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   300752篇
  免费   5317篇
  国内免费   871篇
电工技术   5428篇
综合类   358篇
化学工业   45235篇
金属工艺   10967篇
机械仪表   9285篇
建筑科学   7292篇
矿业工程   1168篇
能源动力   7071篇
轻工业   29622篇
水利工程   2984篇
石油天然气   4068篇
武器工业   80篇
无线电   36362篇
一般工业技术   56757篇
冶金工业   56193篇
原子能技术   5563篇
自动化技术   28507篇
  2021年   3003篇
  2020年   2349篇
  2019年   2979篇
  2018年   5075篇
  2017年   5102篇
  2016年   5390篇
  2015年   3594篇
  2014年   5540篇
  2013年   14444篇
  2012年   8895篇
  2011年   10962篇
  2010年   8718篇
  2009年   9422篇
  2008年   10259篇
  2007年   10048篇
  2006年   8777篇
  2005年   7988篇
  2004年   7696篇
  2003年   7462篇
  2002年   7075篇
  2001年   6954篇
  2000年   6646篇
  1999年   6808篇
  1998年   17139篇
  1997年   12213篇
  1996年   9360篇
  1995年   7125篇
  1994年   6288篇
  1993年   6255篇
  1992年   4808篇
  1991年   4465篇
  1990年   4237篇
  1989年   3977篇
  1988年   3828篇
  1987年   3335篇
  1986年   3223篇
  1985年   3805篇
  1984年   3529篇
  1983年   3148篇
  1982年   3005篇
  1981年   3145篇
  1980年   2940篇
  1979年   2742篇
  1978年   2594篇
  1977年   3273篇
  1976年   4269篇
  1975年   2381篇
  1974年   2375篇
  1973年   2392篇
  1972年   1880篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
101.
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   
102.
103.
Long-term trends in alpine and prairie snow pack accumulation and melt are affecting streamflow within the Oldman River Basin in southern Alberta, Canada. Unchecked rural and urban development also has contributed to changes in water quality, including enhanced microbial populations and increased waterborne pathogen occurrence. In this study we look at changing environment within the Oldman River Basin and its impact on water quality and quantity. The cumulative effects include a decline in net water supplies, and declining quality resulting in increased risk of disease. Our data indicates that decreases in the rate of flow of water can result in sedimentation of bacterial contaminants within the water column. Water for ecosystems, urban consumption, recreation and distribution through irrigation is often drawn from waterholding facilities such as dams and weirs, and concern must be expressed over the potential for contaminate build-up and disproportionate potential of these structures to pose a risk to human and animal health. With disruption of natural flow rates for water resulting from environmental change such as global warming and/or human intervention, increased attention needs to be paid to use of best management practices to protect source water supplies.  相似文献   
104.
The objective of this note is to propose a method for stabilization of structurally fixed modes in expansions of LTI dynamic systems in the scope of overlapping decentralized control design based on the expansion/contraction framework, enabling successful design for a broader class of problems than considered so far. The method is based on a judicious choice of complementary matrices in the expanded space. Numerical examples are provided to illustrate simplicity and efficiency of the proposed approach.  相似文献   
105.
Compositions have been developed for nonshrinking vibrocast thermally insulating light refractory concretes with densities of 1.0, 1.3, 1.5, and 1.8 g/cm3 for temperatures of use up to 1400°C. The structure and properties have been examined for the concrete of density 1.3 g/cm3. __________ Translated from Novye Ogneupory, No. 4, pp. 29–32, April, 2008.  相似文献   
106.
Secondary aluminum waste products, and processes that occur during heating and mineral formation on introducing fine periclase powder into the composition of waste products are studied. It is demonstrated that secondary aluminum production waste may be used as a raw material for synthesizing aluminomagnesia spinels. Translated from Novye Ogneupory, No. 6, pp. 15–18, June 2008.  相似文献   
107.
Methods are proposed for designing interpolation models for the preliminary determination and subsequent forecasting of general and fractional breakthrough coefficients for dust used with granular filters, as employed in energy-saving and high-performance dust trapping from technological gases and ventilation discharges in refractory production. The models are supplied with nomograms, which makes them widely suitable for experts working in environmental protection at refractory-producing organizations. The main factors are identified that influence the performance. The results are of interest to experts in related areas of industry such as building materials and engineering ceramics and so on. Translated from Novye Ogneupory, No. 4, pp. 64–67, April, 2008.  相似文献   
108.
On the basis of periclase powder (70%) and aluminomagnesia spinel (30%), synthesized from secondary aluminum production waste and caustic magnesite, test objects are produced of periclase spinel composition satisfying the requirements of GOST 1579-006-00190495-98. The articles are successfully tested in the working layer for lining tunnel furnace cars of OAO Kombinat Magnezit. __________ Translated from Novye Ogneupory, No. 8, pp. 16–17, August 2008.  相似文献   
109.
The processes of phase formation in the Na2CO3-TiO2 and Na2CO3-TiO2-Nd2O3 systems are investigated in the temperature range 600–900°C. The high-temperature solid-phase reactions underlying the process of formation of complex oxide NaNdTiO4 are studied. It is established that the synthesis of the NaNdTiO4 compound occurs through the reaction of the intermediate product Na8Ti5O14 with neodymium oxide in the temperature range 720–780°C. The optimum method is proposed for synthesizing NaNdTiO4, which makes it possible to reduce the temperature of the synthesis, to avoid the formation of impurities, and to obtain the product in a finely dispersed state.  相似文献   
110.
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