全文获取类型
收费全文 | 1322篇 |
免费 | 149篇 |
国内免费 | 139篇 |
专业分类
电工技术 | 67篇 |
综合类 | 119篇 |
化学工业 | 139篇 |
金属工艺 | 46篇 |
机械仪表 | 129篇 |
建筑科学 | 60篇 |
矿业工程 | 8篇 |
能源动力 | 115篇 |
轻工业 | 53篇 |
水利工程 | 12篇 |
石油天然气 | 23篇 |
武器工业 | 24篇 |
无线电 | 483篇 |
一般工业技术 | 153篇 |
冶金工业 | 15篇 |
原子能技术 | 54篇 |
自动化技术 | 110篇 |
出版年
2024年 | 7篇 |
2023年 | 19篇 |
2022年 | 30篇 |
2021年 | 37篇 |
2020年 | 37篇 |
2019年 | 41篇 |
2018年 | 41篇 |
2017年 | 36篇 |
2016年 | 48篇 |
2015年 | 53篇 |
2014年 | 69篇 |
2013年 | 113篇 |
2012年 | 91篇 |
2011年 | 108篇 |
2010年 | 77篇 |
2009年 | 89篇 |
2008年 | 83篇 |
2007年 | 80篇 |
2006年 | 81篇 |
2005年 | 69篇 |
2004年 | 65篇 |
2003年 | 63篇 |
2002年 | 34篇 |
2001年 | 37篇 |
2000年 | 24篇 |
1999年 | 30篇 |
1998年 | 23篇 |
1997年 | 16篇 |
1996年 | 25篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1976年 | 4篇 |
排序方式: 共有1610条查询结果,搜索用时 15 毫秒
91.
92.
采用计算机模拟的方法,计算了SiO2/Al,ITO/Al,SiO2/Au和ITO/Au全方位反射镜结构和分布式布拉格反射镜的反射特性.用PECVD和溅射设备制作了Glass/SiO2/Au结构,用LP-MOCVD生长了DBR结构,并测量了其反射特性,实验与模拟结果基本吻合.从模拟和实验的结果得到,SiO2/Au ODR结构在波长为630nm的垂直入射光下反射率很高,达到91%以上.对于不同角度的入射光,SiO2/Au在20°~85°都有很高的反射率,远高于DBR结构的反射率.在实际器件测试中,ODR结构的AlGaInP红光LED比无DBR结构的LED提高了115%,比DBR结构的LED提高了28%.这说明,ODR结构与DBR结构相比可以大幅提高红光LED的出光效率. 相似文献
93.
采用传统压电陶瓷固相合成法制得纯钙钛矿相的(1.002-5x)NBT-4xKBT-(x-0.002)BT(x=0.026,0.028,0.030,0.032,0.034)(简写为BNBKT100x)系弛豫铁电体。通过X-射线衍射(XRD)分析,当x=0.030时为三方、四方两相共存,为该体系的准同型相界。系列样品的介电温谱显示在室温到500℃之间存在两个介电反常峰,分别对应于陶瓷材料的铁电-反铁电-顺电相变。同时发现该系列样品显示出弛豫铁电体特性。并用成分起伏理论解释了这种弛豫弥散相变。 相似文献
94.
Muneharu Kuwata Hayato Takeuchi Tomohiro Sasagawa Shinji Yagyu Hiroaki Sugiura 《Journal of the Society for Information Display》2007,15(10):829-836
Abstract— A new light‐collection optics has been developed that enhances the luminance of projection TV which use lamps as the light source. The conventional optical system consists of an elliptical reflector and a flat‐surface front glass, but these systems cannot sufficiently collect the beams coming from the light source, and they cause loss in the coupling with the light pipe. To solve this problem, we devised a new optical system through a structure of an aspherical reflector and an aspherical front glass. This new optical system concentrates the beams coming from the light source to a smaller point which improves the coupling efficiency. Thus, we have successfully increased the luminance of the projection TV by approximately 10%. This paper reports the design principles of the new optical system and the results of a prototype experiment. 相似文献
95.
Abstract We fabricated a Bragg reflector type FBAR using AlN piezoelectric with quarter wavelength thickness, where the Bragg reflector was composed of W-SiO2 pairs. By numerical simulation considering actual acoustic losses of each layer, we analyzed the frequency response of the resonator and could explain it using an equivalent circuit with parasitic elements. The Effective electromechanical coupling constant (K 2 eff ) and the Quality factor (Qs ), figures of merit of the resonator, were about 1.1% and 307, respectively.</ab> 相似文献
96.
Kiyoshi Minoura Shigeaki Mizushima Yasushi Asaoka Ichiro Ihara Eiji Satoh Sayuri Fujiwara Yasuhisa Itoh 《Journal of the Society for Information Display》2008,16(1):129-136
Abstract— A novel reflective color LCD without polarizers has been developed using a PDLC film and a retro‐reflector. Bright color images including moving images are achievable with ambient light. This novel LCD will enable the new application area of electronic paper. 相似文献
97.
Solar radiation models for predicting the average daily and hourly global radiation, beam radiation and diffuse radiation on horizontal surface are reviewed in this article. Estimations of monthly average hourly global radiation from daily summations are discussed. It was observed that Collares‐Pereira and Rabl model as modified by Gueymard (CPRG) yielded the best performance for estimating mean hourly global radiation incident on a horizontal surface for Indian regions. Estimations of monthly average hourly beam and diffuse radiation are discussed. It was observed that Singh‐Tiwari and Jamil‐Tiwari both models generally give better results for climatic conditions of Indian regions. Therefore, their use is recommended for composite climate of Indian regions. Empirical correlations developed to establish a relationship between the hourly diffuse fraction and the hourly clearness index using hourly global and diffuse irradiation measurements on a horizontal surface are discussed. Fifty models using the Angstrom–Prescott equation to predict the average daily global radiation with hours of sunshine are considered. It was reported that Ertekin and Yaldiz model showed the best performance against measured data of Konya, Turkey. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
98.
W. Ronald Fawcett 《Electrochimica acta》2009,54(22):4997-52
Results from Monte Carlo (MC) simulations for restricted electrolytes are presented for both 1:1 and 2:1 electrolytes. It is shown that the potential drop across the diffuse layer for these systems may be expressed by a Taylors series in the Gouy-Chapman (GC) estimate of the same quantity. The coefficients of this series are defined in terms of the MSA volume fraction and the reciprocal thickness of the ionic atmosphere. The series model can also be used to estimate the differential capacity of the diffuse layer. The properties of unrestricted electrolytes are considered at or very close to the potential of zero charge. 相似文献
99.
Christian Larrigaudière Rosa Vilaplana Yolanda Soria Inmaculada Recasens 《Journal of the science of food and agriculture》2008,88(9):1614-1621
BACKGROUND: The main aim of this work was to define how 1‐methylcyclopropene (1‐MCP) treatment affects apple fruit quality by two complementary approaches. RESULTS: The results confirmed that 1‐MCP treatment maintained firmness and acidity of the fruit. Multivariate analysis distinguished treated and untreated fruits and showed that a relationship exists between 1‐MCP treatment and firmness, and also between 1‐MCP and the physiological disorder, ‘diffuse skin browning’ (DSB). Relationships for acidity were low and absent for soluble‐solids concentration (SSC). The PCA model built only with 1‐MCP treated fruit showed a positive correlation between DSB incidence and firmness, and a negative correlation between DSB and SSC or a* values. Collectively, these correlations indicated that the more immature fruits are more susceptible to DSB. This last model also characterised acidity as the best parameter to discriminate the 1‐MCP fruits. CONCLUSION: It is the first time that such a comparative study has been conducted on 1‐MCP treated fruits. The results are of interest because they (1) help to discriminate treated and untreated fruits, and (2) allow discrimination of 1‐MCP‐treated fruit during storage. Copyright © 2008 Society of Chemical Industry 相似文献
100.
Roy H. Stogner Graham F. Carey Bruce T. Murray 《International journal for numerical methods in engineering》2008,76(5):636-661
A variational formulation and C1 finite element scheme with adaptive mesh refinement and coarsening are developed for phase‐separation processes described by the Cahn–Hilliard diffuse interface model of transport in a mixture or alloy. The adaptive scheme is guided by a Laplacian jump indicator based on the corresponding term arising from the weak formulation of the fourth‐order non‐linear problem, and is implemented in a parallel solution framework. It is then applied to resolve complex evolving interfacial solution behavior for 2D and 3D simulations of the classic spinodal decomposition problem from a random initial mixture and to other phase‐transformation applications of interest. Simulation results and adaptive performance are discussed. The scheme permits efficient, robust multiscale resolution and interface characterization. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献