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   302066篇
  免费   23031篇
  国内免费   11723篇
电工技术   16795篇
技术理论   12篇
综合类   17219篇
化学工业   51545篇
金属工艺   16039篇
机械仪表   18659篇
建筑科学   22007篇
矿业工程   7244篇
能源动力   9223篇
轻工业   19573篇
水利工程   4924篇
石油天然气   14224篇
武器工业   2296篇
无线电   37365篇
一般工业技术   39349篇
冶金工业   17107篇
原子能技术   3561篇
自动化技术   39678篇
  2024年   1112篇
  2023年   4399篇
  2022年   7636篇
  2021年   10965篇
  2020年   8341篇
  2019年   7100篇
  2018年   8064篇
  2017年   9133篇
  2016年   8348篇
  2015年   10897篇
  2014年   13932篇
  2013年   17825篇
  2012年   18912篇
  2011年   20798篇
  2010年   18066篇
  2009年   17789篇
  2008年   16987篇
  2007年   15896篇
  2006年   15993篇
  2005年   13861篇
  2004年   10131篇
  2003年   8945篇
  2002年   8568篇
  2001年   7520篇
  2000年   7390篇
  1999年   7583篇
  1998年   7354篇
  1997年   5717篇
  1996年   5362篇
  1995年   4440篇
  1994年   3528篇
  1993年   2741篇
  1992年   2157篇
  1991年   1785篇
  1990年   1369篇
  1989年   1216篇
  1988年   975篇
  1987年   712篇
  1986年   567篇
  1985年   435篇
  1984年   323篇
  1983年   244篇
  1982年   263篇
  1981年   212篇
  1980年   194篇
  1979年   122篇
  1978年   101篇
  1977年   123篇
  1976年   160篇
  1975年   80篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Ji  Chengang  Yang  Chenying  Shen  Weidong  Lee  Kyu-Tae  Zhang  Yueguang  Liu  Xu  Guo  L. Jay 《Nano Research》2019,12(3):543-548

We present a new scheme for visibly-opaque but near-infrared-transmitting filters involving 7 layers based on one-dimensional ternary photonic crystals, with capabilities in reaching nearly 100% transmission efficiency in the near-infrared region. Different decorative reflection colors can be created by adding additional three layers while maintaining the near-infrared transmission performance. In addition, our proposed structural colors show great angular insensitivity up to ±60° for both transverse electric and transverse magnetic polarizations, which are highly desired in various fields. The facile strategy described here involves a simple deposition method for the fabrication, thereby having great potential in diverse applications such as image sensors, anti-counterfeit tag, and optical measurement systems.

  相似文献   
2.
Frequency Insertion Strategy for Channel Assignment Problem   总被引:1,自引:0,他引:1  
This paper presents a new heuristic method for quickly finding a good feasible solution to the channel assignment problem (CAP). Like many other greedy-type heuristics for CAP, the proposed method also assigns a frequency to a call, one at a time. Hence, the method requires computational time that increases only linear to the number of calls. However, what distinguishes the method from others is that it starts with a narrow enough frequency band so as to provoke violations of constraints that we need to comply with in order to avoid radio interference. Each violation is then resolved by inserting frequencies at the most appropriate positions so that the band of frequencies expands minimally. An extensive computational experiment using a set of randomly generated problems as well as the Philadelphia benchmark instances shows that the proposed method perform statistically better than existing methods of its kind and even yields optimum solutions to most of Philadelphia benchmark instances among which two cases are reported for the first time ever, in this paper. Won-Young Shin was born in Busan, Korea in 1978. He received B.S. in industrial engineering from Pohang University of Science and Technology (POSTECH) in 2001 and M.S in operation research and applied statistics from POSTECH in 2003. Since 2003 he has been a researcher of Agency for Defense Development (ADD) in Korea. He is interested in optimization of communication system and applied statistics. Soo Y. Chang is an associate professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH), Pohang, Korea. He teaches linear programming, discrete optimization, network flows and operations research courses. His research interests include mathematical programming and scheduling. He has published in several journals including Discrete Applied Mathematics, Computers and Mathematics with Application, IIE Transactions, International Journal of Production Research, and so on. He is a member of Korean IIE, and ORMSS. Jaewook Lee is an assistant professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH), Pohang, Korea. He received the B.S. degree in mathematics with honors from Seoul National University, and the Ph.D. degree from Cornell University in applied mathematics in 1993 and 1999, respectively. He is currently an assistant professor in the department of industrial engineering at the Pohang University of Science and Technology (POSTECH). His research interests include nonlinear systems, neural networks, nonlinear optimization, and their applications to data mining and financial engineering. Chi-Hyuck Jun was born in Seoul, Korea in 1954. He received B.S. in mineral and petroleum engineering from Seoul National University in 1977, M.S. in industrial engineering from Korea Advanced Institute of Science and Technology in 1979 and Ph.D. in operations research from University of California, Berkeley, in 1986. Since 1987 he has been with the department of industrial engineering, Pohang University of Science and Technology (POSTECH) and he is now a professor and the department head. He is interested in performance analysis of communication and production systems. He has published in several journals including IIE Transactions, IEEE Transactions, Queueing Systems and Chemometrics and Intelligent Laboratory Systems. He is a member of IEEE, INFORMS and ASQ.  相似文献   
3.
基于DTW改进算法的孤立词识别系统的仿真与分析   总被引:5,自引:0,他引:5  
林波  吕明 《信息技术》2006,30(4):56-59
传统的DTW算法在进行孤立词语音识别时着重于时间规整和语音测度的计算,而没有对数据的可靠性和有效性进行分析。本文提出了一种改进的端点检测算法,并采用一种改进的DTW算法,在计算机上进行了仿真。实验结果表明采用改进后的DTW算法有效的降低了识别时间和存储数据量,提高了系统性能。  相似文献   
4.
基于承包商预期收益不变的不平衡报价模型   总被引:1,自引:0,他引:1  
在招标实践中,通常采用最低价中标原则,使得投标人不得不压低其投标价格。基于承包商预期收益不变的不平衡报价模型,是在“工程量清单报价”的条件下,考虑到施工中工程量的变化及施工顺序的影响,体现了资金的时间价值,在保持承包商预期收益不变的前提下,通过调整各分项工程的单价,来降低工程报价,以增加中标机会而建立的。所建立的模型简单,易于操作,并配以具体的工程实例,通过计算机求得其最优解,可供承包商投标报价时参考。  相似文献   
5.
The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, K(I,NO,PAO) was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO4(3-) -P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process.  相似文献   
6.
为了提高注入剖面测井的准确性,研制了一种新型注入剖面组合测井仪。该仪器由流量处理单元、伽马处理单元、井温处理单元、磁性定位处理单元、调制式传输、电源电路六部分组成。一次下井可同时测取流量、伽马、井温、磁性定位四组参数。具有测取资料精度高、单芯电缆传输、流量可单点测量也可连续测量以厦现场监测和维修方便等特点。  相似文献   
7.
水土资源是人类赖以生存的基本资源,是国民经济待续发展的基础。我国的水资源和耕地,人均占有量分别不及世界人均占有量的1/4和1/2,而庄河市据2000年卫星遥感普查结果显示,目前有不同侵蚀强度的水土流失面积1640,占全市总面积的40%以上,远大于全国的平均水平。这种严峻的生态环境形势,对庄河市国民经济的发展极为不利。因此,加强水土保持,改善生  相似文献   
8.
9.
A multi-level attention framework for tracking and segmentation of humans and objects under complex occlusions is investigated, featuring an effective probabilistic appearance-based technique for pixel reclassification during object grouping and splitting. A novel ’spatial-depth affinity metric’ is introduced in the conventional likelihood function, utilising information of both spatial locations of pixels and dynamic depth ordering of the component objects in grouping. Depth ordering estimation is achieved through a combination of top-down and bottom-up approach. Experiments on some realworld difficult scenarios of low quality and highly compressed videos demonstrate the very promising results achieved.  相似文献   
10.
家具制造技术进展   总被引:3,自引:0,他引:3  
许美琪 《家具》2006,(2):44-49
21世纪以来,随着全球经济的发展.家具业的增长十分迅速.国际家具生产总值已超过2500亿美元。发达的家具业大量应用了新材料.在制造及其控制过程中采用了现代计算机技术和信息技术手段.使这个传统产业跻身于现代产业之列。由于家具是人们生活和工作须臾不能离开的器具.它必将以不断改进的结构和日益增多的功能来满足人类的需要.改善人类生活的品质。因此.家具产业将持续以勃勃生机,与人类社会共同进步和发展。  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