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   295041篇
  免费   4161篇
  国内免费   312篇
电工技术   4351篇
综合类   111篇
化学工业   49936篇
金属工艺   15908篇
机械仪表   11031篇
建筑科学   5558篇
矿业工程   3856篇
能源动力   4766篇
轻工业   17911篇
水利工程   4564篇
石油天然气   13158篇
武器工业   34篇
无线电   21934篇
一般工业技术   70153篇
冶金工业   42039篇
原子能技术   11272篇
自动化技术   22932篇
  2021年   3930篇
  2020年   3176篇
  2019年   3850篇
  2018年   7304篇
  2017年   7582篇
  2016年   7989篇
  2015年   4513篇
  2014年   7074篇
  2013年   13753篇
  2012年   10079篇
  2011年   11462篇
  2010年   9433篇
  2009年   9967篇
  2008年   10031篇
  2007年   9615篇
  2006年   7570篇
  2005年   6576篇
  2004年   6404篇
  2003年   6186篇
  2002年   5942篇
  2001年   5518篇
  2000年   5471篇
  1999年   4837篇
  1998年   10322篇
  1997年   7879篇
  1996年   5735篇
  1995年   4439篇
  1994年   4025篇
  1993年   4271篇
  1992年   3427篇
  1991年   3582篇
  1990年   3650篇
  1989年   3548篇
  1988年   3466篇
  1987年   3423篇
  1986年   3301篇
  1985年   3479篇
  1984年   3403篇
  1983年   3255篇
  1982年   3127篇
  1981年   3196篇
  1980年   3238篇
  1979年   3330篇
  1978年   3564篇
  1977年   3734篇
  1976年   4506篇
  1975年   3267篇
  1974年   3344篇
  1973年   3419篇
  1972年   3005篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
101.
The effect of the composition of sensitizing–activating solutions on the activation efficiency and the chemical coppering of diamond powders is studied. The results demonstrate that stabilizing additives improve the stability of the solutions, influence the average coppering rate, and play a key role in determining the morphology and quality of the resultant coatings. The most effective stabilizing additive is synthamid-10, which ensures the deposition of high-quality copper coatings.  相似文献   
102.
New thermodynamic data for the In–Sb system are obtained and compared with calculation results available in the literature. An isothermal vacuum cell and a procedure for electrolyte preparation are described which ensure high measurement accuracy.  相似文献   
103.
The structure and mechanical properties of nanocrystalline aluminum alloy 1570 obtained by means of severe plastic deformation have been studied. Being tested in a temperature range from 300 to 400°C, the alloy exhibits high-strain-rate superplasticity. At 400°C, the superplasticity is manifested in a very broad range of strain rates, extending from 5 × 10?3 to 1 s?1.  相似文献   
104.
105.
106.
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   
107.
The article investigates the state of stress and strain of the surface of an elastic cylindrical shell whose outer part is subjected to the effect of an incident acoustic wave. A qualitative and quantitative analysis of the state of strain of the surface is carried out and recommendations are given for optimizing the functional purpose of the shell and minimizing the arising stresses.Translated from Problemy Prochnosti, No. 4, pp. 43–47, April, 1991.  相似文献   
108.
The influence of the level of defectiveness of design and service origin (grooves and cracks) of a fastener and an impact specimen on the accuracy of determination of the allowable values of the ductile-to-brittle transition temperature is investigated. An evaluation of the allowable ductile-to-brittle transition temperatures making it possible to impose more soundly based requirements for effectiveness of the material in the stages of design, production, and service in relation to the production condition of the steel, the level of defectiveness of the fastener, and the specified operating life of the threaded joint is proposed.Translated from Problemy Prochnosti, No. 5, pp. 35–37, May, 1991.  相似文献   
109.
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   
110.
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   
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