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   332746篇
  免费   29674篇
  国内免费   19063篇
电工技术   25883篇
技术理论   54篇
综合类   43616篇
化学工业   34543篇
金属工艺   12039篇
机械仪表   20811篇
建筑科学   41447篇
矿业工程   17340篇
能源动力   11492篇
轻工业   19053篇
水利工程   15920篇
石油天然气   14910篇
武器工业   3418篇
无线电   22284篇
一般工业技术   24296篇
冶金工业   17639篇
原子能技术   3093篇
自动化技术   53645篇
  2024年   1398篇
  2023年   4047篇
  2022年   7483篇
  2021年   8592篇
  2020年   9302篇
  2019年   7855篇
  2018年   7282篇
  2017年   8871篇
  2016年   10334篇
  2015年   11461篇
  2014年   19736篇
  2013年   18254篇
  2012年   23033篇
  2011年   24201篇
  2010年   18715篇
  2009年   19651篇
  2008年   18156篇
  2007年   23323篇
  2006年   21653篇
  2005年   18772篇
  2004年   15887篇
  2003年   14134篇
  2002年   11643篇
  2001年   9810篇
  2000年   8315篇
  1999年   6667篇
  1998年   5160篇
  1997年   4486篇
  1996年   4067篇
  1995年   3466篇
  1994年   3028篇
  1993年   2281篇
  1992年   2007篇
  1991年   1522篇
  1990年   1313篇
  1989年   1151篇
  1988年   900篇
  1987年   606篇
  1986年   451篇
  1985年   373篇
  1984年   355篇
  1983年   267篇
  1982年   237篇
  1981年   173篇
  1980年   147篇
  1979年   128篇
  1978年   70篇
  1977年   82篇
  1976年   61篇
  1975年   61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.
介绍了造成铁路油槽车底油收不尽的原因,一是节约意识差;二是设备设施陈旧或维护不够;三是操作不当。提出了增强节约意识,挖掘设备潜力,采用合理的吸油方法的对策。  相似文献   
93.
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   
94.
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   
95.
A new practical method is proposed which gives a quasi-optimal solution of the dynamic load-dispatching problem formulated by a multiconstraint multiobjective optimization problem. Here, the multiple constraints are rate reserve constraints and power flow ones, and the multiple objectives are fuel cost and CO2 emission. The proposed method is an integration of the following three techniques: (1) “Group Dispatch Scheme,” which is developed by the authors, is used to satisfy a violated constraint easily. This scheme consists of three steps. The first step is to classify all generators into two groups. One is the group which should be more loaded to satisfy the violated constraint, and the other is the should-be less loaded group. The second step is to add some load to the former group, and to subtract the same load from the latter. The third step is to dispatch each group load to each groups generators, respectively; (2) the dynamic load-dispatching algorithm is used which provides, in practical time, quasi-optimal generation trajectories; (3) the conventional weighting parametric method is used to obtain a Pareto optimal solution of multiobjective problems. The effectiveness of the method is clarified by a computer simulation on the actual power system of Kansai Electric Power Company.  相似文献   
96.
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   
97.
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   
98.
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   
99.
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   
100.
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   
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