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   38746篇
  免费   13031篇
电工技术   758篇
化学工业   17004篇
金属工艺   310篇
机械仪表   697篇
建筑科学   1680篇
矿业工程   1篇
能源动力   824篇
轻工业   7037篇
水利工程   288篇
石油天然气   43篇
无线电   6796篇
一般工业技术   11380篇
冶金工业   580篇
原子能技术   2篇
自动化技术   4377篇
  2023年   15篇
  2022年   28篇
  2021年   220篇
  2020年   1427篇
  2019年   3183篇
  2018年   3103篇
  2017年   3418篇
  2016年   3877篇
  2015年   3969篇
  2014年   3864篇
  2013年   4949篇
  2012年   2672篇
  2011年   2315篇
  2010年   2592篇
  2009年   2479篇
  2008年   2019篇
  2007年   1872篇
  2006年   1637篇
  2005年   1363篇
  2004年   1330篇
  2003年   1303篇
  2002年   1244篇
  2001年   1090篇
  2000年   1062篇
  1999年   442篇
  1998年   57篇
  1997年   51篇
  1996年   17篇
  1995年   11篇
  1994年   26篇
  1993年   15篇
  1992年   9篇
  1991年   15篇
  1990年   13篇
  1989年   7篇
  1987年   8篇
  1986年   8篇
  1985年   3篇
  1984年   4篇
  1983年   4篇
  1980年   3篇
  1978年   3篇
  1977年   4篇
  1936年   2篇
  1933年   6篇
  1932年   5篇
  1931年   11篇
  1930年   3篇
  1919年   2篇
  1910年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A two‐dimensional (2D) spectrofluorometer was used to monitor various fermentation processes with recombinant E coli for the production of 5‐aminolevulinic acid (ALA). The whole fluorescence spectral data obtained during a process were analyzed using artificial neural networks, ie self‐organizing map (SOM) and feedforward backpropagation neural network (BPNN). The SOM‐based classification of the whole spectral data has made it possible to qualitatively associate some process parameters with the normalized weights and variances, and to select some useful combinations of excitation and emission wavelengths. Based on the classified fluorescence spectra a supervised BPNN algorithm was used to predict some of the process parameters. It was also shown that the BPNN models could elucidate some sections of the process's performance, eg forecasting the process's performance. Copyright © 2005 Society of Chemical Industry  相似文献   
62.
The simultaneous contrast effect is investigated in this article. A total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively. Each combination was assessed by nine observers using a matching technique. The test and induction colours used for CRT colours were similar to surface colours using fabric samples. The results indicated a strong lightness contrast effect for both CRT and surface media; that is, the lightness of a test colour surrounded by a lighter induction colour was reduced for both CRT and surface colours. However, the effect in CRT medium was more pronounced than in the surface medium. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 13–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20074  相似文献   
63.
Hydrogen free amorphous carbon coatings ‐ deposited with plasma‐activated high‐rate evaporation By using the technology of the plasmaactivated electron beam evaporation we deposited hydrogen free amorphous carbon coatings with deposition rates of up to 100 μm/h. The results of the mechanical and tribological investigations show the potential of these layers for the use in case of wear resistance. Hardnesses of up to 16GPa were proved. The actual state of the characterisation of the coatings is described and the outlook onto possibilities of further optimisation is given.  相似文献   
64.
65.
Helium leak test devices for the quality inspection of housings for vacuum compressors The well‐known and wide‐spread helium leak test method is a safe and fast quality testing method for construction units of any kind. Due to its safe examination and the short time of examination it is predominantly inserted into automated production lines as e.g. in the automobile supporting industry up to the examination by Airbags and rims of wheel. Likewise in addition, for the construction units, machines and devices of the vacuum engineering. From this the demand results simple and in particular economical devices for the helium leak test of construction units with small numbers of items of under 200 pieces per day. For these manufacturing profiles economical ways for the helium leak test are pointed out.  相似文献   
66.
67.
68.
69.
70.
Imperfection in information can be considered a crosscutting concern that manifests itself in diverse kinds of imprecision, uncertainty, or inconsistency in the data models of a software system. The extension of existing programming and querying interfaces for the different aspects of information imperfection requires a proper modularization of the different concerns of numerical imprecision handling, so that the extensions do not interfere with existing programming practices and do not obscure the original design. Aspect‐oriented design (AOD) enables such a form of nonintrusive extensions to be added to existing software libraries, clearly separating fuzziness or other imperfections in data as a differentiated concern that can be considered from the early phases of development. In this article, a general framework for aspect‐based extension of data models and fuzzy databases is described, and some design and implementation issues of such AOD‐based extensions on OJB database libraries are described as a case study. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 1199–1216, 2006.  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