全文获取类型
收费全文 | 2300篇 |
免费 | 136篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
综合类 | 1篇 |
化学工业 | 542篇 |
金属工艺 | 68篇 |
机械仪表 | 125篇 |
建筑科学 | 83篇 |
矿业工程 | 7篇 |
能源动力 | 98篇 |
轻工业 | 275篇 |
水利工程 | 26篇 |
石油天然气 | 14篇 |
无线电 | 139篇 |
一般工业技术 | 350篇 |
冶金工业 | 117篇 |
原子能技术 | 18篇 |
自动化技术 | 556篇 |
出版年
2024年 | 7篇 |
2023年 | 28篇 |
2022年 | 92篇 |
2021年 | 117篇 |
2020年 | 79篇 |
2019年 | 90篇 |
2018年 | 107篇 |
2017年 | 78篇 |
2016年 | 104篇 |
2015年 | 82篇 |
2014年 | 112篇 |
2013年 | 212篇 |
2012年 | 157篇 |
2011年 | 213篇 |
2010年 | 135篇 |
2009年 | 130篇 |
2008年 | 114篇 |
2007年 | 95篇 |
2006年 | 73篇 |
2005年 | 57篇 |
2004年 | 47篇 |
2003年 | 56篇 |
2002年 | 29篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 21篇 |
1998年 | 37篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有2438条查询结果,搜索用时 15 毫秒
91.
Paulo Leit?o J. Marco Mendes Axel Bepperling Daniel Cachapa Armando W. Colombo Francisco Restivo 《Journal of Intelligent Manufacturing》2012,23(6):2551-2563
Engineering frameworks are currently required to support the easy, low-cost, modular and integrated development of manufacturing systems addressing the emergent requirements of re-configurability, responsiveness and robustness. This paper discusses the integration of 2D/3D digital software tools with Petri net based service-oriented frameworks to allow the design, configuration, analysis, validation, simulation, monitoring and control of manufacturing systems in a virtual environment and its posterior smooth migration into the real ??physical?? environment. An experimental case study was implemented to validate the proposed concepts, using the Continuum platform to design, compose, analyze, validate and simulate the Petri nets based service-oriented manufacturing control system, and the Delmia AutomationTM software suite to support the rapid prototyping and the easy simulation of the designed control solution. The experimental results prove several aspects of the proposed approach, notably the smooth migration between the design and the operation phases, one of the main objectives of the work. 相似文献
92.
Arranging office space into a single open room offers advantages in terms of easy exchange of information and interaction among coworkers, but reduces privacy and acoustic comfort. Thus, the purpose of this work was to evaluate the acoustic quality of a real open-plan office and to propose changes in the room to improve the acoustic conditioning of this office. The computational model of the office under study was calibrated based on RT and STI measurements. Predictions were made of the RT and STI, which generated the radius of distraction r(D), and the rate of spatial decay of sound pressure levels per distance doubling DL(2) in the real conditions of the office and after modifications of the room. The insertion of dividers between work stations and an increase in the ceiling's sound absorption improved the acoustic conditions in the office under study. 相似文献
93.
This paper proposes an output‐feedback sliding mode control design for a class of uncertain multivariable plants with nonlinear disturbances. The approach used here is based on the control parameterization employed in model‐reference adaptive control. The disturbances are allowed to be unmatched and to depend not only on the plant output but also on its unmeas‐urable state. A less restrictive condition on the uncertainty of the high frequency gain matrix is also obtained. 相似文献
94.
Celso M. F. Lapa Paulo A. B. de Sampaio Cludio M. N. A. Pereira 《Nuclear Engineering and Design》2004,229(2-3):205-212
Reduced scale experiments are often employed in engineering because they are much cheaper than real scale testing. Unfortunately, though, it is difficult to design a thermal-hydraulic circuit or equipment in reduced scale capable of reproducing, both accurately and simultaneously, all the physical phenomena that occur in real scale and operating conditions. This paper presents a methodology to designing thermal-hydraulic experiments in reduced scale based on setting up a constrained optimization problem that is solved using genetic algorithms (GAs). In order to demonstrate the application of the methodology proposed, we performed some investigations in the design of a heater aimed to simulate the transport of heat and momentum in the core of a pressurized water reactor (PWR) at 100% of nominal power and non-accident operating conditions. The results obtained show that the proposed methodology is a promising approach for designing reduced scale experiments. 相似文献
95.
The development and computational implementation, on a multibody dynamics environment, of a constitutive relation to model
bushing elements associated with mechanical joints used in the models of road and rail vehicles is presented here. These elements
are used to eliminate vibrations in vehicles, due to road irregularities, to allow small misalignment of axes, to reduce noise
from the transmission, or to decrease wear of the mechanical joints. Bushings are made of a special rubber, used generally
in energy dissipation, which presents a nonlinear viscoelastic relationship between the forces and moments and their corresponding
displacements and rotations. In the methodology proposed here a finite element model of the bushing is developed in the framework
of the finite element code ABAQUS to obtain the constitutive relations of displacement/rotation versus force/moment for different
loading cases. The bushing is modeled in a multibody code as a nonlinear restrain that relates the relative displacements
between the bodies connected with the joint reaction forces, and it is represented by a matrix constitutive relation. The
basic ingredients of the multibody model are the same vectors and points relations used to define kinematic constraints in
any multibody formulation. One particular, and relevant, characteristic of the formulation now presented is its ability to
represent standard kinematic joints, clearance, and bushing joints just by defining appropriate constitutive relations. Spherical,
revolution, cylindrical, and translational bushing joints are modeled, implemented, and demonstrated through the simulation
of two multibody models of a road vehicle, one with perfect kinematic joints for the suspension sub-systems, and other with
bushing joints. The tests conducted include an obstacle avoidance maneuver and a vehicle riding over bumps. It is shown that
the bushing models for vehicle multibody models proposed here are accurate and computationally efficient so that they can
be included in the vehicle models leading reliable simulations. 相似文献
96.
97.
Joana F. B. Barata Paula S. S. Lacerda Maria Graa P. M. S. Neves Jos A. S. Cavaleiro Catarina I. V. Ramos Augusto C. Tom Paulo E. Abreu Alberto A. C. C. Pais 《International journal of molecular sciences》2022,23(21)
Details on the unexpected formation of two new (dimethylamino)methyl corrole isomers from the reaction of 5,10,15-tris(pentafluorophenyl)corrolatogallium(III) with sarcosine and paraformaldehyde are presented. Semi-empirical calculations on possible mechanism pathways seem to indicate that the new compounds are probably formed through a Mannich-type reaction. The extension of the protocol to the free-base 5,10,15-tris(pentafluorophenyl)corrole afforded an unexpected new seven-membered ring corrole derivative, confirming the peculiar behavior of corroles towards known reactions when compared to the well-behaved porphyrin counterparts. 相似文献
98.
Ana Sofia Ferreira Ana Margarida Silva Diana Pinto Manuela M. Moreira Ricardo Ferraz Jaroslava varc-Gaji Paulo C. Costa Cristina Delerue-Matos Francisca Rodrigues 《International journal of molecular sciences》2022,23(23)
Oral mucositis (OM), a common side effect of oncological treatment, is an oral mucosal disorder characterized by painful ulcerations and increased risk of infection. The use of natural antioxidants to suppress the redox imbalance responsible for the OM condition has emerged as an interesting approach to prevent/treat OM. This study aims to explore the chestnut (Castana sativa) shells as potential active ingredient against OM. Therefore, chestnut shells were extracted at different temperatures (110–180 °C) by Subcritical Water Extraction (SWE), aiming to recover antioxidants. The extracts were also evaluated against microorganisms present in the oral cavity as well as on human oral cell lines (TR146 and HSC3). The highest phenolic content was obtained with the extraction temperature of 110 °C, exhibiting the best antioxidant/antiradical activities and scavenging efficiencies against HOCl (IC50 = 4.47 μg/mL) and ROO• (0.73 μmol TE/mg DW). High concentrations of phenolic acids (e.g., gallic and protocatechuic acids) and flavanoids (catechin, epicatechin and rutin) characterized the phenolic profile. The antimicrobial activity against several oral microorganisms present in the oral cavity during OM, such as Streptococcus, Staphylococcus, Enterococcus, and Escherichia, was demonstrated. Finally, the effects on HSC3 and TR146 cell lines revealed that the extract prepared at 110 °C had the lowest IC50 (1325.03 and 468.15 µg/mL, respectively). This study highlights the potential effects of chestnut shells on OM. 相似文献
99.
100.
Srgio R. S. Veloso Raquel G. D. Andrade Valria Gomes Carlos O. Amorim Vítor S. Amaral Vernica Salgueirio Paulo J. G. Coutinho Paula M. T. Ferreira Miguel A. Correa-Duarte Elisabete M. S. Castanheira 《International journal of molecular sciences》2022,23(22)
Superparamagnetic nanoparticles are of high interest for therapeutic applications. In this work, nanoparticles of calcium-doped manganese ferrites (CaxMn1−xFe2O4) functionalized with citrate were synthesized through thermally assisted oxidative precipitation in aqueous media. The method provided well dispersed aqueous suspensions of nanoparticles through a one-pot synthesis, in which the temperature and Ca/Mn ratio were found to influence the particles microstructure and morphology. Consequently, changes were obtained in the optical and magnetic properties that were studied through UV-Vis absorption and SQUID, respectively. XRD and Raman spectroscopy studies were carried out to assess the microstructural changes associated with stoichiometry of the particles, and the stability in physiological pH was studied through DLS. The nanoparticles displayed high values of magnetization and heating efficiency for several alternating magnetic field conditions, compatible with biological applications. Hereby, the employed method provides a promising strategy for the development of particles with adequate properties for magnetic hyperthermia applications, such as drug delivery and cancer therapy. 相似文献