全文获取类型
收费全文 | 77303篇 |
免费 | 7341篇 |
国内免费 | 3993篇 |
专业分类
电工技术 | 5025篇 |
技术理论 | 4篇 |
综合类 | 5593篇 |
化学工业 | 12408篇 |
金属工艺 | 4532篇 |
机械仪表 | 5275篇 |
建筑科学 | 6464篇 |
矿业工程 | 2419篇 |
能源动力 | 2052篇 |
轻工业 | 5287篇 |
水利工程 | 1658篇 |
石油天然气 | 4060篇 |
武器工业 | 706篇 |
无线电 | 9457篇 |
一般工业技术 | 8805篇 |
冶金工业 | 3486篇 |
原子能技术 | 1000篇 |
自动化技术 | 10406篇 |
出版年
2024年 | 361篇 |
2023年 | 1419篇 |
2022年 | 2594篇 |
2021年 | 3478篇 |
2020年 | 2682篇 |
2019年 | 2185篇 |
2018年 | 2276篇 |
2017年 | 2686篇 |
2016年 | 2355篇 |
2015年 | 3452篇 |
2014年 | 4256篇 |
2013年 | 5041篇 |
2012年 | 5348篇 |
2011年 | 5854篇 |
2010年 | 5138篇 |
2009年 | 5111篇 |
2008年 | 4940篇 |
2007年 | 4460篇 |
2006年 | 4220篇 |
2005年 | 3427篇 |
2004年 | 2281篇 |
2003年 | 1892篇 |
2002年 | 1822篇 |
2001年 | 1667篇 |
2000年 | 1422篇 |
1999年 | 1492篇 |
1998年 | 1154篇 |
1997年 | 1000篇 |
1996年 | 960篇 |
1995年 | 837篇 |
1994年 | 699篇 |
1993年 | 515篇 |
1992年 | 364篇 |
1991年 | 304篇 |
1990年 | 215篇 |
1989年 | 182篇 |
1988年 | 142篇 |
1987年 | 91篇 |
1986年 | 73篇 |
1985年 | 48篇 |
1984年 | 31篇 |
1983年 | 35篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 29篇 |
1979年 | 14篇 |
1976年 | 4篇 |
1967年 | 3篇 |
1959年 | 3篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
1.
Data mining extracts implicit, previously unknown, and potentially useful information from databases. Many approaches have been proposed to extract information, and one of the most important ones is finding association rules. Although a large amount of research has been devoted to this subject, none of it finds association rules from directed acyclic graph (DAG) data. Without such a mining method, the hidden knowledge, if any, cannot be discovered from the databases storing DAG data such as family genealogy profiles, product structures, XML documents, task precedence relations, and course structures. In this article, we define a new kind of association rule in DAG databases called the predecessor–successor rule, where a node x is a predecessor of another node y if we can find a path in DAG where x appears before y. The predecessor–successor rules enable us to observe how the characteristics of the predecessors influence the successors. An approach containing four stages is proposed to discover the predecessor–successor rules. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 621–637, 2006. 相似文献
2.
Liang Y.C. Wenjiang Zeng Pick Hong Ong Zhaoxia Gao Jun Cai Balasubramanian N. 《Electron Device Letters, IEEE》2002,23(12):700-703
In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology. 相似文献
3.
Tsu-Hua Ai Jiann-Fuh Chen Tsorng-Juu Liang 《Industrial Electronics, IEEE Transactions on》2002,49(3):595-597
To overcome the problem of unequal switching loss in power switches, in conventional hybrid pulse width modulation (HPWM) full-bridge inverters, a random switching method for HPWM full-bridge inverters is proposed. The proposed method equalizes switching losses of the four switches, while also providing good output performance 相似文献
4.
Water treatment using TiO2 semiconductor as a durable heterogeneous photocatalyst has been the focus of environmentalists in recent years. Currently, we developed an inexpensive and highly efficient approach for synthesizing nitrogen-doped TiO2 with lower band-gap energy that can respond to visible light. Doping on the molecular scale led to an enhanced nitrogen concentration of up to 21.8%. Reflectance measurements showed the synthesized N-doped TiO2 nanoparticles are catalytically active with the absorbance that extends into the visible region up to 600 nm. The water purification potential of this new class of compound was evaluated by studying the photodegradation of Acid Orange 7 (AO7) and E. coli. Experiments were conducted to compare the photocatalytic activities of N-doped TiO2 nanocatalysts and commercially available Degussa P25 power under identical solar light exposure. N-doped TiO2 demonstrated superior photocatalytic activities in both chemical compound degradation and bactericidal reactions. The result of this study shows the potential of applying new generations of catalyst for wastewater purification and disinfection. 相似文献
5.
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
6.
广州近期将出台地方性法规,颁布禁售令,围剿色情、暴力等问题玩具。记者从相关部门证实了这一消息。目前广州市一些批零市场也很少见到此类玩具。[编者按] 相似文献
7.
实施六大工程打造民生水利 总被引:1,自引:1,他引:0
我省针对十年九旱、水资源短缺、生态与环境脆弱的特点,确定了今冬明春农田水利基本建设的目标任务,明确以实施兴水战略为主线,以改善民生为目标,以创新机制为保障,全面掀起冬春农田水利基本建设新高潮。 相似文献
8.
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.
脉冲电镀最佳参数之探索和优化 总被引:3,自引:0,他引:3
本文利用正交实验法对脉冲电镀各控制参数进行试验,对影响分散能力、镀层可靠性及外观质量的各种因素进行探讨,寻找影响外观质量的显著因子并加以控制,同时进一步优化脉冲电镀的工艺参数。 相似文献