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   13830篇
  免费   1206篇
  国内免费   448篇
电工技术   598篇
综合类   636篇
化学工业   2905篇
金属工艺   480篇
机械仪表   553篇
建筑科学   741篇
矿业工程   239篇
能源动力   467篇
轻工业   1654篇
水利工程   191篇
石油天然气   362篇
武器工业   44篇
无线电   1294篇
一般工业技术   1929篇
冶金工业   989篇
原子能技术   191篇
自动化技术   2211篇
  2024年   21篇
  2023年   159篇
  2022年   272篇
  2021年   580篇
  2020年   406篇
  2019年   437篇
  2018年   470篇
  2017年   485篇
  2016年   487篇
  2015年   526篇
  2014年   643篇
  2013年   970篇
  2012年   901篇
  2011年   968篇
  2010年   798篇
  2009年   693篇
  2008年   700篇
  2007年   671篇
  2006年   551篇
  2005年   417篇
  2004年   434篇
  2003年   552篇
  2002年   645篇
  2001年   563篇
  2000年   289篇
  1999年   226篇
  1998年   294篇
  1997年   231篇
  1996年   166篇
  1995年   128篇
  1994年   96篇
  1993年   108篇
  1992年   57篇
  1991年   55篇
  1990年   58篇
  1989年   69篇
  1988年   28篇
  1987年   39篇
  1986年   35篇
  1985年   33篇
  1984年   34篇
  1983年   26篇
  1982年   22篇
  1981年   16篇
  1980年   27篇
  1978年   11篇
  1977年   19篇
  1976年   27篇
  1975年   7篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
71.
72.
The continuous separation of inclusions from aluminum melt flowing in a circular pipe using a high frequency magneticfield was investigated both theoretically and experimentally The separation efficiency was calculated based on thetrajectory method and compared with experimental results. It is found that the separation efficiency is a functilnondimensional parameters t_i·d_p~2B_e~2/μ_fμ_eα~2 and α/δ.The effective way to improve the separation efficiency is to increasethe effective magnetic flux density and decrease the pipe radius. and the value of α/δ should be kept about 2 in orderto obtain the optimum separation efficiency.  相似文献   
73.
74.
本文评述了反应结合氧化铝陶瓷的制备工艺原理,配料组成,研磨与原料细度,成形压力和升温速率等对陶瓷性能的影响。介绍了几种反应结合氧化铝陶瓷制造实例。  相似文献   
75.
In this paper we develop and compare several heuristic methods for solving the general two-dimensional cutting stock problem. We follow the Gilmore-Gomory column generation scheme in which at each iteration a new cutting pattern is obtained as the solution of a subproblem on one stock sheet. For solving this subproblem, in addition to classical dynamic programming, we have developed three heuristic procedures of increasing complexity, based on GRASP and Tabu Search techniques, producing solutions differing in quality and in time requirements. In order to obtain integer solutions from the fractional solutions of the Gilmore-Gomory process, we compare three rounding procedures, rounding up, truncated branch and bound and the solution of a residual problem. We have coded and tested all the combinations of algorithms and rounding procedures. The computational results obtained on a set of randomly generated test problems show their relative efficiency and allow the potential user to choose from among them, according to the available computing time. Rceived: January 9, 2001 / Accepted: December 10, 2001  相似文献   
76.
用于一维图像识别的支撑矢量机方法   总被引:7,自引:1,他引:6       下载免费PDF全文
研究了支撑矢量机的分类机理,并利用支撑矢量机对雷达目标一维像进行了识别.识别的结果表明了该方法的优越性,并显示它可以对残缺不全的样本进行识别.  相似文献   
77.
Ionomeric composites based on sepiolite and hydrogenated poly(styrene butadiene) block copolymer were obtained and characterized from a microstructural and electrical point of view. Before blending, because of the high silanol group concentration in the sepiolite, the latter could be organophilized with suitable coupling agents. The resulting materials were easily processed into thin films or membranes 0.2–0.4 mm thick, their conductivity in some cases approaching 10?1 S/cm. Their suitability for film formation and good electrical properties indicate potential applications as electrolytes in polymer fuel cells. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3512–3519, 2002  相似文献   
78.
大型钢制焊接双层低温储罐设计建造   总被引:3,自引:0,他引:3  
介绍了大型钢制焊接双层低温储罐的结构形式、选材、建造、检验及保冷要求 ,结合所设计的低温液氨储罐 ,对设计建造这类储罐必须考虑的一些问题作了分析  相似文献   
79.
The aim of the present study was to evaluate renal and liver distribution of two monoclonal immunoglobulin light chains. The chains were purified individually from the urine of patients with multiple myeloma and characterized as lambda light chains with a molecular mass of 28 kDa. They were named BJg (high amount of galactose residues exposed) and BJs (sialic acid residues exposed) on the basis of carbohydrate content. A scintigraphic study was performed on male Wistar rats weighing 250 g for 60 min after i.v. administration of 1 mg of each protein (7.4 MBq), as the intact proteins and also after carbohydrate oxidation. Images were obtained with a Siemens gamma camera with a high-resolution collimator and processed with a MicroDelta system. Hepatic and renal distribution were established and are reported as percent of injected dose. Liver uptake of BJg was significantly higher than liver uptake of BJs (94.3 vs 81.4%) (P < 0.05). This contributed to its greater removal from the intravascular compartment, and consequently lower kidney accumulation of BJg in comparison to BJs (5.7 vs 18.6%) (P < 0.05). After carbohydrate oxidation, there was a decrease in hepatic accumulation of both proteins and consequently a higher renal overload. The tissue distribution of periodate-treated BJg was similar to that of native BJs: 82.7 vs 81.4% in the liver and 17.3 vs 18.6% in the kidneys. These observations indicate the important role of sugar residues of Bence Jones proteins for their recognition by specific membrane receptors, which leads to differential tissue accumulation and possible toxicity.  相似文献   
80.
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