全文获取类型
收费全文 | 2042篇 |
免费 | 156篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 789篇 |
金属工艺 | 19篇 |
机械仪表 | 27篇 |
建筑科学 | 72篇 |
矿业工程 | 1篇 |
能源动力 | 54篇 |
轻工业 | 367篇 |
水利工程 | 17篇 |
石油天然气 | 5篇 |
无线电 | 113篇 |
一般工业技术 | 329篇 |
冶金工业 | 144篇 |
原子能技术 | 12篇 |
自动化技术 | 237篇 |
出版年
2023年 | 21篇 |
2022年 | 163篇 |
2021年 | 240篇 |
2020年 | 86篇 |
2019年 | 69篇 |
2018年 | 77篇 |
2017年 | 64篇 |
2016年 | 91篇 |
2015年 | 72篇 |
2014年 | 103篇 |
2013年 | 147篇 |
2012年 | 113篇 |
2011年 | 143篇 |
2010年 | 106篇 |
2009年 | 84篇 |
2008年 | 86篇 |
2007年 | 81篇 |
2006年 | 60篇 |
2005年 | 61篇 |
2004年 | 45篇 |
2003年 | 31篇 |
2002年 | 29篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 48篇 |
1997年 | 36篇 |
1996年 | 29篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 1篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有2199条查询结果,搜索用时 15 毫秒
41.
42.
Controllability questions for discrete-time nonlinear systems are addressed in this paper. In particular, we continue the search for conditions under which the group-like notion of transitivity implies the stronger and semigroup-like property of forward accessibility. We show that this implication holds, pointwise, for states which have a weak Poisson stability property, and globally, if there exists a global attractor for the system.This research was supported in part by US Air Force Grant AFOSR-91-0346, and also by an INDAM (Istituto Nazionale di Alta Matematica Francesco Severi, Italy) fellowship. 相似文献
43.
Gianmarco de Felice Maria Antonietta Aiello Carmelo Caggegi Francesca Ceroni Stefano De Santis Enrico Garbin Natalino Gattesco Łukasz Hojdys Piotr Krajewski Arkadiusz Kwiecień Marianovella Leone Gian Piero Lignola Claudio Mazzotti Daniel Oliveira Corina Papanicolaou Carlo Poggi Thanasis Triantafillou Maria Rosa Valluzzi Alberto Viskovic 《Materials and Structures》2018,51(4):95
Textile Reinforced Mortar (TRM), also known as Fabric Reinforced Mortar or Fabric Reinforced Cementitious Matrix, composites are an emerging technology for the external repair and strengthening of existing structures. For most applications, the effectiveness of the TRM reinforcement relies on its bond performance. This recommendation identifies the best practice to characterize the bond behaviour of TRM. A shear bond test method is proposed to determine the peak axial stress (associated with the maximum load that can be transferred from the structural member to the externally bonded TRM reinforcement), the stress–slip relationship and the failure mode that controls the TRM-to-substrate load transfer capacity. Guidelines on specimen manufacturing, experimental setup, test execution, and determination of test results are provided. 相似文献
44.
Daniel Vázquez-Nion Federica Troiano Patricia Sanmartín Chiara Valagussa Francesca Cappitelli Beatriz Prieto 《Materials and Structures》2018,51(6):158
Salt crystallisation is a very common and powerful weathering agent that can modify the petrophysical properties of building stone such as granite. In addition, the weathering can affect the susceptibility of the stone to biological colonisation. The aims of the present study were to examine the properties of a granite weathered by sodium chloride crystallisation and to evaluate the effects of the weathering on the secondary bioreceptivity of the stone to subaerial phototrophic biofilms. For this purpose, granite samples were subjected to a laboratory-based accelerated salt weathering test, and changes in weight, open porosity, bulk density, capillary water content, abrasion pH and surface roughness of the samples were determined. Samples of both weathered and non-weathered granite were then inoculated with a multi-species phototrophic culture derived from a natural subaerial biofilm and incubated under standardised laboratory conditions for 3 months. The weight loss produced by the weathering process was consistent with significant changes in abrasion pH and surface roughness. The bioreceptivity of the stone was also altered. According to the bioreceptivity index, the granite under study was characterised by ‘mild primary bioreceptivity’, but ‘high secondary bioreceptivity’ after the salt weathering process. Study of the secondary bioreceptivity of stone materials can provide very useful information about response to weathering effects, and the findings can be used to improve the selection of materials for building purposes. 相似文献
45.
A solid state bonding technique under hot pressing was used for joining alumina with thin metal sheets of Ni, Cu and Fe. The microstructure and microchemistry of the ceramic–metal interface and of the fracture interface were examined using scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), in order to identify the adhesion mechanisms and the nature of strength limiting flaws. Interaction between the selected metals and alumina can be physical or physico-chemical in nature: very low amounts of interfacial compounds were formed, depending on the processing conditions and on the presence of oxygen in the system. Fracture and toughness tests indicated that high ceramic–metal interface strengths (up to 177 MPa) were achieved under the adopted processing conditions and that strength and toughness were directly related. Moreover, an increase in hardening in the metal interlayer at a distance of 2–3 m from the interface was observed in the samples with high strength values. The mechanical behaviour was related to several factors that strongly depend on the bonding conditions: plastic deformation of the metal, metal creep, metal intrusion and diffusion into alumina, and chemical reactions at the interface. © 1998 Chapman & Hall 相似文献
46.
Abstract argumentation 总被引:1,自引:0,他引:1
In this paper we explore the thesis that the role of argumentation in practical reasoning in general and legal reasoning in particular is to justify the use of defeasible rules to derive a conclusion in preference to the use of other defeasible rules to derive a conflicting conclusion. The defeasibility of rules is expressed by means of non-provability claims as additional conditions of the rules.We outline an abstract approach to defeasible reasoning and argumentation which includes many existing formalisms, including default logic, extended logic programming, non-monotonic modal logic and auto-epistemic logic, as special cases. We show, in particular, that the admissibility semantics for all these formalisms has a natural argumentation-theoretic interpretation and proof procedure, which seem to correspond well with informal argumentation.In the admissibility semantics there is only one way for one argument to attack another, namely by undermining one of its non-provability claims. In this paper, we show how other kinds of attack between arguments, specifically how rebuttal and priority attacks, can be reduced to the undermining of non-provability claims. 相似文献
47.
48.
Maria Elena Bruni Francesca Guerriero 《International Transactions in Operational Research》2010,17(2):207-220
The aim of this paper is to investigate the use of heuristic information to efficiently solve to optimality the robust shortest path problem. Starting from the exact algorithm proposed by Murty and Her, we describe how this algorithm can be enhanced by using heuristic rules and evaluation functions to guide the search. The efficiency of the proposed enhanced approach is tested over a range of random generated instances. Our computational results indicate that the use of heuristic criteria is able to speed up considerably the search and that the enhanced exact solution method outperforms the state‐of‐the‐art algorithm proposed by Murty and Her in most of the instances. 相似文献
49.
Markov Logic (ML) combines Markov networks (MNs) and first-order logic by attaching weights to first-order formulas and using
these as templates for features of MNs. State-of-the-art structure learning algorithms in ML maximize the likelihood of a
database by performing a greedy search in the space of structures. This can lead to suboptimal results because of the incapability
of these approaches to escape local optima. Moreover, due to the combinatorially explosive space of potential candidates these
methods are computationally prohibitive. We propose a novel algorithm for structure learning in ML, based on the Iterated
Local Search (ILS) metaheuristic that explores the space of structures through a biased sampling of the set of local optima.
We show through real-world experiments that the algorithm improves accuracy and learning time over the state-of-the-art algorithms.
On the other side MAP and conditional inference for ML are hard computational tasks. This paper presents two algorithms for
these tasks based on the Iterated Robust Tabu Search (IRoTS) metaheuristic. The first algorithm performs MAP inference and
we show through extensive experiments that it improves over the state-of-the-art algorithm in terms of solution quality and
inference time. The second algorithm combines IRoTS steps with simulated annealing steps for conditional inference and we
show through experiments that it is faster than the current state-of-the-art algorithm maintaining the same inference quality. 相似文献
50.
Peruzzo D Bertoldo A Zanderigo F Cobelli C 《Computer methods and programs in biomedicine》2011,104(3):e148-e157
Dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) data analysis requires the knowledge of the arterial input function (AIF) to quantify the cerebral blood flow (CBF), volume (CBV) and the mean transit time (MTT). AIF can be obtained either manually or using automatic algorithms. We present a method to derive the AIF on the middle cerebral artery (MCA). The algorithm draws a region of interest (ROI) where the MCA is located. Then, it uses a recursive cluster analysis on the ROI to select the arterial voxels. The algorithm had been compared on simulated data to literature state of art automatic algorithms and on clinical data to the manual procedure. On in silico data, our method allows to reconstruct the true AIF and it is less affected by partial volume effect bias than the other methods. In clinical data, automatic AIF provides CBF and MTT maps with a greater contrast level compared to manual AIF ones. Therefore, AIF obtained with the proposed method improves the estimate reliability and provides a quantitatively reliable physiological picture. 相似文献