全文获取类型
收费全文 | 943篇 |
免费 | 59篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 285篇 |
金属工艺 | 10篇 |
机械仪表 | 28篇 |
建筑科学 | 20篇 |
能源动力 | 25篇 |
轻工业 | 83篇 |
水利工程 | 10篇 |
石油天然气 | 3篇 |
无线电 | 101篇 |
一般工业技术 | 139篇 |
冶金工业 | 89篇 |
原子能技术 | 3篇 |
自动化技术 | 193篇 |
出版年
2023年 | 11篇 |
2022年 | 53篇 |
2021年 | 67篇 |
2020年 | 31篇 |
2019年 | 19篇 |
2018年 | 43篇 |
2017年 | 31篇 |
2016年 | 29篇 |
2015年 | 27篇 |
2014年 | 43篇 |
2013年 | 67篇 |
2012年 | 64篇 |
2011年 | 63篇 |
2010年 | 37篇 |
2009年 | 29篇 |
2008年 | 41篇 |
2007年 | 39篇 |
2006年 | 36篇 |
2005年 | 19篇 |
2004年 | 21篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 21篇 |
1998年 | 25篇 |
1997年 | 15篇 |
1996年 | 17篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1987年 | 5篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1977年 | 9篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1961年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1004条查询结果,搜索用时 93 毫秒
861.
Salvatore Serrano Giuseppe Campobello Alessandro Leonardi Sergio Palazzo Laura Galluccio 《Wireless Communications and Mobile Computing》2016,16(10):1192-1208
Support of Voice over Internet Protocol (VoIP) services in wireless mesh networks requires implementation of efficient policies to support low‐delay data delivery. Multipath routing is typically supported in wireless mesh networks at the network level to provide high fault tolerance and load balancing because links in the proximity of the wireless mesh gateways can be very stressed and overloaded, thus causing scarce performance. As a consequence of using multipath solutions, lower delay and higher throughput can be supported also when a given path is broken because of mobility or bad channel conditions, and alternative routes are available. This can be a relevant improvement especially when assuming that real‐time traffic, such as VoIP, travels into the network. In this paper, we address the problem of Quality of Service (QoS) support in wireless mesh networks and propose a multipath routing strategy that exploits the Mean Opinion Score (MOS) metric to select the most suitable paths for supporting VoIP applications and performing adaptive load balancing among the available paths to equalize network traffic. Performance results assess the effectiveness of the proposed approach when compared with other existing methodologies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
862.
Salvatore Montesanto Gianluca A. Mannella Francesco Carfì Pavia Vincenzo La Carrubba Valerio Brucato 《应用聚合物科学杂志》2015,132(26)
Diffusion Induced Phase Separation (DIPS) is a currently used technique to produce porous membranes for a large variety of applications. A strong limitation is represented by the occurrence of a dense skin, which is formed during the process, highly reducing the membrane permeability. To overcome this issue, two modifications of the standard DIPS protocol were investigated: the use of coagulation baths composed by a solvent/nonsolvent mixture and the desiccation in a controlled environment, by modulating the partial pressure of nonsolvent vapor. An appropriate choice of coagulation bath composition, together with an appropriate desiccation protocol (i.e., the use of a nonsolvent vapor), will produce a skinless membrane, and offers the chance to control the morphology of both membrane surfaces. These results underline the importance of post‐treatment stage in membrane preparation via phase separation, thus suggesting that membrane washing/drying stage will affect the final morphology. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42151. 相似文献
863.
Antonina Pirrotta Stefano Cutrona Salvatore Di Lorenzo Alberto Di Matteo 《International journal for numerical methods in engineering》2015,104(9):869-886
This paper deals with the response determination of a visco‐elastic Timoshenko beam under static loading condition and taking into account fractional calculus. In particular, the fractional derivative terms arise from representing constitutive behavior of the visco‐elastic material. Further, taking advantages of the Mellin transform method recently developed for the solution of fractional differential equation, the problem of fractional Timoshenko beam model is assessed in time domain without invoking the Laplace‐transforms as usual. Further, solution provided by the Mellin transform procedure will be compared with classical Central Difference scheme one, based on the Grunwald–Letnikov approximation of the fractional derivative. Moreover, Timoshenko beam response is generally evaluated by solving a couple of differential equations. In this paper, expressing the equation of the elastic curve just through a single relation, a more general procedure, which allows the determination of the beam response for any load condition and type of constraints, is developed. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
864.
Salvatore Petralia Tony Barbuzzi Giorgio Ventimiglia 《Materials science & engineering. C, Materials for biological applications》2012,32(4):848-850
Metal nanoparticles can be used in polymerase chain reaction methodology to optimize DNA amplification. In this paper, the effect of water soluble β-cyclodextrins capped platinum nanoparticles on polymerase chain reaction efficiency was reported for the first time. The capped nanoparticles were prepared by photochemical reduction of Platinum-acetylacetonate in presence of β-cyclodextrins. The PCR efficiency was evaluated in presence of different amounts of both capped nanoparticles and capping agent (β-cyclodextrins) as reference.The results demonstrated that the capped nanoparticles were able to increase the polymerase chain reaction efficiency mainly by metal thermal efficiency mechanism, whereas the capping agents themselves do not influence the DNA amplification. Capped nanoparticles are very promising for the efficiency improvement of Polymerase Chain Reaction, determining sensitivity improvement and allowing the reduction of the reagent's sample concentration. 相似文献
865.
Determination of amino acid enantiomers is a very important topic in food analysis, since the presence of d-isomers may indicate, e.g., adulteration, microbiological contamination, uncontrolled fermentation processes, etc. In fact, the d- and l-enantiomers contents can be a useful marker for several elements such as quality control, contamination detection, processing monitoring, etc. Here we studied the potentiality of nano-liquid chromatography (nano-LC) coupled with mass spectrometry for the enantiomeric separation of several d- and l-amino acids that can be found in food products. Analytes were derivatized with fluorescein isothiocyanate (FITC). The mixture was injected and compounds focused on a C18 cartridge, then nano-LC analysis was carried out in a capillary column (75 μm i.d.) packed with vancomycin-modified silica–diol particles. The effect of some experimental parameters, such as pH and buffer concentration on enantioresolution and retention factors, was studied for method optimization. The chromatographic separation system was coupled with an ion-trap mass spectrometer through a nano spray interface. It provided a final evaluation on analytes detected in all investigated samples with LOD values as low as 8 ng/mL. That method was applied to the comparative analysis of two different orange juice samples (fresh natural vs. commercial one). Obtained profiles confirmed expected high quality standards. In fact, they mainly contained l-amino acids forms and not their antipodes. 相似文献
866.
Pellegrino Musto Domenico Larobina Salvatore Cotugno Paolo Straffi Giuseppe Di Florio Giuseppe Mensitieri 《Polymer》2013,54(2):685-693
The reaction of zinc oxide (ZnO) with stearic acid (StA) to form zinc stearate (ZnSt) has been investigated experimentally in a model matrix (unvulcanized styrene–butadiene rubber) by using confocal Raman microscopy and FTIR transmission spectroscopy. The heterogeneous nature of the reacting system has been confirmed. The Raman analysis has revealed the core–shell structure of the product, which is formed via the gradual shrinkage of the ZnO core and the concurrent formation of a surrounding ZnSt shell of increasing thickness. FTIR spectroscopy has provided information about the molecular state of aggregation of StA when dissolved in the rubber, as well as quantitative information on the reaction kinetics. The kinetic behaviour of the system has been interpreted using a semi-quantitative heterogeneous reaction model grounded on the Raman imaging results, which was able to catch the essential features of the phenomenon and to simulate reliably the experimental conversion vs time data at three different temperatures. 相似文献
867.
Yingbo Song Michael E. Locasto Angelos Stavrou Angelos D. Keromytis Salvatore J. Stolfo 《Machine Learning》2010,81(2):179-205
Current trends demonstrate an increasing use of polymorphism by attackers to disguise their exploits. The ability for malicious
code to be easily, and automatically, transformed into semantically equivalent variants frustrates attempts to construct simple,
easily verifiable representations for use in security sensors. In this paper, we present a quantitative analysis of the strengths
and limitations of shellcode polymorphism, and describe the impact that these techniques have in the context of learning-based
IDS systems. Our examination focuses on dual problems: shellcode encryption-based evasion methods and targeted “blending”
attacks. Both techniques are currently being used in the wild, allowing real exploits to evade IDS sensors. This paper provides
metrics to measure the effectiveness of modern polymorphic engines and provide insights into their designs. We describe methods
to evade statistics-based IDS sensors and present suggestions on how to defend against them. Our experimental results illustrate
that the challenge of modeling self-modifying shellcode by signature-based methods, and certain classes of statistical models,
is likely an intractable problem. 相似文献
868.
869.
Vincenzo Cunsolo Vera Muccilli Rosaria Saletti Salvatore Foti 《Mass spectrometry reviews》2012,31(4):448-465
In the last decade, the improved performance and versatility of the mass spectrometers together with the increasing availability of gene and genomic sequence database, led the mass spectrometry to become an indispensable tool for either protein and proteome analyses in cereals. Mass spectrometric works on prolamins have rapidly evolved from the determination of the molecular masses of proteins to the proteomic approaches aimed to a large‐scale protein identification and study of functional and regulatory aspects of proteins. Mass spectrometry coupled with electrophoresis, chromatographic methods, and bioinformatics tools is currently making significant contributions to a better knowledge of the composition and structure of the cereal proteins and their structure–function relationships. Results obtained using mass spectrometry, including characterization of prolamins, investigation of the gluten toxicity for coeliac patients, identification of proteins responsible of cereal allergies, determination of the protein pattern and its modification under environmental or stress effects, investigation of genetically modified varieties by proteomic approaches, are summarized here, to illustrate current trends, analytical troubles and challenges, and suggest possible future perspectives. © 2011 Wiley Periodicals, Inc. Mass Spec Rev 31:448–465, 2012 相似文献
870.
Ivan Bartoli Salvatore Salamone Robert Phillips Francesco Lanza di Scalea Charles S. Sikorsky 《Canadian Metallurgical Quarterly》2011,137(5):324-333
This paper presents a technique developed on the basis of ultrasonic guided waves to monitor prestress levels in multiwire prestressing strands. The transducer layout identified for stress measurement is composed of an ultrasound excitation provided by a piezoelectric element bonded on a peripheral wire. Ultrasound detection is performed on the central and peripheral wires at the strand’s end. The ultrasonic feature used for stress monitoring is the interwire leakage between the peripheral and the central wire, occurring across the strand anchorage. A semianalytical finite-element analysis is first used to predict modal and forced wave solutions in seven-wire strands as a function of the applied prestress level. The numerical analysis accounts for the changing interwire contact as a function of applied loads and predicts the attenuation occurring in loaded strand when the wave travels across the anchorage. Results of load monitoring in free strands during laboratory tests are then presented. Finally, a statistical approach is used to enhance the sensitivity of the technique to stress level in the strands. The study presented focuses on unbonded tendons. However, the final goal of the research is to monitor prestress loss in bonded tendons that are found in the majority of the bridges built in California. 相似文献