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   303210篇
  免费   25362篇
  国内免费   16069篇
电工技术   20771篇
技术理论   52篇
综合类   39300篇
化学工业   37652篇
金属工艺   14031篇
机械仪表   15883篇
建筑科学   38390篇
矿业工程   15485篇
能源动力   9384篇
轻工业   19258篇
水利工程   14191篇
石油天然气   12794篇
武器工业   2869篇
无线电   23322篇
一般工业技术   23865篇
冶金工业   17673篇
原子能技术   3100篇
自动化技术   36621篇
  2024年   1047篇
  2023年   3352篇
  2022年   6036篇
  2021年   7283篇
  2020年   7762篇
  2019年   6700篇
  2018年   6282篇
  2017年   7595篇
  2016年   8674篇
  2015年   9542篇
  2014年   16786篇
  2013年   15663篇
  2012年   20008篇
  2011年   21127篇
  2010年   16575篇
  2009年   17421篇
  2008年   16309篇
  2007年   21229篇
  2006年   20116篇
  2005年   17528篇
  2004年   14905篇
  2003年   13580篇
  2002年   11243篇
  2001年   9571篇
  2000年   8148篇
  1999年   6622篇
  1998年   5144篇
  1997年   4517篇
  1996年   4096篇
  1995年   3524篇
  1994年   3110篇
  1993年   2326篇
  1992年   2081篇
  1991年   1564篇
  1990年   1373篇
  1989年   1225篇
  1988年   914篇
  1987年   625篇
  1986年   478篇
  1985年   398篇
  1984年   381篇
  1983年   271篇
  1982年   258篇
  1981年   189篇
  1980年   154篇
  1979年   119篇
  1978年   70篇
  1977年   78篇
  1976年   59篇
  1975年   60篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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   
92.
The paper considers the set-theoretical approach to the joint decomposition of systems of Boolean functions of variables specified in different representation forms. The approach is based on the method of q-partitions of conjuncterms and concept of decomposition clones. Theorems on joint decomposition of a system of full and partial functions are formulated. The approach is illustrated by examples. Parts I and II of this article are published in No. 5 (2001) and No. 1 (2002). __________ Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 39–58, March–April 2007.  相似文献   
93.
紫杉醇的全合成困难,许多工作还只能停留在实验室的模型化合物上。作者以思想实验方法提出了:先以D-A反应形成A环和C环,然后用两步形成B环,最后形成D环,以此完成紫杉醇母核的全合成。  相似文献   
94.
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties.  相似文献   
95.
房地产开发企业会计核算问题探讨   总被引:1,自引:0,他引:1  
本文就房地产开发企业会计核算的现状及特点进行了分析,并提出了完善房地产开发企业会计核算规范的对策。  相似文献   
96.
DS2000-M1是高性能、开放式的LED控制系统,本文从软硬件两方面简述其设计原理。  相似文献   
97.
综述评述最近发展起来的陶瓷材料的烧结后冷加工热处理法“控制破碎成形加工法”,着重介绍该方法的由业,阐明其理论与实验基础,同时,介绍其应用并讨论其发展前景。  相似文献   
98.
The oligosaccharide component compositions of a series of non-reducing oligosaccharides extracted from the roots of Arnica montana L. has been determined by gel permeation chromatography (g.p.c.). The range of oligosaccharides present was found to extend beyond the octasaccharide previously reported. with 16% to 19% of the oligosaccharides having a degree of polymerisation of between 11 and 19 and almost 3% having a degree of polymerisation greater than 20. The chromatographic behaviour of this series of oligosaccharides is compared with that observed for series of D-gluco-oligosaccharides.  相似文献   
99.
Chestnuts were dehydrated by using a combined method of osmotic dehydration followed by air drying. Samples were osmotically pretreated with sucrose (60% w/w) and glucose (56% w/w) for 8 h, air-dried at temperatures of 45, 55, and 65°C, at a relative humidity of 30% and at a velocity of 2.7 m·s-1 and the experimental data of the drying kinetics were obtained. Whole samples were dried with different peelings: (a) removal of endocarp and pericarp (peeled) and (b) additionally the internal rough surface (cut). In all cases, cut chestnuts show greater drying rates than peeled samples, indicating that a significant mass transfer resistance in the layer nearest to the surface takes place. Peeled samples pretreated with sucrose solutions behave in a similar way to untreated samples. For the rest of the samples, the cut samples osmotically treated with sucrose solutions and all the samples treated with the glucose solution, the drying rates decrease during drying. Drying kinetics are successfully modeled by employing a diffusional model that takes the shrinkage into account. The effective coefficient of water diffusion was evaluated and correlated with temperature. The quality of the final product was monitored by color change. In spite of the fact that the total color difference is not modified by the osmotic treatment, the L*, a*, and b* color coordinates of cut samples treated with sucrose and glucose solutions do undergo changes; the L* and a* coordinates change less than the b*.  相似文献   
100.
This paper extends an earlier report of measurements and computer predictions of flows in a cubical cavity exposed on one side to the scavenging effect of an external stream. Further measurements and photographs are presented; they are consistent with each other and with the predictions of the computational model. Specifically, comparisons are made between measured and predicted mean velocities and turbulent shear stresses, and photographs are used to elucidate features of the shear layers generated by accelerating and decelerating external flows. The computer model is used to deduce approximate relations between internal turbulent activity (measured by mean velocity, turbulence energy and shear stress) and external velocity, percentage ‘window’ opening and relative position of the plane walls upstream and downstream of the cavity.  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