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   607325篇
  免费   8279篇
  国内免费   2909篇
电工技术   11981篇
技术理论   5篇
综合类   1461篇
化学工业   92822篇
金属工艺   24630篇
机械仪表   19245篇
建筑科学   13846篇
矿业工程   3540篇
能源动力   15879篇
轻工业   48703篇
水利工程   6521篇
石油天然气   12284篇
武器工业   259篇
无线电   70197篇
一般工业技术   119821篇
冶金工业   113738篇
原子能技术   13047篇
自动化技术   50534篇
  2021年   5807篇
  2020年   4249篇
  2019年   5370篇
  2018年   8907篇
  2017年   8872篇
  2016年   9577篇
  2015年   6522篇
  2014年   10598篇
  2013年   28918篇
  2012年   17262篇
  2011年   23067篇
  2010年   18505篇
  2009年   20435篇
  2008年   21322篇
  2007年   21269篇
  2006年   18973篇
  2005年   16733篇
  2004年   15526篇
  2003年   15046篇
  2002年   14549篇
  2001年   14513篇
  2000年   13651篇
  1999年   14080篇
  1998年   34456篇
  1997年   24241篇
  1996年   18632篇
  1995年   13889篇
  1994年   12384篇
  1993年   12338篇
  1992年   9112篇
  1991年   8568篇
  1990年   8633篇
  1989年   8347篇
  1988年   7839篇
  1987年   6845篇
  1986年   6800篇
  1985年   7581篇
  1984年   7077篇
  1983年   6463篇
  1982年   5840篇
  1981年   6089篇
  1980年   5593篇
  1979年   5673篇
  1978年   5526篇
  1977年   6078篇
  1976年   7933篇
  1975年   4836篇
  1974年   4513篇
  1973年   4592篇
  1972年   3865篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The authors studied the content of volatile N-nitrosamines (NA) in the most common sausage products. It was established that the total content of NA in sausage products is not high and ranges from trace amounts up to 10 micrograms/kg product. The allowable doses of nitrite in the sausage manufacture being low, no relationship was discovered between the content of NA and residual nitrite in meat products.  相似文献   
992.
From the results reported here it is suggested that policy decisions about the potential contribution of decentralized energy supply systems to UK industrial energy requirements should be based on the suitability of individual sectors rather than averaged over all sectors. The suitability of decentralized energy sources is evaluated, based on a themodynamic match between source and demand. This suitability criterion is used to identify the most appropriate sector in manufacturing industries for the adoption of decentralized energy supply, leaving aside economic cost considerations and individual site requirements.  相似文献   
993.
Survival of rotavirus on lettuce, radishes, and carrots was studied to evaluate the potential of rotavirus transmission by vegetables irrigated with wastewater. The vegetables were contaminated with rotavirus SA-11 and stored at 4°C and room temperature in covered and uncovered containers to simulate post harvest conditions. Virus decay rates were greater on radishes and carrots than lettuce. Decay rates of rotavirus on lettuce, radish, and carrot ranged from ?0·057 to ?0·479 (log10 pfu/day). Rotavirus SA-11 survived on lettuce, radish, and carrot for 25 to 30 days at 4°C but at room temperature survival was very different for the various vegetables varying from 5 to 25 days. Greatest survival was always observed on the lettuce. These data suggest that rotaviruses can survive long enough on contaminated vegetables as to be transmitted by this vehicle.  相似文献   
994.
A method is proposed for determining the thermophysical properties of translucent scattering materials in the nonsteady heating regime.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 6, pp. 977–982, December, 1985.  相似文献   
995.
On the basis of a numerical solution of the Stefan problem, the dynamics of nanosecond laser annealing of silicon is investigated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 306–312, February, 1985.  相似文献   
996.
997.
998.
New algorithms for the automatic restoration of antique documents affected by foxing and by yellowing deterioration processes are proposed in the paper. The physical restoration of such objects is both expensive and hard to carry out by nonspecialised library personnel. The proposed algorithms ensure fast and less expensive results, and can be used also by nonqualified operators. Moreover, these techniques improve the performance of optical character recognition operators.  相似文献   
999.
An innovative technology for industrial wastewater treatment has been developed. The main focus of the new system is a transformation of persistent organic compounds (biorecalcitrant COD) into a biodegradable fraction, followed by high efficient biological elimination using specialised bacteria's. To fulfill these targets the Aqua-Biomant process integrates two treatment steps: an aerated biological upflow filter and a electrochemical oxidation technique using boron doped-diamond electrodes. The advantages of the process are high efficient COD removal with reduced energy consumption combined with low total residence time.  相似文献   
1000.
Decentralised systems have the potential to provide a viable option for long term sustainable management of household wastewater. Yet, at present, such systems hold an uncertain status and are frequently omitted from consideration. Their potential can only be realised with improved approaches to their management, and improved methods to decision-making in planning of wastewater systems. The aim of this paper is to demonstrate the value of a novel framework to guide the planning of decentralised systems so that asset management and risk management are explicitly considered. The framework was developed through a detailed synthesis of literature and practice in the area of asset management of centralised water and wastewater systems, and risk management in the context of decentralised systems. Key aspects of the framework are attention to socio-economic risks as well as engineering, public health and ecological risks, the central place of communication with multiple stakeholders and establishing a shared asset information system. A case study is used to demonstrate how the framework can guide a different approach and lead to different, more sustainable outcomes, by explicitly considering the needs and perspectives of homeowners, water authorities, relevant government agencies and society as a whole.  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