全文获取类型
收费全文 | 1395篇 |
免费 | 34篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 138篇 |
综合类 | 4篇 |
化学工业 | 402篇 |
金属工艺 | 62篇 |
机械仪表 | 38篇 |
建筑科学 | 25篇 |
矿业工程 | 5篇 |
能源动力 | 26篇 |
轻工业 | 77篇 |
水利工程 | 4篇 |
石油天然气 | 7篇 |
无线电 | 81篇 |
一般工业技术 | 274篇 |
冶金工业 | 104篇 |
原子能技术 | 52篇 |
自动化技术 | 138篇 |
出版年
2022年 | 12篇 |
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 26篇 |
2014年 | 34篇 |
2013年 | 90篇 |
2012年 | 44篇 |
2011年 | 59篇 |
2010年 | 61篇 |
2009年 | 56篇 |
2008年 | 88篇 |
2007年 | 59篇 |
2006年 | 57篇 |
2005年 | 47篇 |
2004年 | 45篇 |
2003年 | 41篇 |
2002年 | 26篇 |
2001年 | 32篇 |
2000年 | 23篇 |
1999年 | 25篇 |
1998年 | 38篇 |
1997年 | 44篇 |
1996年 | 33篇 |
1995年 | 24篇 |
1994年 | 30篇 |
1993年 | 33篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 20篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 19篇 |
1980年 | 22篇 |
1979年 | 22篇 |
1978年 | 16篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1969年 | 2篇 |
排序方式: 共有1437条查询结果,搜索用时 15 毫秒
31.
Yu Hua Wang Tadashi Endo Xuan Guo Yukio Murakami Mizumoto Ushirozawa 《Journal of the Society for Information Display》2004,12(4):495-499
Abstract— The broad bands at around 155 nm for GdAl3(BO3)4:Eu, at 184 nm for Ca4GdO(BO3)3:Eu, at 183 nm for Gd2SiO5:Eu, and at 170 nm for GdAlO3:Eu were observed. These bands were assigned to the charge‐transfer (CT) transition of Gd3+‐O2?. In the excitation spectrum of (Gd,Y)BO3:Eu, a broadened excitation band was observed in VUV region. It could be considered that this band was composed of two bands at about 160 and 166 nm. The preceding band was assigned to the BO3 group absorption. The later one at about 166 nm could be assigned to the CT transition of Gd3+‐O2?, according to the result of GdAl3(BO3)4:Eu, Ca4GdO(BO3)3:Eu, Gd2SiO5:Eu, and GdAlO3:Eu. The excitation spectra overlapped between the CT transition of Gd3+‐O2? and BO3 groups absorption. It caused the emission of Eu3+ to take place effectively in the trivalent europium‐doped (Gd,Y)BO3 host lattice under 147‐nm excitation. 相似文献
32.
Raimundo Almeida-Filho Fernando P. Miranda Tadashi Yamakawa 《International journal of remote sensing》2013,34(13):2683-2688
Mapping of a tonal anomaly in an area of hydrocarbon microseepage was possible using a Landsat-Thematic Mapper false-colour composite consisting of TM2/3, TM4/3 and of the difference TM2/3-TM4/3, displayed as red, green and blue, respectively. In this false-colour composite, green and yellow express variations in the vegetation cover, whereas hues of magenta are related to terrain conditions representing bleached materials, which occur close to the centre of a soil gas anomaly. Simultaneous occurrence of anomalous soil gas values with magnetic and radioactive minerals suggests that a reducing environment associated with the microseepage phenomenon created the bleached materials, identified as a tonal anomaly in the enhanced TM image. 相似文献
33.
Horiuchi S Hamanaka T Aoki T Miyakawa T Narita R Wakabayashi H 《Journal of electron microscopy》2003,52(3):255-266
Energy-filtering transmission electron microscopy (EFTEM) was applied for investigating interfaces between a polymer and an adhesive. The sample employed in this work is polybutylene terephtharate (PBT) sheets laminated with an epoxy adhesive. It was found that heat aging of the PBT at 180 degrees C in air for > 9 h prior to adhesion decreases the adhesion strength drastically. To investigate this unfavourable aging effect on the adhesion strength, we performed elemental mapping and image EELS using EFTEM. A weak boundary layer with a thickness of < 50 nm was visualized at the PBT-adhesive interface by elemental mapping in the sample subjected to the heat aging and image EELS revealed the origin of this layer. Thus, we clearly correlated the nanoscale interfacial structure with the adhesion strength by EFTEM. 相似文献
34.
We fabricated an original near-field scanning optical microscopy (NSOM) fiber probe made of polarization-maintaining and attenuation-reducing (PANDA)-type polarization-maintaining optical fiber, and observed the polarization property of propagation light in a polymer optical waveguide. The distribution of the transmission coefficient in polarization angles through this NSOM probe showed that the linear polarization is maintained in the two crossing directions: the fast and slow axes. The polarization degree parallel to the slow axis decreases from 1000:1 to 2:1 by bending the fiber probe and the decrease is independent of the bending direction. Using this PANDA-type NSOM probe, we investigated the polarization property of periodic intensity modulation. It was found that the intensity modulation was observed clearly with the electric vector parallel to the radius direction of the waveguide, but was observed vaguely with the electric vector perpendicular to the radius direction. 相似文献
35.
This paper describes a method for designing electromagnetically coupled (EMC) printed dipole arrays. The advantages of EMC dipoles include greater bandwidth, higher efficiency, and an easier match to the feed lines, when compared to classically fed printed antennae. The excitation mechanism is provided by a strip transmission line embedded inside the substrate which couples energy parasitically to the microstrip antenna. Electromagnetically coupled microstrip dipoles have been investigated by empirical or approximate analysis techniques. As a result an approximate model has been derived for microstrip dipoles. The method is based on the method of moments solution to an integral equation derived from the approximate Green function for a grounded dielectric slab. The element lengths and offsets and the stub length of the EMC dipole array are determined by the direct search optimization method of Hooke and Jeeves. To show the feasibility of the proposed method, a mathematical formulation and numerical results are presented for Chebyshev arrays. © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 60–66, 1998 相似文献
36.
This paper considers the optimal spare ordering policies for a cold standby redundant system with two dissimilar units. Especially, the planned maintenance schedule with salvage cost is discussed. The failure time distributions for respective units are assumed to be arbitrary. By applying the expected cost per unit time in the steady-state and the stationary availability as criteria of optimality, the optimal ordering policy minimizing or maximizing each criterion is obtained under some economical and/or physical assumptions. Finally, numerical examples are presented, and the effect of the failure time distributions for the optimal ordering policy is examined in detail. 相似文献
37.
The thermal performance of a chemical heat pump that uses the reaction system of calcium oxide/lead oxide/carbon dioxide, which is developed for utilization of high‐temperature heat above 800°C, is studied experimentally. The thermal performance of a packed‐bed reactor of a calcium oxide/carbon dioxide reaction system, which stores and transforms a high‐temperature heat source in the heat pump operation, is examined under various heat pump operation conditions. The energy analysis based on the experiment shows that it is possible to utilize high‐temperature heat with this heat pump. This heat pump can store heat above 850°C and then transform it into a heat above 900°C under an approximate atmospheric pressure. An applied system that combines the heat pump and a high‐temperature process is proposed for high‐efficiency heat utilization. The scale of the heat pump in the combined system is estimated from the experimental results. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
38.
39.
Tomoya Daito Hiroshi Nishikawa Tadashi Takemoto Takashi Matsunami 《Microelectronics Reliability》2013
Solder joints are required to have high impact strength for use in portable electronic products. To make solder joints with high impact strength, qualitative evaluation methods of impact strength are required. Ball impact tests have been widely adopted in evaluating the impact strength of solder joints because of their easy implementation. Impact load curves obtained from ball impact tests are used as an evaluation indicator of impact strength of solder joint. However, a relation between fracture behavior and impact load curve has not yet been clarified, and an explanation of the impact load curve has not yet been provided in detail. In addition to this, detailed study about the relation between IMC layer thickness and impact strength has not been performed, although the IMC layer thickness formed at the interface would significantly affect the impact strength of the solder joint. This study aimed to explain the impact load curve in the ball impact test and to reveal the effect of the IMC layer thickness on the impact strength of the solder joint. Sn–3.0Ag–0.5Cu solder was reflowed on an electroless Ni–P plated Cu substrate (Ni–P), and a ball impact test was then carried out to evaluate the impact strength. This study found that the ball impact test is effective to evaluate the interfacial strength of solder joints. In the impact load curve, it is estimated that the solder bump keeps deforming until the interfacial crack initiates (maximum load), and the interfacial crack initiates after the maximum load and propagates along the interface between the solder and Ni–P. The suitable evaluation of impact strength became possible by measuring the correspondence relation between the deformation distance of the solder bump after fracture and the energy until maximum load and the relation between the area fraction of the residual solder on the fractured pad and the energy after maximum load. And, it is proved that the impact strength decreased with increasing aging time because the growth of the IMC layer remarkably degraded the interfacial strength of the solder joint. 相似文献
40.
This study was performed to investigate the heat extraction characteristics from shallow geothermal resources using a coaxial heat exchanger. First, a computer simulation program for a coaxial heat exchanger was checked and verified by laboratory experiments. After inspecting the effectiveness of the computer program described herein, a numerical simulation for a real scale model was conducted under the condition that the heat transfer mechanism in the stratum was heat conduction. Unsteady heat extraction characteristics are presented herein, and the effects of the tube material, inner diameter, and circular modes on the heat extraction rate are discussed. From the computer results it was found that the heat extraction performance using a coaxial heat exchanger greatly depended on the factors mentioned above in the range of the parameters covered in this study. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(7): 496–513, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20083 相似文献