全文获取类型
收费全文 | 470294篇 |
免费 | 41328篇 |
国内免费 | 25428篇 |
专业分类
电工技术 | 50567篇 |
技术理论 | 60篇 |
综合类 | 51580篇 |
化学工业 | 37724篇 |
金属工艺 | 17019篇 |
机械仪表 | 31047篇 |
建筑科学 | 48928篇 |
矿业工程 | 21705篇 |
能源动力 | 15926篇 |
轻工业 | 21275篇 |
水利工程 | 16621篇 |
石油天然气 | 18212篇 |
武器工业 | 7432篇 |
无线电 | 48118篇 |
一般工业技术 | 28976篇 |
冶金工业 | 19551篇 |
原子能技术 | 3872篇 |
自动化技术 | 98437篇 |
出版年
2024年 | 1927篇 |
2023年 | 5328篇 |
2022年 | 10157篇 |
2021年 | 13118篇 |
2020年 | 13443篇 |
2019年 | 9902篇 |
2018年 | 9250篇 |
2017年 | 12368篇 |
2016年 | 14807篇 |
2015年 | 16760篇 |
2014年 | 30864篇 |
2013年 | 26933篇 |
2012年 | 34357篇 |
2011年 | 37011篇 |
2010年 | 27830篇 |
2009年 | 28110篇 |
2008年 | 27731篇 |
2007年 | 34013篇 |
2006年 | 30763篇 |
2005年 | 27334篇 |
2004年 | 22668篇 |
2003年 | 20239篇 |
2002年 | 15705篇 |
2001年 | 13042篇 |
2000年 | 10871篇 |
1999年 | 8655篇 |
1998年 | 6329篇 |
1997年 | 5299篇 |
1996年 | 4570篇 |
1995年 | 3819篇 |
1994年 | 3190篇 |
1993年 | 2201篇 |
1992年 | 1810篇 |
1991年 | 1284篇 |
1990年 | 1072篇 |
1989年 | 949篇 |
1988年 | 612篇 |
1987年 | 387篇 |
1986年 | 300篇 |
1985年 | 333篇 |
1984年 | 276篇 |
1983年 | 228篇 |
1982年 | 163篇 |
1981年 | 152篇 |
1980年 | 149篇 |
1979年 | 106篇 |
1978年 | 67篇 |
1977年 | 68篇 |
1964年 | 41篇 |
1959年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
ABSTRACTIn this paper, we review some algebraic control system. Precisely, linear and bilinear systems on Euclidean spaces and invariant and linear systems on Lie groups. The fourth classes of systems have a common issue: to any class, there exists an associated subgroup. From this object, we survey the controllability property. Especially, from those coming from our contribution to the theory. 相似文献
3.
针对现有混合入侵检测模型仅定性选取特征而导致检测精度较低的问题,同时为了充分结合误用检测模型和异常检测模型的优势,提出一种采用信息增益率的混合入侵检测模型.首先,利用信息增益率定量地选择特征子集,最大程度地保留样本信息;其次,采用余弦时变粒子群算法确定支持向量机参数构建误用检测模型,使其更好地平衡粒子在全局和局部的搜索能力,然后,选取灰狼算法确定单类支持向量机参数构建异常检测模型,以此来提高对最优参数的搜索效率和精细程度,综合提高混合入侵检测模型对攻击的检测效果;最后,通过两种数据集进行仿真实验,验证了所提混合入侵检测模型具有较好的检测性能. 相似文献
4.
Temperature history can have a significant effect on the strength of water-saturated chalk.In this study,hydrostatic stress cycles are applied to understand the mechanical response of chalk samples exposed to temperature cycling between each stress cycle,compared to the samples tested at a constant temperature.The total accumulated strain during a stress cycle and the irreversible strain are reported.Chalk samples from Kansas(USA)and Mons(Belgium),with different degrees of induration(i.e.amount of contact cementation),were used.The samples were saturated with equilibrated water(polar)and nonpolar Isopar H oil to quantify water weakening.All samples tested during 10 stress cycles with varying temperature(i.e.temperature cycled in between each stress cycle)accumulated more strain than those tested at constant temperatures.All the stress cycles were performed at 30℃.The two chalk types behaved similarly when saturated with Isopar H oil,but differently when saturated with water.When saturated with water,the stronger Kansas chalk accumulated more total strain and more irreversible strain within each stress cycle than the weaker Mons chalk. 相似文献
5.
Hashim A.
Hashim 《国际强度与非线性控制杂志
》2020,30(10):3848-3870
》2020,30(10):3848-3870
This paper introduces two novel nonlinear stochastic attitude estimators developed on the Special Orthogonal Group with the tracking error of the normalized Euclidean distance meeting predefined transient and steady‐state characteristics. The tracking error is confined to initially start within a predetermined large set such that the transient performance is guaranteed to obey dynamically reducing boundaries and decrease smoothly and asymptotically to the origin in probability from almost any initial condition. The proposed estimators produce accurate attitude estimates with remarkable convergence properties using measurements obtained from low‐cost inertial measurement units. The estimators proposed in continuous form are complemented by their discrete versions for the implementation purposes. The simulation results illustrate the effectiveness and robustness of the proposed estimators against uncertain measurements and large initialization error, whether in continuous or discrete form. 相似文献
6.
分析了冶炼烟气制酸工艺的特点,介绍了由PROFIBUS-DP现场总线构建的冶炼厂烟气制酸监控系统,详细介绍了其硬件配置及相应的软件设计。 相似文献
7.
动态评价技术在塔河碳酸盐岩缝洞型油气藏中的应用 总被引:5,自引:2,他引:3
塔河油田奥陶系油气藏是大型碳酸盐岩溶洞型油气藏,其储渗空间主要为大小不同的溶洞、裂缝带、溶蚀孔隙等组成,该油气藏具有极强的非均质性,单纯用静态资料来认识这类油气藏是非常困难。文章提出利用生产动态资料和信息进行该类型油气藏研究的新思路,利用人工神经网络技术在处理非线性相关参数预测方面的优势,并以渗流理论为基础,结合试井成果,选用已知油井的产量、油嘴、油压、含水率、气油比、原油密度等6个开发动态参数作为样品输入数据,推导出影响油气藏开发的重要参数(地层系数)与生产信息的关系,建立了人工神经网络预测储层参数的结构模型。通过塔里木盆地塔河油气田实例研究,说明了利用动态信息评价油气藏技术在碳酸盐岩缝洞型油气藏储层预测和非均质性分析等方面具有较高的实用价值。 相似文献
8.
介绍一种基于变频调速控制的全自动定量包装机,结构简单,组态灵活,性价比高,可广泛应用于食品饲料等行业,现场运行实践证明其通用性好,准确度和可靠性高、速度快、稳定性好。并论述变频器控制系统的设计及使用中的注意问题。 相似文献
9.
10.
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