全文获取类型
收费全文 | 45204篇 |
免费 | 5559篇 |
国内免费 | 3366篇 |
专业分类
电工技术 | 5611篇 |
综合类 | 4919篇 |
化学工业 | 4204篇 |
金属工艺 | 1207篇 |
机械仪表 | 2427篇 |
建筑科学 | 2839篇 |
矿业工程 | 1116篇 |
能源动力 | 1279篇 |
轻工业 | 2139篇 |
水利工程 | 979篇 |
石油天然气 | 1894篇 |
武器工业 | 681篇 |
无线电 | 5959篇 |
一般工业技术 | 4219篇 |
冶金工业 | 1785篇 |
原子能技术 | 626篇 |
自动化技术 | 12245篇 |
出版年
2024年 | 209篇 |
2023年 | 553篇 |
2022年 | 1070篇 |
2021年 | 1249篇 |
2020年 | 1567篇 |
2019年 | 1490篇 |
2018年 | 1301篇 |
2017年 | 1741篇 |
2016年 | 1909篇 |
2015年 | 2023篇 |
2014年 | 2744篇 |
2013年 | 3145篇 |
2012年 | 3207篇 |
2011年 | 3397篇 |
2010年 | 2519篇 |
2009年 | 2670篇 |
2008年 | 2552篇 |
2007年 | 3037篇 |
2006年 | 2762篇 |
2005年 | 2293篇 |
2004年 | 1898篇 |
2003年 | 1755篇 |
2002年 | 1533篇 |
2001年 | 1313篇 |
2000年 | 1147篇 |
1999年 | 906篇 |
1998年 | 726篇 |
1997年 | 623篇 |
1996年 | 482篇 |
1995年 | 417篇 |
1994年 | 337篇 |
1993年 | 280篇 |
1992年 | 192篇 |
1991年 | 185篇 |
1990年 | 129篇 |
1989年 | 126篇 |
1988年 | 87篇 |
1987年 | 86篇 |
1986年 | 59篇 |
1985年 | 58篇 |
1984年 | 46篇 |
1983年 | 38篇 |
1982年 | 37篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1964年 | 12篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Lean philosophy: implementation in a forging company 总被引:2,自引:2,他引:0
Ajit Kumar Sahoo N. K. Singh Ravi Shankar M. K. Tiwari 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):451-462
This research addresses the implementation of lean philosophy in a forging company with a focus on radial forging production
flow lines. Here, the prime motive is to evolve and test several strategies to eliminate waste on the shop floor. In this
research, a systematic approach is suggested for the implementation of lean principles. This paper describes an application
of value stream mapping (VSM). Consequently, the present and future states of value stream maps are constructed to improve
the production process by identifying waste and its sources. Furthermore, Taguchi’s method of design of experiments is pursued
here to minimize the forging defects produced due to imperfect operating conditions. A noticeable reduction in set-up time
and work-in-process (WIP) inventory level is substantiated. Finally, we conclude with a discussion of managerial implications
and the future scope of research. 相似文献
22.
Takeshi Shiofuku Norihiro Abe Yoshihiro Tabuchi Hirokazu Taki Shoujie He 《Artificial Life and Robotics》2008,13(1):290-293
This paper presents an approach of measuring in real-time the vector of finger that is pointing to an object. DSP is used
in the operation processing unit in order to do the real-time processing. The steps include the extraction of flesh-colored
regions from an image, the labeling of the flesh-colored regions, and the detection of two characteristic positions on the
finger so that the direction that the finger is pointing at will be calculated. The entire process takes about 29 msec, which
makes it possible to have the frame rate of 34 fps. With this frame rate, this measurement approach is considered real-time
and promising to be merged into other application systems.
This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January
31–February 2, 2008 相似文献
23.
24.
25.
Hong Long Chen 《Canadian Metallurgical Quarterly》2007,23(4):171-181
The difficulty in applying the standard curve (S-curve) and cost-schedule integration (CSI) techniques for company-level cost flow forecasting in a project-based industry is the prerequisite of forecasting future unknown individual projects and contract classifications. By analyzing cost flows at the company level through a pool of macroeconomic and internal financial data, this paper proposes an innovative approach to firm-specific model estimation. First, a series of data transformations introduce linear relationships between cost, macroeconomic, and internal financial variables. Second, multivariate regression analysis is employed for initial model building. Third, for the purposes of model restructuring, a subsequent application of Yule–Walker estimates and incomplete principal component analysis is used. This paper uses a sample of four project-based construction firms to demonstrate model performance. Using this methodology, mean absolute percentage error (MAPE) values of the forecasting models range from 0.27 to 0.60%. As such, the transformed cost, macroeconomic, internal financial data could strongly predict company-level cost flow forecasting. While converting the predicted cumulative cost data to periodic cost flows, the MAPE values were augmented, ranging from 7.04 to 17.55%, thus, requiring future research. 相似文献
26.
RT-AGVS是物流管理中十分重要的课题,车辆位置监测网是其重要的组成部分。本文详细介绍了一个基于单片机系统的车辆位置实时监测网,本监测网设计先进,性能价格比高,它的设计方法和技术对其他许多领域有借鉴作用。 相似文献
27.
设{Z,(W)}是定义在概率空间上的独立的随机变量序列,Z(W)具有方差为期望E(Zn)=0.本文证明了对任意算数序列{bn}及任意的存在充分大的整数N>0使当N'>N″>N时.有此不等式在随机级数研究中有重要作用. 相似文献
28.
New technologies such as power electronics have made it possible to change continuously the impedance of a power system not only to control power flow but also to enhance stability. A power system incorporating a variable impedance apparatus such as a variable series capacitor (VSrC) and high-speed phase shifter (HSPS) is called VIPS (Variable Impedance Power System) by the authors. This paper proposes a novel control method of VIPS apparatus such as VSrC and HSPS installed at an interconnecting point for stabilizing inter-area unstable and/or oscillatory modes. The proposed design method of the control system is a kind of hierarchical decentralized control method of a large-scale power system based on a Lyapunov function. Under the proposed control scheme, each subsystem can be stabilized independently by local controllers such as AVR, speed governor and PSS, and then the whole interconnected system can be stabilized by VIPS apparatus taking into account interactions between subsystems. The effectiveness and robustness of the VIPS apparatus control are shown by numerical examples with model systems including a large-scale power system. 相似文献
29.
中针对变井储试井分析问题,给出了确定变井储系数及计算续流量的方法,并用反褶积分析积分析方法解释了未出现径向流的早期测压数据,给出了解决早期试井资料分析问题的有效方法。 相似文献
30.
A serious problem in motion control is the occurrence of torque ripple. Since a direct drive (DD) motor with a magnet rotor uses a rare-earth magnet, the torque ripple is more serious than that of conventional servomotors. This paper presents an auto-compensation of torque ripple using a software-implemented torque observer. The frequency and amplitude of torque ripple can be obtained in the controller by using the estimated torque from an observer, and the autonomous generation of a compensating current component for a torque ripple is possible. The proposed algorithm has been verified by experiments. 相似文献