全文获取类型
收费全文 | 545205篇 |
免费 | 62502篇 |
国内免费 | 43961篇 |
专业分类
电工技术 | 48319篇 |
技术理论 | 3篇 |
综合类 | 58319篇 |
化学工业 | 67426篇 |
金属工艺 | 37285篇 |
机械仪表 | 38652篇 |
建筑科学 | 42272篇 |
矿业工程 | 23085篇 |
能源动力 | 14664篇 |
轻工业 | 58457篇 |
水利工程 | 18213篇 |
石油天然气 | 19589篇 |
武器工业 | 8481篇 |
无线电 | 59024篇 |
一般工业技术 | 46803篇 |
冶金工业 | 21838篇 |
原子能技术 | 9021篇 |
自动化技术 | 80217篇 |
出版年
2024年 | 3426篇 |
2023年 | 8737篇 |
2022年 | 20338篇 |
2021年 | 26536篇 |
2020年 | 19277篇 |
2019年 | 13428篇 |
2018年 | 14159篇 |
2017年 | 16938篇 |
2016年 | 15222篇 |
2015年 | 24386篇 |
2014年 | 30385篇 |
2013年 | 35890篇 |
2012年 | 45072篇 |
2011年 | 47177篇 |
2010年 | 45098篇 |
2009年 | 43470篇 |
2008年 | 44410篇 |
2007年 | 43324篇 |
2006年 | 37703篇 |
2005年 | 30278篇 |
2004年 | 22122篇 |
2003年 | 14974篇 |
2002年 | 13915篇 |
2001年 | 12622篇 |
2000年 | 9993篇 |
1999年 | 4220篇 |
1998年 | 1560篇 |
1997年 | 1223篇 |
1996年 | 987篇 |
1995年 | 805篇 |
1994年 | 638篇 |
1993年 | 591篇 |
1992年 | 447篇 |
1991年 | 348篇 |
1990年 | 300篇 |
1989年 | 303篇 |
1988年 | 183篇 |
1987年 | 159篇 |
1986年 | 144篇 |
1985年 | 92篇 |
1984年 | 78篇 |
1983年 | 82篇 |
1982年 | 60篇 |
1981年 | 101篇 |
1980年 | 156篇 |
1979年 | 85篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1959年 | 104篇 |
1951年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
为研究织物组织结构与复合纱线线密度对织物凉爽性能的影响,将线密度为7.4和9.8 tex涤纶分别与线密度为7.8 tex锦纶反向加捻、并线后作为纬纱,以8.3 tex涤纶/竹浆纤维50/50混纺纱作经纱,设计平纹、二上一下斜纹和透孔组织织物.测试织物的瞬间接触凉感、热湿舒适性能及织物干、湿态升温曲线,并采用凉爽温度指数对织物的综合凉爽性能进行评价.研究结果表明:6种设计织物的瞬间接触凉感均高于标准,且平纹织物最好,纬纱粗细对瞬间接触凉感影响不显著;透孔织物透气性最好,且在人体出汗的状态下具有较好的导湿散热性能.平纹织物凉爽温度指数最高,最大凉爽温度为2.8℃,综合凉爽性能最好. 相似文献
2.
3.
针对传统的小区内开环功率控制算法通常以提升本小区的吞吐量性能为目标,忽略了当前小区用户对邻小区用户同频干扰的问题,为提升边缘用户性能的同时兼顾系统整体性能,提出了一种LTE系统小区间上行联合功率控制(UJPC)算法。该算法采用单基站三扇区为系统模型,以最优化系统吞吐量比例公平函数为目标,首先根据最小信干噪比(SINR)约束值和用户最大发射功率这两个约束条件得到相应的数学优化模型,然后采用连续凸近似的方法求解优化问题得出各个基站所管辖的小区内所有用户的最优发射功率。仿真结果表明,与基准的开环功控方案相比,联合功控方案在保证系统平均频谱利用率的情况下能够较大幅度地提高小区边缘频谱利用率,其最佳性能增益能达到50%。 相似文献
4.
5.
介绍土卡河电站在大坝碾压混凝土现场施工的具体施工技术、工艺措施。大坝自2006年3月碾压混凝土开工以来,其施工工艺、施工质量得到了各方的好评。 相似文献
6.
7.
回顾了异质结光晶体管(HPT)在近年来的重要进展,综合分析了HPT的工作原理以及影响其性能的主要参数。综述了不同材料制作的HPT的研究现状,得出了目前限制HPT发展的主要因素及当前应重点解决由于基区表面复合等效应导致的增益下降和由于结电容的充放电限制的响应带宽等问题的结论。 相似文献
8.
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
9.
10.
多带OFDM-UWB系统峰均功率比降低方法研究 总被引:1,自引:0,他引:1
针对多带OFDM—UWB信号存在高峰均功率比的问题,提出了利用扩展与交织降低系统信号峰均功率比的方法。该方法通过对传输数据进行正交扩展与交织,使得进入多载波调制的数据趋于高斯分布,减小了传输数据自相关函数的旁瓣峰值,降低了OFDM-UWB信号的峰均功率比。由于采用正交矩阵进行扩展,扩展前后的数据传输速率保持不变。仿真结果表明,扩展与交织可以有效地降低信号峰均功率比2-5dB左右。同时该方法还具有抗窄带干扰的鲁棒性。 相似文献