全文获取类型
收费全文 | 724篇 |
免费 | 39篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 199篇 |
金属工艺 | 6篇 |
机械仪表 | 18篇 |
建筑科学 | 40篇 |
矿业工程 | 1篇 |
能源动力 | 40篇 |
轻工业 | 117篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 25篇 |
一般工业技术 | 112篇 |
冶金工业 | 28篇 |
原子能技术 | 4篇 |
自动化技术 | 153篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 25篇 |
2019年 | 31篇 |
2018年 | 31篇 |
2017年 | 43篇 |
2016年 | 43篇 |
2015年 | 27篇 |
2014年 | 22篇 |
2013年 | 65篇 |
2012年 | 41篇 |
2011年 | 41篇 |
2010年 | 38篇 |
2009年 | 43篇 |
2008年 | 30篇 |
2007年 | 27篇 |
2006年 | 32篇 |
2005年 | 21篇 |
2004年 | 20篇 |
2003年 | 13篇 |
2002年 | 20篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有765条查询结果,搜索用时 15 毫秒
51.
52.
The use of a feedback loop to regulate the slip frequency of an inverter-driven induction machine is viewed as replacing the normal independent control of stator frequency with independent control of slip frequency. For steady-state conditions the two modes of operation are shown to produce characteristics analogous to shunt and series dc machines. A method employing closed-form transfer functions, a reduced set of nondimensional parameters, and a general root locus diagram is used to present the dynamic characteristics of controlled slip frequency operation and to compare performance with conventional operation. The parameter range in the general diagram is sufficient to incorporate nearly all standard induction machines over a wide size and frequency range. The results demonstrate that the ratio K? of the rotor transient time constant to the static electromechanical time constant is a critical parameter in the comparison of the two modes. Since this parameter tends to increase with machine size, the relative advantages of slip frequency control are shown to be machine-size dependent. Inclusion of a speed-control loop regulating machine voltage is also Considered and shown to be described by the same general root loci. The performance of this closed-loop system is also shown to be very dependent on K? and hence on machine size. 相似文献
53.
D. Anibal Garcia-hernandez Arturo Manchado 《Fullerenes, Nanotubes and Carbon Nanostructures》2016,24(3):225-233
The iron carbonyl complexes with C60 and C70 fullerenes were synthesized in high yield by photochemical irradiation of solutions of C60 and C70 in presence of Fe(CO)5. The resulting complexes were studied by FT-IR, Raman and electronic absorption spectroscopy. All the data are consistent with the structures [Fe(CO)4(η2C60)] and [Fe(CO)4(η2C70)]. The thermal stability and decomposition reaction of the two complexes were studied by TGA-FTIR and Differential Scanning Calorimetry (DSC). Both complexes decompose at moderate temperatures releasing CO and Fe(CO)5 in the vapor phase leaving a residue of metallic iron and free C60 or C70 fullerenes that can be recovered by solvent extraction of the decomposition residue. 相似文献
54.
Franco Cataldo Mihai V. Putz Ornella Ursini Giancarlo Angelini D. Anibal Garcia-Hernandez Arturo Manchado 《Fullerenes, Nanotubes and Carbon Nanostructures》2016,24(3):195-201
It is shown that graphite oxide (GO) and both heavily ozonized C60 and C70 fullerenes, known as “fullerene ozopolymers,” are paramagnetic materials with a very strong electron spin resonance (ESR) signal at room temperature. When thermally annealed, the paramagnetic centers are gradually lost in large part. This occurs at 350°C in the case of GO, while for fullerene ozopolymers, a higher temperature is required, reaching the same results in the end. The half-width of ESR signal is linked to the distribution of paramagnetic centers. Once again, striking analogies were found in the half-width of the ESR signal measured on GO and fullerene ozopolymers, at least in the temperature range of 25–450°C. Similarly, the same g-factor values, which are diagnostic for understanding the chemical nature of paramagnetic centers, were found on both GO and fullerene ozopolymers in all ranges of temperature considered. 相似文献
55.
Miguel Á. García-Cumbreras Arturo Montejo-Ráez Manuel C. Díaz-Galiano 《Expert systems with applications》2013,40(17):6758-6765
This work presents a novel application of Sentiment Analysis in Recommender Systems by categorizing users according to the average polarity of their comments. These categories are used as attributes in Collaborative Filtering algorithms. To test this solution a new corpus of opinions on movies obtained from the Internet Movie Database (IMDb) has been generated, so both ratings and comments are available. The experiments stress the informative value of comments. By applying Sentiment Analysis approaches some Collaborative Filtering algorithms can be improved in rating prediction tasks. The results indicate that we obtain a more reliable prediction considering only the opinion text (RMSE of 1.868), than when apply similarities over the entire user community (RMSE of 2.134) and sentiment analysis can be advantageous to recommender systems. 相似文献
56.
Martin Enrique Romero-Sanchez Raul Ponce-Hernandez Steven E. Franklin Carlos Arturo Aguirre-Salado 《International journal of remote sensing》2013,34(11):2786-2799
A number of methods to overcome the 2003 failure of the Landsat 7 Enhanced Thematic Mapper (ETM+) scan-line corrector (SLC) are compared in this article in a forest-monitoring application in the Yucatan Peninsula, Mexico. The objective of this comparison is to determine the best approach to accomplish SLC-off image gap-filling for the particular landscape in this region, and thereby provide continuity in the Landsat data sensor archive for forest-monitoring purposes. Four methods were tested: (1) local linear histogram matching (LLHM); (2) neighbourhood similar pixel interpolator (NSPI); (3) geostatistical neighbourhood similar pixel interpolator (GNSPI); and (4) weighted linear regression (WLR). All methods generated reasonable SLC-off gap-filling data that were visually consistent and could be employed in subsequent digital image analysis. Overall accuracy, kappa coefficients (κ), and quantity and allocation disagreement indices were used to evaluate unsupervised Iterative Self-Organizing Data Analysis (ISODATA) land-cover classification maps. In addition, Pearson correlation coefficients (r) and root mean squares of the error (RMSEs) were employed for estimates agreement with fractional land cover. The best results visually (overall accuracy > 85%, κ < 9%, quantity disagreement index < 5.5%, and allocation disagreement index < 12.5%) and statistically (r > 0.84 and RMSE < 7%) were obtained from the GNSPI method. These results suggest that the GNSPI method is suitable for routine use in reconstructing the imagery stack of Landsat ETM+ SLC-off gap-filled data for use in forest-monitoring applications in this type of heterogeneous landscape. 相似文献
57.
Pedro Peris-Lopez Julio Cesar Hernandez-Castro Juan M. Estevez-Tapiador Arturo Ribagorda 《Computer Standards & Interfaces》2009,31(1):88-97
RFID is a relatively heterogenous radio technology, where it is necessary to put an extra effort on security and privacy-related issues. As early as 2004, some authors suggested the use of a PRNG for increasing security. This was later questioned because many thought a PRNG implementation may go well beyond the very limited computational capabilities of low-cost RFID tags. However, its use has been ratified by EPCGlobal (EPC Class-1 Generation-2) and ISO (ISO/IEC 18000-6C). This motivates our proposal of a new PRNG, named LAMED, which is compliant with the standards and successfully passes several batteries of very demanding randomness tests (ENT, DIEHARD, NIST, and SEXTON). A study of its hardware complexity shows that LAMED can be implemented with slightly less than 1.6 K gates, and that pseudo-random numbers can be generated each 1.8 ms. So we can affirm this is a realist proposal both conforming with the EPC-G1C2 standard, and suitable for low-cost RFID tags. 相似文献
58.
Arturo B. Soro Paul Whyte Declan J. Bolton Brijesh K. Tiwari 《Comprehensive Reviews in Food Science and Food Safety》2020,19(4):1353-1377
Campylobacteriosis is one of the most common bacterial infections worldwide causing economic costs. The high prevalence of Campylobacter spp. in poultry meat is a result of several contamination and cross‐contamination sources through the production chain. Moreover, survival mechanisms, such as biofilm formation, viable but nonculturable state, and antimicrobial resistance, enable its persistence during food processing. Therefore, mitigation strategies are necessary in order to avoid and/or inactivate Campylobacter at farm, abattoir, industry, and retail level. In this review, a number of potential strategies and novel technologies that could reduce the prevalence of Campylobacter in poultry meat have been identified and evaluated to provide a useful overview. At farm level for instance, biosecurity, bacteriocins, probiotics, feed and water additives, bacteriophages, and vaccination could potentially reduce colonization in chicken flocks. However, current technologies used in the chicken slaughter and processing industry may be less effective against this foodborne pathogen. Novel technologies and strategies such as cold plasma, ultraviolet light, high‐intensity light pulses, pulsed electric fields, antimicrobials, and modified atmosphere packaging are discussed in this review for reducing Campylobacter contamination. Although these measures have achieved promising results, most have not been integrated within processing operations due to a lack of knowledge or an unwillingness to implement these into existing processing systems. Furthermore, a combination of existing and novel strategies might be required to decrease the prevalence of this pathogen in poultry meat and enhance food safety. Therefore, further research will be essential to assess the effectiveness of all these strategies. 相似文献
59.
Rosendo PEA-EGUILUZ Jos A LPEZ-FERNNDEZ Antonio MERCADO-CABRERA Bethsabet JARAMILLO-SIERRA Rgulo LPEZ-CALLEJAS Benjamn RODRGUEZ-MNDEZ Ral VALENCIA-ALVARADO Allan A FLORES-FUENTES Arturo E MUOZ-CASTRO 《等离子体科学和技术》2017,19(7)
A new configuration of a resonant full-bridge flying capacitor multicell inverter has been designed and constructed with the aim of achieving an extended output voltage frequency range with low harmonic distortion and reduced semiconductor commutation losses. This configuration was tested as a power supply for two different coaxial dielectric barrier discharge reactors, one of them employed for electric characterization and the other one for inorganic compound elimination in an aqueous solution. Two different gas mixtures, 90% Ar–10% O_2 and80% Ar–20% O_2, were individually supplied during the experiments; the results showed a highefficiency removal of meta-cresol(m-cresol) to the order of 98%, which was obtained by adding more oxygen to the plasma gas mixture. 相似文献
60.
Mélanie Lé‐Magda Eric Dargent Jorge Arturo Soto Puente Alain Guillet Emmanuelle Font Jean‐Marc Saiter 《应用聚合物科学杂志》2013,130(2):786-792
Very long aging times, up to 15,100 h (629 days) at 110°C, were achieved on flame‐retardant printed circuit board laminates commonly used in automotive design. This composite was fabricated from glass fibers embedded in an epoxy resin. Aging was performed in an oven under an air atmosphere at a temperature lower than the glass‐transition temperature. Temperature‐modulated differential scanning calorimetric analysis was used to investigate the influence of such aging on the glass‐transition phenomena. A new amorphous phase appeared during aging. By extending the analysis to samples collected at different thicknesses, we demonstrated the existence of a time‐dependent gradient of the properties. A skin–core structure was evidenced, and this slowed down oxidation and allowed physical aging to occur in the bulk sample. An exponential law described the variations of the glass‐transition of the new external compound. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 786‐792, 2013 相似文献