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   252966篇
  免费   2790篇
  国内免费   870篇
电工技术   4811篇
综合类   193篇
化学工业   36147篇
金属工艺   9510篇
机械仪表   7544篇
建筑科学   6072篇
矿业工程   880篇
能源动力   7225篇
轻工业   21093篇
水利工程   2203篇
石油天然气   3230篇
武器工业   15篇
无线电   34309篇
一般工业技术   50008篇
冶金工业   48541篇
原子能技术   5075篇
自动化技术   19770篇
  2021年   2174篇
  2020年   1560篇
  2019年   1918篇
  2018年   3274篇
  2017年   3309篇
  2016年   3401篇
  2015年   2219篇
  2014年   3956篇
  2013年   11477篇
  2012年   6234篇
  2011年   8575篇
  2010年   6907篇
  2009年   7884篇
  2008年   8403篇
  2007年   8298篇
  2006年   7367篇
  2005年   6501篇
  2004年   6285篇
  2003年   6557篇
  2002年   6037篇
  2001年   6516篇
  2000年   5977篇
  1999年   6397篇
  1998年   16484篇
  1997年   11414篇
  1996年   8797篇
  1995年   6611篇
  1994年   5905篇
  1993年   5846篇
  1992年   4135篇
  1991年   4021篇
  1990年   3858篇
  1989年   3649篇
  1988年   3563篇
  1987年   3017篇
  1986年   2943篇
  1985年   3207篇
  1984年   2928篇
  1983年   2829篇
  1982年   2638篇
  1981年   2546篇
  1980年   2463篇
  1979年   2309篇
  1978年   2109篇
  1977年   2605篇
  1976年   3566篇
  1975年   1765篇
  1974年   1730篇
  1973年   1666篇
  1972年   1466篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This paper examines Total Quality Management (TQM) as defined by Dr. W. Edwards Deming including Deming's fourteen points and explains how the United States' Department of Defense (DOD) defines TQM and why TQM is necessary. It also covers how the DOD is planning on implementing TQM and the policy that has been established as guidance in the implementation process.  相似文献   
72.
Abdelguerfi  M. Sood  A.K. 《Micro, IEEE》1991,11(6):35-43
The design and simulation of a bit-sliced processor for relational database aggregation functions, are discussed. The processor, which addresses an important, computationally expensive problem in database computers, takes two tuples as input (one bit at a time) and returns two bits as output every clock cycle. A larger aggregation unit uses a number of identical slice processors, connected according to odd-even network topology, to achieve improved performance on a parallel pipelined processor. The data processing time is completely overlapped with the input and output of data to and from the unit. The design is independent of the tuple size, and since a bit-serial computation is used, the system requires limited interconnection  相似文献   
73.
The state of the art of debugging is examined. A debugged process model that serves as the basis of a general debugging framework is described. The relationship of the model to traditional debugging processes and support tools is discussed. A minimal set of requirements for a general debugging framework is described in terms of both the theory behind debugging methodologies and the support tools. An execution monitor, Eden, that serves as a debugging tool within this general framework is described  相似文献   
74.
75.
Conclusions The change in some properties of polyvinyl fluoride during the process of fibre spinning has been investigated.It has been found that during the process of converting PVF powder into fibre, the degree of polymer crystallinity plus its resistance to thermal and thermooxidative degradation is increased; depending on the spinning regime, the densities and physicomechanical properties of PVF fibres are different.Translated from Khimicheskie Volokna, No. 4, pp. 34–35, July–August, 1984.  相似文献   
76.
77.
This paper identifies the fuel properties for which more data are needed for fast-reactor safety analysis. In addition, a brief review is given of current research on the vapor pressure over liquid UO2 and (U, Pu)O2-x the solid-solid phase transition in actinide oxides, and the thermal conductivity of molten urania.  相似文献   
78.
Floodwaters in Kampung Melayu village, Jakarta, Indonesia, as well as river water and consumable water (including groundwater and tap water) samples in flooded and non-flooded areas, were quantitatively analysed to assess occurrence of viruses and total coliforms and E. coli as bacterial indicators after flooding event. High numbers of enterovirus, hepatitis A virus, norovirus (G1, G2) and adenovirus were detected at high concentration in floodwaters and waters sampled from Ciliwung River which runs across metropolitan Jakarta and is used widely for agriculture and domestic purposes by poor residents. One out of three groundwater wells in the flooded area was contaminated with all viruses tested while no viruses were found in groundwater samples in non-flooded areas and tap water samples. The results revealed that human enteric viruses, especially hepatitis A virus and adenovirus, were prevalent in Jakarta, Indonesia. This study suggested that flooding posed a higher risk of viral infection to the people through contamination of drinking water sources or direct contact with floodwaters.  相似文献   
79.
Nitrification is a key step for reliable biological nitrogen removal. In order to enhance nitrification in the activated sludge (AS) process, membrane-attached biofilm (MAB) was incorporated in a conventional activated sludge tank. Simultaneous organic carbon removal and nitrification of the MAB incorporated activated sludge (AS + MAB) process was investigated with continuous wastewater treatment. The effluent TOC concentration of AS and the AS + MAB processes were about 6.3 mg/L and 7.9 mg/L, respectively. The TOC removal efficiency of both AS and AS + MAB were above 95% during the wastewater treatment, indicating excellent organic carbon removal performance in both processes. Little nitrification occurred in the AS process. On the contrary, successful nitrification was obtained with the AS + MAB process with nitrification efficiency of about 90%. The volumetric and surface nitrification rates were about 0.14 g/Ld and 6.5 g/m2d, respectively. The results clearly demonstrated that nitrification in the conventional AS process was boosted by MAB. Furthermore, the microfaunal population in the AS + MAB process was different from that in the AS process. The high concentration of rotifers in the AS + MAB process was expected to decrease the generation of excess sludge in the process.  相似文献   
80.
The article established the regularities of change of the physicomechanical characteristics and strength of glass textolites in single and repeated thermal loading. It shows that under multiple loading the intense loss of strength of the investigated materials is due to increased porosity on account of the large number of microcracks appearing in the structure. A correlation is obtained between the elastic and strength characteristics and porosity in dependence on the temperature of multiple heating which in the first approximation is described by a polynomial of second degree with respect to temperature, multiplied by the reciprocal of porosity.Translated from Problemy Prochnosti, No. 6, pp. 53–58, June, 1991.  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