全文获取类型
收费全文 | 258篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 62篇 |
金属工艺 | 7篇 |
机械仪表 | 8篇 |
建筑科学 | 6篇 |
矿业工程 | 1篇 |
能源动力 | 15篇 |
轻工业 | 23篇 |
无线电 | 12篇 |
一般工业技术 | 33篇 |
冶金工业 | 8篇 |
原子能技术 | 3篇 |
自动化技术 | 88篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 20篇 |
2012年 | 17篇 |
2011年 | 21篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1988年 | 3篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1911年 | 2篇 |
排序方式: 共有268条查询结果,搜索用时 15 毫秒
1.
2.
Salvatore Lombardo Salvatore Ugo Campisano 《Materials Science and Engineering: R: Reports》1996,17(8):739-336
We have investigated the relationship between microstructure and electrical conductivity in semi-insulating polycrystalline silicon (SIPOS) with oxygen concentrations in the 2–35 at.% range and the effect of doping with boron, phosphorus, arsenic and erbium by ion implantation. SIPOS thin films are mixtures of silicon and silicon oxide phases. The chemical and morphological evolution of these phases upon annealing is emphasized. Electrical conductivity measurements are interpreted in terms of a physical model containing few free parameters related to the material microstructure. A direct extension of this model explains also the conductivity increase in SIPOS doped with elements of the third or the fifth group. In the last part of the paper, data of electroluminescence at 1.54 μm in Er-implanted SIPOS due to intra-4f transitions of the Er3+ ion are shown and discussed. 相似文献
3.
This paper considers the behaviour of a two degree-of-freedom autonomous system with static and dynamic friction consisting of two blocks linked by springs on a moving belt. This system is the simplest model which has been used to simulate the dynamics of seismic faults. The friction force is assumed to be a decreasing function of the relative sliding velocity. The motion of the blocks is composed of a uniform stick motion, during which the divergence of the system is zero, and an accelerated slip motion, during which the divergence is positive. The mathematical model by definition concentrates the dissipation on the point where the slip motion ceases. It is assumed that slip occurs only in one direction. A three-dimensional Poincaré map and a scalar single variable map are discussed which characterize the dynamics of the system in a simple way. The one-dimensional map can be used to diagnose the chaotic behaviour of the full system, and quantities, similar to Lyapunov exponents, can be easily calculated which provide information regarding the system-sensitive dependence on initial conditions. The system dynamics illustrate the idea of studying the earthquake generation mechanism as a chaotic phenomenon. 相似文献
4.
Roberta Bomparola Alessandro Lavacchi Ugo Bardi 《Surface & coatings technology》2007,201(24):9485-9490
The influence of temperature on the kinetics and the morphology of silver deposits obtained from an air and water-stable ionic liquid (the 1-butyl-3-methyl imidazolium tetrafluoroborate) was studied by means of cyclic voltammetry and chronoamperometry. The nucleation and growth mechanisms have been investigated and the effect of temperature evaluated up to 200 °C. Dense, pure and very thin (about 0.3 μm) silver coatings, with decorative properties, have been obtained on commercial copper electrodes at different temperatures. The characterization of the deposits morphology has been performed by visual investigation and SEM microscopy. Data about thickness were acquired by Calotest® measurements. The deposits result constituted by pure silver as determined by combination of EDX microanalysis and Auger Electron Spectroscopy (AES). The deposition method promises to be a new, environmentally friendly, method for silver electrodeposition which is the reason for the absence of cyanide and volatile toxic solvents in the electroplating bath. 相似文献
5.
Konrad Grob Angelo Maria Giuffr Ugo Leuzzi Biagio Mincione 《European Journal of Lipid Science and Technology》1994,96(8):286-290
Recognition of adulteration by other oils via direct analysis of the minor components (“sterol fraction”) is shown for olive oil. 10 % of various oils were admixed, the free alcohols silylated and the minor components analyzed by on-line coupled LC-GC-FID. For most oils, even smaller additions can be recognized. Admixed oils can no longer be determined, however, if their minor components have been removed by strong raffination. Bleaching of rapeseed oil with 7% of earth at 180 °C, in fact, completely removed free and esterified sterols. 相似文献
6.
Mario Mariani Ugo Ravasio Armando Buttafava Antonio Faucitano 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,265(1):245-250
The effect of gamma irradiation in air is investigated in two thermoplastic polyesters (PET and PEN), in order to evaluate the influence of aromatic density and the role of oxygen on radiation resistance. EPR measurements were carried out to detect radical stability against oxygen permeation and to provide radical characterization. Viscometric data reveal a different behaviour between films and thick samples. Positron annihilation spectra show a decrease of ortho-positronium intensity, which is more marked in film samples. ortho-positronium lifetime does not depend on the radiation dose. 相似文献
7.
Ugo Andreaus Michele Colloca Daniela Iacoviello Marcello Pignataro 《Structural and Multidisciplinary Optimization》2011,43(1):43-59
The objective of this paper was solving the optimization problem of lightweight stiffened structures modelled as a two-dimensional
domain in an efficient computational way. The underlying premise was that mass should be distributed in an efficient way,
so as to use a minimum amount of material to accomplish the mechanical function. This premise was expressed as a global, multi-objective
optimization problem in which stiffness and mass were conflicting objectives. Alternative local evolution rules were implemented
to update mass density or Young’s modulus at each step of the iterative procedure. The solution of the structural optimization
problem was accomplished by a novel automatic procedure consisting of two consecutive stages of control and optimization.
In the first stage of Proportional Integral Derivative (PID) control gains were manually selected whereas in the second stage
the finding of optimal values of control gains, target, and cost indices was allowed. In this study a bone-like material was
adopted and a thin slab was analysed as a sample problem. 相似文献
8.
We define realizability semantics for Light Affine Logic (
LAL\mathsf{LAL}
) which has the property that denotations of functions are polynomial time computable by construction of the model. This gives
a new proof of polytime-soundness of
LAL\mathsf{LAL}
which is considerably simpler than the standard proof based on proof nets and is entirely semantical in nature. The model
construction uses a new instance of a resource monoid; a general method for interpreting systems based on Linear Logic introduced
earlier by the authors. 相似文献
9.
New, simple, proofs of soundness (every representable function lies in a given complexity class) for Elementary Affine Logic, LFPL and Soft Affine Logic are presented. The proofs are obtained by instantiating a semantic framework previously introduced by the authors and based on an innovative modification of realizability. The proof is a notable simplification on the original already semantic proof of soundness for the above mentioned logical systems and programming languages. A new result made possible by the semantic framework is the addition of polymorphism and a modality to LFPL, thus allowing for an internal definition of inductive datatypes. The methodology presented proceeds by assigning both abstract resource bounds in the form of elements from a resource monoid and resource-bounded computations to proofs (respectively, programs). 相似文献
10.
Paolo Baldan Fabio Gadducci Ugo Montanari 《Electronic Notes in Theoretical Computer Science》2007,176(1):85
In the theory of graph rewriting, the use of coalescing rules, i.e., of rules which besides deleting and generating graph items, can coalesce some parts of the graph, turns out to be quite useful for modelling purposes, but, at the same time, problematic for the development of a satisfactory partial order concurrent semantics for rewrites. Rewriting over graphs with equivalences, i.e., (typed hyper)-graphs equipped with an equivalence over nodes provides a technically convenient replacement of graph rewriting with coalescing rules, for which a truly concurrent semantics can be easily defined. The expressivity of such a formalism is tested in a setting where coalescing rules typically play a basic role: the encoding of calculi with name passing as graph rewriting systems. Specifically, we show how the (monadic fragment) of the solo calculus, one of the dialect of those calculi whose distinctive feature is name fusion, can be encoded as a rewriting system over graph with equivalences. 相似文献