全文获取类型
收费全文 | 1487篇 |
免费 | 21篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 134篇 |
化学工业 | 201篇 |
金属工艺 | 35篇 |
机械仪表 | 23篇 |
建筑科学 | 23篇 |
能源动力 | 46篇 |
轻工业 | 73篇 |
水利工程 | 9篇 |
石油天然气 | 3篇 |
无线电 | 132篇 |
一般工业技术 | 272篇 |
冶金工业 | 423篇 |
原子能技术 | 61篇 |
自动化技术 | 76篇 |
出版年
2022年 | 14篇 |
2021年 | 26篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 17篇 |
2013年 | 37篇 |
2012年 | 33篇 |
2011年 | 55篇 |
2010年 | 44篇 |
2009年 | 54篇 |
2008年 | 68篇 |
2007年 | 60篇 |
2006年 | 36篇 |
2005年 | 41篇 |
2004年 | 32篇 |
2003年 | 44篇 |
2002年 | 27篇 |
2001年 | 30篇 |
2000年 | 40篇 |
1999年 | 39篇 |
1998年 | 176篇 |
1997年 | 103篇 |
1996年 | 68篇 |
1995年 | 53篇 |
1994年 | 41篇 |
1993年 | 41篇 |
1992年 | 24篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 20篇 |
1985年 | 23篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 15篇 |
1980年 | 15篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 18篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有1511条查询结果,搜索用时 15 毫秒
11.
12.
13.
Takeda H. Ayakawa H. Tsumenaga M. Sanpei M. 《Power Delivery, IEEE Transactions on》1995,10(4):2035-2039
For the third project of the Hokkaido-Honshu HVDC Link in Japan, called the HVDC Link III project (rated at 250 kVDC-1200 A-300 MW), we developed an HVDC transmission line protection method based on a new working principle that allows high-speed and highly sensitive detection of faults, enhancing reliability in the supply of electric power. In general, increasing the sensitivity of relays will lead to an increased likelihood of undesired operation whereas lowering the sensitivity will impair the responsiveness of the relays. Our proposed method meets these apparently incompatible requirements very well. Basically classified as a differential scheme, the HVDC transmission line protection method compensates for a charging and discharging current that flows through the line-to-ground capacitance at times of voltage variations caused by a line fault or by the operation of DC power systems. The developed protection method is also characterized in that it uses current changes induced by voltage variations to restrain the operation of a relay. This configuration has made the proposed method far superior in responsiveness and sensitivity to the conventional protection method. A simulation using an EMTP (Electro-Magnetic Transients Program) was conducted on this method. Developed relay equipment embodying the new protection method was subjected to various verification tests, where this equipment was connected to a power system simulator, before being delivered to the HVDC Link III facility 相似文献
14.
T Yamatsuji T Okamoto S Takeda Y Murayama N Tanaka I Nishimoto 《Canadian Metallurgical Quarterly》1996,15(3):498-509
APP is a transmembrane precursor of beta-amyloid. In dominantly inherited familial Alzheimer's disease (FAD), point mutations V6421, V642F and V642G have been discovered in APP695. Here we show that expression of these mutants (FAD-APPs) causes a clone of COS cells to undergo apoptosis associated with DNA fragmentation. Apoptosis by the three FAD-APPs was the highest among all possible V642 mutants; normal APP695 had no effect on apoptosis, suggesting that apoptosis by APP mutants in this system is phenotypically linked to the FAD trait. FAD-APP-induced apoptosis was sensitive to bcl-2 and most probably mediated by heteromeric G proteins. This study presents a model system allowing analysis of the mechanism for FAD-APP-induced cytotoxicity. 相似文献
15.
Eiji Takeda 《Microelectronics Reliability》1993,33(11-12)
A universal guideline and state-of-the-art hot-carrier effects in scaled MOSFETs are reviewed and discussed from the viewpoints of 1) DC and AC hot-carrier effects, 2) hot-carrier detrapping phenomena, 3) mechanical stress effects on hot-carrier phenomena, and 4) hot-carrier resistant device structures.In the deep-submicron region, the hot-carrier applicable voltage is less than 3 V, so AC hot-carrier effects from the dynamic operation of actual circuits should be taken into account. Despite much experimentation and analysis, there is still no universally accepted theory that explain the AC degradation mechanism. This is because the noise caused by the wiring inductance in ULSI circuits and in measurement systems screens the intrinsic AC hot-carrier effects.Here, AC hot-carrier degradation enhanced by gate pulse-induced-noise is analyzed experimentally and theoretically. After eliminating the noise problem, it is found that AC hot-carrier degradation in LDD (Lightly doped drain) and GOLD (gate-drain overlapped device) structures can be estimated based on DC degradation in terms of the effective stress time which takes the duty ratio into account. In addition, it is found that the noise is negligible when the wiring inductance is smaller that 80 nH (250 mω), which is important for future circuit design.Furthermore, hot-carrier detrapping effects, especially in p-channel MOS devices, and hot-carrier phenomena under mechanical stress are investigated experimentally to better understand the underlying hot-carrier physics. Finally, future hot-carrier resistant device structures are discussed. 相似文献
16.
New integrated optical devices combining an InGaAsP/InP HPT and an inner-stripe LED are proposed and their fabrication processes are described. The device functions of light amplification, optical bistability, and optical switching are demonstrated in the 1-μm wavelength region. 相似文献
17.
18.
Hisamoto D. Nakamura K. Saito M. Kobayashi N. Kimura S. Nagai R. Nishida T. Takeda E. 《Electron Devices, IEEE Transactions on》1994,41(5):745-750
This paper describes a new ultra-thin SOI-CMOS structure offering reduced parasitic diffusion-layer resistance. It addresses ways to deal with the ultra-shallow junctions required by sub-0.1 μm MOSFET's. Based on a CVD tungsten process we experimentally investigate the characteristics of selectively grown tungsten used in the source and drain region made in SOI layers of various thicknesses ranging from 10 to 100 nm. We also investigate certain CMOS device characteristics. The SOI-CMOS structure, with low parasitic diffusion-layer resistance and good contact characteristics for ultra-shallow junction devices exhibits superior device performance and high scalability 相似文献
19.
Photoinduced phase transitions have been observed between the two phases in single crystals of polydiacetylenes with side-groups of alkylurethanes. The threshold of the excitation intensity for the photochromism is extremely low, one absorbed photon per 140 repeated backbone units, indicating a collective nature of the photoconversion. The excitation spectra for the converted fraction clearly show that the photoinduced phase transition is mediated by photogeneration of polaronic species and not of singlet excitons. 相似文献
20.
Y. Uzawa M. Takeda A. Kawakami Z. Wang 《Journal of Infrared, Millimeter and Terahertz Waves》2003,24(10):1749-1757
A novel broadband tuning circuit composed of two low-current-density half-wave NbN/MgO/NbN tunnel junctions connected by a half-wave NbN/MgO/NbN microstrip line has been successfully tested in a quasi-optical mixer at frequencies above 700 GHz. The circuit had a designed center frequency of 870 GHz, was integrated in a center-fed twin-slot antenna, and was fed via a quarter-wave impedance transformer. Heterodyne measurments showed double-side-band receiver noise temperatures equivalent to 6-9 quanta from 675 to 810 GHz for a mixer with a current density of 6.7 kA/cm2. The RF bandwidth was broader than that of a conventional mixer using a full-wave junction with the same current density. 相似文献