全文获取类型
收费全文 | 2848篇 |
免费 | 112篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 30篇 |
综合类 | 1篇 |
化学工业 | 597篇 |
金属工艺 | 42篇 |
机械仪表 | 72篇 |
建筑科学 | 100篇 |
矿业工程 | 1篇 |
能源动力 | 69篇 |
轻工业 | 223篇 |
水利工程 | 26篇 |
石油天然气 | 4篇 |
无线电 | 272篇 |
一般工业技术 | 474篇 |
冶金工业 | 541篇 |
原子能技术 | 28篇 |
自动化技术 | 485篇 |
出版年
2023年 | 39篇 |
2022年 | 142篇 |
2021年 | 142篇 |
2020年 | 70篇 |
2019年 | 69篇 |
2018年 | 69篇 |
2017年 | 80篇 |
2016年 | 98篇 |
2015年 | 68篇 |
2014年 | 101篇 |
2013年 | 183篇 |
2012年 | 133篇 |
2011年 | 180篇 |
2010年 | 114篇 |
2009年 | 137篇 |
2008年 | 117篇 |
2007年 | 100篇 |
2006年 | 71篇 |
2005年 | 78篇 |
2004年 | 50篇 |
2003年 | 62篇 |
2002年 | 37篇 |
2001年 | 25篇 |
2000年 | 33篇 |
1999年 | 38篇 |
1998年 | 192篇 |
1997年 | 112篇 |
1996年 | 94篇 |
1995年 | 41篇 |
1994年 | 51篇 |
1993年 | 44篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 21篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 15篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 7篇 |
1976年 | 15篇 |
1973年 | 3篇 |
1969年 | 3篇 |
1967年 | 7篇 |
排序方式: 共有2965条查询结果,搜索用时 15 毫秒
61.
A dynamic variational multiscale method for viscoelasticity using linear tetrahedral elements 下载免费PDF全文
Xianyi Zeng Guglielmo Scovazzi Nabil Abboud Oriol Colomés Simone Rossi 《International journal for numerical methods in engineering》2017,112(13):1951-2003
In this article, we develop a dynamic version of the variational multiscale (D‐VMS) stabilization for nearly/fully incompressible solid dynamics simulations of viscoelastic materials. The constitutive models considered here are based on Prony series expansions, which are rather common in the practice of finite element simulations, especially in industrial/commercial applications. Our method is based on a mixed formulation, in which the momentum equation is complemented by a pressure equation in rate form. The unknown pressure, displacement, and velocity are approximated with piecewise linear, continuous finite element functions. To prevent spurious oscillations, the pressure equation is augmented with a stabilization operator specifically designed for viscoelastic problems, in that it depends on the viscoelastic dissipation. We demonstrate the robustness, stability, and accuracy properties of the proposed method with extensive numerical tests in the case of linear and finite deformations. 相似文献
62.
Ornella Rondinone Alessio Murgia Jole Costanza Silvia Tabano Margherita Camanni Luigi Corsaro Laura Fontana Patrizia Colapietro Luciano Calzari Silvia Motta Carlo Santaniello Tatjana Radaelli Enrico Ferrazzi Silvano Bosari Davide Gentilini Silvia Maria Sirchia Monica Miozzo 《International journal of molecular sciences》2022,23(10)
63.
Rosa De Finis Davide Palumbo Umberto Galietti 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(9):2085-2100
The stiffness degradation represents one of the most interesting damage phenomena used for describing the fatigue behaviour of composites. A critical aspect of modelling the damage is represented by the simulation of the whole behaviour of the composite and by the assessment of the actual stiffness for the models validation. In this work, the stiffness degradation of quasi‐isotropic carbon fibre reinforced polymer (CFRP) obtained by automated fibre placement has been assessed by means of thermoelastic stress analysis. The amplitude of temperature signal at the mechanical frequency (thermoelastic signal) was considered as an indicator of material degradation and compared with the data provided by an extensometer. The correlation between thermoelastic and mechanical data allowed to build a new experimental model for evaluating and predicting material stiffness degradation by just using thermoelastic data. The proposed approach seems to be very promising for stiffness degradation assessment of real and complex mechanical components subjected to actual loading conditions. 相似文献
64.
Febbraio F Merone L Cetrangolo GP Rossi M Nucci R Manco G 《Analytical chemistry》2011,83(5):1530-1536
Pesticides are the plague of modern times, although much needed in agriculture, causing damage to the entire ecosystem, including humans. The high operative costs and the requirement of specialized personnel for pesticide detection, incentive to develop alternative solutions such as the set up of cheap, rapid, and simple to use biosensors. In this work, we evaluate the possibility to use the esterase 2 from Alicyclobacillus acidocaldarius as a biosensor for the detection of specific organophosphate pesticides. With the recent demonstration of the very high affinity of esterase 2 toward paraoxon, a more complete analysis on the detection methods in water as well as in purposely contaminated fruit juices was carried out. The inhibitory effects of a wide range of other pesticides on esterase 2 were investigated, showing a better selectivity with respect to nonspecific reaction of acethylcholinesterases, the main target of organophosphate pesticides. The applied methodology allowed one to detect 2.75 × 10(-3) ppm of neurotoxic agent, comparable to the efficiency of other acethylcholinesterase-based biosensors. Finally, a raw biosensor, based on EST2 immobilization on a nitrocellulose membrane, was devised and tested for paraoxon detection, showing longtime stability, reproducibility, and sensibility. 相似文献
65.
Low-velocity impact tests are performed on fiberglass/AZ31B-H24 magnesium fiber-metal laminates (FMLs) with various configurations in order to gain a better understanding of the effect of an impactor's features on the response of this type of FML. For that, impactors with two different shapes (hemispherical and sharp-edged) and sizes are used to impact the specimens. The impact response data, such as the deformation of the contact location and energy absorption, is obtained directly during the impact tests through the impact equipment, while mechanical sectioning was carried out to establish the extent of delaminated area and post-impact residual deformation. While the sharp-edged impactor caused the development of cracks on the metal constituent, and delamination within the specimens, the hemispherical ones imposed more influence over the residual deformation. Noticeable differences are observed in response of FML specimens made with two and three layers of magnesium, especially with respect to the energy absorption capacity. Moreover, finite-element analysis, as a major part of this study, has been employed to simulate the low-velocity impact response of FML specimens. The behavior of specimens has been simulated using the commercial finite-element code ABAQUS. The results imply that there is a good agreement between the experimental and numerical results. 相似文献
66.
As software development comes to be viewed more and more as an engineering discipline, Software Configuration Management is
increasingly recognised as a key technology in the development of software. The Esprit VISCOUNT project1 aim is to implement an innovative Software Configuration Management (SCM) tool to use in a geographically distributed software
development environment, a Virtual Software Corporation (VSC).
The features implemented by the tool will be the following:
·Configurable process modelling
·Inter-working capabilities with COTS SCM tools
·Selective replication of archives
·Open to include plug-in applications (security mechanism, encryption, etc)
This paper is based on the work undertaken as part of the VISCOUNT project, partially funded by European Union's Esprit Programme,
and it describes the SIA (Societa' Italiana Avionica) requirements defined in the framework of VISCOUNT.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
67.
68.
Chiara Rossi Antonio Salvati Mariarosaria Distaso Daniela Campani Francesco Raggi Edoardo Biancalana Domenico Tric Maurizia Rossana Brunetto Anna Solini 《International journal of molecular sciences》2022,23(13)
P2X7R-NLRP3 and AIM2 inflammasomes activate caspase-1 and the release of cytokines involved in viral-related liver disease. Little is known about their role in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steato-hepatitis (NASH). We characterized the role of inflammasomes in NAFLD, NASH, and HCV. Gene expression and subcellular localization of P2X7R/P2X4R-NLRP3 and AIM2 inflammasome components were examined in histopathological preparations of 46 patients with biopsy-proven viral and metabolic liver disease using real-time PCR and immunofluorescence. P2X7R, P2X4R, and Caspase-1 are two- to five-fold more expressed in patients with NAFLD/NASH associated with chronic HCV infection than those with metabolic damage only (p ≤ 0.01 for all comparisons). The AIM2 inflammasome is 4.4 times more expressed in patients with chronic HCV infection, regardless of coexistent metabolic abnormalities (p = 0.0006). IL-2, a cytokine playing a pivotal role during chronic HCV infection, showed a similar expression in HCV and NASH patients (p = 0.77) but was virtually absent in NAFLD. The P2X7R-NLRP3 complex prevailed in infiltrating macrophages, while AIM2 was localized in Kupffer cells. Caspase-1 expression correlated with elastography-based liver fibrosis (r = 0.35, p = 0.02), whereas P2X7R, P2X4R, NRLP3, Caspase-1, and IL-2 expression correlated with circulating markers of disease severity. P2X7R and P2X4R play a major role in liver inflammation accompanying chronic HCV infection, especially when combined with metabolic damage, while AIM2 is specifically expressed in chronic viral hepatitis. We describe for the first time the hepatic expression of IL-2 in NASH, so far considered a peculiarity of HCV-related liver damage. 相似文献
69.
Davide Martinenghi Riccardo Torlone 《The VLDB Journal The International Journal on Very Large Data Bases》2014,23(5):747-769
Traditional information search in which queries are posed against a known and rigid schema over a structured database is shifting toward a Web scenario in which exposed schemas are vague or absent and data come from heterogeneous sources. In this framework, query answering cannot be precise and needs to be relaxed, with the goal of matching user requests with accessible data. In this paper, we propose a logical model and a class of abstract query languages as a foundation for querying relational data sets with vague schemas. Our approach relies on the availability of taxonomies, that is, simple classifications of terms arranged in a hierarchical structure. The model is a natural extension of the relational model in which data domains are organized in hierarchies, according to different levels of generalization between terms. We first propose a conservative extension of the relational algebra for this model in which special operators allow the specification of relaxed queries over vaguely structured information. We also study equivalence and rewriting properties of the algebra that can be used for query optimization. We then illustrate a logic-based query language that can provide a basis for expressing relaxed queries in a declarative way. We finally investigate the expressive power of the proposed query languages and the independence of the taxonomy in this context. 相似文献
70.
In this paper, we develop a theory of regular ω-languages that consist of ultimately periodic words only and we provide it
with an automaton-based characterization. The resulting class of automata, called ultimately periodic automata (UPA), is a
subclass of the class of Büchi automata and inherits some properties of automata over finite words (NFA). Taking advantage
of the similarities among UPA, Büchi automata, and NFA, we devise efficient solutions to a number of basic problems for UPA,
such as the inclusion, the equivalence, and the size optimization problems. The original motivation for developing a theory
of ultimately periodic languages and automata was to represent and to reason about sets of time granularities in knowledge-based
and database systems. In the last part of the paper, we show that UPA actually allow one to represent (possibly infinite)
sets of granularities, instead of single ones, in a compact and suitable to algorithmic manipulation way. In particular, we
describe an application of UPA to a concrete time granularity scenario taken from clinical medicine. 相似文献