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   624103篇
  免费   7116篇
  国内免费   2447篇
电工技术   11229篇
综合类   839篇
化学工业   95998篇
金属工艺   24991篇
机械仪表   18736篇
建筑科学   15605篇
矿业工程   3405篇
能源动力   15426篇
轻工业   55585篇
水利工程   6450篇
石油天然气   11940篇
武器工业   61篇
无线电   72425篇
一般工业技术   122738篇
冶金工业   112103篇
原子能技术   14516篇
自动化技术   51619篇
  2021年   4428篇
  2019年   4272篇
  2018年   7311篇
  2017年   7382篇
  2016年   7980篇
  2015年   5344篇
  2014年   9034篇
  2013年   26903篇
  2012年   14781篇
  2011年   20538篇
  2010年   16351篇
  2009年   18787篇
  2008年   19602篇
  2007年   19659篇
  2006年   17255篇
  2005年   16125篇
  2004年   15580篇
  2003年   15100篇
  2002年   15000篇
  2001年   14825篇
  2000年   14083篇
  1999年   14398篇
  1998年   32926篇
  1997年   24264篇
  1996年   19074篇
  1995年   14801篇
  1994年   13263篇
  1993年   13058篇
  1992年   10019篇
  1991年   9804篇
  1990年   9488篇
  1989年   9439篇
  1988年   9033篇
  1987年   8018篇
  1986年   7930篇
  1985年   9078篇
  1984年   8489篇
  1983年   7865篇
  1982年   7425篇
  1981年   7497篇
  1980年   7260篇
  1979年   7081篇
  1978年   6996篇
  1977年   8003篇
  1976年   10433篇
  1975年   6263篇
  1974年   5948篇
  1973年   5990篇
  1972年   5101篇
  1971年   4660篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Given the enormous size of the genome and that there are potentially many other types of measurements we need to do to understand it, it has become necessary to pick and choose one's targets to measure because it is still impossible to evaluate the entire genome all at once. What has emerged is a need to have rapidly customizable microarrays. There are two dominant methods to accomplish custom microarray synthesis, Affymetrix-like microarrays manufactured using light projection rather than semiconductor-like masks used by Affymetrix to mass manufacture their GeneChip/sup TM/ arrays now, or the ink-jet printing method employed by Agilent. The manufacture of these custom Affymetrix-like microarrays can now be done on a digital optical chemistry (DOC) machine developed at the University of Texas Southwestern Medical Center, and this method offers much higher feature numbers and feature density than is possible with ink-jet printed arrays. On a microarray, each feature contains a single genetic measurement. The initial DOC prototype has been described in several publications, but that has now led to a second-generation machine. This machine reliably produces a number of arrays daily, has been deployed against a number of biomedical questions, is being used in new ways and has also led to a number of spin-off technologies.  相似文献   
102.
A new system based on the harnessing of solar and wind power is presented for heat dissipation in air conditioning facilities. The innovation offered by the new system is the integration of two well-known subsystems: a cooling tower and a solar chimney which increases the air flow without the use of electric power. The system is described and presented together with a model for its study. The field data acquired from the prototype built in southern Spain establishes the actual potential of the system, which provides a new approach to a sustainable technological development.  相似文献   
103.
104.
105.
Field surveys of a series of conjugated diunsaturated straight-chain primary alcohols, acetates, and aldehydes (dienes), including the 3,5-dode-cadienyl, 8,10-dodecadienyl, 3,5-tetradecadienyl, 8,10-tetradecadienyl, 9,11-tetradecadienyl, and 10,12-tetradecadienyl primary alcohols, acetates, and most aldehydes, and the related monounsaturated straight-chain primary alcohols, acetates, and aldehydes (monoenes), including the 3-dodecadienyl alcohol and acetates, attracted the following species from the title families. Diene attractants have been demonstrated for at least onePhyllonorycter sp.,Chionodes lugubrella (Fabr.),Leptostales ferruminaria (Zell.),Drepana bilineata (Pack.),Pyrausta fodinalis (Led.),Notocelia purpurissatana Heinr.,Phaneta alterana Heinr. Monoene attractants were demonstrated forHedya separatana (Kft.),Cydia fletcherana (Kft.),Barbara mappana Free.,Ancylis burgessiana (Zell.),Ancylis nubeculana Clem.,Evippe prunifoliella Cham.,Phlyctaenia coronata tertialis (Gn.), aChionodes sp., a Gelechiidae sp., and an unidentifiedPhyllonorycter sp. Replicated field experiments showed attraction-inhibition relationships for most species. Electroantennagram data are presented forLeptostales ferruminaria andDrepana bilineata.  相似文献   
106.
Summary Starting with Z-2, 3-diamino-2-butenedinitrile as diamine component the synthesis of the low molecular N,N,O,O-chelate 3.Co and its ligand 3 is optimized. An easy synthesis of the chelate 8.Co covalently bound on macroreticular resins is presented. The chelates 8.Co are the most active heterogenous catalysts for the valence isomerization of quadricyclane to norbornadiene today.  相似文献   
107.
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing.  相似文献   
108.
The Six Sigma approach is one of the more recent initiatives adopted by organisations who seek to make a paradigm shift in performance improvement (attacking at least one of the cost, quality, delivery measurements for improved competitiveness). Is there anything new about Six Sigma, does it offer improvements that other approaches cannot, or is it just a clever delivery of repackaged goods? The author investigates the above questions related to the Six Sigma approach  相似文献   
109.
G. C. Bakos   《Applied Energy》2002,72(3-4):609-619
This paper deals with the technical feasibility and economic viability of a grid connected wind-energy conversion system (WECS) used to cover the energy demand of an average habitable dwelling. The various parts of the wind-energy system are described and the useful electrical energy production is determined using a simulation program based on the Monte Carlo method. An economic analysis of the WEC system is performed using a computerized assessment tool. Important financial indices are calculated and financial scenarios investigated.  相似文献   
110.
A method for fabricating single crystal blades that combines the techniques of seed crystals and selection is suggested. The method realizes the advantages of both techniques, i.e., the high structural perfection and the possibility of fabricating single crystals with specified spatial orientation. Metallographic and x-ray diffraction analyses are used to study the processes of nucleation of the single crystal structure of blade castings fabricated from high-temperature nickel alloys by the method of selection and seed crystals. A commercial process for fabricating cast single crystal turbine blades by the new method is suggested.  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