全文获取类型
收费全文 | 996篇 |
免费 | 70篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 8篇 |
综合类 | 7篇 |
化学工业 | 199篇 |
金属工艺 | 14篇 |
机械仪表 | 26篇 |
建筑科学 | 35篇 |
能源动力 | 59篇 |
轻工业 | 151篇 |
水利工程 | 15篇 |
石油天然气 | 2篇 |
无线电 | 153篇 |
一般工业技术 | 190篇 |
冶金工业 | 40篇 |
原子能技术 | 3篇 |
自动化技术 | 177篇 |
出版年
2024年 | 2篇 |
2023年 | 32篇 |
2022年 | 78篇 |
2021年 | 106篇 |
2020年 | 69篇 |
2019年 | 60篇 |
2018年 | 73篇 |
2017年 | 58篇 |
2016年 | 71篇 |
2015年 | 37篇 |
2014年 | 54篇 |
2013年 | 70篇 |
2012年 | 47篇 |
2011年 | 61篇 |
2010年 | 42篇 |
2009年 | 27篇 |
2008年 | 22篇 |
2007年 | 26篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有1079条查询结果,搜索用时 15 毫秒
1.
2.
Bushra Bashir Muhammad Usman Khalid Muhammad Aadil Sonia Zulfiqar Muhammad Farooq Warsi Philips O. Agboola Imran Shakir 《Ceramics International》2021,47(3):3603-3613
NiO nanostructure was synthesized using a simple co-precipitation method and was embedded on reduced graphene oxide surface via ultrasonication. Structural investigations were made through X-ray diffraction (XRD) and functional groups were confirmed by Fourier transform infrared spectroscopy (FTIR). XRD analysis revealed the grain size reduction with doping. Fourier transform infrared spectroscopy confirmed the presence of metal-oxygen bond in pristine and doped NiO nanostructure as well as the presence of carbon containing groups. Scanning electron microscopy (SEM) indicated that the particle size decreased when NiO nanostructure was doped with copper. BET surface area was found to increase almost up to 43 m2/g for Cu doped NiO nanostructure/rGO composite. Current-voltage measurements were performed using two probe method. UV–Visible spectroscopic profiles showed the blue and red shift for Cu doped NiO nanostructure and Cu doped NiO Nanostructure/rGO composite respectively. Rate constant for Cu doped NiO nanostructure/rGO composite found to increase 4.4 times than pristine NiO nanostructure. 相似文献
3.
AbstractIndustry 4.0 aims at providing a digital representation of a production landscape, but the challenges in building, maintaining, optimizing, and evolving digital models in inter-organizational production chains have not been identified yet in a systematic manner. In this paper, various Industry 4.0 research and technical challenges are addressed, and their present scenario is discussed. Moreover, in this article, the novel concept of developing experience-based virtual models of engineering entities, process, and the factory is presented. These models of production units, processes, and procedures are accomplished by virtual engineering object (VEO), virtual engineering process (VEP), and virtual engineering factory (VEF), using the knowledge representation technique of Decisional DNA. This blend of the virtual and physical domains permits monitoring of systems and analysis of data to foresee problems before they occur, develop new opportunities, prevent downtime, and even plan for the future by using simulations. Furthermore, the proposed virtual model concept not only has the capability of Query Processing and Data Integration for Industrial Data but also real-time visualization of data stream processing. 相似文献
4.
Fabrication and thermal characterization of a resistance temperature detector (RTD) heater and microthermocouples (MTs) on silicon substrates have been reported in this paper. The influence of film thickness and nickel-gold (Au) electroplating on RTD on its steady-state temperature with respect to its steady-state electrical power input and resistance is studied. Further, the thermal effects of multiple thermocouples in a thermopile as well as the effects of Au layers in the contact pads of the thermopiles on their open-circuit Seebeck voltage are studied. Therein lies the novelty of this paper. The in situ operating relationships for the RTD heater and the MT are provided 相似文献
5.
Algebraic properties of cryptosystem PGM 总被引:2,自引:0,他引:2
In the late 1970s Magliveras invented a private-key cryptographic system calledPermutation Group Mappings (PGM). PGM is based on the prolific existence of certain kinds of factorization sets, calledlogarithmic signatures, for finite permutation groups. PGM is an endomorphic system with message space ℤ|G| for a given finite permutation groupG. In this paper we prove several algebraic properties of PGM. We show that the set of PGM transformations ℐ
G
is not closed under functional composition and hence not a group. This set is 2-transitive on ℤ|G| if the underlying groupG is not hamiltonian and not abelian. Moreover, if the order ofG is not a power of 2, then the set of transformations contains an odd permutation. An important consequence of these results
is that the group generated by the set of transformations is nearly always the symmetric group ℒ|G|. Thus, allowing multiple encryption, any permutation of the message space is attainable. This property is one of the strongest
security conditions that can be offered by a private-key encryption system.
S. S. Magliveras was supported in part by NSF/NSA Grant Number MDA904-82-H0001, by U.S. West Communications, and by the Center
for Communication and Information Science of the University of Nebraska. 相似文献
6.
Imran N Junejo Xiaochun Cao Hassan Foroosh 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2007,37(4):803-816
In order to monitor sufficiently large areas of interest for surveillance or any event detection, we need to look beyond stationary cameras and employ an automatically configurable network of nonoverlapping cameras. These cameras need not have an overlapping field of view and should be allowed to move freely in space. Moreover, features like zooming in/out, readily available in security cameras these days, should be exploited in order to focus on any particular area of interest if needed. In this paper, a practical framework is proposed to self-calibrate dynamically moving and zooming cameras and determine their absolute and relative orientations, assuming that their relative position is known. A global linear solution is presented for self-calibrating each zooming/focusing camera in the network. After self-calibration, it is shown that only one automatically computed vanishing point and a line lying on any plane orthogonal to the vertical direction is sufficient to infer the dynamic network configuration. Our method generalizes previous work which considers restricted camera motions. Using minimal assumptions, we are able to successfully demonstrate promising results on synthetic, as well as on real data. 相似文献
7.
Kiani Azaz Ahmed Hafeez Yaser Imran Muhammad Ali Sadia 《The Journal of supercomputing》2021,77(8):8391-8432
The Journal of Supercomputing - Agile software development (ASD) and software product line (SPL) have shown significant benefits for software engineering processes and practices. Although both... 相似文献
8.
Radio frequency identification (RFID) tag delegation enables a centralized back-end server to delegate the right to identify
and authenticate a tag to specified readers. This should be used to mitigate the computational load on the server side and
also to solve the issues in terms of latency and dependency on network connectivity. In this study, we describe a basic RFID
delegation architecture and then under this model, we investigate the security of an RFID delegation protocol: Song Mitchell
delegation (SMD), which is recently proposed by Song and Mitchell. We point out security flaws that have gone unnoticed in
the design and present two attacks namely, a tag impersonation attack and a desynchronization attack against it. We also discover
a subtle flaw by which a delegated entity can still keep its delegation rights after the expire of them—this infringes security
policy of the scheme. More precisely, we show that the protocol will be still vulnerable to previously mentioned attacks,
even if the back-end server ends the delegation right of a delegated reader and update the secrets of the delegated tags.
To counteract such flaws, we improve the SMD protocol with a stateful variant so that it provides the claimed security properties. 相似文献
9.
A.c. susceptibility measurements were carried out on the disordered spinel system Co2–x
Zn
x
TiO4 (0<x<1) between 10 and 80 K. Our measurements show three peaks in the versus T curve for Co2TiO4 and CoZnTiO4 compounds. In both compounds two peaks are very close to each other, indicating that the Néel and semi-spin glass temperatures are very close. A third peak indicates the presence of the semi-spin glass to spin glass transition. In Co1.5Zn0.5TiO4 only one peak is observed which indicates spin glass ordering at 26 K. Furthermore, the A-site canting present in Co2TiO4 and CoZnTiO4 has a collinear and magnetic structure, indicating strong A-B coupling. X-ray analysis indicated that compounds of the system Co2ZnxTiO4 synthesized with cubic symmetry. From transport properties it was found that the activation energy and thermoelectric coefficient decrease with increasing concentration of Zn in the system. The mobility of the system calculated from infrared measurements is typically of the order of 10–9cm2V–1s–1. 相似文献
10.
The optical properties of vanadium-phosphate glasses containing various amounts of (V2O5)50(P2O5)50–x
(VCl3)
x
, wherex = 0.05, 0.06, 0.08 and 0.1, were measured as a function of VCl3 content. It is found that by adding VCl3 to the melt when the glass is formed, the added chlorine which acts as an oxidizing agent alters the ratio of concentration of vanadium ions and thus the absorption coefficient. Data on absorption in this study show that the power law,() =B() –E
0)
n
/ is best followed forn = 3, and the absorption is solely due to vanadium oxide. Furthermore, the infrared absorption spectra of this system were investigated in the wave number range 400 to 4600cm–1. The addition of VCl3 to the vanadium-phosphate glasses does not seem to introduce any new absorption band in this range as compared with the spectrum of a pure vanadium-phosphate glass. Furthermore, no significant difference in the absorption spectra was observed by annealing the V2O5-P2O5 glasses up to 200° C. 相似文献