全文获取类型
收费全文 | 2833篇 |
免费 | 196篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 60篇 |
综合类 | 1篇 |
化学工业 | 946篇 |
金属工艺 | 17篇 |
机械仪表 | 79篇 |
建筑科学 | 104篇 |
矿业工程 | 2篇 |
能源动力 | 87篇 |
轻工业 | 420篇 |
水利工程 | 27篇 |
石油天然气 | 5篇 |
无线电 | 235篇 |
一般工业技术 | 388篇 |
冶金工业 | 86篇 |
原子能技术 | 12篇 |
自动化技术 | 561篇 |
出版年
2023年 | 34篇 |
2022年 | 172篇 |
2021年 | 189篇 |
2020年 | 90篇 |
2019年 | 84篇 |
2018年 | 110篇 |
2017年 | 85篇 |
2016年 | 136篇 |
2015年 | 91篇 |
2014年 | 117篇 |
2013年 | 200篇 |
2012年 | 168篇 |
2011年 | 220篇 |
2010年 | 153篇 |
2009年 | 180篇 |
2008年 | 126篇 |
2007年 | 130篇 |
2006年 | 109篇 |
2005年 | 88篇 |
2004年 | 66篇 |
2003年 | 59篇 |
2002年 | 61篇 |
2001年 | 36篇 |
2000年 | 30篇 |
1999年 | 24篇 |
1998年 | 32篇 |
1997年 | 23篇 |
1996年 | 31篇 |
1995年 | 16篇 |
1994年 | 27篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 18篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 2篇 |
1965年 | 2篇 |
1909年 | 2篇 |
排序方式: 共有3030条查询结果,搜索用时 15 毫秒
951.
952.
The contexts of real use of information technology (IT) tools may be highly specific. Their distinctive features, especially normative and informational influences related to the social roles involved, can affect deeply both design and actual use of the artefact. Analysis and evaluation of the ongoing human-artefact interaction, particularly in systems addressed to multi-actor multi-goal environments like Vocational Guidance Systems (VGS), should thus be viewed as basically context-dependent. Studying three types of VGS (currently developed and running in public and private vocational agencies in Northern Italy), we constructed a taxonomy connecting types of systems and types of social environments, in order to explain differences between systems in design, communication and outcome. To assess the characteristics of the different types of VGS as dialogue tools, we considered their Social Design Structure (SDS) and Operating Social Structure (OSS), connecting steps and distance in each user-artefact interaction to the flow of the communication processes between designers, VG officers, and final users. 相似文献
953.
954.
955.
Clelia Dispenza Giuseppe Tripodo Caterina LoPresti Giuseppe Spadaro Gaetano Giammona 《Reactive and Functional Polymers》2009,69(8):565-575
A family of poly(amino acid)-maleic anhydride hydrogels were designed and synthesized. Water soluble polymeric precursors were prepared by partially substituting the hydroxyl groups of the α,β-poly(N-2-hydroxyethyl)-dl-aspartamide backbone with maleic anhydride, so as to provide double bonds for crosslinking and carboxylic acid groups for pH and electric field responsiveness. Reaction conditions (reactive mixture composition and catalysis) were systematically varied in order to obtain PHEA–MA precursors with different and reliable graft-maleic anhydride levels. PHEA–MA precursors were characterised by titration, Nuclear Magnetic Resonance (1H NMR), Fourier-Transformed Infrared Spectroscopy (FTIR) and Size Exclusion Chromatography (SEC) for structural and molecular determination. Aqueous solutions of selected PHEA–MA precursors were subjected to gamma-irradiation at different irradiation doses and polymer to water concentrations in order to induce chemical crosslinking without the addition of crosslinking agents. The yield of crosslinking reactions was evaluated by solubility tests as well as the effect of ammonium persulphate, as assistant radical initiator for gamma crosslinking. Selected hydrogels were tested through swelling measurements to prove their pH and electric field responsiveness. Structural features of the different variants produced were related to the swelling behaviour. 相似文献
956.
Luca Repetto Renato BuzioCarlo Denurchis Giuseppe FirpoEmanuele Piano Ugo Valbusa 《Ultramicroscopy》2009
A quantitative surface reconstruction technique has been developed for the geometric characterization of three-dimensional structures by using a combined focused ion beam—scanning electron microscopy (FIB–SEM) instrument. A regular pattern of lines is milled at normal incidence on the sample to be characterized and an image is acquired at a large tilt angle. By analyzing the pattern under the tilted view, a quantitative estimation of surface heights is obtained. The technique has been applied to a test sample and nanoscale resolution has been achieved. The reported results are validated by a comparison with atomic force microscopy measurements. 相似文献
957.
Multi-objective optimization by genetic algorithm of structural systems subject to random vibrations 总被引:1,自引:0,他引:1
Giuseppe Carlo Marano Giuseppe Quaranta Rita Greco 《Structural and Multidisciplinary Optimization》2009,39(4):385-399
This paper deals with a multi-objective optimization criterion for linear viscous-elastic device utilised for decreasing vibrations
induced in mechanical and structural systems by random loads. The proposed criterion for the optimum design is the minimization
of a vector objective function. The multi-objective optimization is carried out by means of a stochastic approach. The design
variables are the device frequency and the damping ratio. As cases of study, two different problems are analysed: the base
isolation of a rigid mass and the tuned mass damper positioned on a multi degree of freedom structural system subject to a
base acceleration. The non-dominated sorting genetic algorithm in its second version (NSGA-II) is adopted to obtain the Pareto
sets and the corresponding optima for different characterizations of the system and input. 相似文献
958.
Giuseppe Ferro Alberto Carpinteri Giulio Ventura 《International Journal of Fracture》2007,146(4):213-231
The problem of the assessment of minimum reinforcement in concrete members has been examined both theoretically and experimentally
by the bridged crack model. The model has been demonstrated to be an efficient numerical tool for investigating the behavior
of structural elements in bending, and allowed to show the minimum reinforcement percentage depends on the structural element
size, and decreases with increasing beam depths. In the model, Linear Elastic Fracture Mechanics concepts are used to determine
the equilibrium and the compatibility equations of a beam segment subjected to bending in presence of a mode I crack. Recently,
the model has been extended to include the presence of closing stresses as a function of the crack opening in addition to
steel reinforcement closing traction. This allows to characterize the mechanical behavior of fiber reinforced structural elements.
A criterion for accounting for crushing in compression has been introduced as well, to bound from below (minimum reinforcement)
and from above (maximum reinforcement) a region of stable and ductile mechanical behavior as a function of the mechanical
properties as well as of the size of the structural element. Some experimental results are commented under this light. 相似文献
959.
960.
Giuseppe Razzano Francesco Delli Priscoli Roberto Cusani 《Wireless Personal Communications》2006,39(1):25-40
The paper describes the design and simulation of a radio modem architecture, which provides wireless access to Internet in a single-hop, ad hoc network.The main emphasis is on the Medium Access Control (MAC) and Dynamic Link Control (DLC) layer’s design, and in particular on the adopted innovative scheduling algorithm, which has been developed to satisfy the system requirements of the WIND-FLEX radio modem. The algorithm is presented and compared to the Earliest Deadline First (EDF) solution.Several software simulation tests have been executed on the network, to test the performance of the system, in order to verify the capability of the scheduler algorithm to satisfy the expected requirements and the efficiency of the implemented solutions.
Giuseppe Razzano was born in Roma, Italy, in 1974. He has graduated in Electronic Engineering “summa cum laude” and has received PhD in Communication Systems and Computer Science, in 2004 from University of Rome “La Sapienza”. From 2000 to 2001 he worked as research assistant at VTT electronics, in Finland. From 2004 to 2005 he worked as senior researcher at Forschungzentrum Telekommunikation Wien (Telecommunication Research Centre Vienna) in Austria. Currently, he works as System Engineer for Vitrociset S.p.A., working in a project funded by European Space Agency (ESA), for the development of a new generation space launcher vehicle (VEGA). In the past years, he worked in several projects funded by EC within the IST (Information Societies Technology) program, being also involved in projects in collaboration with Italian companies. His research is focused on resource management algorithms for wireless LANs and cellular networks. He is also interested in object-oriented programming and development methodologies. In these fields, he is author of several papers published in international journals and conferences.
Francesco Delli Priscoli was born in Rome in 1962. He graduated in Electronic Engineering “summa cum laude” from the University of Rome “La Sapienza” in 1986. He received the Ph.D. in system engineering from the University of Rome “La Sapienza” in 1991. From 1986 to 1991 he worked in the “Studies and Experimentation” Department of Telespazio (Rome). Since 1991 he is working for the University of Rome “La Sapienza” where, at present, he is “Full Professor” and holds the courses “Automatic Controls”, “System Theory” and “Network Control and Management I and II”. In the framework of his activity, he researches in the nonlinear control theory and in the area of control-based resource management procedures for the third and forth generation of mobile systems. He is the author of about 150 technical papers on the above topics appeared on major international reviews (about 50) and conferences (about 100). In 2000 he has been scientific consultant for the Italian Council of Ministers in the framework of the auction for the assignment of the Italian Universal Mobile Telecommunication System (UMTS) licensees. He is an associate editor of Control Engineering Practice and a member of the IFAC Technical Committee on “Networked Systems”. He is/has been scientific responsible, for the University of Rome “La Sapienza”, of 17 projects financed by the European Union (fourth, fifth and sixth framework programmes) or by the European Space Agency (ESA), dealing with resource management for UMTS and broadband terrestrial and satellite wireless systems. He is also a project evaluator for the European Commission.
Roberto Cusani received the “laurea” degree in Electronic Engineering (cum laude) and the Ph.D. in Communication Systems and Computer Science from the University of Rome “La Sapienza”. From 1986 to 1990 he was research engineer at the University of Rome “Tor Vergata”, teaching Digital Signal Processing. In 1991 he joined the University of Rome “La Sapienza” as Associate Professor of Signal Theory. In 2000 he becomes Full Professor and teaches Information Theory and Coding, and Mobile Communications. His former research activities concern transmission and coding of signals and images, with emphasis on random processes, spectral estimation and image coding. Since 1992 he focused his activities in the field of the digital communication systems, with emphasis on channel equalisation and coding for HF and radio-mobile (GSM) links, on the design of CDMA receivers for UMTS and, in general, on the use of digital techniques within telecommunication equipments. More recently his interests also includes the study of MAC (Multiple Access Control) protocols with application to wireless area networks (WLANs), reconfigurable ad-hoc networks and satellite links. He is author of more than 100 publications in international journals and conferences, of the text-book “Teoria dei Segnali” and of five patents regarding telecommunication applications. He was involved in many research programs, both national and international, and in projects with the industrie. 相似文献