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   332567篇
  免费   4255篇
  国内免费   5899篇
电工技术   7212篇
综合类   5519篇
化学工业   51100篇
金属工艺   17252篇
机械仪表   11425篇
建筑科学   8458篇
矿业工程   2744篇
能源动力   7349篇
轻工业   28378篇
水利工程   4076篇
石油天然气   10403篇
武器工业   319篇
无线电   35411篇
一般工业技术   61718篇
冶金工业   52541篇
原子能技术   9026篇
自动化技术   29790篇
  2021年   2127篇
  2018年   4523篇
  2017年   4731篇
  2016年   5094篇
  2015年   3019篇
  2014年   4777篇
  2013年   12620篇
  2012年   7821篇
  2011年   13883篇
  2010年   9529篇
  2009年   9807篇
  2008年   10161篇
  2007年   9733篇
  2006年   8870篇
  2005年   12257篇
  2004年   13315篇
  2003年   10792篇
  2002年   9244篇
  2001年   8012篇
  2000年   7150篇
  1999年   7875篇
  1998年   15967篇
  1997年   12258篇
  1996年   9207篇
  1995年   7057篇
  1994年   6347篇
  1993年   7660篇
  1992年   5934篇
  1991年   5461篇
  1990年   5269篇
  1989年   5050篇
  1988年   4750篇
  1987年   3884篇
  1986年   3802篇
  1985年   4280篇
  1984年   4042篇
  1983年   3670篇
  1982年   3464篇
  1981年   3591篇
  1980年   3492篇
  1979年   3425篇
  1978年   3454篇
  1977年   3939篇
  1976年   5040篇
  1975年   3159篇
  1974年   3010篇
  1973年   3030篇
  1972年   2654篇
  1971年   2474篇
  1970年   2107篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
While Fickian diffusion models are commonly used in other applications, there are few reports of them being applied to the batch drying of a mineral concentrate. Diffusion coefficients estimated from small-scale oven-drying tests were used to predict the drying behavior of a concentrate sample 1 m × 1 m in area and 50 cm deep, with a heated bottom pad. These pilot-scale tests included both daily turning of the sample and turning every three days. The excellent quantitative agreement between the predicted and observed pilot-scale behavior gives a high level of confidence in the model predictions and suggests that a Fickian diffusion model is adequate to predict the behavior of mineral concentrates at the low moisture contents used here.  相似文献   
32.
Support effects form important aspect of hydrodesulfurization (HDS) studies and mixed oxide supports received maximum attention in the last two decades. This review will focus attention on studies on mixed oxide supported Mo and W catalysts. For convenience of discussion, these are divided into Al2O3 containing mixed oxide supports, TiO2 containing mixed oxide supports, ZrO2 containing mixed oxide supports and other mixed oxide supports containing all the rest. TiO2 containing mixed oxides received maximum attention, especially TiO2–Al2O3 supported catalysts. A brief discussion about their prospects for application to ultradeep desulfurization is also included. An overview of the available literature with emphasis on research carried out in our laboratory form the contents of this publication.  相似文献   
33.
Thirty patients who had undergone either a right or left unilateral temporal lobectomy (14 RTL; 16 LTL) and 16 control participants were tested on a computerized human analogue of the Morris Water Maze. The procedure was designed to compare allocentric and egocentric spatial memory. In the allocentric condition, participants searched for a target location on the screen, guided by object cues. Between trials, participants had to walk around the screen, which disrupted egocentric memory representation. In the egocentric condition, participants remained in the same position, but the object cues were shifted between searches to prevent them from using allocentric memory. Only the RTL group was impaired on the allocentric condition, and neither the LTL nor RTL group was impaired on additional tests of spatial working memory or spatial manipulation. The results support the notion that the right anterior temporal lobe stores long-term allocentric spatial memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
34.
35.
Mathematical models of thermomechanical processes which are based on the laws of rational thermodynamics of irreversible processes are treated. Singular features of the unsteady-state behavior of a continuous medium are demonstrated within different models, such as a medium with internal parameters of state, a medium with memory, and a medium of the velocity type.  相似文献   
36.
Managing sewerage systems is a highly complex task due to the dynamic nature of the facilities. Their performance strongly depends on the know-how applied by the operators. In order to define optimal operational settings, two decision support tools based on mathematical models have been developed. Moreover, easy-to-use interfaces have been created as well, aiding operators who presumably do not have the necessary skills to use modelling software. The two developed programs simulate the behaviour of both wastewater treatment plants (WWTP) and sewer network systems, respectively. They have essentially the same structure, including raw data management and statistical analysis, a simulation layer using the application programming interface of the applied software and a layer responsible for the representation of the obtained results. Four user modes are provided in the two software including the simulation of historical data using the applied and novel operational settings, as well as modes concerning prediction of possible operation periods and updates. Concerning the WWTP software, it was successfully installed in Nantes (France) in June 2004. Moreover, the one managing sewer networks has been deployed in Saint-Malo (France) in January 2005. This paper presents the structure of the developed software and the first results obtained during the commissioning phase.  相似文献   
37.
38.
39.
通过比较煤矿生产、安全调度显示方式的优缺点,提出和分析了适合于煤矿生产安全调度的LED电子大屏幕显示系统配置、功能及特点。  相似文献   
40.
For pt.I see ibid., vol.43, no.6, pp.1150-9 (1996). An exact solution of the electrostatic problem for calculating the surface charge and electric field distributions in an arbitrary periodic interdigital transducer (IDT) is given using the results of our companion paper. An arbitrary external electric field may be specified along the electrode structure with the unit cell containing one electrode, or several electrodes, of different widths. The potentials of the electrodes that may be specified are also arbitrary. It is shown that in the case without an external field, the solution includes all the known results as special cases. The case of shorted electrodes in the external electric field is investigated in detail. The surface charge and electric field distributions are calculated for a spatially harmonic external field with an arbitrary wavenumber. The results of the calculations are represented graphically for various ratios between the period of the electrode structure and the wavelength of the external field for the case of a unit cell containing one or two electrodes of different widths  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