全文获取类型
收费全文 | 14669篇 |
免费 | 1118篇 |
国内免费 | 27篇 |
学科分类
工业技术 | 15814篇 |
出版年
2024年 | 12篇 |
2023年 | 188篇 |
2022年 | 156篇 |
2021年 | 516篇 |
2020年 | 375篇 |
2019年 | 374篇 |
2018年 | 491篇 |
2017年 | 502篇 |
2016年 | 602篇 |
2015年 | 526篇 |
2014年 | 749篇 |
2013年 | 1026篇 |
2012年 | 1047篇 |
2011年 | 1280篇 |
2010年 | 914篇 |
2009年 | 867篇 |
2008年 | 799篇 |
2007年 | 655篇 |
2006年 | 543篇 |
2005年 | 468篇 |
2004年 | 441篇 |
2003年 | 376篇 |
2002年 | 312篇 |
2001年 | 270篇 |
2000年 | 268篇 |
1999年 | 242篇 |
1998年 | 430篇 |
1997年 | 265篇 |
1996年 | 225篇 |
1995年 | 134篇 |
1994年 | 118篇 |
1993年 | 105篇 |
1992年 | 68篇 |
1991年 | 48篇 |
1990年 | 44篇 |
1989年 | 45篇 |
1988年 | 39篇 |
1987年 | 33篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 22篇 |
1981年 | 11篇 |
1980年 | 18篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 19篇 |
1974年 | 13篇 |
1972年 | 10篇 |
1970年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Sungmoon Jung Jamshid Ghaboussi Soon-Duck Kwon 《Canadian Metallurgical Quarterly》2004,130(11):1356-1364
A new method of estimating flutter derivatives using artificial neural networks is proposed. Unlike other computational fluid dynamics based numerical analyses, the proposed method estimates flutter derivatives utilizing previously measured experimental data. One of the advantages of the neural networks approach is that they can approximate a function of many dimensions. An efficient method has been developed to quantify the geometry of deck sections for neural network input. The output of the neural network is flutter derivatives. The flutter derivatives estimation network, which has been trained by the proposed methodology, is tested both for training sets and novel testing sets. The network shows reasonable performance for the novel sets, as well as outstanding performance for the training sets. Two variations of the proposed network are also presented, along with their estimation capability. The paper shows the potential of applying neural networks to wind force approximations. 相似文献
102.
103.
104.
105.
The gas flow sputter technique was invented a few years ago particularly for the inexpensive fabrication of sophisticated ceramic layers. Meanwhile, it has matured and become increasingly powerful. Today it is on the verge of being applied in industrial fabrication processes. The present article gives an overview over the method, its characteristics and the numerous applications. 相似文献
106.
Ln2B2O7 (Ln=Sm, Eu, Gd and Tb; B=Zr or Ti) with pyrochlore structure was prepared by sol–gel method for the high-temperature catalytic combustion. The crystal structure of Ln2B2O7 was identified by XRD and their surface area was about 4 m2/g after calcinations at 1200 °C. Catalytic activity of methane combustion was observed for Ln2Zr2O7 series and the best catalyst was Sm2Zr2O7. Its relative reaction rate per unit surface area at 600 °C was 2 cm3/m2 min, which was twice higher than that of Mn-substituted Sr hexaaluminate. From surface analysis by XPS, the low binding energy of each Ln element of Ln2Zr2O7 compared to that of Ln2Ti2O7, gave the catalytic activity of methane combustion. 相似文献
107.
JaeHyunKim JounHoLee JiChulLim ChangHoonLee MooHyoungSong JuYeonYoon HeeDongChoi JeomJaeKim ChangHoOh SangDeogYeo 李路海 《现代显示》2004,31(5):31-33
薄膜晶体管液晶电视(TFT-LCD TV)因为具有薄、轻、紧凑和可随意放置的特点,已经占据了大部分电视机市场。除了这些物理特性以外,最重要的特性是已具有了良好像质的对比度。为了将对比度提高到1:600以上,对偏振片膜、背光源板、滤色片树脂、电极锥角和摩擦条件等都进行了研究。优化的背光板组合,光滑的电极锥角和摩擦方法的控制是提高对比度的主要控制因素。应用新开发的滤色片树脂,对获得高对比度最为有效。 相似文献
108.
In general, this paper deals with general nonlinear oscillations of a nonconservative and single degree-of-freedom system with odd nonlinearity and, in particular, it presents accurate higher-order analytical approximate solutions to van der Pol damped nonlinear oscillators having odd nonlinearity and the Rayleigh equation. By combining the linearization of the governing equation with harmonic balancing and the method of averaging, we establish accurate analytical approximate solutions for the general weakly damped nonlinear systems. Unlike the classical harmonic balance method, simple linear algebraic equations instead of nonlinear algebraic equations are obtained upon linearization prior to harmonic balancing. The combination of these two methods results in very accurate transient response of the periodic solution. In addition and for the first time, this paper also presents a method for deducing fourth-, fifth- and higher-order linearized governing equations from the lower-order equations without the requirement of formulating the problem from the first principle. Three examples including the van der Pol damped nonlinear oscillator are presented to illustrate the excellent agreement with approximate solution using the exact frequency. 相似文献
109.
110.
This paper presents the model of a k-out-of-n: G system with common mode outages. The objective is to analytically derive the mean operating mode between failures for a non-repairable component system. The average system failure time and the system availability are also considered. Then, the model is extended to a system with repairable components and unrestricted repair, in which service times are exponentially distributed. 相似文献