全文获取类型
收费全文 | 5436篇 |
免费 | 353篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 160篇 |
综合类 | 7篇 |
化学工业 | 1623篇 |
金属工艺 | 113篇 |
机械仪表 | 143篇 |
建筑科学 | 174篇 |
矿业工程 | 10篇 |
能源动力 | 195篇 |
轻工业 | 803篇 |
水利工程 | 38篇 |
石油天然气 | 25篇 |
无线电 | 353篇 |
一般工业技术 | 1009篇 |
冶金工业 | 455篇 |
原子能技术 | 30篇 |
自动化技术 | 662篇 |
出版年
2024年 | 19篇 |
2023年 | 96篇 |
2022年 | 265篇 |
2021年 | 285篇 |
2020年 | 197篇 |
2019年 | 216篇 |
2018年 | 196篇 |
2017年 | 218篇 |
2016年 | 208篇 |
2015年 | 153篇 |
2014年 | 266篇 |
2013年 | 371篇 |
2012年 | 321篇 |
2011年 | 373篇 |
2010年 | 255篇 |
2009年 | 289篇 |
2008年 | 261篇 |
2007年 | 239篇 |
2006年 | 214篇 |
2005年 | 132篇 |
2004年 | 113篇 |
2003年 | 120篇 |
2002年 | 96篇 |
2001年 | 72篇 |
2000年 | 39篇 |
1999年 | 67篇 |
1998年 | 137篇 |
1997年 | 108篇 |
1996年 | 57篇 |
1995年 | 48篇 |
1994年 | 44篇 |
1993年 | 49篇 |
1992年 | 23篇 |
1991年 | 23篇 |
1990年 | 24篇 |
1989年 | 19篇 |
1988年 | 31篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1972年 | 5篇 |
排序方式: 共有5800条查询结果,搜索用时 15 毫秒
1.
2.
Piedade M. Sousa L. A. de Almeida T. M. Germano J. da Costa B. A. Lemos J. M. Freitas P. P. Ferreira H. A. Cardoso F. A. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(11):2384-2395
This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays 相似文献
3.
Imre T.G. Cronje W.A. van Wyk J.D. Ferreira J.A. 《Industry Applications, IEEE Transactions on》2002,38(6):1613-1621
This paper covers the experimental investigation and theoretical calculation of losses in a planar inductor under load. Finite-element software is used to perform the loss calculations. Thermally controlled experiments are performed for a range of frequencies to validate the corresponding finite-element method loss calculations. The thermal dependence of the loss mechanisms is also considered. 相似文献
4.
Sol–gel films are actively investigated during the last decade as possible candidates for environmentally friendly pre-treatments. However, the important drawback in this case is the lack of active corrosion protection and self-healing ability. 相似文献
5.
From visual data exploration to visual data mining: a survey 总被引:8,自引:0,他引:8
Ferreira de Oliveira M.C. Levkowitz H. 《IEEE transactions on visualization and computer graphics》2003,9(3):378-394
We survey work on the different uses of graphical mapping and interaction techniques for visual data mining of large data sets represented as table data. Basic terminology related to data mining, data sets, and visualization is introduced. Previous work on information visualization is reviewed in light of different categorizations of techniques and systems. The role of interaction techniques is discussed, in addition to work addressing the question of selecting and evaluating visualization techniques. We review some representative work on the use of information visualization techniques in the context of mining data. This includes both visual data exploration and visually expressing the outcome of specific mining algorithms. We also review recent innovative approaches that attempt to integrate visualization into the DM/KDD process, using it to enhance user interaction and comprehension. 相似文献
6.
Daniel X. Gouveia Odair P. Ferreira Antonio G. Souza Filho M. G. da Silva J. A. C. de Paiva Oswaldo L. Alves Josué Mendes Filho 《Journal of Materials Science》2007,42(2):534-538
The thermal decomposition properties of Mg–Fe hydrotalcites were studied through in situ 57Fe Mössbauer spectroscopy and in situ X-ray diffraction. Abrupt changes in the quadrupolar splitting measured in the Mössbauer spectra revealed a phase transition from the starting lamellar structure to a new crystalline arrangement. By analyzing the Mössbauer parameters we show that the material is highly disordered in the 300–400 °C temperature range. This hypothesis is confirmed by the X-ray results whose diffractograms indicated the collapse of the lamellar structure and the formation of a solid solution. 相似文献
7.
Reveliotis S.A. Lawley M.A. Ferreira P.M. 《Automatic Control, IEEE Transactions on》1997,42(10):1344-1357
The development of efficient deadlock avoidance policies (DAPs) for sequential resource allocation systems (RASs) is a problem of increasing interest in the scientific community, largely because of its relevance to the design of large-scale flexibly automated manufacturing systems. Much of the work on this problem existing in the literature is focused on the so-called single-unit RAS model, which is the simplest model in the considered class of RASs. Furthermore, due to a well-established result stating that, even for single-unit RASs, the computation of the maximally permissive DAP is intractable (NP-hard), many researchers (including our group) have focused on obtaining good suboptimal policies which are computationally tractable (scalable) and provably correct. In the first part of the paper, it is shown, however, that for a large subset (in fact, a majority) of single-unit RASs, the optimal DAP can be obtained in real-time with a computational cost which is a polynomial function of the system size (i.e., the number of resource types and the distinct route stages of the processes running through the system). The implications of this result for the entire class of single-unit RASs are also explored. With a result on the design of optimal DAPs for single-unit RASs, the second part of the paper concentrates on the development of scalable and provably correct DAPs for the more general case of conjunctive RASs 相似文献
8.
How senile plaques and neurofibrillary tangles are linked represents a major gap in our understanding of the pathophysiology of Alzheimer's disease. We characterized a hippocampal neuronal culture system in which tau undergoes maturation in vivo; rat neurons maintained in culture for more than 3 weeks replicated the splicing and phosphorylation changes that tau undergoes upon maturation in situ. Using this model system, we induced an Alzheimer-like neuritic dystrophy following the application of fibrillar beta-amyloid. The dystrophy consisted of focal distortions and swellings within the neurites and an altered phosphorylation of the adult tau isoforms. Fibrillar beta-amyloid induced the concomitant activation of MAP kinase and GSK3 beta. The aberrant activation of several signaling pathways may lead to the abnormal phosphorylation of tau and neuritic degeneration. 相似文献
9.
Vibro-fluidized beds are widely used in drying sticky powders and agglomerated materials as milk powder. Using a vibro-fluidized laboratory scale dryer, this work is aiming at analyzing preliminarily the effect of its operational variables on the drying kinetics and characteristics of whole milk powder. The full-factorial design technique with three replications at the central point has been employed to generate data and correlations to quantify the effect of inlet air temperature, air flow rate, and vibration bed amplitude on the drying curves and the milk powder properties related to its faster reconstitution in water (as tapped density, Hausner cohesion ratio, agglomerate size distribution, and internal pore concentration). Results obtained are analyzed and discussed to identify the adequate operation condition for final drying whole milk powder in vibro-fluidized beds, assuring a high product quality. 相似文献
10.
Silveira T. G. Teixeira A. L. J. Ferreira A. P. S. Monteiro P. M. N. P. 《Photonics Technology Letters, IEEE》2006,18(21):2212-2214
An all-optical setup to generate vestigial sideband signals based on self-phase modulation in a semiconductor optical amplifier is experimentally demonstrated at 10 Gb/s. Sideband suppressions higher than 15 dB are reported with improved eye opening. Wavelength-independent operation over 26 nm is demonstrated. Increased chromatic dispersion tolerance is verified: a receiver sensitivity penalty of 5.3 dB, relative to back-to-back, is obtained after transmission over 2720 ps/nm; whereas conventional double sideband is penalized by 4.0 dB after 1360 ps/nm 相似文献