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   76116篇
  免费   4183篇
  国内免费   1123篇
电工技术   2014篇
综合类   1121篇
化学工业   13972篇
金属工艺   3400篇
机械仪表   4484篇
建筑科学   2457篇
矿业工程   660篇
能源动力   2876篇
轻工业   5305篇
水利工程   556篇
石油天然气   1179篇
武器工业   116篇
无线电   12415篇
一般工业技术   14059篇
冶金工业   6909篇
原子能技术   792篇
自动化技术   9107篇
  2024年   150篇
  2023年   922篇
  2022年   1524篇
  2021年   2367篇
  2020年   1725篇
  2019年   1600篇
  2018年   2039篇
  2017年   1993篇
  2016年   2300篇
  2015年   2106篇
  2014年   2999篇
  2013年   4642篇
  2012年   4427篇
  2011年   5279篇
  2010年   4191篇
  2009年   4330篇
  2008年   3980篇
  2007年   3344篇
  2006年   3112篇
  2005年   2694篇
  2004年   2423篇
  2003年   2255篇
  2002年   2168篇
  2001年   1728篇
  2000年   1627篇
  1999年   1614篇
  1998年   2570篇
  1997年   1753篇
  1996年   1498篇
  1995年   1195篇
  1994年   914篇
  1993年   810篇
  1992年   594篇
  1991年   563篇
  1990年   487篇
  1989年   460篇
  1988年   363篇
  1987年   309篇
  1986年   283篇
  1985年   252篇
  1984年   215篇
  1983年   157篇
  1982年   158篇
  1981年   144篇
  1980年   139篇
  1979年   107篇
  1978年   100篇
  1977年   129篇
  1976年   168篇
  1975年   82篇
排序方式: 共有10000条查询结果,搜索用时 26 毫秒
101.
102.
A method for modeling the learning of belief combination in evidential reasoning using a neural network is presented. A centralized network composed of multiple exponential bidirectional associative memories (eBAM's) sharing a single output array of neurons is proposed to process the uncertainty management of many pieces of evidence simultaneously. The stability of the proposed multiple eBAM network is proved. The sufficient condition to recall a stored pattern pair is discussed. Most important of all, a majority rule of decision making in presentation of multiple evidence is also found by the study of signal-noise-ratio of multiple eBAM network. A guaranteed stable state condition, i.e., the condition for the fastest recall of a pattern pair, is also studied. The result is coherent with the intuition of reasoning.  相似文献   
103.
The importance of the misframe times for DS1 frame synchronization has often been addressed in designing and using network elements and mediation units. By extending the work of J. H. Eu and W. W. Rollins (1991), Markov chain first passage time analysis is used to derive higher moments of the misframe times in both random and burst error environments. This methodology is of great value in evaluating frame synchronization techniques for digital transmission systems. By experimenting with several out-of-frame detection schemes and reasonable values for bit error ratio (BER), it is shown that misframe times are always approximately exponentially distributed for all schemes  相似文献   
104.
A wide variety of speech recognition distortion measures have been proposed and tested, including some especially effective ones. It is shown that there is a general framework, based on the concepts of information theory, linking most of these measures. The distortion measure between any two speech spectra can be defined in terms of the distortions between the associated probability distributions. This general framework defines three broad families of distortion measures for speech recognition and provides a consistent way of combining the energy and the spectral information of a phonetic event. In addition, the cepstral-domain representation for several distortion measures is derived, allowing comparison of these measures in a domain that also yields convenient equations for their practical implementation  相似文献   
105.
106.
To ensure the core status can meet the requirements of thermal limits, stability and other constraints during the power ascension process of a nuclear power plant, operators usually gradually increase power based on onsite measurements and experience. To reduce the operator’s burden, this research develops a method to find an optimal power ascension path that can be followed by operators. The power ascension path is formulated as a multiobjective optimization problem with the following constraints: power ascension time, thermal limits, core stability and maximum rod line. A genetic algorithm is adopted to obtain the optimal power ascension path. The results show that using our approach full power can be achieved quickly, while maintaining reasonable margins of thermal limit and stability, in addition to satisfying maximum rod line criteria.  相似文献   
107.
The purpose of this study was to analyze the symbolization of colors as cultural codes, based on costume colors. In order to study the significance of colors in cultural changes, we carried out a quantitative analysis and interpreted it from the perspective of cultural semiotics. The range of this study was focused on Korean costume colors, over diverse diachronic stages of Korean culture. For this study 1535 color samples were collected, measured with a spectrophotometer, and analyzed quantitatively according their diachronic stages of origin. As a result, red, blue, and yellow were found to be the most frequently used colors during the Chosun Dynasty, a period based on Confucianism. These colors acted as cultural codes with cultural significance. During the Modern times pink, light blue, and black increased in frequency and represented the reception of western culture, the changing sex role of women in society, and utilitarianism. In these days, neutral colors and grayish tones of all colors are the most significant colors of high frequency. The use of such colors is closely related to industrialization, mechanization, functionalism, and the changes of women's sex roles in the societies. They are used as cultural codes, especially to emphasize a rational and masculine image rather than a feminine image. © 2006 Wiley Periodicals, Inc. Col Res Appl, 32, 71–79, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20290  相似文献   
108.
The final closed-form expression for bit error probability (BEP) is presented for a DS-CDMA system using a maximal ratio combining (MRC) diversity over a Rician fading channel. The accuracy of the BEP estimate evaluated by this expression is verified by comparison with a semi-analytic simulation result. The effect that diversity order has on the BEP is also considered for typical multipath delay profiles with different Rician ratios  相似文献   
109.
The electrical properties of thin-film ferroelectric capacitors are known to degrade severely when exposed to hydrogen. In this study, we directly measured the effects of the grain boundary on the hydrogen-induced degradation in ferroelectric Pb(Zr, Ti)O3 (PZT) thin films by the location of the top Pt electrode either inside the grains or at the grain boundary. A strong relationship between the grain boundary and the electrical properties of ferroelectric capacitors as a result of hydrogen annealing was found. The degradation of the electrical properties in thin-film ferroelectric capacitors after hydrogen annealing is mainly due to the presence of the grain boundary in the ferroelectric thin film  相似文献   
110.
Language-level support for object persistence frees programmers from having to confront a broad class of database issues from within their applications. By virtue of its metaobject protocol, CLOS is a language whose semantics can be tailored by individual programmers. We used the metaobject protocol to extend CLOS with support for object persistence. Our goal was to obtain a version of CLOS with persistence to which we could easily port a commercial geometric CAD modeling system. We describe the design and implementation of our persistence extension and highlight the strengths and weaknesses exhibited by the CLOS metaobject protocol during our experiment. For many aspects of the implementation we found that the metaobject protocol was ideal. In other cases we had to choose among paying a large performance penalty, extending the protocol, and bypassing the protocol by modifying the language implementation directly.  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