全文获取类型
收费全文 | 2352篇 |
免费 | 34篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 122篇 |
综合类 | 19篇 |
化学工业 | 407篇 |
金属工艺 | 64篇 |
机械仪表 | 57篇 |
建筑科学 | 31篇 |
能源动力 | 62篇 |
轻工业 | 200篇 |
水利工程 | 16篇 |
石油天然气 | 1篇 |
无线电 | 317篇 |
一般工业技术 | 309篇 |
冶金工业 | 651篇 |
原子能技术 | 35篇 |
自动化技术 | 105篇 |
出版年
2023年 | 8篇 |
2022年 | 21篇 |
2021年 | 27篇 |
2020年 | 7篇 |
2019年 | 17篇 |
2018年 | 23篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 23篇 |
2014年 | 46篇 |
2013年 | 87篇 |
2012年 | 66篇 |
2011年 | 68篇 |
2010年 | 46篇 |
2009年 | 63篇 |
2008年 | 71篇 |
2007年 | 77篇 |
2006年 | 75篇 |
2005年 | 70篇 |
2004年 | 53篇 |
2003年 | 63篇 |
2002年 | 73篇 |
2001年 | 67篇 |
2000年 | 42篇 |
1999年 | 78篇 |
1998年 | 239篇 |
1997年 | 168篇 |
1996年 | 121篇 |
1995年 | 64篇 |
1994年 | 69篇 |
1993年 | 77篇 |
1992年 | 33篇 |
1991年 | 53篇 |
1990年 | 41篇 |
1989年 | 38篇 |
1988年 | 20篇 |
1987年 | 25篇 |
1986年 | 28篇 |
1985年 | 37篇 |
1984年 | 22篇 |
1983年 | 25篇 |
1982年 | 13篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 18篇 |
1976年 | 17篇 |
1973年 | 4篇 |
1972年 | 8篇 |
排序方式: 共有2396条查询结果,搜索用时 15 毫秒
31.
Raman fiber oscillator as optical amplifier 总被引:1,自引:0,他引:1
S.S.-H. Yam M.E. Marhic Y. Akasaka K. Shimizu N. Kikuchi L.G. Kazovsky 《Photonics Technology Letters, IEEE》2004,16(6):1456-1458
A Raman fiber oscillator used for optical amplification is demonstrated to have lower double Rayleigh scattering, transient spikes, cross-phase modulation, and higher saturation input threshold compared with a conventional discrete Raman amplifier at similar operating conditions. This could be a promising technology for deployment in practical systems. 相似文献
32.
Compact solid-State switched pulsed power and its applications 总被引:4,自引:0,他引:4
Weihua Jiang Yatsui K. Takayama K. Akemoto M. Nakamura E. Shimizu N. Tokuchi A. Rukin S. Tarasenko V. Panchenko A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2004,92(7):1180-1196
Power semiconductor devices, such as insulated-gate bipolar transistors, metal-oxide-semiconductor field-effect transistors, and static-induction thyristors, are used in different kinds of pulsed power generators developed for different applications. In addition, the semiconductor opening switch is found to have very effective applications in pulsed power generation by inductive energy storage. Semiconductor switches have greatly extended the scales of pulsed power parameters, especially in repetition rate and lifetime. They have also enabled new areas of pulsed power applications, such as accelerators, flue-gas treatment, and gas lasers. 相似文献
33.
Al Amin A. Shimizu K. Takenaka M. Tanemura T. Inohara R. Nishimura K. Horiuchi Y. Usami M. Takita Y. Kai Y. Aoki Y. Onaka H. Miyazaki Y. Miyahara T. Hatta T. Motoshima K. Kagimoto T. Kurobe T. Kasukawa A. Arimoto H. Tsuji S. Uetsuka H. Nakano Y. 《Photonics Technology Letters, IEEE》2007,19(10):726-728
We report a bit-rate transparent optical burst switching (OBS) router prototype using a fast 5 times 5 PLZT [(Pb,La)(Zr,Ti)O3 ] optical matrix switch. Dynamic switching in a two-wavelength, 2 times 2 OBS switch is demonstrated. Contention resolution using a tunable Mach-Zehnder interferometer wavelength converter for both 40- and 10-Gb/s bursts is demonstrated for the first time. Error-free operation was achieved for both bit rates under the same settings, as required in autonomous networks 相似文献
34.
E.M. Lopes R.S. Ywata N. Alves F.M. Shimizu D.M. Taylor C.P. Watson A.J.F. Carvalho J.A. Giacometti 《Organic Electronics》2012,13(10):2109-2117
The admittance spectra and current–voltage (I–V) characteristics are reported of metal–insulator–metal (MIM) and metal–insulator–semiconductor (MIS) capacitors employing cross-linked poly(amide–imide) (c-PAI) as the insulator and poly(3-hexylthiophene) (P3HT) as the active semiconductor. The capacitance of the MIM devices are constant in the frequency range from 10 Hz to 100 kHz, with tan δ values as low as 7 × 10−3 over most of the range. Except at the lowest voltages, the I–V characteristics are well-described by the Schottky equation for thermal emission of electrons from the electrodes into the insulator. The admittance spectra of the MIS devices displayed a classic Maxwell–Wagner frequency response from which the transverse bulk hole mobility was estimated to be ∼2 × 10−5 cm2 V−1s−1 or ∼5 × 10−8 cm2 V−1s−1 depending on whether or not the surface of the insulator had been treated with hexamethyldisilazane (HMDS) prior to deposition of the P3HT. From the maximum loss observed in admittance-voltage plots, the interface trap density was estimated to be ∼5 × 1010 cm−2 eV−1 or ∼9 × 1010 cm−2 eV−1 again depending whether or not the insulator was treated with HMDS. We conclude, therefore, that HMDS plays a useful role in promoting order in the P3HT film as well as reducing the density of interface trap states. Although interposing the P3HT layer between the insulator and the gold electrode degrades the insulating properties of the c-PAI, nevertheless, they remain sufficiently good for use in organic electronic devices. 相似文献
35.
Shuyan Gao Naoto Koshizaki Hideo Tokuhisa Emiko Koyama Takeshi Sasaki Jae‐Kwan Kim Joonghyun Ryu Deok‐Soo Kim Yoshiki Shimizu 《Advanced functional materials》2010,20(1):78-86
Colloidal Au‐amplified surface plasmon resonance (SPR), like traditional SPR, is typically used to detect binding events on a thin noble metal film. The two major concerns in developing colloidal Au‐amplified SPR lie in 1) the instability, manifested as a change in morphology following immersion in organic solvents and aqueous solutions, and 2) the uncontrollable interparticle distance, determining probe spacing and inducing steric hindrance between neighboring probe molecules. This may introduce uncertainties into such detecting techniques, degrade the sensitivity, and become the barricade hampering colloidal Au‐based transducers from applications in sensing. In this paper, colloidal Au‐amplified SPR transducers are produced by using ultrathin Au/Al2O3 nanocomposite films via a radio frequency magnetron co‐sputtering method. Deposited Au/Al2O3 nanocomposite films exhibit superior stability, and average interparticle distances between Au nanoparticles with similar average sizes can be tuned by changing surface coverage. These characteristics are ascribed to the spacer function and rim confinement of dielectric Al2O3 and highlight their advantages for application in optimal nanoparticle‐amplified SPR, especially when the probe size is smaller than the target molecule size. This importance is demonstrated here for the binding of protein (streptavidin) targets to the probe (biotin) surface. In this case, the dielectric matrix Al2O3 is a main contributor, behaving as a spacer, tuning the concentration of Au nanoparticles, and manipulating the average interparticle distance, and thus guaranteeing an appropriate number of biotin molecules and expected near‐field coupling to obtain optimal sensing performance. 相似文献
36.
Optical amplification characteristics for Er-doped silica core single-mode fiber amplifiers with different Er concentrations pumped by 1.48-μm-wavelength laser diodes are studied. Optical gain drastically depends on Er concentration, even when the Er concentration is less than 1000 p.p.m. In the case of the 40-mW incident pump power, the maximum net gain for the fiber containing 77 p.p.m. Er is higher than that for the fiber containing 970 p.p.m. Er by 11.4 dB 相似文献
37.
A bidirectional common polarization control method with a single polarization controller for a coherent optical FDM bidirectional transmission system is discussed. This method is promising for realizing a reliable and low-cost terminal in a coherent multichannel distribution system because the polarization controller can be placed in common only at a central office. Theoretical and experimental results show that the frequency separation δf has to be 6×bit rate<δf <120/Δτ (GHz) for FSK bidirectional transmission. The method is effective not only for reducing the complexity of the subscriber terminal but also for improving the reliability in a coherent CATV system 相似文献
38.
Sung Tae Choi Ki Seok Yang Nishi S. Shimizu S. Tokuda K. Yong Hoon Kim 《Microwave Theory and Techniques》2006,54(5):1953-1960
A 60-GHz point-to-multipoint wireless access link with data rate of 156 Mb/s incorporating 60-GHz transceiver modules and full-duplex fiber-optic millimeter-wave transmission is developed for short-range applications such as indoor wireless local area networks and intelligent transport systems. For compact system configuration, a small-size millimeter-wave transceiver module with planar antennas is developed. The transceiver module is based on broadband planar integration and packaging of millimeter-wave circuits. The RF output power is +10 dBm and the measured 3-dB antenna beamwidth is 30/spl deg/. The total size of the developed 60-GHz transceiver module, except input and output connectors, is 50 mm /spl times/ 75 mm /spl times/ 35 mm. A point-to-point full duplex fiber-optic configuration is extended to the scheme with multiple access points (APs) by using a tree coupler and a dense wavelength division multiplexing multiplexer. The AP has a simple configuration without frequency conversion. The bit error rate and packet error rate performances of the 60-GHz fiber-radio access link are evaluated. Furthermore, the effect of the extension to the scheme with multiple APs is investigated. 相似文献
39.
Yasuo Watanabe Masahiro Yamaguchi Jun Sakamoto Youichi Tamai 《Yeast (Chichester, England)》1993,9(3):213-220
Plasma membrane was isolated from the salt-tolerant yeast Candida versatilis and the ATPase in plasma membrane was characterized. The ATPase was a typical H+-ATPase with similar properties to the Saccharomyces cerevisiae and Zygosaccharomyces rouxii enzymes. It was reacted with antibody (IgG) raised against S. cerevisiae plasma membrane H+-ATPase. The ATPase activity was not changed by adding NaCl and KCl to the assay solutions, but was increased by NH, especially by ammonium sulfate. In vivo stimulation of ATPase activity was observed by the addition of NaCl into the culture medium, as observed in Z. rouxii. No in vivo activation of H+-ATPase by glucose metabolism was observed in C. versatilis cells and the activity was independent of the growth phase, like Z. rouxii and unlike S. cerevisiae cells. 相似文献
40.
This paper describes a new write/erase method for flash memory to improve the read disturb characteristics by means of drastically reducing the stress leakage current in the tunnel oxide. This new write/erase operation method is based on the newly discovered three decay characteristics of the stress leakage current. The features of the proposed write/erase method are as follows: 1) the polarity of the additional pulse after applying write/erase pulse is the same as that of the control gate voltage in the read operation; 2) the voltage of the additional pulse is higher than that of a control gate in a read operation, and lower than that of a control gate in a write operation; and 3) an additional pulse is applied to the control gate just after a completion of the write/erase operation. With the proposed write/erase method, the degradation of the read disturb life time after 106 write/erase cycles can be drastically reduced by 50% in comparison with the conventional bipolarity write/erase method used for NAND type flash memory. Furthermore, the degradation can he drastically reduced by 90% in comparison with the conventional unipolarity write/erase method fur NOR-, AND-, and DINOR-type flash memory. This proposed write/erase operation method has superior potential for applications to 256 Mb flash memories and beyond 相似文献