全文获取类型
收费全文 | 1828篇 |
免费 | 173篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 29篇 |
技术理论 | 1篇 |
综合类 | 5篇 |
化学工业 | 405篇 |
金属工艺 | 24篇 |
机械仪表 | 32篇 |
建筑科学 | 44篇 |
能源动力 | 54篇 |
轻工业 | 90篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 402篇 |
一般工业技术 | 481篇 |
冶金工业 | 133篇 |
原子能技术 | 9篇 |
自动化技术 | 293篇 |
出版年
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 37篇 |
2020年 | 22篇 |
2019年 | 39篇 |
2018年 | 41篇 |
2017年 | 38篇 |
2016年 | 69篇 |
2015年 | 73篇 |
2014年 | 76篇 |
2013年 | 195篇 |
2012年 | 101篇 |
2011年 | 99篇 |
2010年 | 99篇 |
2009年 | 100篇 |
2008年 | 90篇 |
2007年 | 103篇 |
2006年 | 81篇 |
2005年 | 77篇 |
2004年 | 59篇 |
2003年 | 51篇 |
2002年 | 39篇 |
2001年 | 37篇 |
2000年 | 33篇 |
1999年 | 25篇 |
1998年 | 57篇 |
1997年 | 39篇 |
1996年 | 41篇 |
1995年 | 37篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 5篇 |
排序方式: 共有2009条查询结果,搜索用时 15 毫秒
21.
Summary Styrene polymerization was initiated by methylaluminoxane in the presence of haloalkane. The propagating species are shown by trapping experiments and electron paramagnetic resonance to be both radicals and cations. 相似文献
22.
Lead zirconate titanates (Pb (Zrx Ti1–x )O3 or PZT) are well-known materials with useful ferroelectric properties for nonvolatile memory applications. The device applications usually require processes which form the ferroelectric perovskite phase at low temperatures. Understanding the various aspects of structure development of PZT films is the key to develop low-temperature processes. An effective, versatile, and nondestructive optical method was developed for the study of the structure development in PZT films. Also, models for the structure development were proposed and were verified by this optical method. Using this method, the characteristic temperatures at which both pyrochlore phase and perovskite phase are initiated and completed were identified. The pyrochloreperovskite transformation was initiated at lower temperature and completed faster for the films on the titanium-rich side than those on the zirconium-rich side. In addition, the volume fractions of the perovskite phase were obtained as a function of annealing temperature by this optical method. 相似文献
23.
P. Kundu K.R. Justin Thomas J.T. Lin Y.‐T. Tao C.‐H. Chien 《Advanced functional materials》2003,13(6):445-452
A series of dicarbazolyl derivatives bridged by various aromatic spacers and decorated with peripheral diarylamines were synthesized using Ullmann and Pd‐catalyzed C–N coupling procedures. These derivatives emit blue light in solution. In general, they possess high glass‐transition temperatures (Tg > 125 °C) which vary with the bridging segment and methyl substitution on the peripheral amine. Double‐layer organic light‐emitting devices were successfully fabricated using these molecules as hole‐transporting and emitting materials. Devices of the configuration ITO/HTL/TPBI/Mg:Ag (ITO: indium tin oxide; HTL: hole‐transporting layer; TPBI: 1,3,5‐tris(N‐phenylbenzimidazol‐2‐yl)benzene) display blue emission from the HTL layer. The EL spectra of these devices appear slightly distorted due to the exciplex formation at the interfaces. However, for the devices of the configuration ITO/HTL/Alq3/Mg:Ag (Alq3 = tris(8‐hydroxyquinoline)aluminum) a bright green light from the Alq3 layer was observed. This clearly demonstrates the facile hole‐transporting property of the materials described here. 相似文献
24.
Lyubomirsky I. Cheng-Chung Chien Yi-Hsiang Wang 《Photonics Technology Letters, IEEE》2008,20(7):511-513
We propose and analyze a novel differential quadrature phase-shift-keying (DQPSK) receiver architecture based on optical frequency discriminator filtering and direct detection. Our simulations show that such a receiver provides significantly enhanced tolerance to chromatic dispersion compared with the conventional delay-interferometer-based receiver. Preliminary measurement results demonstrate the novel DQPSK demodulator concept at 20 Gb/s. 相似文献
25.
Kuo‐Hsiung Wang Tzong‐Ming Wu Yeng‐Fong Shih Chien‐Ming Huang 《Polymer Engineering and Science》2008,48(9):1833-1839
The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the powder obtained from the water bamboo husk was added to poly(lactic acid) (PLA) to form novel reinforced biodegradable composites. Morphologies, mechanical properties, and heat resistance of these water bamboo powder reinforced composites were investigated. The results indicate that the char yields were increased as plant powder was incorporated to PLA. In addition, the mechanical properties were also enhanced due to the addition of powders. The increments of storage moduli of PLA were about 50–200%. Moreover, the increments of loss moduli of PLA were about 70–200%. On the other hand, the Tg of PLA was slightly decreased by the addition of powder, and this may improve the brittle characteristics of PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive‐reinforced one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
26.
Raybon G. Young M.G. Koren U. Miller B.I. Chien M. Zirngibl M. Dragone C. Froberg N.M. Burrus C.A. 《Electronics letters》1995,31(14):1147-1149
Five wavelength multiplexed pulse streams are generated in an integrated 16×1 laser modulator array by sinusoidally driving five of the potential 16 electroabsorption modulators. At a repetition rate of 2.5 GHz, near transform-limited pulses spaced in wavelength over 7.6 nm are observed. Pseudorandom coding of one channel is achieved by applying an electrical RZ data signal to the modulator 相似文献
27.
28.
Cyclic hot corrosion conducted on Haynes 230 at temperatures of 871 and 1093 C indicated that catastrophic corrosion occurred. The corrosion rate was related to the high content of tungsten and chromium in the alloy. The concept of basic and acid fluxing was applied to explain the dissolution of the protective film of Cr2O3 and volatile WO3 by an Na2SO4-rich liquid due to the formation of Na2CrO4 and Na2WO4. As the basic melts were acidified by continuously consuming oxygen ions, plate-like crystals of Cr2O3 were precipitated on the free surface by conversion from Na2CrO4. Acid fluxing was achieved by the refractory oxide, WO3, consuming oxygen ions. The presence of sulphur suppressed the diffusion of chromium outward to form protective Cr2O3. Internal chromium-rich sulphide particles were observed. It was suggested that at very lowP
O2, sulphur reacted with chromium to form CrS initially. As oxygen penetrated through the porous layer, the CrS was oxidized internally to Cr2O3. 相似文献
29.
Fu KS Chien YT Cardillo GP 《IEEE transactions on pattern analysis and machine intelligence》1986,(3):313-326
This paper presents the dynamic programming approach to the design of optimal pattern recognition systems when the costs of feature measurements describing the pattern samples are of considerable importance. A multistage or sequential pattern classifier which requires, on the average, a substantially smaller number of feature measurements than that required by an equally reliable nonsequential classifier is defined and constructed through the method of recursive optimization. Two methods of reducing the dimensionality in computation are presented for the cases where the observed feature measurements are 1) statistically independent, and 2) Markov dependent. Both models, in general, provide a ready solution to the optimal sequential classification problem. A generalization in the design of optimal classifiers capable of selecting a best sequence of feature measurements is also discussed. Computer simulated experiments in character recognition are shown to illustrate the feasibility of this approach. 相似文献
30.
To maintain competitive advantages, semiconductor industry has strived for continuous technology migrations and quick response to yield excursion. As wafer fabrication has been increasingly complicated in nano technologies, many factors including recipe, process, tool, and chamber with the multicollinearity affect the yield that are hard to detect and interpret. Although design of experiment (DOE) is a cost effective approach to consider multiple factors simultaneously, it is difficult to follow the design to conduct experiments in real settings. Alternatively, data mining has been widely applied to extract potential useful patterns for manufacturing intelligence. However, because hundreds of factors must be considered simultaneously to accurately characterize the yield performance of newly released technology and tools for diagnosis, data mining requires tremendous time for analysis and often generates too many patterns that are hard to be interpreted by domain experts. To address the needs in real settings, this study aims to develop a retrospective DOE data mining that matches potential designs with a huge amount of data automatically collected in semiconductor manufacturing to enable effective and meaningful knowledge extraction from the data. DOE can detect high-order interactions and show how interconnected factors respond to a wide range of values. To validate the proposed approach, an empirical study was conducted in a semiconductor manufacturing company in Taiwan and the results demonstrated its practical viability. 相似文献