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   436985篇
  免费   18016篇
  国内免费   8941篇
电工技术   15259篇
技术理论   14篇
综合类   11402篇
化学工业   69605篇
金属工艺   20850篇
机械仪表   19088篇
建筑科学   21894篇
矿业工程   6358篇
能源动力   12040篇
轻工业   31542篇
水利工程   5798篇
石油天然气   16192篇
武器工业   1353篇
无线电   51104篇
一般工业技术   74294篇
冶金工业   53949篇
原子能技术   7770篇
自动化技术   45430篇
  2023年   3711篇
  2022年   6934篇
  2021年   9779篇
  2020年   7158篇
  2019年   6844篇
  2018年   8487篇
  2017年   9338篇
  2016年   8993篇
  2015年   9469篇
  2014年   13145篇
  2013年   22999篇
  2012年   18242篇
  2011年   22193篇
  2010年   18271篇
  2009年   19054篇
  2008年   18465篇
  2007年   18220篇
  2006年   17425篇
  2005年   15702篇
  2004年   12393篇
  2003年   11438篇
  2002年   10562篇
  2001年   10187篇
  2000年   10145篇
  1999年   11091篇
  1998年   18264篇
  1997年   13743篇
  1996年   11441篇
  1995年   8735篇
  1994年   7612篇
  1993年   6845篇
  1992年   5368篇
  1991年   4786篇
  1990年   4301篇
  1989年   4197篇
  1988年   3786篇
  1987年   3209篇
  1986年   2985篇
  1985年   3350篇
  1984年   2966篇
  1983年   2777篇
  1982年   2510篇
  1981年   2602篇
  1980年   2452篇
  1979年   2502篇
  1978年   2429篇
  1977年   2806篇
  1976年   3812篇
  1975年   2135篇
  1973年   2079篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Two hundred and fifteen patients with pulmonary involvement of lobar (regional, segmental) extent were examined. The examination procedure included clinical and laboratory tests, X-ray tomographic study, and computed tomography, bronchoscopy with biopsy, cyto- and histological studies. The nosological diagnosis was established in 96.5% of cases. Differential diagnosis was found to be difficult in 3.5% of cases.  相似文献   
32.
A comprehensive survey of photosensitivity in silica glasses and optical fiber is reviewed. Recent work on understanding the mechanisms contributing to germanium or aluminum doped fiber photosensitivity is discussed within the framework of photoelastic densification models  相似文献   
33.
P Le Xuan  B Hoang 《Canadian Metallurgical Quarterly》1997,181(9):1781-91; discussion 1792-3
To prevent post-transfusional hepatitis B and C, two epidemiologic studies were performed. The first, based on the frequencies distribution of hepatitis B virus serological markers versus sex and classes of age, has permitted the assessment of the profile of the infection in a population composed of 573 north vietnamese blood donors. There is no significant difference between men and women frequencies of HBs antigen (11.5%), anti-HBs antibody (70.2%) and anti-HBc antibody alone (3.8%), but a significant difference of no-marker frequencies: 7.8% and 17.9% in men and women respectively (X2 = 9.11; p = 0.010). The percentage of no-marker decreases when the mean age of each class increases. The second, using the increase of the serum alanine aminotransferase (ALAT) activity as an indirect marker of non-A, non-B hepatitis for determining in a population of more than 25,000 parisian blood donors, the percentage of donors eliminated. They are between 0.70 and 0.76 in women and 2.26 and 2.46 in men. These investigations can be applied to prevent the hepatitis B transmission in a population of 102 south vietnamese women in age to procreate or to determine the percentage of blood donors eliminated (3.12%) in a population of 2,950 Parisians composed in majority (50.9%) of new donors. The hemobiologist will have an important role to elaborate strategies for orientation of blood gifts with hepatitis B and C virus markers.  相似文献   
34.
The three-dimensional structure of glutathione S-transferase from Arabidopsis thaliana has been solved at 2.2 A resolution (Reinemer et al., 1996). The enzyme forms a dimer of two identical subunits. The structure shows a new G-site architecture and a novel and unique dimer interface. Each monomer of the protein forms a separate G-site. Therefore, the requirements on the dimer interface are reduced. As a consequence, the interactions between the monomers are weaker and residues at the dimer interface are more variable. Thus, the dimer interface looses its relevance for a classification of plant glutathione S-transferases and the formation of heterodimers becomes even more difficult to predict.  相似文献   
35.
Uses a Markov process to model a real-time expert system architecture characterized by message passing and event-driven scheduling. The model is applied to the performance evaluation of rule grouping for real-time expert systems running on this architecture. An optimizing algorithm based on Kernighan-Lin heuristic graph partitioning for the real-time architecture is developed and a demonstration system based on the model and algorithm has been developed and tested on a portion of the advanced GPS receiver (AGR) and manned manoeuvring unit (MMU) knowledge bases  相似文献   
36.
Implementing a neural network on a digital or mixed analog and digital chip yields the quantization of the synaptic weights dynamics. This paper addresses this topic in the case of Kohonen's self-organizing maps. We first study qualitatively how the quantization affects the convergence and the properties, and deduce from this analysis the way to choose the parameters of the network (adaptation gain and neighborhood). We show that a spatially decreasing neighborhood function is far more preferable than the usually rectangular neighborhood function, because of the weight quantization. Based on these results, an analog nonlinear network, integrated in a standard CMOS technology, and implementing this spatially decreasing neighborhood function is then presented. It can be used in a mixed analog and digital circuit implementation.  相似文献   
37.
本文介绍了一种在微机上实现的印制板自动布线方法──多级线探索法及其编程方法。这种方法是基于完备布线算法的概念,通过分析李氏算法和传统线探索法的不足之处而得到的。虽然它也是一种线探索法,但有较传统线探索法更强的探索能力,不需要结合李氏算法而能单独完成布线任务,是一种较理想的算法,通过实验获得了较为满意的效果。  相似文献   
38.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.  相似文献   
39.
40.
Fuzzy controller design by using neural network techniques   总被引:2,自引:0,他引:2  
This paper investigates the relationship between the piecewise linear fuzzy controller (PLFC), in which the membership functions for fuzzy variables and the associated inference rules are all in piecewise linear forms, and a Gaussian potential function network based controller (GPFNC), in which the network output is a weighted summation of hidden responses from a series of Gaussian potential function units (GPFU's). Systematic procedures are proposed for transformation from a PLFC to its GPFNC counterpart, and vice versa. Based on these transformation principles, a series of systematic and feasible steps is presented for the design of an optimized PLFC (PLFC*) by using neural network techniques. In the design procedures, the simplified PLFC is used as the initial controller structure, then a GPFNC, which gives the approximate control response to the initially given PLFC, is found for further optimization. A neutralization process is used to demonstrate the feasibility and the potential applicability of these intelligent controllers on the regulation of highly nonlinear chemical processes  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