全文获取类型
收费全文 | 69404篇 |
免费 | 10734篇 |
国内免费 | 6112篇 |
专业分类
电工技术 | 12102篇 |
技术理论 | 2篇 |
综合类 | 6164篇 |
化学工业 | 2360篇 |
金属工艺 | 1538篇 |
机械仪表 | 4800篇 |
建筑科学 | 2187篇 |
矿业工程 | 1470篇 |
能源动力 | 837篇 |
轻工业 | 4449篇 |
水利工程 | 558篇 |
石油天然气 | 1206篇 |
武器工业 | 959篇 |
无线电 | 17706篇 |
一般工业技术 | 3916篇 |
冶金工业 | 1052篇 |
原子能技术 | 708篇 |
自动化技术 | 24236篇 |
出版年
2024年 | 626篇 |
2023年 | 1717篇 |
2022年 | 2740篇 |
2021年 | 3034篇 |
2020年 | 3017篇 |
2019年 | 2338篇 |
2018年 | 2005篇 |
2017年 | 2721篇 |
2016年 | 2944篇 |
2015年 | 3335篇 |
2014年 | 5263篇 |
2013年 | 4443篇 |
2012年 | 5629篇 |
2011年 | 5991篇 |
2010年 | 4532篇 |
2009年 | 4466篇 |
2008年 | 4576篇 |
2007年 | 5094篇 |
2006年 | 4220篇 |
2005年 | 3512篇 |
2004年 | 2786篇 |
2003年 | 2336篇 |
2002年 | 1776篇 |
2001年 | 1365篇 |
2000年 | 1136篇 |
1999年 | 861篇 |
1998年 | 676篇 |
1997年 | 554篇 |
1996年 | 527篇 |
1995年 | 393篇 |
1994年 | 329篇 |
1993年 | 246篇 |
1992年 | 226篇 |
1991年 | 176篇 |
1990年 | 140篇 |
1989年 | 105篇 |
1988年 | 105篇 |
1987年 | 47篇 |
1986年 | 41篇 |
1985年 | 39篇 |
1984年 | 39篇 |
1983年 | 29篇 |
1982年 | 20篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
前向反冲分析和非卢瑟福背散射 总被引:1,自引:0,他引:1
赵国庆 《理化检验(物理分册)》2002,38(2):88-91
介绍了弹性散射分析中的另外两种分析方法——前向反冲分析和非卢瑟福背散射分析。前向反冲分析适用于材料中H和He同位素分析。高能质子和He离子背散射分析可提高对重基体中C,N和O等轻元素分析的灵敏度。给出了这两种分析方法的应用实例。 相似文献
62.
63.
This paper presents a method to compensate voltage sags with minimum energy injection for a series‐connected voltage restorer using a micro‐SMES. A circuit for extracting the fundamental symmetrical components from sag voltages and a minimum energy injection algorithm is described. Simulations of voltage sag compensation have been carried out using PSCAD/EMTDC for various faults. The simulation results confirm the validity of the proposed method and show the possibility of reducing the size of energy storage devices. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(3): 70–80, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10047 相似文献
64.
65.
Oleg A. Mezentsev Rixin Zhu Richard E. DeVor Shiv G. Kapoor William A. Kline 《International Journal of Machine Tools and Manufacture》2002,42(4)
A model-based method for fault detection in tapping based on torque and radial forces is proposed. The method allows the identification of faults typical of a tapping operation including axial misalignment, tap runout, tooth breakage both singly and together. The validation experiments have been run on aluminum 356 workpieces for different combinations of process faults. Results have shown that the model predictions are in good agreement with the experimental radial force and torque signals under various fault conditions. 相似文献
66.
文章通过分析多相流模拟井的实际工作要求 ,提出了简单实用的流量自动控制模型。应用成型的计算机数据采集和控制模块及稳定可靠的流量控制部件 ,实现了各相流量的自动控制过程。该流量自动控制系统调节精度高、速度快、整体造价低 ,在实际应用中取得了良好的效果。 相似文献
67.
68.
LW15-252型SF_6断路器存在的问题和对策 总被引:1,自引:1,他引:0
国产SF6断路器已在电力系统中得到了广泛的应用,随着时间的推移,这种断路器存在的问题也逐渐地暴露出来。笔者介绍了LW15-252型SF6断路器在实际运用中存在的问题和采取的对策。 相似文献
69.
Corner detection is a low-level feature detection operator that is of great use in image processing applications, for example, optical flow and structure from motion by image correspondence. The detection of corners is a computationally intensive operation. Past implementations of corner detection techniques have been restricted to software. In this paper we propose an efficient very large-scale integration (VLSI) architecture for detection of corners in images. The corner detection technique is based on the half-edge concept and the first directional derivative of Gaussian. Apart from the location of the corner points, the algorithm also computes the corner orientation and the corner angle and outputs the edge map of the image. The symmetrical properties of the masks are utilized to reduce the number of convolutions effectively, from eight to two. Therefore, the number of multiplications required per pixel is reduced from 1800 to 392. Thus, the proposed architecture yields a speed-up factor of 4.6 over conventional convolution architectures. The architecture uses the principles of pipelining and parallelism and can be implemented in VLSI. 相似文献
70.
Conceptual damage-sensitive features for structural health monitoring: Laboratory and field demonstrations 总被引:2,自引:0,他引:2
F. Necati Catbas Mustafa Gul Jason L. Burkett 《Mechanical Systems and Signal Processing》2008,22(7):1650-1669
The use of damage-sensitive features to evaluate structural condition or health is a very critical aspect of structural health monitoring. The purpose of this paper is to investigate the potential of two different damage-sensitive features for detecting damage. Different damage scenarios are simulated on a large-scale laboratory structure and a three-span highway bridge for demonstration. The features presented in this paper are the modal flexibility-based deflection and curvature both of which are obtained directly from dynamic properties. In the literature, flexibility associated with mode shapes and mode shapes curvatures have been mostly explored. In this study, multi-input–multi-output dynamic data are used to obtain modal flexibility, which is a close approximation to the actual flexibility. A main novelty is that the curvature is calculated from the deflected shapes using the modal flexibility as opposed to using modal vectors. In this paper, the theory of the methodology is explained and then experimental studies and results are presented. For the experimental studies, the laboratory specimen and the three-span bridge were gradually damaged. It is shown that both deflection and curvature are conceptual and physically meaningful features for damage detection and localization. The issues and the requirements for these features to perform successfully are also presented. 相似文献