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   266112篇
  免费   3032篇
  国内免费   1236篇
电工技术   4684篇
综合类   183篇
化学工业   40565篇
金属工艺   12774篇
机械仪表   9012篇
建筑科学   5392篇
矿业工程   2505篇
能源动力   6257篇
轻工业   18547篇
水利工程   3606篇
石油天然气   9265篇
武器工业   61篇
无线电   27353篇
一般工业技术   58063篇
冶金工业   44744篇
原子能技术   8623篇
自动化技术   18746篇
  2021年   2723篇
  2019年   2574篇
  2018年   4773篇
  2017年   4834篇
  2016年   5265篇
  2015年   2976篇
  2014年   4955篇
  2013年   11638篇
  2012年   7479篇
  2011年   9453篇
  2010年   7710篇
  2009年   8582篇
  2008年   8721篇
  2007年   8546篇
  2006年   7302篇
  2005年   6611篇
  2004年   6135篇
  2003年   6004篇
  2002年   5763篇
  2001年   5860篇
  2000年   5584篇
  1999年   5521篇
  1998年   13394篇
  1997年   9415篇
  1996年   7191篇
  1995年   5463篇
  1994年   4774篇
  1993年   5008篇
  1992年   3803篇
  1991年   3859篇
  1990年   3767篇
  1989年   3707篇
  1988年   3620篇
  1987年   3200篇
  1986年   3253篇
  1985年   3587篇
  1984年   3313篇
  1983年   3166篇
  1982年   2845篇
  1981年   2812篇
  1980年   2860篇
  1979年   2876篇
  1978年   2859篇
  1977年   3112篇
  1976年   3672篇
  1975年   2638篇
  1974年   2498篇
  1973年   2599篇
  1972年   2315篇
  1971年   2114篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The paper discusses optimal control of ecosystem state for observation of a generalized monotonically varying random parameter. A model is proposed for the controlled vector random process, whose components are assigned acceptable ranges and the observations are performed discretely. __________ Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 6, pp. 40–44, June, 2006.  相似文献   
72.
Co-browsing is an activity in which a group of users navigate their way through of a set of Web pages together for a shared purpose. Effective co-browsing among users with different device capabilities requires a shared understanding of those Web pages. This paper demonstrates the concept of shared viewpoints (SVPs), and personal viewpoints (PVPs), for co-browsing, before detailing a framework for implementing these concepts. Finally, the effectiveness of the framework is presented through a perceptual experiment.  相似文献   
73.
The Magnitogorsk Metallurgical Combine has conducted a study of the effect of technological factors on the hydrogen content of chromium-nickel-molybdenum steel after vacuum degassing. It was established that the most important factor is the hydrogen content of the steel before the degassing operation. The study also determined the effects of the circulation coefficient, the duration of the degassing operation, and the vacuum used in the treatment. __________ Translated from Metallurg, No. 7, pp. 68–69, July, 2006.  相似文献   
74.
Holmes  N. 《Computer》2006,39(2):112-111
Using a temporary substitution of format, the author offers a fairy tale to demonstrate that we can’t expect understanding when computers take the place of humans in our interactions with service providers.  相似文献   
75.
Note on B-splines, wavelet scaling functions, and Gabor frames   总被引:3,自引:0,他引:3  
Let g be a continuous, compactly supported function on such that the integer translates of g constitute a partition of unity. We show that the Gabor system (g,a,b), with window g and time-shift and frequency-shift parameters a,b>0 has no lower frame bound larger than 0 if b=2,3,... and a>0. In particular, (g,a,b) is not a Gabor frame if g is a continuous, compactly supported wavelet scaling function and if b=2,3,... and a>0. We give an example for our result for the case that g=B/sub 1/, the triangle function supported by [-1,1], by showing pictures of the canonical dual corresponding to (g,a,b) where ab=1/4 and b crosses the lines N=2,3,.  相似文献   
76.
The basic methods of verifying continuous automatic belt weighers are described. A comparative analysis of these methods on the basis of experimental studies is made and ways of implementing the results in industry are recommended.  相似文献   
77.
Rheological properties of MR fluids under large step strain shear are presented in this paper. The experiments were carried out using a rheometer with parallel-plate geometry. Under the large step strain shear, MR fluids behave as nonlinear viscoelastic properties, where the stress relaxation modulus, G(tγ), shows a decreasing trend with step strain. The experimental results indicate that G(tγ) obeys time-strain separability. Thus, a mathematical form based on finite exponential serials is proposed to predict MR behavior. In this model, G(tγ) is represented as the product of a linear stress relaxation, G(t), and the damping function, h(γ), i.e. G(tγ)=G(t) h(γ). G(t) is simply represented as a three-parameter exponential serial and h(γ) has a sigmoidal form with two parameters. The parameters are identified by adopting an efficient optimization method proposed by Stango et al. The comparison between the experimental results and the model-predicted values indicates that this mathematical model can accurately predict MR behavior.  相似文献   
78.
Breakdown of a company is examined and the concept of its stability is given. A system of indexes for characterizing the market position of an enterprise in the chemical industry and predicting its dynamics is proposed. An integral index can be an effective tool in the hands of managers in making managerial decisions related to effectively reacting to changes in the company's market position.  相似文献   
79.
Using Java-based tools in multimedia collaborative environments accessed over the Internet can increase an application's client base. Most operating systems support Java, and its "compile once-run everywhere" architecture is easy to maintain and update. The Java-based tools presented here let users share Internet resources, including resources originally designed for single use.  相似文献   
80.
The design of a sylphon bellows sensor and the basic circuits of an LC-generator and of a microprocessor unit are presented. An analytical pressure–frequency conversion function and a special method of adjusting the sensor ensure an error of less than 0.05%. The dynamic range is up to 105. The instruments developed cover the ranges 103, 104, and 105 Pa.  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