全文获取类型
收费全文 | 2809篇 |
免费 | 215篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 37篇 |
化学工业 | 795篇 |
金属工艺 | 52篇 |
机械仪表 | 129篇 |
建筑科学 | 131篇 |
矿业工程 | 8篇 |
能源动力 | 107篇 |
轻工业 | 452篇 |
水利工程 | 17篇 |
石油天然气 | 11篇 |
无线电 | 193篇 |
一般工业技术 | 377篇 |
冶金工业 | 105篇 |
原子能技术 | 12篇 |
自动化技术 | 599篇 |
出版年
2024年 | 11篇 |
2023年 | 37篇 |
2022年 | 73篇 |
2021年 | 151篇 |
2020年 | 112篇 |
2019年 | 133篇 |
2018年 | 110篇 |
2017年 | 115篇 |
2016年 | 126篇 |
2015年 | 98篇 |
2014年 | 144篇 |
2013年 | 250篇 |
2012年 | 182篇 |
2011年 | 220篇 |
2010年 | 178篇 |
2009年 | 168篇 |
2008年 | 122篇 |
2007年 | 125篇 |
2006年 | 110篇 |
2005年 | 80篇 |
2004年 | 66篇 |
2003年 | 54篇 |
2002年 | 55篇 |
2001年 | 36篇 |
2000年 | 34篇 |
1999年 | 23篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 17篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1970年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有3025条查询结果,搜索用时 15 毫秒
71.
Web resources in Latin American higher education institutions have been reported to show a much stronger emphasis on Information than on Communication. A Course Management System (CMS), according to Social Constructivism framework, is an opportunity for fostering learning through interaction in a virtual environment for learning; hence, stimulating the use of a CMS for communication purposes seems quite appropriate. A quantitative analysis of 63.06% of the virtual classrooms was conducted, using the users log database to describe five variables: Participation, Informational Interaction Level, Communicational Interaction Level, and the use of Informational Resources and Communicational Resources in the CMS. An assessment of the first 2 years of implementation of Moodle in a campus confirmed prominence levels of interaction and resources that favor Information over Communication purposes in the use of the CMS. It is not conclusive whether this necessarily implies more or better learning; a profound qualitative study would be needed to answer these questions. Teachers and students show different behaviors in the face of this new ICT campus resource, while faculty members appear to have behaved in an erratic manner, students show steady levels of CMS usage. 相似文献
72.
I am presenting a new design for the head sub-system of the humanoid robot iCub. ICub is a humanoid robot platform that has been conceived as a result of the development of the European Project RobotCub. Mechanical problems of the current head sub-system of iCub robot have been studied in order to figure out improvements for a new design. The feasibility of the new design has been checked through dynamic simulations of the head operations. The successful results have shown plots with curve evolutions of smooth shapes and suitable values of important kinematic and dynamic parameters of the head structure. 相似文献
73.
Eduardo Eyng Ana M.F. Fileti 《Engineering Applications of Artificial Intelligence》2010,23(2):271-282
The alcohol lost by evaporation during the bioethanol fermentation process may be collected and recovered using an absorption column. This equipment is also used in the carbonic gas treatment, a by-product from the sugar cane fermentation. In the present work, the development of nonlinear feedforward–feedback controllers, based on neural network inverse models, was proposed and tested to manipulate the absorbent flow rates. The control purposes are: to keep low ethanol concentration in the effluent gas phase from the first absorption column (ethanol recovery column); and to reduce the residual water concentration in the CO2 gas effluent from the second tower (CO2 treatment column).Based on simulation studies, the neural network (ANN) controller performance was compared with the conventional PID control scheme application. The best ANN architecture was set up according to the Foresse and Hagan (1997) criterion, while the PID parameters were found from the well-known Cohen–Coon Equations and trial-and-error fine tuning.Initially, performances were evaluated for the system without concentration measurement uncertainties. From these tests, the ANN controller presented the smallest response time and overshoot for regulator and servo problems. Three uncertainty levels were applied afterwards: 5%, 10%, and 15%.The ANN controller outperformed the PID for all uncertainty levels tested for the ethanol recovery column. For the CO2 treatment column, the ANN controller proceeded successfully under uncertainties of 5% and 10%, while the PID did not deal properly with uncertainties above 5%. The statistical F-test, besides the ITAE, ISE, and IAE performance criteria, were calculated for both controllers applications and then compared. They proved the superiority of the ANN control scheme.Using appropriately the proposed well-controlled absorption columns increases the efficiency of the bioethanol production plant and can also provide carbon credits by avoiding CO2 emission into the atmosphere. 相似文献
74.
Alfonso Rodríguez Ignacio García-Rodríguez de Guzmán Eduardo Fernández-Medina Mario Piattini 《Information and Software Technology》2010,52(9):945-971
ContextModel-Driven Development (MDD) is an alternative approach for information systems development. The basic underlying concept of this approach is the definition of abstract models that can be transformed to obtain models near implementation. One fairly widespread proposal in this sphere is that of Model Driven Architecture (MDA). Business process models are abstract models which additionally contain key information about the tasks that are being carried out to achieve the company’s goals, and two notations currently exist for modelling business processes: the Unified Modelling Language (UML), through activity diagrams, and the Business Process Modelling Notation (BPMN).ObjectiveOur research is particularly focused on security requirements, in such a way that security is modelled along with the other aspects that are included in a business process. To this end, in earlier works we have defined a metamodel called secure business process (SBP), which may assist in the process of developing software as a source of highly valuable requirements (including very abstract security requirements), which are transformed into models with a lower abstraction level, such as analysis class diagrams and use case diagrams through the approach presented in this paper.MethodWe have defined all the transformation rules necessary to obtain analysis class diagrams and use case diagrams from SBP, and refined them through the characteristic iterative process of the action-research method.ResultsWe have obtained a set of rules and a checklist that make it possible to automatically obtain a set of UML analysis classes and use cases, starting from SBP models. Our approach has additionally been applied in a real environment in the area of the payment of electrical energy consumption.ConclusionsThe application of our proposal shows that our semi-automatic process can be used to obtain a set of useful artifacts for software development processes. 相似文献
75.
This paper presents a solution to the problem of unsupervised classification of dynamic obstacles in urban environments. A track‐based model is introduced for the integration of two‐dimensional laser and vision information that provides a robust spatiotemporal synthesis of the sensed moving obstacles and forms the basis for suitable algorithms to perform unsupervised classification by clustering. This work presents various contributions in order to achieve accurate and efficient performance, initially using laser tracks for classification and then incorporating visual tracks to the model. A procedure is proposed for accurate unsupervised classification of dynamic obstacles using a laser stamp representation of the tracks. Laser data are then integrated with visual information through a single‐instance visual stamp representation, which is finally extended using a multiple‐instance framework to robustly deal with challenges associated with perception in real‐world scenarios. The proposed algorithms are extensively validated with a simulated environment. Experiments with a research vehicle in an urban environment demonstrate the performance of the approach with real data. The experimental results reach an accuracy of more than 92% for obstacle classification, finding the clusters that correspond to the main obstacle classes in the data. © 2010 Wiley Periodicals, Inc. 相似文献
76.
Eduardo Sáenz-de-Cabezón L. Javier HernándezM. Teresa Rivas Esteban García-RuizVicente Marco Ignacio Pérez-MorenoF. Javier Sáenz-de-Cabezón 《Mathematics and computers in simulation》2011,82(1):2-14
This paper presents a new procedure to construct families of spatial approximation-prediction functions which depend on several parameters. The method is based on partitions of the unity. In order to find optimal functions in these families we introduce a Vietoris simplicial set associated to an influence radius. We consider error estimators induced by these Vietoris simplicial sets. A computational implementation of these mathematical models has been developed to be applied to any kind of finite discrete data. Our methods provide a useful tool for the analysis of the spatial distribution of species, which is imperative for developing accurate and efficient management of endangered and invasive species, biological conservation programs, etc. We demonstrate the application of our method to the analysis of the spatial distribution of the grape moth Lobesia botrana (Lepidoptera: Tortricidae) in the vineyards of La Rioja obtaining useful results for the management of this pest. 相似文献
77.
A novel humid electronic nose combined with an electronic tongue for assessing deterioration of wine 总被引:2,自引:0,他引:2
Luis Gil-SánchezAuthor Vitae Juan SotoAuthor Vitae Ramón Martínez-MáñezAuthor Vitae Eduardo Garcia-BreijoAuthor Vitae Javier IbáñezAuthor Vitae Eduard LlobetAuthor Vitae 《Sensors and actuators. A, Physical》2011,171(2):152-158
We report herein the use of a combined system for the analysis of the spoilage of wine when in contact with air. The system consists of a potentiometric electronic tongue and a humid electronic nose. The potentiometric electronic tongue was built with thick-film serigraphic techniques using commercially available resistances and conductors for hybrid electronic circuits; i.e. Ag, Au, Cu, Ru, AgCl, and C. The humid electronic nose was designed in order to detect vapours that emanate from the wine and are apprehended by a moist environment. The humid nose was constructed using a piece of thin cloth sewn, damped with distilled water, forming five hollows of the right size to introduce the electrodes. In this particular case four electrodes were used for the humid electronic nose: a glass electrode, aluminium (Al), graphite and platinum (Pt) wires and an Ag-AgCl reference electrode. The humid electronic nose together with the potentiometric electronic tongue were used for the evaluation of the evolution in the course of time of wine samples. Additionally to the analysis performed by the tongue and nose, the spoilage of the wines was followed via a simple determination of the titratable (total) acidity. 相似文献
78.
José Luis Crespo Marta Zorrilla Pilar Bernardos Eduardo Mora 《The Visual computer》2009,25(4):309-323
The objective of this paper is to present an overall approach to forecasting the future position of the moving objects of
an image sequence after processing the images previous to it. The proposed method makes use of classical techniques such as
optical flow to extract objects’ trajectories and velocities, and autoregressive algorithms to build the predictive model.
Our method can be used in a variety of applications, where videos with stationary cameras are used, moving objects are not
deformed and change their position with time. One of these applications is traffic control, which is used in this paper as
a case study with different meteorological conditions to compare with.
相似文献
Marta Zorrilla (Corresponding author)Email: |
79.
In this paper, we consider the problem of generating a well sampled discrete representation of the Pareto manifold or the Pareto front corresponding to the equilibrium points of a multi-objective optimization problem. We show how the introduction of simple additional constraints into a continuation procedure produces equispaced points in either of those two sets. Moreover, we describe in detail a novel algorithm for global continuation that requires two orders of magnitude less function evaluations than evolutionary algorithms commonly used to solve this problem. The performance of the methods is demonstrated on problems from the current literature. 相似文献
80.
In this paper we describe briefly a set of procedures for the optimal design of full mission aerospace systems. This involves multi-physics simulations at various fidelity levels, surrogates, distributed computing and multi-objective optimization. Low-fidelity analysis is used to populate a database of inputs and outputs of the system simulation and Neural Networks are then designed to generate inexpensive surrogates. Higher fidelity is used only where is warranted and also to do a local exploration after global optimization techniques have been used on the surrogates in order to provide plausible initial values. The ideas are exemplified on a generic supersonic aircraft configuration, where one of the main goals is to reduce the ground sonic boom. 相似文献