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   39732篇
  免费   13086篇
  国内免费   12篇
电工技术   744篇
综合类   8篇
化学工业   17236篇
金属工艺   351篇
机械仪表   717篇
建筑科学   1720篇
矿业工程   15篇
能源动力   885篇
轻工业   7087篇
水利工程   291篇
石油天然气   96篇
无线电   6926篇
一般工业技术   11554篇
冶金工业   632篇
原子能技术   28篇
自动化技术   4540篇
  2023年   65篇
  2022年   98篇
  2021年   303篇
  2020年   1487篇
  2019年   3206篇
  2018年   3151篇
  2017年   3465篇
  2016年   3933篇
  2015年   3994篇
  2014年   3910篇
  2013年   5044篇
  2012年   2712篇
  2011年   2335篇
  2010年   2638篇
  2009年   2530篇
  2008年   2057篇
  2007年   1908篇
  2006年   1644篇
  2005年   1382篇
  2004年   1353篇
  2003年   1301篇
  2002年   1243篇
  2001年   1101篇
  2000年   1069篇
  1999年   458篇
  1998年   68篇
  1997年   54篇
  1996年   33篇
  1995年   13篇
  1994年   21篇
  1993年   26篇
  1992年   15篇
  1991年   18篇
  1990年   23篇
  1989年   17篇
  1988年   8篇
  1987年   12篇
  1986年   14篇
  1985年   10篇
  1984年   10篇
  1983年   9篇
  1982年   8篇
  1981年   5篇
  1980年   7篇
  1978年   9篇
  1977年   9篇
  1976年   12篇
  1975年   8篇
  1974年   8篇
  1973年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
The purpose of this study was to analyze the symbolization of colors as cultural codes, based on costume colors. In order to study the significance of colors in cultural changes, we carried out a quantitative analysis and interpreted it from the perspective of cultural semiotics. The range of this study was focused on Korean costume colors, over diverse diachronic stages of Korean culture. For this study 1535 color samples were collected, measured with a spectrophotometer, and analyzed quantitatively according their diachronic stages of origin. As a result, red, blue, and yellow were found to be the most frequently used colors during the Chosun Dynasty, a period based on Confucianism. These colors acted as cultural codes with cultural significance. During the Modern times pink, light blue, and black increased in frequency and represented the reception of western culture, the changing sex role of women in society, and utilitarianism. In these days, neutral colors and grayish tones of all colors are the most significant colors of high frequency. The use of such colors is closely related to industrialization, mechanization, functionalism, and the changes of women's sex roles in the societies. They are used as cultural codes, especially to emphasize a rational and masculine image rather than a feminine image. © 2006 Wiley Periodicals, Inc. Col Res Appl, 32, 71–79, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20290  相似文献   
192.
A general model, based on double film theory, is developed to study absorption with chemical reactions. In the liquid film region, the model is a set of differential equations that describe the mass transfer accompanying several chemical reactions; the resolution of the system is achieved by the finite difference method using an implicit scheme combined with Newton's method. Continuity equations and equilibrium coefficients are exploited in the treatment of the bulk region, which is based on the Newton‐Raphson method; the results are used directly as boundary conditions in the liquid film equations. Maxwell‐Stefan equations have been used as a rigorous approach in this model.  相似文献   
193.
194.
Abstract— Among various barrier‐rib manufacturing processes, the mold‐pattern‐transfer method has potential to reduce processing cost as well as the manufacture of high‐resolution pixels. In this study, the effects of major processing variables of the mold‐pattern‐transfer process on the formation of air‐trapped pores within barrier ribs were examined. The results indicated that with an optimum combination of the processing variables, barrier ribs without trapped defects can be produced, demonstrating the possibility of reducing the number of processing steps and costs of barrier ribs.  相似文献   
195.
Abstract— Several rare‐earth‐doped fluoride crystals that are excited to emit visible light by sequential two‐photon absorption have been investigated as display‐medium candidates for static volumetric three‐dimensional displays. Dispersion of powders of these materials in a refractive‐index‐matched polymer is reported because such a medium may result in a scalable display. The scattering problem in such a medium is greatly reduced by index‐matching the polymer to the crystalline particles. An index‐matching condition that optimizes the performance is identified.  相似文献   
196.
The microstructural evolution during the hot rolling of coarse grain sized austenite has been modeled considering all the microstructural mechanisms (dynamic, static and metadynamic recrystallization, strain induced precipitation) that can take place during an industrial TSDR production of three Nb microalloyed steels. Based on the results obtained from the model, processing maps have been drawn for 0.02%, 0.035% and 0.05% Nb microalloyed steels. Optimum processing conditions to exploit all the benefits of the Nb microalloying have been defined considering a final gauge thickness range between 1.5 and 12.65 mm. In addition, and facing the difficulties present in the production of thick hot strip, several alternative thermomechanical schedules are proposed, which would originate microstructures with a suitable combination of homogeneity and retained strain prior to transformation.  相似文献   
197.
Abstract: This article combines the neighborhood effects and spatial mismatch frameworks into a single model explaining how geographic factors contribute to unemployment. Using National Longitudinal Survey of Youth (1979) data, I estimate a two‐step model that separately models the effects of segregation and spatial mismatch. The first model predicts educational attainment as a function of exposure to residential segregation as a youth. The second model predicts unemployment probability as an adult as a function of educational attainment and spatial mismatch. The empirical results show that segregation does have discernable effects on educational attainment for blacks, but not for whites. I also find that spatial mismatch affects unemployment probability for blacks, but such an effect is hardly present for whites. A partial equilibrium analysis using predictions from the models shows that large changes in either segregation levels or the central city/suburban distribution of the black population would yield only moderate decreases in unemployment probability for the black population overall. Yet despite small predicted effects, these results should be viewed with caution because the general equilibrium effects of a large scale movement of blacks and whites across metropolitan space are largely impossible to predict with current data.  相似文献   
198.
199.
A modified CIECAM02 colour appearance model, named CIECAM02‐m2, is proposed to enable CIECAM02 to predict the simultaneous contrast effect. The structure of the CIECAM02‐m2 is a development from CIECAM02, and contains two different procedures for modifying the reference white; one is for lightness and the other is for hue. The model was tested using a data set accumulated in this study and the LUTCHI data. The CV values for three colour attributes between predictions and experimental data were used to evaluate the accuracy of the model. The low CV values obtained show the performance of the CIECAM02‐m2 model to predict the simultaneous contrast effect satisfactorily. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 121 – 129, 2007  相似文献   
200.
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