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   30227篇
  免费   3171篇
  国内免费   1832篇
电工技术   1697篇
技术理论   1篇
综合类   2181篇
化学工业   4670篇
金属工艺   1569篇
机械仪表   1728篇
建筑科学   2269篇
矿业工程   736篇
能源动力   901篇
轻工业   2793篇
水利工程   730篇
石油天然气   1168篇
武器工业   269篇
无线电   4062篇
一般工业技术   3711篇
冶金工业   1504篇
原子能技术   395篇
自动化技术   4846篇
  2024年   147篇
  2023年   432篇
  2022年   892篇
  2021年   1217篇
  2020年   959篇
  2019年   800篇
  2018年   948篇
  2017年   1008篇
  2016年   968篇
  2015年   1207篇
  2014年   1504篇
  2013年   2027篇
  2012年   2125篇
  2011年   2147篇
  2010年   2056篇
  2009年   2030篇
  2008年   1957篇
  2007年   1954篇
  2006年   1725篇
  2005年   1374篇
  2004年   1128篇
  2003年   1082篇
  2002年   1175篇
  2001年   1042篇
  2000年   632篇
  1999年   465篇
  1998年   425篇
  1997年   350篇
  1996年   277篇
  1995年   212篇
  1994年   173篇
  1993年   123篇
  1992年   100篇
  1991年   75篇
  1990年   59篇
  1989年   81篇
  1988年   44篇
  1987年   44篇
  1986年   49篇
  1985年   39篇
  1984年   29篇
  1983年   20篇
  1982年   14篇
  1981年   15篇
  1980年   13篇
  1979年   10篇
  1978年   9篇
  1977年   15篇
  1976年   12篇
  1959年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This study relates to the development of coatings for optical discs in high-density digital versatile disc systems (HD-DVD or blue lay disk) that use a high numerical aperture of 0.85 at 405 nm wavelength and have a protective top layer over a primer layer for protection against damage and dust. Ultraviolet-curable raw materials of two acrylic monofunctional monomers ( isobornylacrylate, IBA and tetrahydrofurfurylacrylate, THFA) and two kinds of urethaneacrylate oligomers (OUMD and OUME) have been easily mixed with photoinitiators. Curing rate of these materials was characterized by FT-IR. In case of top coats, VTES (vinyltriethoxysilane) and acrylic acid were added to enhance the abrasion resistance. These two kinds of UV-curable resinous materials having no solvent were synthesized and investigated as means for making a blue ray disk having good optical and mechanical properties. In addition, dynamic characteristics including reflectivity, fluctuation of RF signal and noise level were also investigated.  相似文献   
52.
A measurement method has been developed to determine the full-field deformation of a simply supported plane plate under transverse load. The method utilizes strain information provided by a set of four fiber Bragg grating sensors mounted on the plate in a way that all sensors measure strains along one certain direction. The sensors were interrogated using a wavelength swept fiber laser. Utilizing the strain information and the first four terms of Navier solution of simply supported rectangular plate, the necessary parameters for determining the deflection could be computed. By substituting the values of x- and -y- coordinates of each position on the rectangle plate, the full-field deformation information can be obtained. Single-point loading tests were experimentally performed to verify the accuracy of the method.  相似文献   
53.
国内主要参展商 1.益阳橡机 益阳橡胶塑料机械集团有限公司在本次展会上,推出了一款GE-5实验室用密炼机,容积5升,啮合型转子,用于橡胶制品、白炭黑、特种胶的混炼.  相似文献   
54.
钢样成分化验分析结果网络传输系统将碳硫分析仪、光谱分析仪和相应的计算机控制系统按以太网络结构组联,形成"炉前分析网络",采用分析网主服务器系统软件和网络分析系统软件实现网络传输。该系统可将炉前钢样化验分析结果实时传输到炉前大屏,具有传输速度快、准确率高的特点,提高了工作效率和产品合格率,降低了生产成本。  相似文献   
55.
不同粒度松散煤体的氧扩散特性实验研究   总被引:1,自引:0,他引:1  
梁运涛  罗海珠 《煤炭学报》2003,28(5):470-472
以自行研制的煤对氧扩散特性测试装置为实验手段,在常温环境条件下测试了不同粒度松散煤体对氧的自由扩散特性.实验结果表明:煤样粒度的变化对取气腔氧浓度流出曲线的影响表现出2个极限值,煤样粒度在20~100目之间时,取气腔氧气浓度梯度随煤样粒度的增大而增大;当煤样粒度<20目或>100目时,煤样粒度的再变化对氧浓度流出曲线的影响则微乎其微;取气腔氧浓度曲线流形基本符合指数曲线的变化规律.  相似文献   
56.
57.
R. Mujoo    P.K.W. Ng 《Journal of food science》2003,68(8):2448-2452
ABSTRACT: Grain of the soft white wheat cultivar Harus was harvested weekly from anthesis to maturity and fructooligosaccharides (FOS) contents were determined by reversed-phase high-performance liquid chromatography. Tests were carried out to determine the effect of adding immature wheat meal to a base flour of cultivar Russ (hard red spring) on the quality characteristics of bread. FOS content was also analyzed in baked bread, and the effect of transglutaminase in improving bread quality was examined. Marked decreases in FOS contents, such as 1-kestose and nystose, were observed with grain maturation. The overall quality of bread appeared to be acceptable, and the added FOS were retained after baking.  相似文献   
58.
Academically selective schools are intended to affect academic self-concept positively, but theoretical and empirical research demonstrates that the effects are negative. The big-fish--little-pond effect (BFLPE), an application of social comparison theory to educational settings, posits that a student will have a lower academic self-concept in an academically selective school than in a nonselective school. This study, the largest cross-cultural study of the BFLPE ever undertaken, tested theoretical predictions for nationally representative samples of approximately 4,000 15-year-olds from each of 26 countries (N=103,558) who completed the same self-concept instrument and achievement tests. Consistent with the BFLPE, the effects of school-average achievement were negative in all 26 countries (M beta=-.20, SD=.08), demonstrating the BFLPE's cross-cultural generalizability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
59.
An adaptive contour smoothing algorithm designed as a preprocessor for shape coders is presented. In the method, the degree of the adaptive smoothing is controlled based on the significance of each contour point, which is quantified according to inter-region contrast in an intensity image. The actual smoothing consists of an expansion operator and a thinning algorithm.  相似文献   
60.
NMR structure and mutagenesis of the FADD (Mort1) death-effector domain   总被引:1,自引:0,他引:1  
When activated, membrane-bound receptors for Fas and tumour-necrosis factor initiate programmed cell death by recruiting the death domain of the adaptor protein FADD to the membrane. FADD then activates caspase 8 (also known as FLICE or MACH) through an interaction between the death-effector domains of FADD and caspase 8. This ultimately leads to the apoptotic response. Death-effector domains and homologous protein modules known as caspase-recruitment domains have been found in several proteins and are important regulators of caspase (FLICE) activity and of apoptosis. Here we describe the solution structure of a soluble, biologically active mutant of the FADD death-effector domain. The structure consists of six antiparallel, amphipathic alpha-helices and resembles the overall fold of the death domains of Fas and p75. Despite this structural similarity, mutations that inhibit protein-protein interactions involving the Fas death domain have no effect when introduced into the FADD death-effector domain. Instead, a hydrophobic region of the FADD death-effector domain that is not present in the death domains is vital for binding to FLICE and for apoptotic activity.  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