全文获取类型
收费全文 | 876篇 |
免费 | 57篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 256篇 |
金属工艺 | 9篇 |
机械仪表 | 23篇 |
建筑科学 | 21篇 |
能源动力 | 43篇 |
轻工业 | 55篇 |
水利工程 | 4篇 |
无线电 | 113篇 |
一般工业技术 | 161篇 |
冶金工业 | 37篇 |
原子能技术 | 2篇 |
自动化技术 | 196篇 |
出版年
2023年 | 12篇 |
2022年 | 35篇 |
2021年 | 61篇 |
2020年 | 30篇 |
2019年 | 30篇 |
2018年 | 30篇 |
2017年 | 22篇 |
2016年 | 48篇 |
2015年 | 17篇 |
2014年 | 38篇 |
2013年 | 69篇 |
2012年 | 45篇 |
2011年 | 74篇 |
2010年 | 58篇 |
2009年 | 66篇 |
2008年 | 57篇 |
2007年 | 36篇 |
2006年 | 34篇 |
2005年 | 31篇 |
2004年 | 17篇 |
2003年 | 17篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 17篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有934条查询结果,搜索用时 15 毫秒
111.
S. Fiameni A. Famengo F. Agresti S. Boldrini S. Battiston M. Saleemi M. Johnsson M. S. Toprak M. Fabrizio 《Journal of Electronic Materials》2014,43(6):2301-2306
Magnesium silicide (Mg2Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion in the middle–high temperature range. The detrimental effect of the presence of MgO on the TE properties of Mg2Si based materials is widely known. For this reason, the conditions used for synthesis and sintering were optimized to limit oxygen contamination. The effect of Bi doping on the TE performance of dense Mg2Si materials was also investigated. Synthesis was performed by ball milling in an inert atmosphere starting from commercial Mg2Si powder and Bi powder. The samples were consolidated, by spark plasma sintering, to a density >95%. The morphology, and the composition and crystal structure of samples were characterized by field-emission scanning electronic microscopy and x-ray diffraction, respectively. Moreover, determination of Seebeck coefficients and measurement of electrical and thermal conductivity were performed for all the samples. Mg2Si with 0.1 mol% Bi doping had a ZT value of 0.81, indicative of the potential of this method for fabrication of n-type bulk material with good TE performance. 相似文献
112.
This article uses document co-citation analysis to objectively explore the underlying structure of the intellectual property research domain, taken from a managerial and strategic standpoint. The goal of this study is identifying its main research areas, understanding its current state of development and suggesting potential future directions, by analyzing the co-citations from 181 papers published between 1992 and 2011 in the most influential academic journals. Five main clusters have been identified, mapped, and labeled as follows: Economics of patent system, technological and institutional capabilities, university patenting, intellectual property exploitation, and division of labor. Their most active areas on this topic, and the most influential and co-cited papers have been identified and described. Also, intra- and inter-cluster knowledge base diversity has been assessed by using indicators stemming from the domains of information theory and biology. A t test has been performed to assess the significance of the inter-cluster diversity. The knowledge bases of these five clusters are significantly diverse, this meaning that they are five co-existing paradigms. 相似文献
113.
Plasmonic Nanostructures: 3D Nanostar Dimers with a Sub‐10‐nm Gap for Single‐/Few‐Molecule Surface‐Enhanced Raman Scattering (Adv. Mater. 15/2014)
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
114.
Writing and Functionalisation of Suspended DNA Nanowires on Superhydrophobic Pillar Arrays
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ermanno Miele Angelo Accardo Andrea Falqui Monica Marini Andrea Giugni Marco Leoncini Francesco De Angelis Roman Krahne Enzo Di Fabrizio 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(1):134-140
Nanowire arrays and networks with precisely controlled patterns are very interesting for innovative device concepts in mesoscopic physics. In particular, DNA templates have proven to be versatile for the fabrication of complex structures that obtained functionality via combinations with other materials, for example by functionalisation with molecules or nanoparticles, or by coating with metals. Here, the controlled motion of the a three‐phase contact line (TCL) of DNA‐loaded drops on superhydrophobic substrates is used to fabricate suspended nanowire arrays. In particular, the deposition of DNA wires is imaged in situ, and different patterns are obtained on hexagonal pillar arrays by controlling the TCL velocity and direction. Robust conductive wires and networks are achieved by coating the wires with a thin layer of gold, and as proof of concept conductivity measurements are performed on single suspended wires. The plastic material of the superhydrophobic pillars ensures electrical isolation from the substrate. The more general versatility of these suspended nanowire networks as functional templates is outlined by fabricating hybrid organic–metal–semiconductor nanowires by growing ZnO nanocrystals onto the metal‐coated nanowires. 相似文献
115.
116.
Study of liquid sloshing: numerical and experimental approach 总被引:1,自引:0,他引:1
In this paper, sloshing phenomenon in a rectangular tank under a sway excitation is studied numerically and experimentally.
Although considerable advances have occurred in the development of numerical and experimental techniques for studying liquid
sloshing, discrepancies exist between these techniques, particularly in predicting time history of impact pressure. The aim
of this paper is to study the sloshing phenomenon experimentally and numerically using the Smoothed Particle Hydrodynamics
method. The algorithm is enhanced for accurately calculating impact load in sloshing flow. Experiments were conducted on a
1:30 scaled two-dimensional tank, undergoing translational motion along its longitudinal axis. Two different sloshing flows
corresponding to the ratio of exciting frequency to natural frequency were studied. The numerical and experimental results
are compared for both global and local parameters and show very good agreement. 相似文献
117.
Igor Maria De Rosa José M. KennyMohd. Maniruzzaman Md. MoniruzzamanMarco Monti Debora PugliaCarlo Santulli Fabrizio Sarasini 《Composites Science and Technology》2011,71(2):246-254
The effect of a number of chemical treatments on the mechanical (tensile), thermal (FTIR, TGA) and water absorption properties of okra (Abelmoschus esculentus) fibres has been studied. These included: bare scouring of the fibres; bleaching (pure, and followed by acetylation or alkalisation); pure acetylation; sodium sulphite; sulphuric acid with potassium permanganate. Tensile properties of the fibres were studied using Weibull statistics and correcting the values obtained by the void content measured from SEM images. A separate set of SEM images allowed also characterising their failure mode. The general trend of the results shows some decrease in mechanical properties by all treatments, although the effect is partially concealed by the high variation of fibre dimensions and the relative variation of void content. Fracture surfaces present an increased level of twisting as an effect of chemical modification resulting in reduced adhesion force between the fibrils, though seldom in their physical separation. Treatments involving acetylation result in limited fibre degradation, whilst bleaching, scouring and particularly permanganate treatment, though mechanically damaging for the fibres, have lower influence on their thermal behaviour. Water absorption profile is significantly improved by all applied treatments. 相似文献
118.
Fabrizio De MattiaIlaria Bruni Andrea GalimbertiFrancesca Cattaneo Maurizio CasiraghiMassimo Labra 《Food research international (Ottawa, Ont.)》2011,44(3):693-702
The objective of the present work is to evaluate the efficacy of a DNA barcoding approach as a tool for the recognition of commercial kitchen spices belonging to the Lamiaceae family that are usually sold as enhancers of food flavor. A total of 64 spices samples, encompassing six different genera (i.e. Mentha, Ocimum, Origanum, Salvia, Thymus and Rosmarinus) were processed with a classical DNA barcoding approach by amplifying and sequencing four candidate barcode regions (rpoB, rbcL, matK and trnH-psbA) with universal primers. Results suggest that the non-coding trnH-psbA intergenic spacer is the most suitable marker for molecular spices identification followed by matK, with interspecific genetic distance values ranging between about 0% to 7% and 0% to 5%, respectively. Both markers were almost invariably able to distinguish spices species from closest taxa with the exclusion of samples belonging to the genus Oregano. Moreover, in a context of food traceability the two markers are useful to identify commercial processed spice species (sold as dried plant material). We also evaluated the potential benefits of a multilocus barcode approach over a single-marker and although the most suitable combination was the matK + trhH-psbA, the observed genetic distances values were very similar to the discriminatory performance of the trnH-psbA. Finally, this preliminary work provide clear evidences that the efficacy of a DNA barcoding approach to the recognition of commercial spices is biased by the occurrence of taxonomic criticisms as well as traces of hybridization events within the family Lamiaceae. For this reason, to better define a more practical and standardized DNA barcoding tool for spices traceability, the building of a dedicated aromatic plants database in which all species and cultivars are described (both morphologically and molecularly) is strongly required. 相似文献
119.
Fabrizio Bezzo Francesco Micheletti Riccardo Muradore Massimiliano Barolo 《Journal of Process Control》2005,15(8):1609-930
The use of model predictive control (MPC) in middle-vessel continuous distillation column (MVCC) is discussed. It is shown that using a 5 × 5 MPC implementation (where all levels are included in MPC as integral process variables) allows using a smaller middle-vessel, particularly when disturbances can be measured: a good performance is ensured without having the middle vessel drained or overfilled. Also, it is shown that MPC practically circumvents the issue of tuning the middle-vessel level controller. Furthermore, the MVCC design makes conventional decentralised control perform comparably to MPC. 相似文献
120.