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   189237篇
  免费   16587篇
  国内免费   9722篇
电工技术   13953篇
技术理论   8篇
综合类   18164篇
化学工业   20666篇
金属工艺   8790篇
机械仪表   17802篇
建筑科学   20710篇
矿业工程   7062篇
能源动力   8477篇
轻工业   13764篇
水利工程   7562篇
石油天然气   8443篇
武器工业   2044篇
无线电   10916篇
一般工业技术   19892篇
冶金工业   7380篇
原子能技术   2720篇
自动化技术   27193篇
  2024年   738篇
  2023年   2292篇
  2022年   4626篇
  2021年   5401篇
  2020年   5665篇
  2019年   4734篇
  2018年   4651篇
  2017年   5705篇
  2016年   6918篇
  2015年   7289篇
  2014年   11834篇
  2013年   12324篇
  2012年   13613篇
  2011年   15439篇
  2010年   11024篇
  2009年   11379篇
  2008年   10714篇
  2007年   12719篇
  2006年   11036篇
  2005年   9249篇
  2004年   7911篇
  2003年   6778篇
  2002年   5500篇
  2001年   4462篇
  2000年   3812篇
  1999年   3234篇
  1998年   2783篇
  1997年   2355篇
  1996年   1927篇
  1995年   1604篇
  1994年   1408篇
  1993年   1068篇
  1992年   960篇
  1991年   720篇
  1990年   598篇
  1989年   509篇
  1988年   432篇
  1987年   292篇
  1986年   253篇
  1985年   236篇
  1984年   262篇
  1983年   239篇
  1982年   199篇
  1981年   96篇
  1980年   98篇
  1979年   65篇
  1978年   55篇
  1977年   46篇
  1976年   45篇
  1959年   30篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Work system improvements are implemented in various manufacturing processes to prevent problems caused by human errors. However, they are almost always applied to problems which have already occurred. This paper examines a method of identifying latent human errors existing within the work systems beforehand. A procedure for applying failure mode and effect analysis to this identification problem was defined based on over 1000 empirical errors: a work system decomposition criterion and fundamental error modes for listing latent human errors, and then applied to three practical manufacturing processes in order to evaluate its effectiveness.  相似文献   
32.
In this paper, symbolic code matrix ,constant matrix and count matrix are defined .The first twomatrices are used to describe the elemental expression of augmented matrix and the nede admittance equa-tion is thus obtained. The third matrix is used to obtain the incoming degree matrix, and according to thematrix all the 1- factors of the Coates graph are given. By using the data code, the determinant is expandedand the same items in the expansion are merged. Thus the symbolic network function in which no term can-cellation occurs is generated.  相似文献   
33.
This paper considers the principles of algorithmic and software implementation of the software system NADRA 3D designed to analyze processes in three-dimensional multicomponent soil media. The principles of operation of NADRA 3D are described. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 157–174, November–December 2006.  相似文献   
34.
甲醇氧化羰化制碳酸二甲酯产物气相色谱分析   总被引:6,自引:1,他引:5  
以Chromosorb 10 1为固定相 ,气相色谱法分析甲醇氧化羰化制碳酸二甲酯产物中水、甲醇、乙酸甲酯和碳酸二甲酯等组份的含量 ,考察了柱温 ,载气流量对分离度的影响 ,确定了适宜的分析条件 ,并用校正面积归一化法定量。该方法操作简便 ,快速 ,精度高 ,重现性好  相似文献   
35.
综述了分型全蒸发器技术在啤酒发酵过程中的应用状况,并介绍了分析型全蒸发器模型结构及与之配合使用的连续多分支管。  相似文献   
36.
One of the goals of computational chemistry is the automated de novo design of bioactive molecules. Despite significant progress in computational approaches to ligand design and efficient evaluation of binding energy, novel procedures for ligand design are required. Evolutionary computation provides a new approach to this design issue. This paper presents an automated methodology for computer-aided peptide design based on evolutionary algorithms. It provides an automatic tool for peptide de novo design, based on protein surface patches defined by user. Regarding the restrictive constrains of this problem a special emphasis has been made on the design of the evolutionary algorithms implemented.  相似文献   
37.
当今的回转头式贴装设备能够以相对低廉的价格 ,提供高速度和准确的贴装 ,以及先进的识别操作。  相似文献   
38.
A method constructinq C~1 Piecewise quintic polynomial over a triangular grid to interpo-late function values and partial derivatives at vertices is presented in this paper.The set of precise poly-nomials of this method is discussed.  相似文献   
39.
The failure of the conductor of the 460 kV overhead transmission line located along the crossing of the Paraná River was investigated. As a result of this failure, a blackout took place in the southern states of Brazil in January of 2002, reaching approximately 67 million inhabitants. Investigation of the external aluminium layer of the ACSR conductor near the fracture showed typical static deformation marks and dynamic fretting wear tangential marks, both associated with the presence of Al2O3 debris. Additionally, encrusted silicon particles were observed on the external surface of the strands. The internal Al layer showed elliptical deformation marks also associated with Al2O3 debris. Both Al2O3 and Si particles are efficient abrasive material, which associated with slight relative motion of metallic surfaces (clamp/strand and strand/strand) can promote fretting wear. Two types of fracture surface of the Al strands were identified: 45° and quasi-normal surfaces, the former being the predominant type. Delamination and particle detachment were the mechanisms of superficial degradation observed on the Al strands, indicating that the rupture of the strands occurred under a gross slip fretting regime induced by sub-conductor oscillation. Inspection of the internal surface of as-cast Al–10%Si spacer clamps revealed different stages of intense circumferential wear caused by the preferential cracking and particle detachment of the eutectic constituent of the as-cast microstructure. This intense wear reduces the clamping contact pressure, which allows higher displacement amplitude and leads to the critical fretting regime. Finally, a few suggestions are discussed to minimise the occurrence of future failures.  相似文献   
40.
从范围、原材料要求、组分要求、物理力学性能等方面对比分析了我国现行油毡瓦标准与欧美标准的区别,提出了我国制订沥青油毡瓦国家标准的的原则。  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