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   282748篇
  免费   3298篇
  国内免费   1315篇
电工技术   4852篇
综合类   522篇
化学工业   41222篇
金属工艺   11298篇
机械仪表   8710篇
建筑科学   6493篇
矿业工程   1576篇
能源动力   7175篇
轻工业   22892篇
水利工程   3049篇
石油天然气   5784篇
武器工业   43篇
无线电   34298篇
一般工业技术   57370篇
冶金工业   51190篇
原子能技术   7547篇
自动化技术   23340篇
  2021年   2329篇
  2019年   2195篇
  2018年   3726篇
  2017年   3817篇
  2016年   4064篇
  2015年   2633篇
  2014年   4566篇
  2013年   12246篇
  2012年   7344篇
  2011年   10066篇
  2010年   7791篇
  2009年   9018篇
  2008年   9327篇
  2007年   9321篇
  2006年   7985篇
  2005年   7405篇
  2004年   7345篇
  2003年   7082篇
  2002年   6829篇
  2001年   6925篇
  2000年   6572篇
  1999年   6848篇
  1998年   16424篇
  1997年   11671篇
  1996年   8990篇
  1995年   6905篇
  1994年   6063篇
  1993年   6074篇
  1992年   4426篇
  1991年   4203篇
  1990年   4093篇
  1989年   4069篇
  1988年   3764篇
  1987年   3402篇
  1986年   3409篇
  1985年   3746篇
  1984年   3463篇
  1983年   3221篇
  1982年   3028篇
  1981年   3041篇
  1980年   3031篇
  1979年   2830篇
  1978年   2870篇
  1977年   3147篇
  1976年   4101篇
  1975年   2418篇
  1974年   2382篇
  1973年   2398篇
  1972年   2018篇
  1971年   1781篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem.  相似文献   
92.
93.
A combination of concept (the product portfolio and the product life cycle) and empirical research (the PIMS study) can aid in clarifying the key issues involved in the selection of a firm's core strategies. Strategy control is multistage: periodic re-evaluation of strategy alternatives by use of the marketing audit; an analytical framework for control of chosen strategies by breaking down components and reporting their performance variances; and 'marketing segment' analysis for control of the detailed marketing plan.?  相似文献   
94.
Polystyrene packaging material taint was sensorily evaluated in cocoa powder for drinks and chocolate flakes using short-cut signal detection measures on differences between control and test samples and on recognition of styrene. No differences were observed in cocoa powder for drinks and plain chocolate flakes treated with 0.5 dm2 polystyrene of 1 mm thickness. However, differences were detected in milk chocolate flakes and plain chocolate flakes, which were in contact with a larger area or thicker polystyrene packaging material. The latter results were confirmed by the styrene recognition test, so polystyrene is a potential source of off-flavour for chocolate products. The amount of residual styrene in the polystyrene used was about 320 ppm, while the amounts of styrene ranged from 7 to 132 ppb in cocoa drinks and from 414 to 1447 ppb in chocolate flakes.  相似文献   
95.
96.
The application of the diophantine frequency synthesis (DFS) methodology is presented and certain practical aspects of it are illustrated through the design and frequency planning of two forward DFS synthesizers each using two Integer-N phase-locked loops (PLLs). Both synthesizers achieve frequency resolution about 100 times times better that their constituent PLLs without compromising hopping speed performance or spectral purity.  相似文献   
97.
The wetting of Ti–Cu alloys on Si3N4 was analyzed by the sessile drop method, using an imaging system with a CCD camera during the heating under argon flow. The contact angle was measured as a function of temperature and time. The samples were cut transversally and characterized by scanning electron microscopy and energy dispersive spectrometry (SEM/EDS). Wettability of the Ti–Cu alloy on Si3N4 is influenced by the reaction between the Ti and the ceramic. The TC1 and TC2 alloys presented low final contact angle values around 2° and 26°, respectively, indicating good wetting on Si3N4.  相似文献   
98.
Filled fibrous sorbents modified with transition metal ferro- and ferricyanides capable to recover americium(III) and rare-earth metals(III) from nitric acid solutions were prepared. The most complete and rapid recovery is attained on complex-forming and cation-exchange sorbents (as filled fibrous materials) saturated with nickel ions. The sorbents are characterized by good kinetic properties and can be used for recovery of the above metals.  相似文献   
99.
Samples can be measured with different precisions and reliabilities in different experiments, or even within the same experiment. These varying levels of measurement noise may deteriorate the performance of a pattern recognition system, if not treated with care. Here we seek to investigate the benefit of incorporating prior knowledge about measurement noise into system construction. We propose a kernel density classifier which integrates such prior knowledge. Instead of using an identical kernel for each sample, we transform the prior knowledge into a distinct kernel for each sample. The integration procedure is straightforward and easy to interpret. In addition, we show how to estimate the diverse measurement noise levels in a real world dataset. Compared to the basic methods, the new kernel density classifier can give a significantly better classification performance. As expected, this improvement is more obvious for small sample size datasets and large number of features.  相似文献   
100.
A range of refractories is presented for handling steel outside a furnace, which are produced by the Borovichi Refractories Corporation. The refractory characteristics and working features are given. Translated from Novye Ogneupory, No. 9, pp. 29–35, September, 2008.  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