全文获取类型
收费全文 | 1391篇 |
免费 | 67篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 41篇 |
化学工业 | 389篇 |
金属工艺 | 13篇 |
机械仪表 | 30篇 |
建筑科学 | 42篇 |
矿业工程 | 3篇 |
能源动力 | 75篇 |
轻工业 | 154篇 |
石油天然气 | 2篇 |
无线电 | 110篇 |
一般工业技术 | 303篇 |
冶金工业 | 35篇 |
原子能技术 | 26篇 |
自动化技术 | 237篇 |
出版年
2023年 | 10篇 |
2022年 | 35篇 |
2021年 | 88篇 |
2020年 | 37篇 |
2019年 | 36篇 |
2018年 | 46篇 |
2017年 | 27篇 |
2016年 | 49篇 |
2015年 | 50篇 |
2014年 | 54篇 |
2013年 | 112篇 |
2012年 | 95篇 |
2011年 | 110篇 |
2010年 | 98篇 |
2009年 | 69篇 |
2008年 | 78篇 |
2007年 | 58篇 |
2006年 | 58篇 |
2005年 | 43篇 |
2004年 | 46篇 |
2003年 | 32篇 |
2002年 | 36篇 |
2001年 | 16篇 |
2000年 | 22篇 |
1999年 | 16篇 |
1998年 | 26篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有1460条查询结果,搜索用时 15 毫秒
181.
Acoustic coupling in capacitive microfabricated ultrasonic transducers: modeling and experiments 总被引:1,自引:0,他引:1
Caronti A Savoia A Caliano G Pappalardo M 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2005,52(12):2220-2234
In the design of low-frequency transducer arrays for active sonar systems, the acoustic interactions that occur between the transducer elements have received much attention. Because of these interactions, the acoustic loading on each transducer depends on its position in the array, and the radiated acoustic power may vary considerably from one element to another. Capacitive microfabricated ultrasonic transducers (CMUT) are made of a two-dimensional array of metallized micromembranes, all electrically connected in parallel, and driven into flexural motion by the electrostatic force produced by an applied voltage. The mechanical impedance of these membranes is typically much lower than the acoustic impedance of water. In our investigations of acoustic coupling in CMUTs, interaction effects between the membranes in immersion were observed, similar to those reported in sonar arrays. Because CMUTs have many promising applications in the field of medical ultrasound imaging, understanding of cross-coupling mechanisms and acoustic interaction effects is especially important for reducing cross-talk between array elements, which can produce artifacts and degrade image quality. In this paper, we report a finite-element study of acoustic interactions in CMUTs and experimental results obtained by laser interferometry measurements. The good agreement found between finite element modeling (FEM) results and optical displacement measurements demonstrates that acoustic interactions through the liquid represent a major source of cross coupling in CMUTs. 相似文献
182.
183.
Stochastic simulation of hourly global radiation carried out with Auto-Regressive Moving Average and Factor Analysis techniques is found unable to describe the statistical features of time sequences. A Markov transition-matrix approach operating on atmospheric transmittance provides a simple yet effective simulation device. Two novel sophisticated models, the transmittance transition tensor and the Gaussian mapping technique are not justified in this context. 相似文献
184.
The use of on-line densimetry to monitor conversion in batch emulsion polymerization reactors are investigated. Some characteristics of the sampling circuit connecting the reactor to the densitometer, which allow one to obtain reliable on-line estimations of monomer conversion in the whole range of conversion, are discussed in detail. Moreover, the amount of collected data provides a practically continuous monitoring of the system evolution in time, which allows one to estimate directly the rate of conversion as a function of time. The technique has been applied both to homopolymerization systems [i.e., styrene (STY) and methyl methacrylate (MMA)] as well as to copolymerization systems [i.e., STY–MMA, acrylonitrile (ACN)–MMA, vinyl acetate (VAC)–MMA]. In the latter case, the density measurements are combined with a reliable model which provides for polymer composition as a function of conversion, in order to obtain accurate measurements of monomers conversion. © 1993 John Wiley & Sons, Inc. 相似文献
185.
Structure control, coating properties, and durability of fluorinated acrylic-based polymers 总被引:1,自引:0,他引:1
Valter Castelvetro Mauro Aglietto Francesco Ciardelli Oscar Chiantore Massimo Lazzari Lucia Toniolo 《Journal of Coatings Technology》2002,74(928):57-66
Fluorinated acrylates were employed for the synthesis of conventional, side-chain fluorinated, fully acrylic random copolymers,
and of more unusual hybrid copolymers with vinyl ethers. The latter can feature alternating structure and peculiar material
properties associated with fluorine or fluorinated groups substitution onto the polymer backbone. Improved efficacy and durability
of the resulting coating, highly desirable for the consolidation and protection of highly valued works of art, was achieved
through a systematic approach involving a detailed study of their photodegradation behavior, and extensive testing of protection
efficacy upon application onto micro-and macroporous stone substrates of different chemical composition and morphology.
Presented on behalf of FATIPEC (AITIVA) at the 78th Annual Meeting of the FSCT in Chicago, IL on October 16–20, 2000.
Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, 56126 Pisa, Italy.
Dipartimento di Chimica IFM, via Pietro Giuria 7, 10125 Torino, Italy.
Piazza Leonardo da Vinci 32, 20133 Milano, Italy, Lucia. 相似文献
186.
Andrea Baschirotto Enrico Dallago Massimo Ferri Piero Malcovati Andrea Rossini Giuseppe Venchi 《Measurement》2010
In this paper we present an Earth magnetic field measurement system and an automated acquisition setup to characterize it. The measurement system consists of a fluxgate sensor and an integrated front-end circuit, both realized in CMOS technology. The couple of orthogonal axes of the sensor makes the system suitable for realizing an electronic compass device. Indeed, we can measure not only the amplitude of the Earth magnetic field (whose full-scale value is of the order of 60 μT), but also its direction. The complete measurement system achieves a maximum angular error of 1.5° in the measurement of the Earth magnetic field direction. Furthermore, an acquisition setup was developed to evaluate the measurement system performance. It consists of a precision mechanical plastic structure, in tower form, a microcontroller-based interface circuit, that provides a digital output through an RS232 serial interface, a PC software suitably developed to post-process the data from the acquisition system and a couple of Helmholtz coils to evaluate the linearity of the system. This setup allows us to perform a completely automated and numerically controlled characterization of the measurement system. 相似文献
187.
Massimo F. Bertino Bernd Smarsly Antonio Stocco Arne Stark 《Advanced functional materials》2009,19(8):1235-1240
A technique is presented that allows for altering of the physical characteristics of films of TiO2 nanoparticles by exposure to visible light. In this technique, dye‐sensitized oxide nanoparticles are deposited on a substrate by dip‐coating. Photodissociation of the organic ligand layer leads to cross‐linking of the nanoparticles. Consequently, irradiated films have a decreased porosity, an increased index of refraction and an increased hydrophobicity. Films irradiated with green light are compared to films irradiated with UV light. Within experimental error, visible‐ and UV‐illumination induces the same changes in the films. The mechanism of surfactant elimination in dye‐sensitized oxide particles is discussed, patterning is demonstrated, and prospective applications of the technique are considered. 相似文献
188.
The impurities present in recombinant protein drugs produced by large-scale refolding processes can not only affect the product safety but also interact with the expressed protein. To relate the impurity profile to conformation and functionality of the protein drug, analytical methods able not to degrade the sample components should be preferred. In this work, an urate oxidase (uricase) drug from Aspergillus flavus expressed in Saccharomyces cerevisiae, and a reagent-grade uricase from Candida sphaerica expressed in Escherichia coli, are analyzed by combining hollow-fiber flow field-flow fractionation with matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI/TOFMS) and with chemiluminescence enzyme activity assay. Preliminary detection and identification of sample impurities is performed by means of conventional methods such as RP HPLC with electrospray ionization quadrupole-TOF MS and MALDI/TOFMS with SDS PAGE and 2D SDS PAGE. Results show that the recombinant uricase samples obtained from different microorganisms have different impurities and different enzymatic activity and that different uricase oligomers are present in solution. 相似文献
189.
190.