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   322238篇
  免费   5959篇
  国内免费   923篇
电工技术   5554篇
综合类   387篇
化学工业   49987篇
金属工艺   11387篇
机械仪表   9590篇
建筑科学   8078篇
矿业工程   1199篇
能源动力   7953篇
轻工业   32124篇
水利工程   3128篇
石油天然气   4197篇
武器工业   74篇
无线电   37945篇
一般工业技术   60019篇
冶金工业   59877篇
原子能技术   5757篇
自动化技术   31864篇
  2022年   2174篇
  2021年   3621篇
  2020年   2685篇
  2019年   3284篇
  2018年   5586篇
  2017年   5587篇
  2016年   5987篇
  2015年   3983篇
  2014年   6236篇
  2013年   15541篇
  2012年   10079篇
  2011年   12529篇
  2010年   9819篇
  2009年   10537篇
  2008年   11424篇
  2007年   11057篇
  2006年   9694篇
  2005年   8733篇
  2004年   8346篇
  2003年   8034篇
  2002年   7557篇
  2001年   7258篇
  2000年   6964篇
  1999年   7176篇
  1998年   18501篇
  1997年   12932篇
  1996年   9938篇
  1995年   7462篇
  1994年   6613篇
  1993年   6474篇
  1992年   4872篇
  1991年   4540篇
  1990年   4353篇
  1989年   4109篇
  1988年   3918篇
  1987年   3428篇
  1986年   3319篇
  1985年   3915篇
  1984年   3618篇
  1983年   3220篇
  1982年   3082篇
  1981年   3191篇
  1980年   2962篇
  1979年   2801篇
  1978年   2648篇
  1977年   3271篇
  1976年   4173篇
  1975年   2424篇
  1974年   2394篇
  1973年   2422篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
A newly developed membrane performance enhancer (MPE) was used to prevent membrane fouling in a membrane bioreactor (MBR) process. It transpired that 1,000 mg/l of MPE reduced polysaccharide levels from 41 mg/I to 21 mg/I on average under the experimental condition. Repeated experiments also confirmed that 50-1,000 mg/l of MPE could reduce membrane fouling significantly and increase the intervals between membrane cleanings. Depending on MPE dosages and experimental conditions, trans-membrane pressure (TMP) increase was suppressed for 20-30 days, while baseline TMP surged within a few days. In addition, MPE allowed MBR operation even at 50,000 mg/l of total solid and reduced permeate COD. However, no evidence of toxicity for sludge was found from respiratory works.  相似文献   
92.
The biochemical composition can be seen as a good indicator of both the biodegradability and the methane potential of a given waste. The work presented here is an attempt to elaborate a typology of wastes and to compare it to the anaerobic degradation characteristics. The first data indicate that there is a link between the ligno-cellulosic content of the waste and the biodegradability. When dealing with application to anaerobic digestion processes, having a tool to predict the ability of the waste to be degraded could be of the greatest interest for preventing failures, estimating biogas production, methane content, or for the management of co-digestion processes.  相似文献   
93.
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   
94.
95.
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   
96.
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   
97.
Physically based simulation of human hair is a well studied and well known problem. But the “pure” physically based representation of hair (and other animation elements) is not the only concern of the animators, who want to “control” the creation and animation phases of the content. This paper describes a sketch-based tool, with which a user can both create hair models with different styling parameters and produce animations of these created hair models using physically and key frame-based techniques. The model creation and animation production tasks are all performed with direct manipulation techniques in real-time.  相似文献   
98.
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   
99.
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   
100.
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   
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