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   19097篇
  免费   743篇
  国内免费   44篇
电工技术   238篇
综合类   24篇
化学工业   3755篇
金属工艺   469篇
机械仪表   400篇
建筑科学   968篇
矿业工程   108篇
能源动力   610篇
轻工业   1644篇
水利工程   172篇
石油天然气   67篇
无线电   1460篇
一般工业技术   3392篇
冶金工业   3503篇
原子能技术   116篇
自动化技术   2958篇
  2023年   118篇
  2022年   207篇
  2021年   329篇
  2020年   238篇
  2019年   270篇
  2018年   370篇
  2017年   378篇
  2016年   414篇
  2015年   340篇
  2014年   513篇
  2013年   1226篇
  2012年   828篇
  2011年   1173篇
  2010年   811篇
  2009年   832篇
  2008年   934篇
  2007年   881篇
  2006年   762篇
  2005年   749篇
  2004年   596篇
  2003年   545篇
  2002年   531篇
  2001年   334篇
  2000年   306篇
  1999年   330篇
  1998年   377篇
  1997年   308篇
  1996年   334篇
  1995年   314篇
  1994年   295篇
  1993年   268篇
  1992年   264篇
  1991年   163篇
  1990年   233篇
  1989年   206篇
  1988年   169篇
  1987年   167篇
  1986年   157篇
  1985年   190篇
  1984年   205篇
  1983年   164篇
  1982年   174篇
  1981年   173篇
  1980年   144篇
  1979年   165篇
  1978年   125篇
  1977年   121篇
  1976年   164篇
  1975年   127篇
  1973年   110篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
In this paper, the cutoff characteristic of rectangular-shaped microshield transmission line has been analysed by edge element method. Dependence of cutoff wavelengths on the thickness of metallic signal strip, dielectric constant of dielectric substrate and the width of the rectangular-shaped ground conductor are presented in tabular form. Numerical results in this paper have important values in design of rectangular-shaped microshield lines in microwave and millimeter wave integrated circuits.  相似文献   
152.
在谈到商品包装装潢市场的发展趋势时,有必要先分析一下整个供应链.从根本上讲,推动整个供应链发展的是消费者.CPG(综合性消费品)公司将会影响消费者的选择,而消费者的这些选择对整个供应链会产生很大的波动性影响,使供应链的各个环节都发生动态变化.另外,由于技术、需求、生产力和交货期等因素的影响,也会使整个供应链发生一些折衷性的变化.  相似文献   
153.
Research has consistently documented that the quality of the therapeutic alliance is related to the outcome of diverse psychotherapies. Insufficient attention, however, has been directed at identifying the nature and magnitude of the causal relationship between the alliance and outcome. In this commentary, we discuss the major threats to causal interpretation of alliance-outcome correlations and provide suggestions for future research that would help clarify the extent to which the alliance causes positive outcomes. Assuming the alliance is a causal factor in relation to outcome, we provide recommendations for research on the alliance that would attempt to improve patient care by enhancing the alliance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
154.
Nano-crystal embedded PbO-P2O5 glass has been prepared and characterized by XRD and TEM measurements. The ultrasonic velocity and attenuation measured within the temperature range 80–300 K show significant structure and interesting feature with the presence of nano-crystalline region. The glass samples were prepared by melt-quench method and nano-crystals of different sizes were produced by heat treatment of the glasses for different durations of heating. All the processes were carried out at or above glass transition temperature. A theoretical model that takes account of the effects of thermally activated relaxation, anharmonicity as well as microscopic elastic inhomogeneities arising out of fluctuations has been successfully applied to interpret the variation of ultrasonic velocity and attenuation data. An interesting outcome of this application has been to propose a method for the determination of the size of nano-crystals from the ultrasonic attenuation data.  相似文献   
155.
欠采样或违反奈奎斯特(Nyquist)准则是ADC应用上经常使用的一种技术。射频(RF)通信和诸如示波器等高性能测试设备就是其中的一此实例。在这个“灰色”地带中经常出现一些困惑,如是否有必要服从Nyquist准则,以获取一个信号的内容。对于Nyquist和Shannon定理的检验将证明;  相似文献   
156.
Describes a unique multidisciplinary division in which 8 clinical programs are all administered by psychologists working in a university medical center setting. The increasingly complex environment of a university medical center is discussed in terms of academic mission, competitiveness of health care, and professional roles. The development of this division is reviewed in relation to a number of critical issues, such as organizational structure, academic vs clinical demands, business operations, and 1 version of a scientist–practitioner model in practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
157.
158.
Object substitution masking (OSM) is said to occur when a perceptual object is hypothesized that is mismatched by subsequent sensory evidence, leading to a new hypothesized object being substituted for the first. For example, when a brief target is accompanied by a longer lasting display of nonoverlapping mask elements, reporting of target features may be impaired. J. T. Enns and V. Di Lollo (2000) considered it an outstanding question whether OSM masks some or all aspects of a target. The authors report three experiments demonstrating that OSM can selectively affect target features. Participants may be able to detect a target while being unable to report other aspects of it or to report the color but not the orientation of a target (or vice versa). We discuss these findings in relation to two other visual phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
159.
New electron micrographs, produced using the technique of Field Emission Scanning Electron Microscopy, showing the details of the micellar surface, are presented. The images show the micellar surfaces without any coating, and suggest that the surface of the micelle may have a much more complex structure than has previously been demonstrated. Although there appear to be no spherical subunits (submicelles), there is evidence for the organization of the caseins into tubular structures within the micelle. The surface is not smooth, and contains gaps between the substructures. The observations are discussed in terms of published models of micellar structure, where is it suggested how the depiction of the micellar surface can be used to explain certain factors of its reactivity and behaviour.  相似文献   
160.
Five individuals participated in an extensive practice study (10 1-hr sessions, 11,000 trials total) on a self-paced identity-judgment n-back task (n ranging from 1 to 5). Within Session 1, response time increased abruptly by about 300 ms in passing from n = 1 to n > 1, suggesting that the focus of attention can accommodate only a single item (H. Caravan, 1998; B. McElree, 2001). Within Session 10, response time was dramatically reduced and increased linearly with n for n ≤ 4, with a slope of about 30 ms. The data suggest that working memory consists of a focus of attention governed by a limited-capacity search, expandable through practice, and a content-addressable region outside the focus of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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