全文获取类型
收费全文 | 519210篇 |
免费 | 45950篇 |
国内免费 | 25903篇 |
专业分类
电工技术 | 32364篇 |
技术理论 | 75篇 |
综合类 | 60751篇 |
化学工业 | 61632篇 |
金属工艺 | 26644篇 |
机械仪表 | 29096篇 |
建筑科学 | 75649篇 |
矿业工程 | 29387篇 |
能源动力 | 17365篇 |
轻工业 | 34389篇 |
水利工程 | 25448篇 |
石油天然气 | 24638篇 |
武器工业 | 5909篇 |
无线电 | 32193篇 |
一般工业技术 | 41424篇 |
冶金工业 | 29998篇 |
原子能技术 | 4446篇 |
自动化技术 | 59655篇 |
出版年
2024年 | 2181篇 |
2023年 | 6427篇 |
2022年 | 12136篇 |
2021年 | 15204篇 |
2020年 | 15394篇 |
2019年 | 12187篇 |
2018年 | 11626篇 |
2017年 | 14460篇 |
2016年 | 16765篇 |
2015年 | 18198篇 |
2014年 | 32096篇 |
2013年 | 29296篇 |
2012年 | 36074篇 |
2011年 | 38759篇 |
2010年 | 29590篇 |
2009年 | 30261篇 |
2008年 | 27900篇 |
2007年 | 35210篇 |
2006年 | 32629篇 |
2005年 | 28371篇 |
2004年 | 24043篇 |
2003年 | 21301篇 |
2002年 | 17537篇 |
2001年 | 14738篇 |
2000年 | 12565篇 |
1999年 | 10181篇 |
1998年 | 7589篇 |
1997年 | 6579篇 |
1996年 | 5745篇 |
1995年 | 4873篇 |
1994年 | 4246篇 |
1993年 | 3178篇 |
1992年 | 2698篇 |
1991年 | 1975篇 |
1990年 | 1755篇 |
1989年 | 1546篇 |
1988年 | 1110篇 |
1987年 | 773篇 |
1986年 | 582篇 |
1985年 | 534篇 |
1984年 | 467篇 |
1983年 | 356篇 |
1982年 | 302篇 |
1981年 | 233篇 |
1980年 | 222篇 |
1979年 | 157篇 |
1978年 | 82篇 |
1977年 | 88篇 |
1975年 | 72篇 |
1959年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献
22.
通过对镍氢电池性能的研究,给出了一个应用ISA总线技术构建的、基于DELPHI编程平台的镍氢电池管理系统的设计方案,重点介绍了该系统的软件技术和实现方法。 相似文献
23.
Visual evaluation experiments of color discrimination threshold and suprathreshold color‐difference comparison were carried out using CRT colors based on the psychophysical methods of interleaved staircase and constant stimuli, respectively. A large set of experimental data was generated ranged from threshold to large suprathreshold color difference at the five CIE color centers. The visual data were analyzed in detail for every observer at each visual scale to show the effect of color‐difference magnitude on the observer precision. The chromaticity ellipses from this study were compared with four previous published data, of CRT colors by Cui and Luo, and of surface colors by RIT‐DuPont, Cheung and Rigg, and Guan and Luo, to report the reproducibility of this kind of experiment using CRT colors and the variations between CRT and surface data, respectively. The present threshold data were also compared against the different suprathreshold data to show the effect of color‐difference scales. The visual results were further used to test the three advance color‐difference formulae, CMC, CIE94, and CIEDE2000, together with the basic CIELAB equation. In their original forms or with optimized KL values, the CIEDE2000 outperformed others, followed by CMC, and with the CIELAB and CIE94 the poorest for predicting the combined dataset of all color centers in the present study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 198–208, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20106 相似文献
24.
The objective of this note is to propose a method for stabilization of structurally fixed modes in expansions of LTI dynamic systems in the scope of overlapping decentralized control design based on the expansion/contraction framework, enabling successful design for a broader class of problems than considered so far. The method is based on a judicious choice of complementary matrices in the expanded space. Numerical examples are provided to illustrate simplicity and efficiency of the proposed approach. 相似文献
25.
Human facial gestures often exhibit such natural stochastic variations as how often the eyes blink, how often the eyebrows and the nose twitch, and how the head moves while speaking. The stochastic movements of facial features are key ingredients for generating convincing facial expressions. Although such small variations have been simulated using noise functions in many graphics applications, modulating noise functions to match natural variations induced from the affective states and the personality of characters is difficult and not intuitive. We present a technique for generating subtle expressive facial gestures (facial expressions and head motion) semi‐automatically from motion capture data. Our approach is based on Markov random fields that are simulated in two levels. In the lower level, the coordinated movements of facial features are captured, parameterized, and transferred to synthetic faces using basis shapes. The upper level represents independent stochastic behavior of facial features. The experimental results show that our system generates expressive facial gestures synchronized with input speech. 相似文献
26.
27.
蒋成德 《徐州工程学院学报》2008,23(6):85-88
孔子是否删诗,这是一个历史遗留问题。司马迁首言在前,孔颖达怀疑在后。宋之后,争议遂起,延至近代。今人夏传才先生断日:孔子是否删诗,“在没有发掘出新史料的情况下,哪怕再争论八百年,也是搞不清楚的”。以此止息纷争。话虽不错,但问题并没有解决。我认为,在没有发掘出新史料的情况下,可以从《左传》入手,来考察孔子是否删诗。 相似文献
28.
肖起清 《机械工业高教研究》2008,(2):34-37
大学在办学资源、办学过程、办学质量、办学形象的竞争中出现大量的不良倾向。大学的不良竞争是由于政府主导资源配置、资源和制度供给不足、大学系统重构等因素导致。必须通过控制主体、控制手段的转变和控制对象的发展形成新的控制机制,以保证大学竞争的秩序化和规范化。 相似文献
29.
Vjacheslav V. Zuev 《Journal of Polymer Research》2008,15(5):351-356
Functionalized polyanilines containing biphenyl, terphenyl, carbazole, anthracene, and 4-n-hexylphenyl moieties were synthesized though the reaction of polyaniline in emeraldine base form with sodium salt of corresponding
vinylketoaromatics with quantitative yields. Polymers were characterized with Fourier transform infrared spectroscopy, proton
nuclear magnetic resonance spectroscopy, and thermogravimetry. The emission characteristics of these polymers in N-methyl-2-pyrrolidone solution were examined. The functionalized polyanilines exhibited an intense green emission. 相似文献
30.
向春 《机械工业高教研究》2008,(3):85-89
校园文化看不见、摸不着,却支撑着大学的脊梁,它潜移默化影响和造就一所大学的文化品格。它不仅对大学发展起着重要作用,也是大学发展的重要内容,是大学建设的题中应有之义。为此,需要建设民主和谐,具有学术自由、人文精神和创新精神的校园文化,并将它提高到学校战略发展的高度来看,以校园文化整合学校发展战略。 相似文献