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   278183篇
  免费   3328篇
  国内免费   1304篇
电工技术   4803篇
综合类   520篇
化学工业   40350篇
金属工艺   11127篇
机械仪表   8416篇
建筑科学   6412篇
矿业工程   1575篇
能源动力   6968篇
轻工业   22471篇
水利工程   3035篇
石油天然气   5781篇
武器工业   43篇
无线电   33502篇
一般工业技术   56458篇
冶金工业   51032篇
原子能技术   7494篇
自动化技术   22828篇
  2021年   2153篇
  2019年   2061篇
  2018年   3576篇
  2017年   3671篇
  2016年   3899篇
  2015年   2487篇
  2014年   4347篇
  2013年   11968篇
  2012年   7065篇
  2011年   9702篇
  2010年   7534篇
  2009年   8753篇
  2008年   9103篇
  2007年   9139篇
  2006年   7810篇
  2005年   7256篇
  2004年   7206篇
  2003年   6980篇
  2002年   6718篇
  2001年   6851篇
  2000年   6486篇
  1999年   6767篇
  1998年   16316篇
  1997年   11603篇
  1996年   8934篇
  1995年   6853篇
  1994年   6020篇
  1993年   6063篇
  1992年   4399篇
  1991年   4181篇
  1990年   4076篇
  1989年   4057篇
  1988年   3753篇
  1987年   3393篇
  1986年   3397篇
  1985年   3749篇
  1984年   3465篇
  1983年   3221篇
  1982年   3033篇
  1981年   3044篇
  1980年   3035篇
  1979年   2835篇
  1978年   2881篇
  1977年   3150篇
  1976年   4107篇
  1975年   2421篇
  1974年   2385篇
  1973年   2397篇
  1972年   2022篇
  1971年   1785篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
931.
Learning vector quantization for the probabilistic neural network   总被引:5,自引:0,他引:5  
A modified version of the PNN (probabilistic neural network) learning phase which allows a considerable simplification of network structure by including a vector quantization of learning data is proposed. It can be useful if large training sets are available. The procedure has been successfully tested in two synthetic data experiments. The proposed network has been shown to improve the classification performance of the LVQ (learning vector quantization) procedure.  相似文献   
932.
Zave  P. 《Software, IEEE》1989,6(5):15-25
The author points out that although different aspects of a system require different approaches, programmers are confined to their language's one paradigm. Multiparadigm programming makes it possible to match the paradigm to the problem. The potential of paradigm composition as an approach to multiparadigm programming is explored. In paradigm composition, a multiparadigm program is written as a collection of single-paradigm programs. The single-paradigm programs are composed, which means that they execute concurrently and cooperatively to form the whole of a functioning system. Interactions between paradigms are defined at the conceptual levels of the participating paradigms. The case of a small prototype telephone network is considered as an example of paradigm composition.<>  相似文献   
933.
934.
The magnetic readback signal is generally assumed to be made up of linearly superposed single transition responses. As the transition spacing is reduced, this property is seen not to hold, With particulate disks, we find the head signal can be reconstructed as a linear superposition of variably spaced individual transitions, while with cobalt alloy film disks, both the spacing and the amplitude of individual transitions vary as a function of the data. This behavior is interpreted by a self consistent 2D recording model, linear superposition improves dramatically with lowM_{r}tdisk media.  相似文献   
935.
The quality-estimation and decision-making criteria based on the values of error possibility likelihood measures, error necessity likelihood, error possibility confidence, and error necessity confidence are considered. The criteria are formulated for the adequacy of an uncertain fuzzy (UF) model and conclusions based on the UF model for the object under investigation and the UF observation model.  相似文献   
936.
Space asymptotic theory is shown to be a suitable model for the study of pulsed experiments in neutron multiplying systems. After a short revisitation of the basic aspects of space asymptotic theory applied on the Laplace transformed one-group transport equation, the full solution is derived. It is shown how results are exact in representing localized pulse propagation in the first portion of the transient, until the boundary is reached by the neutron signal, since it propagates with a finite velocity. Approximate models are then derived starting from the exact formulation and the BN method is used to account for anisotropy effects. Numerical results are presented for one-dimensional systems, discussing the physical phenomena and noting the distortions introduced by approximate models, which may then turn out to be inadequate for the simulation of realistic pulsed experiments situations.  相似文献   
937.
938.
This social research project investigated community receptivity to using rainwater and greywater as alternative domestic water sources. It was focused in the Ku-ring-gai local government area in northern Sydney, and involved a household questionnaire followed by community leader interviews and resident focus groups. Trends, such as a prolonged drought and increasing population, compound the current crisis and concern facing Sydney's available water supply. Substitution of domestic potable water has been promoted as part of the solution. The research results revealed that community receptivity was highest for external uses, such as watering gardens and flushing toilets, and progressively decreased with increasing personal contact. Receptivity to greywater reuse fell more rapidly with the community believing there was a higher health risk associated with its use. Gender and cultural background were revealed as significant variables and give insight into the design of strategies to target these demographic groups. This evidence provides a reliable stocktake of current receptivity revealing that the community has good awareness and positive association with water reuse for many household activities. This now needs to be harnessed through programs targeted at developing skills, resources and motivation for new water reuse practices and technologies across diverse social groupings.  相似文献   
939.
Wideband miniature G-shaped antenna for dual-band WLAN applications   总被引:1,自引:0,他引:1  
A wideband miniature G-shaped coplanar waveguide fed dual-band antenna for a wireless local area network (WLAN) is proposed. The proposed antenna has good radiation pattern and can provide two separate measured impedance bandwidths of 0.55 GHz (about 22.9% centred at 2.42 GHz) and 2.85 GHz (about 50.9% centred at 5.60 GHz), so that it easily covers the required bandwidths for WLAN operation. This design results in a small antenna size of 22 times 18.5 mm with the ground plane regarded as part of the antenna structure.  相似文献   
940.
Listed are the grades of heat-resistant adhesives developed under the Andrianov’s scientific guidance at the All-Russia Institute of Aviation Materials on the basis of organosilicon polymers.  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