全文获取类型
收费全文 | 235812篇 |
免费 | 21098篇 |
国内免费 | 11569篇 |
专业分类
电工技术 | 15234篇 |
技术理论 | 15篇 |
综合类 | 15947篇 |
化学工业 | 37847篇 |
金属工艺 | 13288篇 |
机械仪表 | 15288篇 |
建筑科学 | 18546篇 |
矿业工程 | 7216篇 |
能源动力 | 6811篇 |
轻工业 | 16347篇 |
水利工程 | 4621篇 |
石油天然气 | 13579篇 |
武器工业 | 1988篇 |
无线电 | 28420篇 |
一般工业技术 | 27506篇 |
冶金工业 | 11280篇 |
原子能技术 | 2577篇 |
自动化技术 | 31969篇 |
出版年
2024年 | 1154篇 |
2023年 | 4374篇 |
2022年 | 8270篇 |
2021年 | 11124篇 |
2020年 | 8383篇 |
2019年 | 6597篇 |
2018年 | 7329篇 |
2017年 | 8384篇 |
2016年 | 7440篇 |
2015年 | 10195篇 |
2014年 | 12605篇 |
2013年 | 15083篇 |
2012年 | 16326篇 |
2011年 | 17429篇 |
2010年 | 15038篇 |
2009年 | 14295篇 |
2008年 | 13770篇 |
2007年 | 12544篇 |
2006年 | 12399篇 |
2005年 | 10486篇 |
2004年 | 6889篇 |
2003年 | 5737篇 |
2002年 | 5204篇 |
2001年 | 4710篇 |
2000年 | 4474篇 |
1999年 | 5061篇 |
1998年 | 4200篇 |
1997年 | 3552篇 |
1996年 | 3326篇 |
1995年 | 2756篇 |
1994年 | 2233篇 |
1993年 | 1638篇 |
1992年 | 1273篇 |
1991年 | 993篇 |
1990年 | 709篇 |
1989年 | 580篇 |
1988年 | 462篇 |
1987年 | 307篇 |
1986年 | 260篇 |
1985年 | 160篇 |
1984年 | 138篇 |
1983年 | 112篇 |
1982年 | 106篇 |
1981年 | 84篇 |
1980年 | 81篇 |
1979年 | 41篇 |
1978年 | 27篇 |
1977年 | 27篇 |
1976年 | 30篇 |
1975年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 3 毫秒
1.
杨宇 《中国室内装饰装修天地》2006,(7):54-61
华风气象影视大楼总面积4万平方米,根据空间功能不同分为办公大楼和商务写字楼两部分,办公大楼是集演播室、制作机房、办公室为一体的九层综合性建筑。设计师杨宇在刚接触到这个项目的时候,面对的是一个既成事实的建筑。 相似文献
2.
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
3.
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
4.
Guangbin Yang 《Reliability, IEEE Transactions on》2002,51(3):288-293
ESS (environmental stress screening) has been extensively used to reduce infant mortality by precipitating defects. The existing ESS plans precipitate defects by stressing all products for specified durations. The plans usually require long screen durations to allow nearly all defective items to fail, and thus generate excessive aging effects on good items. For some products, failures are defined in terms of performance characteristics exceeding their critical values. This paper describes the principles of using degradation measurements of performance characteristics to screen the products. In an ESS, the performance characteristics of defective items degrade considerably faster than those of good ones, yielding a bimodal distribution of the characteristics. As screen duration increases, the 2 modes of the distribution shift apart. It is possible to find a tightened critical value to weed out the defective items before they fail. This paper, based on these principles, further designs the optimal 2-level screen plans which minimize a segment of life-cycle cost and which simultaneously meet the reliability requirement. The minimum cost is achieved by choosing optimal part-level and unit-level screen durations and tightened critical values of parts. A numerical example is followed by discussion. Because the ESS regime of this paper allows defective parts to be screened out before they fail, the developed optimal ESS plans can reduce life-cycle cost, shorten part-level screen duration, and alleviate aging effects on good products 相似文献
5.
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
6.
Jian-Bo Yang 《国际自动化与计算杂志》2006,3(1):I0001-I0002
The UK-China Research Network on Intelligent Automation, Computing and Manufacturing has been established since September 2004 by grants from the Engineering and Physical Sciences Research Council (EPSRC) of the UK and the National Natural Science Foundation of China. The initiative of the network is motivated by the last visit of the UK Science Minister Lord Sainsbury to China to open the first UK-China Hi-Tech Forum and by the current EPSRC initiative to set up specific network programmes in collaboration with partners in China. 相似文献
7.
Poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐para‐phenylene vinylene] (MEH‐PPV)/silica nanoparticle hybrid films were prepared and characterised. Three kinds of materials were compared: parent MEH‐PPV, MEH‐PPV/silica (hybrid A films), and MEH‐PPV/coupling agent MSMA/silica (hybrid B films), in which MSMA is 3‐(trimethoxysilyl) propyl methacrylate. It was found that the hybrid B films could significantly prevent macrophase separation, as evidenced by scanning electron and fluorescence microscopy. Furthermore, the thermal characteristics of the hybrid films were largely improved in comparison with the parent MEH‐PPV. The UV‐visible absorption spectra suggested that the incorporation of MSMA‐modified silica into MEH‐PPV could confine the polymer chain between nanoparticles and thus increase the conjugation length. The photoluminescence (PL) studies also indicated enhancement of the PL intensity and quantum efficiency by incorporating just 2 wt% of MSMA‐modified silica into MEH‐PPV. However, hybrid A films did not show such enhancement of optoelectronic properties as the hybrid B films. The present study suggests the importance of the interface between the luminescent organic polymers and the inorganic silica on morphology and optoelectronic properties. Copyright © 2004 Society of Chemical Industry 相似文献
8.
本文评价了塑料闪烁片用作软β核素探测器时的计数效率、β谱、本底谱和康普顿电子谱的特征。文中强调:采用胶合光导剂构成的系统是一种新型探测器(软β核素内部样品塑料闪烁探测器)。本文提出内部样品固体探测器、胶合光导剂和胶合闪烁光导剂的新概念。 相似文献
9.
10.