全文获取类型
收费全文 | 69722篇 |
免费 | 6846篇 |
国内免费 | 4399篇 |
专业分类
电工技术 | 5399篇 |
技术理论 | 4篇 |
综合类 | 5889篇 |
化学工业 | 10116篇 |
金属工艺 | 4242篇 |
机械仪表 | 4431篇 |
建筑科学 | 5457篇 |
矿业工程 | 2154篇 |
能源动力 | 1830篇 |
轻工业 | 7724篇 |
水利工程 | 1724篇 |
石油天然气 | 3130篇 |
武器工业 | 796篇 |
无线电 | 7778篇 |
一般工业技术 | 6926篇 |
冶金工业 | 2757篇 |
原子能技术 | 791篇 |
自动化技术 | 9819篇 |
出版年
2024年 | 353篇 |
2023年 | 1136篇 |
2022年 | 2342篇 |
2021年 | 2992篇 |
2020年 | 2303篇 |
2019年 | 1803篇 |
2018年 | 2066篇 |
2017年 | 2291篇 |
2016年 | 2142篇 |
2015年 | 3203篇 |
2014年 | 3882篇 |
2013年 | 4568篇 |
2012年 | 5398篇 |
2011年 | 5824篇 |
2010年 | 5269篇 |
2009年 | 4991篇 |
2008年 | 5118篇 |
2007年 | 4689篇 |
2006年 | 4181篇 |
2005年 | 3370篇 |
2004年 | 2423篇 |
2003年 | 2005篇 |
2002年 | 1935篇 |
2001年 | 1639篇 |
2000年 | 1210篇 |
1999年 | 907篇 |
1998年 | 584篇 |
1997年 | 499篇 |
1996年 | 394篇 |
1995年 | 340篇 |
1994年 | 251篇 |
1993年 | 186篇 |
1992年 | 146篇 |
1991年 | 134篇 |
1990年 | 104篇 |
1989年 | 64篇 |
1988年 | 42篇 |
1987年 | 28篇 |
1986年 | 33篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 22篇 |
1979年 | 6篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1959年 | 10篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
2.
This paper presents the design criteria, procedure, and implementation of a soft-switched power-factor-correction (PFC) circuit based on the extended-period quasi-resonant (EPQR) principles. All power electronic devices including switches and diodes in the circuit are fully soft switched. The design method is demonstrated in a prototype circuit. The operating principles are confirmed with computer simulation and experimental results. A comparison of the EP-QR operation and zero-voltage-transition (ZVT) pulse-width modulation (PWM) method 相似文献
3.
本文运用一典型的人工神经网络模型─“反向传播”模型,对高氧化态(Ⅱ─Ⅳ)三核金属簇合物的构型分布进行了分析,得到了较好的分类、预报结果为化合物结构分析提供了新的工具。 相似文献
4.
David Hui 《International Journal of Mechanical Sciences》1985,27(6):397-408
This paper deals with the effects of initial geometric imperfections and in-plane boundary conditions on the large-amplitude vibration behavior of angle- and cross-ply rectangular thin plates. It is found that the presence of imperfection amplitudes of the order of only half the total laminated-plate thickness may significantly raise the vibration frequencies and change the large-amplitude vibration behavior from the well-known hard-spring to soft-spring behavior. The effects of fibre angles and bending-stretching coupling for angle-ply plates and Young's moduli ratios and number of layers for antisymmetric cross-ply plates are examined. 相似文献
5.
6.
结合兰州市的水泥标准稠度用水量方法测定 (代用法 )的实例 ,分析代用法测定标准稠度用水量的缺点 ,并对此方法提出了一些改进措施 相似文献
7.
本文通过对压电量测系统等效电路图的逐步简化,得出矩形脉冲信号的漏电方程;并对系统在各种情况下的时间常数,漏电相对误差进行了计算,最后就系统在校准和现场测试中经常碰到的几种情况,进行了定量估算,从而解决了压电量测系统在使用中的一些具体问题。 相似文献
8.
The texture effect on visual colour difference evaluation was investigated in this study. Five colour centers were selected and textured colour pairs were generated using scanned textile woven fabrics and colour‐mapping technique. The textured and solid colour pairs were then displayed on a characterized cathode ray tube (CRT) monitor for colour difference evaluation. The colour difference values for the pairs with texture patterns are equal to 5.0 CIELAB units in lightness direction. The texture level was represented by the half‐width of histogram, which is called texture strength in this study. High correlation was found between texture strength and visual colour difference for textured colour pairs, which indicates that an increasing of 10 units of texture strength in luminance would cause a decreasing of 0.25 units visual difference for the five colour centers. The ratio of visual difference between textured and solid colour pairs also indicates a high parametric effect of texture. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 341–347, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col. 相似文献
9.
Wai-Chuen Gan Li Qiu 《Industrial Electronics, IEEE Transactions on》2003,50(2):272-282
It is well known that the system performance for an indirect-field-oriented-control induction motor drive degrades under the variation of rotor resistance and in the presence of external load torque. In this paper, a plug-in robust compensator for speed and position control enhancement of an indirect-field-oriented-control induction machine drive is developed. In the case where a controller for the induction machine already exists or is in operation with satisfactory nominal tracking performance, this plug-in compensator, designed using the H/sub /spl infin// loop-shaping techniques, can be plugged into the existing controller without affecting the already satisfactory nominal tracking performance of the existing closed-loop system but with the capability to improve the system performance under plant parameter variations and in the presence of external disturbances. Simulation and experimental results are given to validate the proposed plug-in robust compensator. 相似文献
10.