全文获取类型
收费全文 | 6481篇 |
免费 | 251篇 |
国内免费 | 44篇 |
专业分类
电工技术 | 130篇 |
综合类 | 24篇 |
化学工业 | 793篇 |
金属工艺 | 110篇 |
机械仪表 | 198篇 |
建筑科学 | 346篇 |
矿业工程 | 3篇 |
能源动力 | 148篇 |
轻工业 | 297篇 |
水利工程 | 23篇 |
石油天然气 | 25篇 |
武器工业 | 3篇 |
无线电 | 1472篇 |
一般工业技术 | 1024篇 |
冶金工业 | 1118篇 |
原子能技术 | 33篇 |
自动化技术 | 1029篇 |
出版年
2023年 | 37篇 |
2022年 | 42篇 |
2021年 | 89篇 |
2020年 | 58篇 |
2019年 | 70篇 |
2018年 | 106篇 |
2017年 | 81篇 |
2016年 | 135篇 |
2015年 | 112篇 |
2014年 | 134篇 |
2013年 | 319篇 |
2012年 | 305篇 |
2011年 | 322篇 |
2010年 | 238篇 |
2009年 | 297篇 |
2008年 | 328篇 |
2007年 | 317篇 |
2006年 | 305篇 |
2005年 | 253篇 |
2004年 | 205篇 |
2003年 | 213篇 |
2002年 | 158篇 |
2001年 | 171篇 |
2000年 | 167篇 |
1999年 | 189篇 |
1998年 | 474篇 |
1997年 | 274篇 |
1996年 | 209篇 |
1995年 | 173篇 |
1994年 | 108篇 |
1993年 | 126篇 |
1992年 | 77篇 |
1991年 | 61篇 |
1990年 | 52篇 |
1989年 | 48篇 |
1988年 | 47篇 |
1987年 | 41篇 |
1986年 | 39篇 |
1985年 | 60篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 37篇 |
1981年 | 34篇 |
1980年 | 28篇 |
1979年 | 24篇 |
1978年 | 17篇 |
1977年 | 22篇 |
1976年 | 44篇 |
1975年 | 17篇 |
1973年 | 19篇 |
排序方式: 共有6776条查询结果,搜索用时 15 毫秒
41.
42.
5类网络电缆由四对双绞线组成,并有耐用的外套,这种电缆能为分量视频信号的传输提供一种通用而有良好性价比的选择。三个线对可以承载RGB视频信号,而第四对线可以承载音频信号、同步信号和其它传输信号。不幸的是,5类电缆缺乏屏蔽,因此容易遭受共模噪声耦合 相似文献
43.
A method for the historical elastoplastic analysis of plane frames under the assumption of small deformation theory is presented. Interaction of bending moment and axial force is taken into account. A major feature of the procedure lies in the piecewise linearization of the convex nonlinear yield surface, thereby guaranteeing the satisfaction of both equilibrium and yield conditions. Local unloading can also be catered for. A computer program based on this technique has been written and three simple numerical examples are given to illustrate its capabilities. 相似文献
44.
Yan T Wong Norbert Dommel Philip Preston Luke E Hallum Torsten Lehmann Nigel H Lovell Gregg J Suaning 《IEEE transactions on neural systems and rehabilitation engineering》2007,15(3):425-434
A neurostimulator application-specific integrated circuit (ASIC) with scalable circuitry that can stimulate 14 channels, has been developed for an epi-retinal vision prosthesis. This ASIC was designed to allow seven identical units to be connected to control up to 98 channels, with the ability to stimulate 14 electrodes simultaneously. The neurostimulator forms part of a vision prosthesis, designed to restore vision to patients who have lost their sight due to retinal diseases such as retinitis pigmentosa and macular degeneration. For charge balance, the neurostimulator was designed to stimulate with current sources and sinks operating together, and with the ability to drive a hexagonal mosaic of electrodes to reduce the electrical crosstalk that occurs when multiple bipolar stimulation sites are active simultaneously. A hexagonal mosaic of electrodes surrounds each stimulation site and has been shown to effectively isolate each site, increasing the ability to inject localized independent charge into multiple regions simultaneously. 相似文献
45.
46.
In recent years, the Asia-Pacific region has experienced several financial setbacks, including speculative attacks in 1998 and the SARS outbreak in 2003. Financial stresses of this nature are unanticipated, and not all of the dangers can be predicted by the examination of market information and macroeconomic indicators. The Early Warning System (EWS) that has been adopted by the International Monetary Fund may not be able to predict future financial crises for all possible scenarios, because shocks come in many different forms. To supplement the EWS, this paper proposes a data mining framework to measure the resilience of an economy. The resilience framework does not predict a crisis, but rather assesses the current state of health of an economy and its ability to withstand a financial shock should one occur. The framework is based on a feedback system consisting of two stages. The first stage assigns a resilience score to each economy based on a fuzzy logic scoring scheme that is built on the ambiguous reasoning of experts. The second stage uses the classification tree approach to estimate thresholds for each economic indicator, and examines the quality of the fuzzy score. The result from the second stage is then passed back to the first stage as feedback. The final result is obtained when the feedback system reaches its equilibrium state. The proposed resilience framework is applied to the external-sector and the public-sector economies of several countries to illustrate its applicability. 相似文献
47.
Kin-Lu Wong Chih-Hua Chang 《Antennas and Propagation, IEEE Transactions on》2005,53(11):3496-3499
A novel wireless local-area network (WLAN) chip antenna suitable to be mounted above the system ground plane of a mobile device is presented. The antenna in the study is easily fabricated from folding a single metal plate onto a foam base, and mainly comprises a short-circuited radiating strip and an antenna ground. The antenna ground occupies the bottom surface and two adjacent side surfaces of the foam base. When the antenna is mounted at the corner of the system ground plane, this antenna ground structure is expected to effectively reduce the antenna's possible fringing electromagnetic fields inside the mobile device. In this case, when the associated element such as the radio-frequency shielding metal case is placed under the proposed antenna, small or negligible variations in the antenna performance are obtained. Design considerations of the proposed antenna for WLAN operation in the 2.4 GHz band are described, and results of the constructed prototypes are presented. 相似文献
48.
Chia-Ching Lin Gwo-Yun Lee Kin-Lu Wong 《Electronics letters》2003,39(18):1302-1304
A surface-mount dual-loop antenna suitable for dual-frequency WLAN operation is presented. For achieving dual-frequency operation with a compact size, the antenna comprises two loop strips of different sizes printed on a flexible printed circuit board, which is then bent and attached onto a foam base of compact size. The antenna shows an attractive feature of high antenna gain, about 4 and 5 dBi for frequencies across the 2.4 and 5 GHz WLAN bands, respectively. 相似文献
49.
A jet-printed digital-lithographic method, in place of conventional photolithography, was used to fabricate 64 /spl times/ 64 pixel (300 /spl mu/m pitch) matrix addressing thin-film transistor (TFT) arrays. The average hydrogenated amorphous silicon TFT device within an array had a threshold voltage of /spl sim/3.5 V, carrier mobility of 0.7 cm/sup 2//V/spl middot/s, subthreshold slope of 0.76 V/decade, and an on/off ratio of 10/sup 8/. 相似文献
50.
Zukerman M. Wong E.W.M. Rosberg Z. Gyu Myoung Lee Hai Le Vu 《Communications Letters, IEEE》2004,8(2):116-118
We provide teletraffic models for loss probability evaluation of optical burst switching (OBS). We show that the popular Engset formula is not exact for OBS modeling and demonstrate that in certain cases it is not appropriate. A new exact model is provided. The various models are compared using numerical results for various OBS alternatives with and without burst segmentation. 相似文献