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   26483篇
  免费   1979篇
  国内免费   1636篇
电工技术   1433篇
技术理论   1篇
综合类   2195篇
化学工业   2626篇
金属工艺   1290篇
机械仪表   1516篇
建筑科学   3052篇
矿业工程   1137篇
能源动力   771篇
轻工业   1791篇
水利工程   941篇
石油天然气   2113篇
武器工业   603篇
无线电   3992篇
一般工业技术   2152篇
冶金工业   1276篇
原子能技术   798篇
自动化技术   2411篇
  2024年   31篇
  2023年   191篇
  2022年   297篇
  2021年   351篇
  2020年   378篇
  2019年   370篇
  2018年   391篇
  2017年   528篇
  2016年   621篇
  2015年   609篇
  2014年   1121篇
  2013年   1272篇
  2012年   1594篇
  2011年   1734篇
  2010年   1423篇
  2009年   1483篇
  2008年   1798篇
  2007年   2336篇
  2006年   2142篇
  2005年   1904篇
  2004年   1641篇
  2003年   1419篇
  2002年   1088篇
  2001年   1017篇
  2000年   827篇
  1999年   648篇
  1998年   516篇
  1997年   415篇
  1996年   370篇
  1995年   324篇
  1994年   254篇
  1993年   194篇
  1992年   167篇
  1991年   136篇
  1990年   109篇
  1989年   89篇
  1988年   75篇
  1987年   44篇
  1986年   49篇
  1985年   26篇
  1984年   8篇
  1983年   10篇
  1982年   8篇
  1981年   15篇
  1980年   15篇
  1966年   6篇
  1964年   4篇
  1959年   7篇
  1957年   7篇
  1955年   8篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
161.
The simultaneous contrast effect is investigated in this article. A total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively. Each combination was assessed by nine observers using a matching technique. The test and induction colours used for CRT colours were similar to surface colours using fabric samples. The results indicated a strong lightness contrast effect for both CRT and surface media; that is, the lightness of a test colour surrounded by a lighter induction colour was reduced for both CRT and surface colours. However, the effect in CRT medium was more pronounced than in the surface medium. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 13–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20074  相似文献   
162.
In many situations such as the cores of a rotating electrical machine and the T joints of a multiphase transformer, the local flux density varies with time in terms of both magnitude and direction, i.e. the flux density vector is rotating. Therefore, the magnetic properties of the core materials under the rotating flux density vector excitation should be properly measured, modeled and applied in the design and analysis of these electromagnetic devices. This paper presents an extensive review on the development of techniques and apparatus for measuring the rotational core losses of soft magnetic materials based on the experiences of various researchers in the last hundred years.  相似文献   
163.
N. Kamoun  B. Rezig 《Thin solid films》2007,515(15):5949-5952
We have investigated synthesis conditions and some properties of sprayed Cu2ZnSnS4 (CZTS) thin films in order to determine the best preparation conditions for the realization of CZTS based photovoltaic solar cells. The thin films are made by means of spraying of aqueous solutions containing copper chloride, zinc chloride, tin chloride and thiourea on heated glass substrates at various temperatures. In order to optimize the synthesis conditions of the CZTS films, two series of experiments are performed. In the first series the sprayed duration was fixed at 30 min and in the second it is fixed at 60 min. In each series, the substrate temperature was changed from 553°K to 633°K. The X-ray diffraction shows, on one hand, that the best crystallinity was obtained for 613°K as substrate temperature and 60 min as sprayed duration. On the other hand, these CZTS films exhibit the kesterite structure with preferential orientation along the [112] direction. Atomical Force Microscopy was used to determine the grain sizes and the roughness of these CZTS thin film. After the annealing treatment, we estimated the optical band-gap energy of the CZTS thin film exhibiting the best crystallinity as 1.5 eV which is quite close to the optimum value for a solar cell.  相似文献   
164.
航空放射性遥感系统采用航空γ能谱仪,在空中飞行探测地表放射性,能够快速进行大面积环境放射性调查。结合已经开始进行的首次大面积航空放射性遥感调查工作,简要介绍了航空放射性遥感系统构成、核探测γ能谱测量和数据处理技术。对系统转换因子刻度和剥离系数刻度方法进行了讨论,并对初步应用情况进行了总结。  相似文献   
165.
高国富  王安 《煤矿机电》2003,(5):101-104,108
煤矿机电一体化技术的发展,对生产技术与管理人员提出愈来愈高的要求,培养跨世纪的机电一体化人才已成现代化煤炭企业的当务之急。神东公司通过公开招聘、现场培训、实施人才工程、联合办学、采用多媒体网络教学等多种形式培养跨世纪机电一体化人才。  相似文献   
166.
陈其安 《钢铁》2003,38(12):62-67
在可持续发展原则指导下,强化控轧控冷、高精度轧制和改进表面与外形质量是当前特钢轧制技术发展的重点。  相似文献   
167.
多媒体技术在化学教学中应用的探讨   总被引:4,自引:2,他引:2  
文中介绍了多媒体教学的发展及多媒体课件、文献资料和仿真实验等教学的基本形式;分析了多媒体教学所具有的信息量丰富、表现力多样化、交互性较强和内容更新快的特点;讨论了多媒体教学可提高教学效率、提高学生理解能力、减轻教师负担和因材施教的优越性;提出了在教学中应用多媒体技术时,应以学生为主体,教师为主导,为学习者提供认知帮助是关键而有效策略的教学思想。  相似文献   
168.
Summary We introduce a very simple model for thermally activated atomic migration on a lattice, and several techniques to handle it. For thermodynamical systems, the model can be used for simulating decomposition paths taking into account relevant metallurgical features. Close to equilibrium, the simplest mean-field approximation of the model can be linearized with respect to the departure from equilibrium; one then gets a microscopic interpretation of classical phenomenological coefficients, such as mobility, interfacial transfer coefficient, rate constants for the coupled relaxation of concentration and order fields. Further away from the equilibrium, the nonlinearities can be taken into account in a consistent way. For driven alloys, i.e. alloys submitted to external forcing, forced atomic migration is added to the model and new features emerge: the model is supported by several experimental results some of which confirmed its predictions a posteriori.  相似文献   
169.
170.
The condition of the surfaces is of crucial importance for the deuterium permeation through materials. In this work a study of the surface constants for the adsorption (σk1) and release (σk2) of deuterium under different surface conditions on the martensitic steel DIN 1.4914 (MANET) has been carried out. The growth of an oxide surface layer (Cr2O3) of about 25–30 nm in a MANET sample, heat treated in an oxidizing environment, compared to the bare MANET that have a ‘natural' oxide of about 5 nm has provoked a reduction of both the permeation rate and the recombination coefficient (about 3 orders of magnitude). In addition, the permeation governing process has changed from diffusion-limited to surface-limited. The measurements of the permeation rate of deuterium were performed by a gas-phase permeation technique over the temperature range 574–746 K and for deuterium driving pressures in the range from 3 to 105 Pa.  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