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   44721篇
  免费   4544篇
  国内免费   3222篇
电工技术   2212篇
技术理论   1篇
综合类   4215篇
化学工业   6323篇
金属工艺   2326篇
机械仪表   2348篇
建筑科学   5022篇
矿业工程   2496篇
能源动力   1735篇
轻工业   3051篇
水利工程   1482篇
石油天然气   2357篇
武器工业   520篇
无线电   5697篇
一般工业技术   6753篇
冶金工业   2283篇
原子能技术   982篇
自动化技术   2684篇
  2024年   182篇
  2023年   732篇
  2022年   1264篇
  2021年   1607篇
  2020年   1632篇
  2019年   1422篇
  2018年   1244篇
  2017年   1573篇
  2016年   1636篇
  2015年   1720篇
  2014年   2590篇
  2013年   2694篇
  2012年   3110篇
  2011年   3303篇
  2010年   2545篇
  2009年   2630篇
  2008年   2460篇
  2007年   2922篇
  2006年   2691篇
  2005年   2229篇
  2004年   1902篇
  2003年   1685篇
  2002年   1489篇
  2001年   1158篇
  2000年   1067篇
  1999年   846篇
  1998年   669篇
  1997年   622篇
  1996年   510篇
  1995年   440篇
  1994年   378篇
  1993年   315篇
  1992年   240篇
  1991年   210篇
  1990年   172篇
  1989年   143篇
  1988年   102篇
  1987年   67篇
  1986年   44篇
  1985年   33篇
  1984年   36篇
  1983年   23篇
  1982年   19篇
  1981年   12篇
  1980年   18篇
  1979年   23篇
  1966年   7篇
  1959年   10篇
  1957年   5篇
  1951年   6篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
91.
钟晓瑜 《钻采工艺》2003,26(Z1):57-59
介绍了池27井实施机抽排水工艺取得累计排水13 334.4m3的明显效果.分析了五次检泵的原因.提出了对池27井机抽排水的四点认识.  相似文献   
92.
煤矿局部通风的设计与应用技术   总被引:3,自引:0,他引:3  
分析了现有煤矿局部通风工程中普遍存在的问题,采用符合矿井实际的设计和施工技术,就能在使用过程中获得显著效果,可大大减少漏风,提高有效风量,满足安全生产的需要,从而解决长距离独头掘进通风的难题。  相似文献   
93.
Polymer matrix RE-Fe giant magnetostrictire composite (GMPC) was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC.  相似文献   
94.
本文详细分析了解吸塔换热器结堵的原因和对环保装置正常运行的影响,并针对性地提出了防范和处理措施。  相似文献   
95.
The effects of NOx on the performance of proton exchange membrane (PEM) fuel cell were investigated through the introduction of a mixture containing NO and NO2, in a ratio of 9:1, into the cathode stream of a single PEM fuel cell. The NOx concentrations used in the experiments were 1480 ppm, 140 ppm and 10 ppm, which cover a range of three orders. The experimental results obtained from the tests of durability, polarization, reversibility and electrochemical impedance spectroscopy (EIS) showed a detrimental effect of NOx on the cell performance. The electrochemical measurements results suggested that the impacts of NOx are mainly resulted from the superposition of the oxygen reduction reaction (ORR), NO and HNO2 oxidation reactions, and the increased cathodic impedance. Complete recovery of the cell performance was reached after operating the cell with clean air and then purging with N2 for hours.  相似文献   
96.
Halo effects in rating specific pieces of work, as in educational grading, have received little attention. Grades awarded by 2 independent graders to undergraduate projects were analyzed with a correlated uniqueness model. Grades showed substantial halo despite being awarded by expert assessors at the time of reading the work. There was greater halo between different grades applying to the same section of the project than between grades applying to different sections. Supervisors who had regular contact with the student whose work they were grading showed no more halo than other graders. More reliable graders showed less within-section halo than graders of lower reliability but equal between-sections halo. The halo effects observed cannot be entirely attributable to a unitary general impression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
97.
动态多目标决策问题的灰色分析方法   总被引:2,自引:0,他引:2  
将用于固定时间截面下静态多目标决策的灰色关联理论推广到动态情形,引入局部理想最优效果和整体理想最优效果的概念,提出一种新型的动态多目标决策问题的灰色关联模型,并通过算例说明该方法的合理可行性。  相似文献   
98.
The fracture toughness of brittle thermoset resins could be improved significantly by perfectly bonded tough, short fibers through both crack trapping and bridging effects. In this paper, the crack trapping effect was studied through the analysis of the change of strain energy associated with the crack propagation across a regular array of fibers, and the bridging effect was discussed based on the Andersson–Bergkvist model. The fracture resistance increases with the fiber volume fraction, and is independent of the elastic properties of the matrix, the crack length, and the cross-sectional diameter of the fibers.  相似文献   
99.
Thecokesolutionlossreactionisoneofthemostimportanteffectsresultingincokepulverizinginblastfurnace .Thefactorswhichaffectreactionincludecokeporestructure ,micro crystalstructureonporewall ,thecontentandconstituentofminer als ,etc .Amongthesefactors ,theconstituentofmineralsisemphasizedallovertheworldinrecentyears .Buttheemphasisofmoststudieswasputontheeffectofalkalimetals (K ,Na)oncokesolutionlossreactionandtheeffectofotherelementswassel domreported[1-5] .Theeffectofthirteenmineralsoncokesolut…  相似文献   
100.
This paper describes the creep‐fatigue life of Sn–8Zn–3Bi under push–pull loading. Creep‐fatigue tests were carried out using Sn–8Zn–3Bi specimens in fast–fast, fast–slow, slow–fast, slow–slow and hold–time strain waveforms. Creep‐fatigue lives in the slow–slow and hold‐time waveforms showed a small reduction from the fast–fast lives but those in the slow–fast and fast–slow waveforms showed a significant reduction from the fast–fast lives. Conventional creep‐fatigue life prediction methods were applied to the experimental data and the applicability of the methods was discussed. Creep‐fatigue characteristics of Sn–8Zn–3Bi were compared with those of Sn–3.5Ag and Sn–37Pb.  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