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   325228篇
  免费   2222篇
  国内免费   615篇
电工技术   6390篇
综合类   591篇
化学工业   49537篇
金属工艺   10549篇
机械仪表   9056篇
建筑科学   8514篇
矿业工程   952篇
能源动力   8989篇
轻工业   32272篇
水利工程   2789篇
石油天然气   3832篇
武器工业   9篇
无线电   40687篇
一般工业技术   60503篇
冶金工业   59465篇
原子能技术   5576篇
自动化技术   28354篇
  2021年   2548篇
  2019年   2525篇
  2018年   3768篇
  2017年   3616篇
  2016年   3795篇
  2015年   2725篇
  2014年   4655篇
  2013年   14999篇
  2012年   7754篇
  2011年   10652篇
  2010年   8262篇
  2009年   9534篇
  2008年   10096篇
  2007年   10059篇
  2006年   8977篇
  2005年   8286篇
  2004年   8077篇
  2003年   7802篇
  2002年   7675篇
  2001年   7760篇
  2000年   7434篇
  1999年   7783篇
  1998年   17849篇
  1997年   13045篇
  1996年   10308篇
  1995年   8090篇
  1994年   7418篇
  1993年   7166篇
  1992年   5515篇
  1991年   5228篇
  1990年   5117篇
  1989年   4972篇
  1988年   4821篇
  1987年   4075篇
  1986年   4187篇
  1985年   4929篇
  1984年   4462篇
  1983年   4195篇
  1982年   3761篇
  1981年   3916篇
  1980年   3596篇
  1979年   3569篇
  1978年   3372篇
  1977年   3923篇
  1976年   4972篇
  1975年   2920篇
  1974年   2773篇
  1973年   2788篇
  1972年   2293篇
  1971年   2026篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
101.
Su  J. Ritter  P.R. 《Software, IEEE》1991,8(2):26-33
The testing and quality assurance of the Motif 1.0 graphical user-interface software are described. The testing goals, which fell into three general categories (code coverage, defect-density, and defect-arrival rate), and a deliverable formal test suite are examined. The three phases of the testing process-evaluation, test development, and regression testing-and the tools used in testing are discussed  相似文献   
102.
Pent et al. (see ibid., vol.SAC-6, no.1, p.34-41, 1988) proposed a semianalytic method for performance evaluation of communication channels with a bandpass nonlinearity. This method is based on a decomposition of the composite signal at the output of the nonlinear device which leads to the definition of an equivalent nonlinearity. In Pent et al. such an equivalent model is evaluated via numerical integration. In the present comment it is shown that a suitable series expansion of the nonlinearity characteristic yields to an evaluation of the equivalent nonlinearity in closed form  相似文献   
103.
104.
The paper describes a computerized facility layout designer, COMLAD II, for plant layout development. Besides developing an efficient layout, COMLAD II has useful features which allow fixing the departments, changing the shape of the departments and changing the length and width dimensions of the overall layout.  相似文献   
105.
The IBM RISC System/6000, a superscalar microprocessor, is presented. The architecture of this processor has its instruction set specifically designed for a superscalar machine containing three independent units-branch, fixed-point, and floating-point. The design also emphasizes high-performance floating-point operations. The design principles are to offer maximum overlap of the three functional units, avoid dead cycles, and define instructions that can (for the most part) be completed at a rate of one per cycle. The branch cycle, fixed- and floating-point units, cache management, and performance are described. Benchmark results are given  相似文献   
106.
Pull-out experiments have been carried out on single production fibres under carefully controlled conditions. Four parameters were determined. The interfacial yield stresses, of about 9–14 MPa, were very much smaller than the shear strengths of the bulk polymers in the case of an epoxy, whether post-cured or not, and a non-post-cured polyester. Values for the work of fracture of the interface varied from 140 to 300 Jm?2, and again were less than those of the polymer. Interface failure sometimes took place in the epoxy rather than at the fibre surface, whereas with the polyester it always took place at the fibre surface. After interface failure, pull-out was governed by friction, with maximum shear stresses of 7–10 MPa for polyester, and 21–34 MPa for epoxy, the higher values being obtained for the post-cured resins. Average frictional shear stresses were sometimes less than a half of the maximum shear stress, indicating that the fibre Poisson's shrinkage was playing an important role in the pull-out process. A silicone release agent reduced the frictional shear stresses to 2·5 MPa, with both resins.  相似文献   
107.
108.
Presents a model suitable for computing images of absorption cross sections of thick tissue structures illuminated at near infrared (NIR) wavelengths from tomographic projection data. Image reconstruction is accomplished by solving a system of linear equations derived from transport theory. Reconstruction results using different algebraic solvers are shown for anatomical maps of the breast, derived from magnetic resonance imaging data, containing two simulated pathologies, in which case qualitatively good reconstructions were obtained. Evaluation of magnetic resonance (MR) data to optimize NIR optical tomographic imaging methods and to assess the feasibility of a combined MR-optical measurement scheme is discussed  相似文献   
109.
The design and application of an apparatus for measuring pain threshold by controlling the conditions of an experiment carefully and measuring stimulus and response parameters precisely are described. Heat generated by an incandescent source, focused on a small area of the subject's forehead, was used as the stimulus to determine the cutaneous pain threshold. The equipment was in different experiments in which the threshold of thermocutaneous pain was evaluated with and without the use of an analgesic. The analgesic Pirazolane was found to reduce thermocutaneous pain threshold and to diminish the average duration of alpha rhythm blockade and the response of galvanic skin resistance. The results of these experiments with constituents of marijuana indicated that canabidiol provokes and increases the sensibility of pain reactions while both Δ9 THC and canabinol do not modify the pain threshold  相似文献   
110.
A survey of perceptions of IS personnel – managers, technical specialists and programmer/analysts – was conducted by the Association for Technical Information in Spain, using the JDS/DP, a modification of the job diagnostic survey instrument. Data were collected on fifteen job variables, related to four motivation aspects: job components, satisfaction levels, need for growth/achievement and goal participation/feedback. The results were compared with those of a similar survey for the same job types in Finland. Results were also compared with the norms developed for computer personnel in the USA. The survey revealed that personnel attracted to the computer field have a high need for growth and a low need for social interaction. It also revealed that the work itself was ranked highest among eleven motivating factors. For both Spain and Finland, the technical specialist job had a mis-match between the job's motivating potential and the employee's need for growth, compared with similar personnel in the USA. By examining the core job dimensions, managers can redesign the job to produce a match between these two major components of motivation.  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