全文获取类型
收费全文 | 2448篇 |
免费 | 204篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 31篇 |
综合类 | 1篇 |
化学工业 | 795篇 |
金属工艺 | 38篇 |
机械仪表 | 42篇 |
建筑科学 | 87篇 |
矿业工程 | 5篇 |
能源动力 | 83篇 |
轻工业 | 542篇 |
水利工程 | 11篇 |
石油天然气 | 8篇 |
无线电 | 108篇 |
一般工业技术 | 330篇 |
冶金工业 | 299篇 |
原子能技术 | 7篇 |
自动化技术 | 273篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 105篇 |
2021年 | 121篇 |
2020年 | 76篇 |
2019年 | 77篇 |
2018年 | 90篇 |
2017年 | 92篇 |
2016年 | 85篇 |
2015年 | 99篇 |
2014年 | 94篇 |
2013年 | 156篇 |
2012年 | 147篇 |
2011年 | 184篇 |
2010年 | 133篇 |
2009年 | 128篇 |
2008年 | 123篇 |
2007年 | 99篇 |
2006年 | 88篇 |
2005年 | 50篇 |
2004年 | 58篇 |
2003年 | 53篇 |
2002年 | 53篇 |
2001年 | 51篇 |
2000年 | 33篇 |
1999年 | 35篇 |
1998年 | 109篇 |
1997年 | 68篇 |
1996年 | 48篇 |
1995年 | 35篇 |
1994年 | 27篇 |
1993年 | 27篇 |
1992年 | 3篇 |
1991年 | 13篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 3篇 |
排序方式: 共有2660条查询结果,搜索用时 31 毫秒
51.
I. N. Mihailescu Adriana Lita V. S. Teodorescu A. Luches M. Martino A. Perrone Maria Gartner 《Journal of Materials Science》1996,31(11):2839-2847
We report the deposition of Si-N films by multipulse excimer laser ( = 308 nm, FWHM = 30 ns) ablation of Si wafers placed in a slow flow of NH3 in the pressure range (1 bar-1 mbar). The films are deposited on to a Si collector placed parallel to the Si target. We succeeded in depositing pure amorphous Si3N4 films at a pressure of 1 mbar of NH3. The deposition rate reached a maximum value of 0.2–0.3 nm per pulse. At lower pressures, the deposited films consist of a fine mixture of three amorphous phases (amorphous stoichiometric silicon nitride, amorphous non-stoichiometric silicon nitride and amorphous silicon). The amorphous silicon is prevalent in films deposited at a pressure of several to several tens of bars. Droplets of polycrystalline -Si are sometimes visible on the film surface. The experimental evidence, is analysed with a view to elucidating the participation in the chemical synthesis of the three main stages of the process: the substance expulsion from the target by laser ablation, the transition through the gas of the expulsed substance and it's final impact on the collector. We conclude that silicon nitride is mostly synthesized during the impact on the collector of the flow of the ablated substance. 相似文献
52.
Parallel programming for multimedia applications 总被引:2,自引:2,他引:0
Hari Kalva Aleksandar Colic Adriana Garcia Borko Furht 《Multimedia Tools and Applications》2011,51(2):801-818
Computing capabilities are continuing to increase with the availability of multi core and many core processors. The wide availability
of multi core processors has made parallel programming possible for end user applications running on desktops, workstations,
and mobile devices. While parallel hardware has become common, software that exploits parallel capabilities is just beginning
to take hold. Multimedia applications, with their data parallel nature and large computing requirements will benefit significantly
from parallel programming. In this paper an overview of parallel programming is presented and languages and tools for parallel
programming such as OpenMP and CUDA are introduced within the scope of multimedia applications. 相似文献
53.
Mark Anderson Rajiv D. Banker Nirup M. Menon Jorge A. Romero 《Information Technology and Management》2011,12(3):197-212
This paper examines the impact of the duration of ERP implementation on firm performance both during and after implementation.
Organizations choose either an accelerated implementation approach or a traditional (longer) implementation approach. The
former approach gives the organization the advantage of speed, but the disadvantage of fitting its processes to that of a
packaged (thus, undifferentiated from competitors) ERP. The latter approach allows the organization to redesign strategy and
processes, and thus, search for ways to be unique from its competition. The study uses a regression model to capture the changes
in various performance measures during and after implementation between firms that implemented the ERP, using the performance
measure of a matched group of firms that did not implement an ERP as a benchmark/control sample, on the basis of the duration
of the implementation. Financial data from Compustat, and data on start date and end date of ERP implementation between 1990
and 2005 for firms in the Oil and Gas industry was collected from an ERP vendor. Results show that measures such as return
on sales improved after implementation. However, measures such as inventory turnover, which reflect operational benefits,
improve during implementation. We find that accelerated implementation confers both operational and strategic benefits. This
study highlights the strategic consequences of the different choices of implementation. 相似文献
54.
Ignacio Romero 《Computer Methods in Applied Mechanics and Engineering》2010,199(33-36):2235-2248
This article proposes a new type of discretizations for initial boundary value problems of thermodynamical systems. Based on a combination of finite elements in space and fractional step methods in time, we formulate algorithms that exactly preserve the symmetries and the laws of thermodynamics of the continuum problem. The algorithmic design is based on the GENERIC formalism of irreversible thermodynamics which naturally suggests the split of the evolution operator upon which our fractional step method is based. Although the emphasis of the article is on the generality of the results, as an illustration, a discretization of nonlinear, finite strain, thermoelasticity is presented. Numerical simulations are provided that verify the excellent performance of the new methods. 相似文献
55.
Quality control and safety related issues have become more and more important in industrial production of high added value products and chemical specialities during last years. In this regard, many successful applications of multivariate statistical process control (MSPC) for monitoring and diagnosis of batch processes have been presented. It is a common industrial practice to monitor the batch progress by exploiting the information contained in a historical database of successful batches using projection techniques such as principal components analysis (PCA), partial least squares (PLS) and independent component analysis (ICA). In this work, a new MSPC strategy for batch process monitoring is presented. Its distinctive feature is that it works in the space of the original variables. The technique uses only the T2-statistic for detection and identification purposes. The identification of the set of observations that signal the fault is accomplished by decomposing the T2-statistic as a unique sum of each variable contribution. Performance comparisons among the proposed strategy and the most popular PCA-based approaches are carried out by simulation of polymerization and penicillin cultivation batch processes. Results show that the new approach can be successfully applied to monitor this kind of processes since it works very well during both fault detection and identification stages. 相似文献
56.
Adriana S. Vivacqua Ana Cristina B. Garcia Angela Gomes 《Expert systems with applications》2011,38(2):1139-1147
Facilitating meetings is not an easy task. To assist the facilitator, we have been designing intelligent support systems, which can help contextual sensemaking, decision making and action. However, these systems are constructed based on behavioral models that provide guidelines to understand participant behaviors. This paper presents an ontology to describe participants’ behaviors in collaborative design meetings and rules that correlate them with the group’s acceptance of the final product. This ontology describes the group dynamics at collocated meetings, using verbal and non-verbal cues of attention shifts and attention maintenance as its basic constructs. The objective of creating this ontology was to better understand face-to-face meetings to eventually help meeting facilitators identify issues that may lead to dissatisfaction with the final product through behavioral cues. The ontology was derived through extensive analysis of a series of engineering design session videos. The design group was composed of experts with similar backgrounds, but working in different divisions of the same company. Different points of view were argued and decisions were made at the end of each meeting. After each meeting, participants were asked to asynchronously commit to the decisions made in the group. Our ontology can be used to identify the factors that lead to an undesired outcome, and now serves as a basis for a new project, which uses rules to support design meetings, improve final artifact acceptance and reduce rework. Our conclusions point out correlations between designers’ behaviors and future artifact acceptance and actions that interrupt or bring back group attention. The ontology was validated through application to other meeting situations. These findings may guide software developers in the creation of tools to support group design, and may be applied by an intelligent system. 相似文献
57.
Amelia Zafra Cristóbal Romero Sebastián Ventura 《Expert systems with applications》2011,38(12):15020-15031
In this paper, a new approach based on multiple instance learning is proposed to predict student’s performance and to improve the obtained results using a classical single instance learning. Multiple instance learning provides a more suitable and optimized representation that is adapted to available information of each student and course eliminating the missing values that make difficult to find efficient solutions when traditional supervised learning is used. To check the efficiency of the new proposed representation, the most popular techniques of traditional supervised learning based on single instances are compared to those based on multiple instance learning. Computational experiments show that when the problem is regarded as a multiple instance one, performance is significantly better and the weaknesses of single-instance representation are overcome. 相似文献
58.
Paulo Anselmo da Mota Silveira Neto Ivan do Carmo Machado John D. McGregorEduardo Santana de Almeida Silvio Romero de Lemos Meira 《Information and Software Technology》2011,53(5):407-423
Context
In software development, Testing is an important mechanism both to identify defects and assure that completed products work as specified. This is a common practice in single-system development, and continues to hold in Software Product Lines (SPL). Even though extensive research has been done in the SPL Testing field, it is necessary to assess the current state of research and practice, in order to provide practitioners with evidence that enable fostering its further development.Objective
This paper focuses on Testing in SPL and has the following goals: investigate state-of-the-art testing practices, synthesize available evidence, and identify gaps between required techniques and existing approaches, available in the literature.Method
A systematic mapping study was conducted with a set of nine research questions, in which 120 studies, dated from 1993 to 2009, were evaluated.Results
Although several aspects regarding testing have been covered by single-system development approaches, many cannot be directly applied in the SPL context due to specific issues. In addition, particular aspects regarding SPL are not covered by the existing SPL approaches, and when the aspects are covered, the literature just gives brief overviews. This scenario indicates that additional investigation, empirical and practical, should be performed.Conclusion
The results can help to understand the needs in SPL Testing, by identifying points that still require additional investigation, since important aspects regarding particular points of software product lines have not been addressed yet. 相似文献59.
Ignacio Peñarrocha Daniel Dolz Julio Ariel Romero Roberto Sanchis 《International journal of systems science》2016,47(2):283-299
This work presents a strategy to minimise the network usage and the energy consumption of wireless battery-powered sensors in the observer problem over networks. The sensor nodes implement a periodic send-on-delta approach, sending new measurements when a measure deviates considerably from the previous sent one. The estimator node implements a jump observer whose gains are computed offline and depend on the combination of available new measurements. We bound the estimator performance as a function of the sending policies and then state the design procedure of the observer under fixed sending thresholds as a semidefinite programming problem. We address this problem first in a deterministic way and, to reduce conservativeness, in a stochastic one after obtaining bounds on the probabilities of having new measurements and applying robust optimisation problem over the possible probabilities using sum of squares decomposition. We relate the network usage with the sending thresholds and propose an iterative procedure for the design of those thresholds, minimising the network usage while guaranteeing a prescribed estimation performance. Simulation results and experimental analysis show the validity of the proposal and the reduction of network resources that can be achieved with the stochastic approach. 相似文献
60.
Simulated environments with animated agents: effects on visual attention,emotion, performance,and perception 下载免费PDF全文
E. Romero‐Hall G. S. Watson A. Adcock J. Bliss K. Adams Tufts 《Journal of Computer Assisted Learning》2016,32(4):360-373
This research assessed how emotive animated agents in a simulation‐based training affect the performance outcomes and perceptions of the individuals interacting in real time with the training application. A total of 56 participants consented to complete the study. The material for this investigation included a nursing simulation in which participants interacted with three animated agents. The results of this investigation indicated that both experienced and novice participants focused more visual attention time on the body of the animated agent than the other defined areas of interest in the simulated environment. The results also indicated that novice participants conveyed more neutral facial expressions during the interaction with the animated agents than experience participants. The results of the simulation performance scores indicated that novice participants achieved higher simulation performance scores on the simulation task than experienced participants. Lastly, the results of the agent persona instrument showed that experienced and novice participants perceived the animated agents as facilitators of learning, credible, human‐like and engaging. 相似文献