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   58987篇
  免费   6208篇
  国内免费   5503篇
电工技术   2296篇
技术理论   2篇
综合类   6420篇
化学工业   7639篇
金属工艺   2400篇
机械仪表   1838篇
建筑科学   15109篇
矿业工程   2928篇
能源动力   2053篇
轻工业   3645篇
水利工程   5423篇
石油天然气   2432篇
武器工业   453篇
无线电   5163篇
一般工业技术   6849篇
冶金工业   2481篇
原子能技术   1071篇
自动化技术   2496篇
  2024年   223篇
  2023年   862篇
  2022年   1611篇
  2021年   1989篇
  2020年   1979篇
  2019年   1868篇
  2018年   1625篇
  2017年   2093篇
  2016年   2122篇
  2015年   2229篇
  2014年   3558篇
  2013年   3393篇
  2012年   4171篇
  2011年   4535篇
  2010年   3517篇
  2009年   3665篇
  2008年   3383篇
  2007年   4175篇
  2006年   3740篇
  2005年   3260篇
  2004年   2778篇
  2003年   2360篇
  2002年   1997篇
  2001年   1584篇
  2000年   1431篇
  1999年   1142篇
  1998年   918篇
  1997年   803篇
  1996年   658篇
  1995年   584篇
  1994年   495篇
  1993年   369篇
  1992年   299篇
  1991年   256篇
  1990年   212篇
  1989年   174篇
  1988年   132篇
  1987年   101篇
  1986年   71篇
  1985年   46篇
  1984年   56篇
  1983年   30篇
  1982年   29篇
  1981年   22篇
  1980年   26篇
  1979年   55篇
  1965年   5篇
  1963年   5篇
  1959年   11篇
  1951年   8篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
161.
The Gd substituting effects for La in La0.67Ca0.33MnO3 has been studied .With increasing the substituting amount of Gd,the phase transition temperature of metal-isolator for the samples decreases,the corresponding peak resistivity increases,the Curie temperature decreases monotonically.The substitution of La-Ca-Mn-O with 11% Gd for La improved the magnetoresistance ratio by an order of magnitude.The effects of substituting Gd can be explained in terms of the lattice effects.An irreversible MR behaviour was observed in Gd-substituting compounds.This effect became marked when the substituting amount of Gd was greater than 7%.A maximum irreversible increment of MR ratio as large as 91% was obtained when Gd substituting amount was 11%.  相似文献   
162.
磁热效应的测量有间接测量和直接测量两种方法。本文在比较两种测量方法各自特点的基础上,重点综述了直接测量装置的种类及特点;指出直接测量装置在室温磁制冷技术研究中的重要作用。  相似文献   
163.
纪晓岚 《现代城市研究》2002,17(3):52-56,61
揭示了城市环境的基本性质的基本特征,研究了城市环境对人的心理影响和生理影响。指出城市环境建设不公要满足人的物质需要,还要满足人的精神需要。  相似文献   
164.
The effect of steel fibre used in concrete was systematically analyzed by model testing of 30 2-pile thick caps of steel-fibre reinforced concrete, in which the model scale was 1:5. The experiment system composed of a loading device, strain measurement system and a data-acquisition system was used, also an electromechanic centigrade scale, a lens and a Y J-25 static resistance strainometer were used.The experimental results show that the volumetric rate of steel fibre and draw ratio have an important influence on its load-bearing capacity. The incorporation of steel fibre can effectively improve the extension and reduce the thickness of the caps.  相似文献   
165.
Manual responses can be defined by differing response parameters. Any of them may generate a Simon effect. For all those response parameters, the same implementation of the Simon effect (in terms of subserving mechanism) is assumed. In 3 experiments, subjects had to respond with either fingers or sticks. Temporal properties of the Simon effect changed with response parameters relevant in a task. The Simon effect for manual responses decayed. For stick responses, in which the action goal differed from the anatomical mapping of the acting hand, a sustained Simon effect was observed. However, if the action goal for stick responses was not instrumental for selecting the correct response, the Simon effect decayed. The findings are consistent with the notion of different mechanisms involved in generating a Simon effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
166.
The magnitude of the Stroop effect is known to be modulated by the proportion of trials on which the irrelevant word and relevant ink color correspond. This has often been attributed to a conscious strategy of increased (or decreased) reliance on the irrelevant words when these are more likely (or less likely) to correspond to the ink colors. However, the present data from a Stroop-like task involving successively presented arrows indicate instead that this type of modulation can be automatic because it can occur even if the irrelevant stimuli are not phenomenally visible. In this case participants cannot determine the proportion of compatible trials to direct their strategy. An automatic, item-specific associative interpretation can account for these findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
167.
An ideal topology type convergent theorem on scale effect algebras   总被引:1,自引:0,他引:1  
The famous Antosik-Mikusinski convergent theorem on the Abel topological groups has very extensive applications in measure theory, summation theory and other analysis fields. In this paper, we establish the theorem on a class of effect algebras equipped with the ideal topology. This paper shows also that the ideal topology of effect algebras is a useful topology in studying the quantum logic the- ory.  相似文献   
168.
The CdO:F samples have been deposited onto microscope glass substrates at 250 °C by ultrasonic spray pyrolysis method. With the incorporation of fluorine into CdO, the direct optical transition has shifted towards the shorter wavelengths, and the transparency of the material has increased at a given wavelength above the fundamental absorption edge. The shift in the absorption edge is explained by means of the Moss–Burstein effect, which is also supported with the results of the current–voltage characteristics. Here, a correlation has been established between the band broadening and the increase in conductivity due to the increase in carrier density.  相似文献   
169.
从理论计算分离器处理能力和现场开展试验两方面入手,对靖边气田目前在用的不同规格分离器的分离效果进行了对比分析,通过对现场数据统计和整理,得到了靖边气田不同规格分离器合理的处理气量,给气田开发建设中分离器的选型和维护改造中分离器的调整提供了依据。  相似文献   
170.
杨晓军  林敏  杨志民  杜军 《核技术》2006,29(11):817-820
运用MULASSIS计算程序模拟计算了不同组成的屏蔽材料对空间辐射环境的屏蔽效果,在此基础上进行屏蔽材料的初步设计,并制备了一系列不同组成的金属/聚合物复合材料,结合中能电子照射的实验结果,讨论了组成对金属/聚合物复合材料的屏蔽效果的影响.研究发现,高原子序数和低原子序数金属混合添加的复合物样品具有较好的屏蔽效果.  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