全文获取类型
收费全文 | 6045篇 |
免费 | 386篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 27篇 |
综合类 | 7篇 |
化学工业 | 2172篇 |
金属工艺 | 72篇 |
机械仪表 | 115篇 |
建筑科学 | 231篇 |
矿业工程 | 11篇 |
能源动力 | 126篇 |
轻工业 | 1124篇 |
水利工程 | 54篇 |
石油天然气 | 18篇 |
无线电 | 293篇 |
一般工业技术 | 761篇 |
冶金工业 | 746篇 |
原子能技术 | 36篇 |
自动化技术 | 648篇 |
出版年
2024年 | 12篇 |
2023年 | 88篇 |
2022年 | 456篇 |
2021年 | 441篇 |
2020年 | 202篇 |
2019年 | 201篇 |
2018年 | 211篇 |
2017年 | 206篇 |
2016年 | 217篇 |
2015年 | 222篇 |
2014年 | 260篇 |
2013年 | 400篇 |
2012年 | 363篇 |
2011年 | 461篇 |
2010年 | 328篇 |
2009年 | 329篇 |
2008年 | 315篇 |
2007年 | 271篇 |
2006年 | 208篇 |
2005年 | 155篇 |
2004年 | 159篇 |
2003年 | 138篇 |
2002年 | 121篇 |
2001年 | 54篇 |
2000年 | 59篇 |
1999年 | 56篇 |
1998年 | 55篇 |
1997年 | 42篇 |
1996年 | 44篇 |
1995年 | 43篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 19篇 |
1989年 | 21篇 |
1988年 | 25篇 |
1987年 | 22篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有6441条查询结果,搜索用时 5 毫秒
41.
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
42.
Laura Hollink Véronique Malaisé Guus Schreiber 《Multimedia Tools and Applications》2010,49(1):235-257
It is common practice in audiovisual archives to disclose documents using metadata from a structured vocabulary or thesaurus.
Many of these thesauri have limited or no structure. The objective of this paper is to find out whether retrieval of audiovisual
resources from a collection indexed with an in-house thesaurus can be improved by enriching the thesaurus structure. We propose
a method to add structure to a thesaurus by anchoring it to an external, semantically richer thesaurus. We investigate the
added value of this enrichment for retrieval purposes. We first anchor the thesaurus to an external resource, WordNet. From
this anchoring we infer relations between pairs of terms in the thesaurus that were previously unrelated. We employ the enriched
thesaurus in a retrieval experiment on a TRECVID 2007 dataset. The results are promising: with simple techniques we are able
to enrich a thesaurus in such a way that it adds to retrieval performance. 相似文献
43.
Giacomo Bucci Laura Carnevali Lorenzo Ridi Enrico Vicario 《International Journal on Software Tools for Technology Transfer (STTT)》2010,12(5):391-403
Oris is a tool for qualitative verification and quantitative evaluation of reactive timed systems, which supports modeling
and analysis of various classes of timed extensions of Petri Nets. As most characterizing features, Oris implements symbolic
state space analysis of preemptive Time Petri Nets, which enable schedulability analysis of real-time systems running under
priority preemptive scheduling; and stochastic Time Petri Nets, which enable an integrated approach to qualitative verification
and quantitative evaluation. In this paper, we present the current version of the tool and we illustrate its application to
two different case studies in the areas of qualitative verification and quantitative evaluation, respectively. 相似文献
44.
In this paper we analyze an elliptic partial differential equation involving variable exponent growth conditions coupled with a nonlinear boundary condition. We show the existence of infinitely many bounded weak solutions provided there is a suitable oscillatory behavior of the nonlinearity either at infinity or at zero. Our proofs rely on a method due to Saint Raymond. 相似文献
45.
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
46.
Laura H. Ikuma Maury A. Nussbaum Kari L. Babski-Reeves 《International Journal of Industrial Ergonomics》2009,39(5):813-820
Responses to physical and psychosocial exposures can be measured using diverse methods, but their reliability, particularly under multiple exposures, is largely unknown. Five classes of methods were used to assess physiological and subjective responses among 24 participants to four combinations of physical and psychosocial exposures while performing two identical sessions of a simulated overhead manufacturing task. As an exploratory analysis, test–retest reliability was quantified using intraclass correlation coefficients (ICC) and coefficients of variation (CV). Discomfort ratings were reliable under less favorable exposures, and ratings of the psychosocial environment were most reliable under favorable social support. Workload ratings were most reliable with high physical exposure and favorable social support, and task performance was reliable overall. EMG and heart rate had relatively low reliability. Slightly less than half of the variables were considered reliable, but reliability depended on exposure conditions.Relevance to industry: The study provides information on the reliability of commonly used exposure measurement methods. The results can guide the selection of physiological and psychological work outcome measurements in future studies and work evaluations. 相似文献
47.
48.
Laura Sánchez-González Félix García Francisco Ruiz Mario Piattini 《Software and Systems Modeling》2017,16(3):759-788
Organizations are increasingly concerned about business process model improvement in their efforts to guarantee improved operational efficiency. Quality assurance of business process models should be addressed in the most objective manner, e.g., through the application of measures, but the assessment of measurement results is not a straightforward task and it requires the identification of relevant indicators and threshold values, which are able to distinguish different levels of process model quality. Furthermore, indicators must support the improvements of the models by using suitable guidelines. In this paper, we present a case study to evaluate the BPMIMA framework for BP model improvement. This framework is composed of empirically validated measures related to quality characteristics of the models, a set of indicators with validated thresholds associated with modeling guidelines and a prototype supporting tool. The obtained data suggest that the redesign by applying guidelines driven by the indicator results was successful, as the understandability and modifiability of the models were improved. In addition, the changes in the models according to guidelines were perceived as acceptable by the practitioners who participated in the case study. 相似文献
49.
Mihai Tanase Juan de la Riva Fernando Pérez-Cabello 《Remote sensing of environment》2011,115(8):2075-2085
Disturbed forests may need decades to reach a mature stage and optically-based vegetation indices are usually poorly suited for monitoring purposes due to the rapid saturation of the signal with increasing canopy cover. Spaceborne synthetic aperture radar (SAR) data provide an alternate monitoring approach since the backscattered microwave energy is sensitive to the vegetation structure. Images from two regions in Spain and Alaska were used to analyze SAR metrics (cross-polarized backscatter and co-polarized interferometric coherence) from regrowing forests previously affected by fire. TerraSAR-X X-band backscatter showed the lowest sensitivity to forest regrowth, with the average backscatter increasing by 1-2 dB between the most recent fire scar and the unburned forest. Increased sensitivity (around 3-4 dB) was observed for C-band Envisat Advanced Synthetic Aperture (ASAR) backscatter. The Advanced Land Observing Satellite (ALOS) Phased Array-type L-band Synthetic Aperture Radar (PALSAR) L-band backscatter presented the highest dynamic range from unburned to recently burned forests (approximately 8 dB). The interferometric coherence showed low sensitivity to forest regrowth at all SAR frequencies. For Mediterranean forests, five phases of forest regrowth were discerned whereas for boreal forest, up to four different regrowth phases could be discerned with L-band SAR data. In comparison, the Normalized Difference Vegetation Index (NDVI) provided reliable differentiation only for the most recent development stages. The results obtained were consistent in both environments. 相似文献
50.
We investigate the complexity of preorder checking when the specification is a flat finite-state system whereas the implementation is either a non-flat finite-state system or a standard timed automaton. In both cases, we show that simulation checking is Exptime-hard, and for the case of a non-flat implementation, the result holds even if there is no synchronization between the parallel components and their alphabets of actions are pairwise disjoint. Moreover, we show that the considered problems become Pspace-complete when the specification is assumed to be deterministic. Additionally, we establish that comparing a synchronous non-flat system with no hiding and a flat system is Pspace-hard for any relation between trace containment and bisimulation equivalence, even if the flat system is assumed to be fixed. 相似文献