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   1851篇
  免费   189篇
  国内免费   68篇
电工技术   82篇
综合类   66篇
化学工业   305篇
金属工艺   68篇
机械仪表   92篇
建筑科学   112篇
矿业工程   28篇
能源动力   64篇
轻工业   184篇
水利工程   43篇
石油天然气   30篇
武器工业   23篇
无线电   290篇
一般工业技术   291篇
冶金工业   116篇
原子能技术   16篇
自动化技术   298篇
  2024年   14篇
  2023年   40篇
  2022年   80篇
  2021年   123篇
  2020年   91篇
  2019年   68篇
  2018年   73篇
  2017年   74篇
  2016年   75篇
  2015年   74篇
  2014年   97篇
  2013年   111篇
  2012年   154篇
  2011年   125篇
  2010年   83篇
  2009年   95篇
  2008年   98篇
  2007年   95篇
  2006年   77篇
  2005年   64篇
  2004年   32篇
  2003年   37篇
  2002年   24篇
  2001年   28篇
  2000年   28篇
  1999年   21篇
  1998年   40篇
  1997年   18篇
  1996年   24篇
  1995年   25篇
  1994年   18篇
  1993年   17篇
  1992年   9篇
  1991年   9篇
  1990年   11篇
  1989年   12篇
  1988年   7篇
  1987年   8篇
  1986年   7篇
  1985年   2篇
  1984年   4篇
  1983年   4篇
  1982年   2篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1975年   1篇
  1974年   3篇
  1972年   1篇
  1971年   1篇
排序方式: 共有2108条查询结果,搜索用时 375 毫秒
111.
112.
本文探讨一种采用中低档微处理器的嵌入式直流伺服电机控制系统,该系统用户软件设计采用嵌入式实时操作系统Salvo,系统功能扩展和裁剪方便,可移植到各个应用领域。  相似文献   
113.
从非法信号攻击卫星转发器的原理入手,探讨了有线电视前端卫星信号安全接收的措施,对保证有线电视的安全播出具有重要的参考意义。  相似文献   
114.
The 2005 DARPA Grand Challenge, a 212-kilometer race through the Mojave Desert, showcased the state of the art in high-speed, autonomous navigation of trails and roads. To win the challenge, a team's robot had to complete the course faster than any other robot, and it had to do so within 10 hours. Carnegie Mellon University's Red Team developed two robots, which used a combination of autonomous and human preplanning to become two of only four robots to complete the Grand Challenge. The robots used onboard sensors to adjust a preplanned route to avoid obstacles and correct for position-estimation errors. To be successful, teams had to develop innovative algorithms and systems - and rigorously test them to verify performance. The Red Team used the tests regressively to evaluate how unit changes in hardware and software affected the robots' overall driving ability  相似文献   
115.
钛酸锶铋介电陶瓷中MgO掺杂研究   总被引:1,自引:0,他引:1  
本文研究了锶铋钛陶瓷中MsO的掺杂效应,发现MgO对材料的相结构和介电性能产生很大影响,随MgO含量的增加,材料介电温度稳定性提高.作者根据K.Lichtenecher规则以及元素替代效应,讨论了MgO相、材料体内元素替代以及电荷施受主补偿对材料缺陷机构和介电性能的影响.  相似文献   
116.
本文研究了(Ba,Pb)TiO_3系高温PTC半导体陶瓷中半导化与其烧结工艺、铅空位、钡空位和施、受主杂质等相互之间的关系。着重分析讨论了引入受主杂质Mn对材料的半导化的影响,并采用复合缺陷模型自洽地解释了实验现象。  相似文献   
117.
分析8279芯片的显示接口及十六段和八段LED显示驱动电路的特点,提出了十六段和八段LED混合显示驱动的方法,并介绍了一种经济、实用的显示驱动电路。  相似文献   
118.
Carcinoma of the large bowel is the second leading cause of cancer mortality in Singapore. Although the great majority of patients are discovered at a stage where resection with curative intent is possible, almost half of the patients afflicted will die of it. The combination of 5-fluorouracil + levamisole used in patients with curatively resected high risk Dukes B2 and all Dukes' C colon cancers has been shown to reduce cancer recurrence rate and improve overall survival. Since 1990 adjuvant chemotherapy has been recommended for this group of patients. This report describes patients treated in Singapore, their toxicities and their outcome. A total of 341 patients were treated between 1990 and 1996. Treatment compliance was 71.8%. Toxicity was moderate with mainly grade 1-2 nausea and vomiting, diarrhoea, stomatitis, alopecia, and neutropenia. There was 1 treatment-related death. Median recurrence-free interval was 81 months and median survival was not reached at 90 months. This regimen is tolerable. Until further randomised reports comparing 5-fluorouracil + levamisole to other combinations are available, this combination chemotherapy is recommended to patients after surgical resection of the high risk Dukes' B2 and Dukes' C colon cancer to reduce cancer recurrence and improve overall survival.  相似文献   
119.
PREDICTOL is a PC program used to determine the thermophysiological duration limited exposures (DLE) in humans, nude or clothed, submitted to various climatic conditions (hot and cold climates) at rest or during a physical exercise. DLE are determined following different standards of the International Standardization Organization (ISO), especially ISO 7933 for hot environment and ISO-TR 11079 for cold environment. The original aspect of this program is that it can be used whatever the climatic conditions. The program presents two modes: an educational interactive mode and a scenario mode. The educational interactive mode demonstrates the thermophysiological effects, expressed as DLE, of different parameter changes (temperature, humidity, wind speed, metabolic heat production by physical exercise, clothing insulation and water vapor permeability). The scenario mode determines DLE for given various linked sequences as encountered in occupational, military or even recreational activities, each sequence being characterized by its climatic conditions, physical activities performed and by physical clothing properties. DLE given by PREDICTOL are correlated to those obtained in various controlled climatic laboratory conditions (r = 0.86; P < 0.001). PREDICTOL is written in Visual Basic 6.0. A "help menu" is provided to explain the use of the program and give information concerning the equations used to calculate both the thermal balance and DLE.  相似文献   
120.
This paper attempts to set a unified scene for various linear time-invariant (LTI) control system design schemes, by transforming the existing concept of "computer-aided control system design" (CACSD) to novel "computer-automated control system design" (CAutoCSD). The first step towards this goal is to accommodate, under practical constraints, various design objectives that are desirable in both time and frequency domains. Such performance-prioritised unification is aimed at relieving practising engineers from having to select a particular control scheme and from sacrificing certain performance goals resulting from pre-commitment to such schemes. With recent progress in evolutionary computing based extra-numeric, multi-criterion search and optimisation techniques, such unification of LTI control schemes becomes feasible, analytical and practical, and the resultant designs can be creative. The techniques developed are applied to, and illustrated by, three design problems. The unified approach automatically provides an integrator for zero-steady state error in velocity control of a DC motor, and meets multiple objectives in the design of an LTI controller for a non-minimum phase plant and offers a high-performance LTI controller network for a non-linear chemical process.  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