全文获取类型
收费全文 | 2564篇 |
免费 | 44篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 120篇 |
综合类 | 1篇 |
化学工业 | 477篇 |
金属工艺 | 75篇 |
机械仪表 | 78篇 |
建筑科学 | 61篇 |
能源动力 | 107篇 |
轻工业 | 165篇 |
水利工程 | 13篇 |
无线电 | 281篇 |
一般工业技术 | 439篇 |
冶金工业 | 545篇 |
原子能技术 | 93篇 |
自动化技术 | 160篇 |
出版年
2023年 | 15篇 |
2022年 | 30篇 |
2021年 | 43篇 |
2020年 | 26篇 |
2019年 | 31篇 |
2018年 | 46篇 |
2017年 | 37篇 |
2016年 | 47篇 |
2015年 | 32篇 |
2014年 | 48篇 |
2013年 | 115篇 |
2012年 | 95篇 |
2011年 | 145篇 |
2010年 | 109篇 |
2009年 | 100篇 |
2008年 | 96篇 |
2007年 | 118篇 |
2006年 | 82篇 |
2005年 | 71篇 |
2004年 | 60篇 |
2003年 | 60篇 |
2002年 | 71篇 |
2001年 | 43篇 |
2000年 | 35篇 |
1999年 | 52篇 |
1998年 | 219篇 |
1997年 | 145篇 |
1996年 | 91篇 |
1995年 | 63篇 |
1994年 | 48篇 |
1993年 | 63篇 |
1992年 | 22篇 |
1991年 | 36篇 |
1990年 | 15篇 |
1989年 | 25篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 28篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 26篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 7篇 |
1978年 | 14篇 |
1977年 | 7篇 |
1976年 | 22篇 |
1974年 | 8篇 |
1972年 | 7篇 |
排序方式: 共有2615条查询结果,搜索用时 0 毫秒
31.
Methods and results of on-board antenna pattern measurements of Medium-scale Broadcasting Satellite for Experimental Purpose (BSE) are described in this paper. The measurements were carried out by means of satellite attitude offsets about the pitch and roll axes. Measured antenna patterns at both up-and down-link frequencies (14 and 12GHz) agree with the pre-launch data in the eastwards of the patterns, while they have more gentle gain slopes in the westwards. Further, antenna pattern deformation is observed along with the change in the antenna temperature. The whole appearance of the deformation seems to be complicated, however, in the center regions of the patterns which almost covers Honshu island, the dominant behavior of the deformation looks like antenna beam shift of 0.1°to 0.2°in the east-west direction. 相似文献
32.
Harumi Yokokawa Natsuko Sakai Tatsuya Kawada Masayuki Dokiy 《Journal of the American Ceramic Society》1990,73(3):649-658
The thermodynamic properties of double oxides in rare earth-transition metal (V and Mn)-oxygen ternary systems have been collected and evaluated to examine their stability using chemical potential diagrams plotted as log (αA /αB ) vs log ( P (O2 )). The thermodynamic regularities of perovskites, pyrochlores, and other compounds have been discussed in terms of the effective ionic radii across a series of rare earths. The obtained regularities have been used to estimate tentatively the thermodynamic properties of some rare-earth vanadium and manganese oxides. 相似文献
33.
Masugi Inoue Khaled Mahmud Homare Murakami Mikio Hasegawa Hiroyuki Morikawa 《Wireless Personal Communications》2005,35(1-2):53-70
A context-based adaptive communication system is introduced for use in heterogeneous networks. Context includes the user's
presence, location, available network interfaces, network availability, network priority, communication status, terminal features,
and installed applications. An experimental system was developed to clarify the feasibility of using context information to
flexibly control networks and applications. The system operates on a seamless networking platform we developed for heterogeneous
networks. By using contexts, the system can inform the caller and callee of applications they can access, which are available
through the network before communication occurs. Changes in contexts can switch an on-going application to another during
actual communication. These functions provide unprecedented styles of communication. A business scenario for a seamless networking
provider is also presented.
Dr. Morikawa has also been in charge of NICT's Mobile Networking Group.
Masugi Inoue received his B.E. from Kyoto University in 1992 and his M.E. and D.E. from the University of Tokyo in 1994 and 1997, all
in the field of Electrical Engineering. He is currently a senior researcher at the Yokosuka Radio Communications Research
Center under the National Institute of Information and Communications Technology (NICT), Japan, and has been engaged in R&D
on ultrahigh-speed WLANs and mobile networking. He joined the Communications Research Laboratory (CRL) of the Ministry of
Posts and Telecommunications, Japan, in 1997, which was reorganized as NICT in April 2004. He was a visiting researcher at
Polytechnic University in Brooklyn, New York in 2000.
Khaled Mahmud received his B.Sc. (Eng.) in Electrical and Electronics Engineering from the Bangladesh University of Engineering and Technology
in Dhaka in 1991. He received his M.E. and Ph.D. in the same field from Shizuoka University in Japan, in 1997 and 2000, respectively.
He was a research fellow at NICT, Japan, from 2000 to 2004. He is currently an Assistant Professor in the Department of Computer
Science and Engineering at North South University, Bangladesh. His research interests include modulation-demodulation techniques,
software radio, mobile communication systems, wireless Internet, and IP mobility technologies.
Homare Murakami received his B.E. and M.E. in Electronic Engineering from Hokkaido University in 1997 and 1999. In 2004, he received the
Young Investigators Award from IEICE. He is currently a researcher at NICT's Mobile Networking Group. He is also an industrial
PhD student in Aalborg University since 2003. His interest areas are naming scheme, wireless TCP and new transport protocol,
IP mobility, fast handover method, and location management.
Mikio Hasegawa received his B. Eng, M. Eng., and Dr. Eng. in 1995, 1997, and 2000 from Science University of Tokyo. From 1997 to 2000, he
was a Research Fellow of the Japan Society for the Promotion of Science (JSPS). He is currently a senior researcher in Mobile
Networking Group, National Institute of Information and Communications Technology, and a technical advisor in ChaosWare Inc.
His research interests include applications of chaotic dynamical theory, combinatorial optimization, mobile networks, and
ubiquitous computing.
Hiroyuki Morikawa received his B.E., M.E., and D.E. in Electrical Engineering from the University of Tokyo in 1987, 1989, and 1992. He is currently
an Associate Professor in the Department of Frontier Informatics at the University of Tokyo and is in charge of NICT's Mobile
Networking Group. His research interests are in the areas of computer networks, mobile computing/networks, ubiquitous computing,
and network services. He serves as Editor of Transactions of the IEICE and has been on the technical program committees of
IEEE/ACM conferences and workshops. He sits on numerous telecommunications advisory committees and frequently serves as a
consultant to the government. 相似文献
34.
NiInGe ohmic contact materials, which are attractive to use in future GaAs devices, were previously developed in our laboratories.
Although the NiInGe contacts provided low contact resistances of about 0.3 Ω-mm and excellent thermal stability, further reduction
of the contact resistance (RC) of the NiInGe contacts was mandatory to use these contacts in submicron devices. In this paper, the microstructural parameters,
which influence the RC values, were investigated by correlating the RC values with the microstructure at the interface between the contact materials and the GaAs substrate. The RC values of the NiInGe contacts were found to depend strongly on the volume fraction and the In concentration (x) of the InxGa1−xAs compound semiconductor layers, which were formed at the metal/GaAs interface. Both the volume fraction and the In concentration
of the InxGa1−xAs layers were found to depend on the thickness of the In layer used in the NiInGe contact and the annealing temperature to
form the ohmic contact. A RC value of 0.18 Ω-mm was obtained for the Ni (18 nm)/In (13 nm)/Ge (30 nm) contact (where a slash “/” indicates the deposition
sequence) after annealing at temperature of 650°C for 5 sec. 相似文献
35.
Murakami M. Matsuda T. Maeda H. Tada Y. Imai T. 《Lightwave Technology, Journal of》2001,19(11):1665-1674
This paper describes the WDM upgrading of a submarine optical amplifier system installed for single-channel transmission in commercial use. The key technologies used include 10-Gb/s high-speed forward error correction, preemphasis to overcome the optical passband-width constraint, optimized signal pulse format that leads to partial return-to-zero (PRZ) signaling, and dispersion compensation to suppress the degradation caused by fiber nonlinearity and dispersion. It also reports field experimental results on upgraded system performance. The results confirm that simply upgrading the terminal equipment allows the transmission capacity of a submersed line consisting of submarine repeaters and cables to be flexibly increased from 10 Gb/s to 40 Gb/s per fiber pair 相似文献
36.
Koh M. Mizubayashi W. Iwamoto K. Murakami H. Ono T. Tsuno M. Mihara T. Shibahara K. Miyazaki S. Hirose M. 《Electron Devices, IEEE Transactions on》2001,48(2):259-264
We report on a new roadblock which will limit the gate oxide thickness scaling of MOSFETs. It is found that statistical distribution of direct tunnel leakage current through 1.2 to 2.8 nm thick gate oxides induces significant fluctuations in the threshold voltage and transconductance when the gate oxide tunnel resistance becomes comparable to gate poly-Si resistance. By calculating the measured tunnel current based on multiple scattering theory, it is shown that the device characteristics fluctuations will be problematic when the gate oxide thickness is scaled down to less than 1 nm 相似文献
37.
Shiratori A Shibata T Arisawa M Hanaoka F Murakami Y Eki T 《Yeast (Chichester, England)》1999,15(3):219-253
38.
New low-sensitivity second-order digital-filter structures are proposed which are suited for implementation on an integrated signal processor with an on-chip fast multiplier. The inherent parallelism in such a processor is utilised to design very low sensitivity digital filters without any remarkable decrease in the overall throughput. 相似文献
39.
Hyun Soon Park Yasukazu Murakami Keiichi Yanagisawa Tsuyoshi Matsuda Ryosuke Kainuma Daisuke Shindo Akira Tonomura 《Advanced functional materials》2012,22(16):3434-3437
Peculiar magnetic domain walls produced in Heusler alloys, which have attracted renewed interest due to their potential application to actuators and spintronic devices, are studied here using electron holography. The observations reveal unexpectedly narrow magnetic domain walls, the width of which showed perfect agreement with that of the antiphase boundaries (APB, e.g., only 3 nm). While the results can be explained by the significant depression of ferromagnetism due to the local chemical disorder, the electron phase shift indicates that ferromagnetic correlation still remains in the APB region. 相似文献
40.
Nagashima K. Iwasa Y. Sawa K. Murakami M. 《Applied Superconductivity, IEEE Transactions on》2000,10(3):1642-1648
Levitation of bulk Y-Ba-Cu-O superconductors could successfully be controlled using a Bi-Sr-Ca-Cu-O superconducting electromagnet. It was found that stable levitation without tilting was obtained only when the sample trapped a certain amount of field, the minimum of which depended on the external field and the sample dimensions. We also employed a novel analysis method for levitation based on the total energy balance, which is much simpler than the force method and could be applied to the understanding of general levitation behavior. Numerical analyzes thus developed suggested that stable levitation of superconductors with large dimensions can only be achieved when the induced currents can flow with three dimensional freedom 相似文献