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   8993篇
  免费   188篇
  国内免费   157篇
电工技术   428篇
综合类   314篇
化学工业   1478篇
金属工艺   763篇
机械仪表   1075篇
建筑科学   512篇
矿业工程   108篇
能源动力   729篇
轻工业   562篇
水利工程   77篇
石油天然气   274篇
武器工业   57篇
无线电   746篇
一般工业技术   830篇
冶金工业   488篇
原子能技术   164篇
自动化技术   733篇
  2024年   9篇
  2023年   97篇
  2022年   131篇
  2021年   164篇
  2020年   175篇
  2019年   130篇
  2018年   125篇
  2017年   174篇
  2016年   207篇
  2015年   221篇
  2014年   435篇
  2013年   489篇
  2012年   436篇
  2011年   704篇
  2010年   492篇
  2009年   511篇
  2008年   434篇
  2007年   587篇
  2006年   500篇
  2005年   494篇
  2004年   416篇
  2003年   394篇
  2002年   314篇
  2001年   225篇
  2000年   203篇
  1999年   236篇
  1998年   214篇
  1997年   176篇
  1996年   150篇
  1995年   117篇
  1994年   83篇
  1993年   72篇
  1992年   52篇
  1991年   44篇
  1990年   32篇
  1989年   20篇
  1988年   27篇
  1987年   12篇
  1986年   9篇
  1985年   11篇
  1984年   7篇
  1983年   2篇
  1982年   4篇
  1981年   2篇
  1975年   1篇
排序方式: 共有9338条查询结果,搜索用时 15 毫秒
41.
本文用热源法对简单热传导问题进行了解析解的计算,并应用PDE工具箱求解热传导偏微分方程得到数值解。通过两种温度场的计算结果求出相应的位移场结果,比较可知MATLAB中PDE工具箱对难以用解析法求解的热传导问题有一定的指导作用。  相似文献   
42.
本文分析了离心复合铸造轧辊生产过程中离心机停机温度和时间对轧辊质量的影响 ,提出了用先进的红外测温技术来预报停机温度和时间 ,以实现微机监控适时停机 ,保证轧辊内外层熔合良好 ;同时指出了红外测温技术在离心复合铸造轧辊生产上的应用前景  相似文献   
43.
胡可城 《上海金属》1996,18(6):57-59
介绍应用中频快速感应加热方法对弹簧钢、轴承钢、工模具钢等冷变形抗力大的材料及某些异型材在再结晶温度以下进行温轧的成功经验。利用快速加热还可对轧后需保持原有组织和特性的材料进行轧制。  相似文献   
44.
On The Measurement of Temperature in Material Removal Processes   总被引:5,自引:0,他引:5  
Because it is key to understanding the performance of material removal processes and resultant workpiece quality, the measurement of temperature during material removal is done extensively. We review several widely used temperature measurement methods and show how they can be applied to temperature monitoring during material removal. Since there is little documentation on measurement uncertainties as relates to material removal, this paper outlines the physics of each method, detailing the sources and evaluation of uncertainty. Finally, using criteria critical in measuring material removal, methods are compared, and the results presented in guide-format for participants in this field of work.  相似文献   
45.
A critical analysis on the friction modelling in orthogonal machining   总被引:3,自引:3,他引:3  
Despite the development of high performance finite element-based codes, the simulation of machining still represents a very hard task due to the geometric complexity of the real chip-tool systems and the high cutting speed that requires very long simulation times. For these reasons, many aspects related to machining are not very clear and so easy to simulate. In this paper a rigorous investigation on the role played by the implemented friction model within a 2D simulation of orthogonal cutting was carried out, taking into account different models proposed by the researchers in the last years. The main simulation results were compared with experimental measurements in order to verify if it is possible to identify the best model. Once the comparison with mechanical variables was completed, a subsequent study on temperature predictions utilizing the above friction models was executed as well. The results of this integrated numerical and experimental work are carefully reported in the paper.  相似文献   
46.
红外辐射吸收法测量火焰温度   总被引:3,自引:0,他引:3  
李疏芬  张雪松 《火炸药》1997,20(4):32-34
简述了几种温度测量的方法,介绍了红外辐射吸收法测温原理及实验装置,并对稳定的煤气火焰进行温度测量,试图在此基础上测量固体推进剂火焰的温度。  相似文献   
47.
This study investigates the effects of cement type, curing temperature, and age on the relationships between dynamic and static elastic moduli or compressive strength. Based on the investigation, new relationship equations are proposed. The impact-echo method is used to measure the resonant frequency of specimens from which the dynamic elastic modulus is calculated. Types I and V cement concrete specimens with water-cement ratios of 0.40 and 0.50 are cured isothermally at 10, 23, and 50 °C and tested at 1, 3, 7, and 28 days.Cement type and age do not have a significant influence on the relationship between dynamic and static elastic moduli, but the ratio of static to dynamic elastic modulus approaches 1 as temperature increases. The initial chord elastic modulus, which is measured at low strain level, is similar to the dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic moduli for various cement types, temperatures, and ages.  相似文献   
48.
介绍了焦炭高温反应炉的温控工艺及程控曲线,给出了程控曲线的控制结构、主回路以及实现多套PI参数控制的方法。  相似文献   
49.
赵红松 《乙烯工业》2004,16(2):34-37
针对北京东方化工厂乙烯装置汽油分馏塔、稀释蒸汽发生系统以及急冷水、酸性水pH值等在运行中出现的问题,说明了问题的原因所在。通过优化操作、改造等方式对系统进行了整改,阐述了整改后的效果。  相似文献   
50.
Calcium silicate hydrate is a porous hydrate that is sensitive to temperature and readily loses strength at elevated temperatures. Mechanical and chemical changes in the microstructure, due to escaping water, can significantly affect the mechanical properties, but these changes occur over different temperature ranges. By measuring Young's modulus as a function of temperature using the dynamic mechanical analyzer, the temperature range in which the greatest change in stiffness occurs can be identified. Additional mineralogy, pore size distribution, and composition analysis from high temperature X-ray diffraction, nitrogen sorption, and thermogravimetric analysis will demonstrate the changes in the microstructure. The results demonstrate that over 90% of the loss in stiffness occurs below 120 °C. Therefore, the damage is due to microcracking caused by pore water expansion and evaporation and not the change in mineralogy or composition. More damage, as indicated by greater loss in stiffness, occurs in stiffer and less permeable samples where higher stresses can develop.  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