomer with the diallyl counterion and polymeric acrylate and diallyl ion pairs. It follows from IR and 1H NMR data that guanidine methacrylate has the same structure (with two hydrogen bonds) in the solid state and in solutions. Guanidine acrylate structures in the solid state and in dimethylsulfoxide are identical and analogous to guanidine methacrylate structure in this solvent. In water, the guanidine acrylate structure has another type of hydrogen bonding (with one hydrogen bond, where the proton is shifted toward the guanidine group). These features of hydrogen bonding of guanidine acrylate and guanidine methacrylate are also retained in their homopolymers and copolymers with diallyldimethylammonium chloride. It was shown that the thermal stability of the copolymers was higher than that of their homopolymers, confirming the formation of intramolecular ion pairs of oppositely charged units of ampholytic copolymers. Moreover, the thermal stability of guanidine methacrylate-diallyldimethylammonium chloride copolymers is higher than that of guanidine acrylate-diallyldimethylammonium chloride copolymers.  相似文献   
48.
It is established that the capillary rise of a liquid has an oscillatory character, in contrast to the commonly accepted opinion that a vertical capillary is filled at a monotonically varying velocity. The value of the tangential shear stress arising in an ascending liquid is evaluated for ethyl alcohol and distilled water.  相似文献   
49.
The purpose and current construction status, at the Institute of Theoretical and Experimental Physics, of an experimental electronuclear setup, combining a pulsed proton linear accelerator (36 MeV, 0.5 mA) and a subcritical blanket thermal-power assembly 100 kW, are discussed. The main equipment is already available or is being built in industry. The setup can be used to investigate the dynamics of the interaction of a linac–driver and a subcritical reactor and problems concerning the accelerator–driver and the target–blanket assembly. The proton beams and neutron fluxes will be used for applied purposes. In the future it will be possible to increase substantially the current and energy of the proton beam.  相似文献   
50.
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   
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