全文获取类型
收费全文 | 235篇 |
免费 | 33篇 |
学科分类
工业技术 | 268篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 35篇 |
2020年 | 12篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 12篇 |
2016年 | 11篇 |
2015年 | 15篇 |
2014年 | 14篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 16篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有268条查询结果,搜索用时 265 毫秒
61.
Silvia Ruggieri Valeria Longo Cinzia Perrino Silvia Canepari Gaspare Drago Luca LAbbate Martin Balzan Giuseppina Cuttitta Gianluca Scaccianoce Remo Minardi Giovanni Viegi Fabio Cibella 《Indoor air》2019,29(2):276-290
This study aimed at surveying lower secondary schools in southern Italy, in a highly polluted area. A community close to an industrial area and three villages in rural areas was investigated. Indoor temperature, relative humidity (RH), gaseous pollutants (CO2 and NO2), selected biological pollutants in indoor dust, and the indoor/outdoor mass concentration and elemental composition of PM2.5 were ascertained. Temperature and RH were within, or close to, the comfort range, while CO2 frequently exceeded the threshold of 1000 ppm, indicating inadequate air exchange rate. In all the classrooms, median NO2 levels were above the WHO threshold value. Dermatophagoides p. allergen concentration was below the sensitizing threshold, while high endotoxin levels were detected in the classrooms, suggesting schools may produce significant risks of endotoxin exposure. Concentration and solubility of PM2.5 elements were used to identify the sources of indoor particles. Indoor concentration of most elements was higher than outdoors. Resuspension was responsible for the indoor increase in soil components. For elements from industrial emission (Cd, Co, Ni, Pb, Sb, Tl, V), the indoor concentration depended on penetration from the outside. For these elements, differences in rural vs industrial concentrations were found, suggesting industrial sources may influence indoor air quality nearby schools. 相似文献
62.
This work presents a truly concurrent operational semantics for nondeterministic data flow networks. We introduce a model, the df-process, which is a notion similar to that of non-sequential process for a Petri net: a df-process is defined as a mapping from an occurrence net K to a data flow net N, such that the places and the transitions of K are mapped onto the channels and the nodes of N. A df-process contains, by means of some labelling of the places, information on the value and the order in which data flow through the channels during a computation. Df-processes for a data flow network are characterized in an abstract way by a set of properties and in general a df-process corresponds to a set of computations of the network. We give a way to build the df-process corresponding to a computation incrementally at each event occurrence: a main result of the paper is that the incremental construction yields exactly the same set of df-processes as abstractly defined. We also show that df-processes are compositional. The model is intended to be used by distributed systems designers: it contains enough information to be a guideline for the designer and to be a base to develop dynamic checking tools. We outline how df-processes can be used in the design phase of a system.Research supported in part by Progetto Coordinato CNR ANATRA 相似文献
63.
64.
65.
Useful model checking tools can be constructed by measuring the distance between a prior distribution that concentrates most
of its mass around a model of interest, and the resulting posterior distribution. In this paper we use this approach to construct
a diagnostic measure for detecting lack of fit in discrete data, with special focus on binomial data. We begin by constructing
a suitable probability model “around” the model of interest, via a Dirichlet Process elaboration. We derive the resulting
diagnostic and show that, approximately, it is the sum of two terms: the first is the logarithm of the Bayes factor and the
second is proportional to the Pearson chi-square statistics. We give details of a simulation algorithm for computing the diagnostic
and illustrate its use in an application to biomedical data. 相似文献
66.
Efficiency,effectiveness, and impacts assessment in the rail transport sector: a state‐of‐the‐art critical analysis of current research
下载免费PDF全文
![点击此处可从《International Transactions in Operational Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Giuseppe Catalano Cinzia Daraio Marco Diana Martina Gregori Giorgio Matteucci 《International Transactions in Operational Research》2019,26(1):5-40
This paper aims at being a comprehensive reference for stakeholders, policy makers, and scholars interested in analyzing the problem of efficiency, effectiveness, and impacts of rail transport systems in a sound empirical way, paying specific attention to passenger transport services. The paper combines different analytical frameworks (engineering, economics, impacts), systematic review techniques, and advanced mappings. Framing economic efficiency studies into a transport planning perspective permits to move from efficiency to effectiveness issues. In addition, including impacts offers a critical discussion of the existing empirical studies, relating them to the main methodological approaches used. This analysis can be useful for those interested in developing new techniques for the evaluation of this sector. The critical analysis developed in this paper provides a catalog of inputs, outputs, external factors, possible impacts to account for, data, and approaches, which allows us to identify areas in which new methodological developments, new approaches, are needed to address the relevant societal challenges of the rail transport sector. 相似文献
67.
Cinzia Bernardeschi Marco Di Natale Gianluca Dini Maurizio Palmieri 《Journal in Computer Virology》2018,14(4):269-289
This paper presents an approach for enhancing the design phase of AUTOSAR models when security annotations are required. The approach is based on information flow analysis and abstract interpretation. The analysis evaluates the correctness of the model by assessing if the flow of data is secure with respect to causal data dependencies within the model. To find these dependencies an exhaustive search through the model would be required. Abstract interpretation is used as a trade-off between the precision and complexity of the analysis. The approach also provides annotated models without oversizing the set of annotations. 相似文献
68.
SRAM-Based FPGA Systems for Safety-Critical Applications:A Survey on Design Standards and Proposed Methodologies
下载免费PDF全文
![点击此处可从《计算机科学技术学报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
As the ASIC design cost becomes affordable only for very large-scale productions, the FPGA technology is currently becoming the leading technology for those applications that require a small-scale prod... 相似文献
69.
In this investigation, silica aerogel (SA)/Rigid Polyurethane (PUR) foam composites and silica aerogel/Polyurethane (PU) composites were prepared by dry mixing of granular and grinded silica aerogels with polyol part. They were then combined with diisocyanate part. Three different types of PUR foams and an elastomeric coating grade of PU were studied as well. Results show that thermal conductivity of foams did not decrease by adding silica aerogel. It even increased for some grades which is assumed to be due to the change in cell configuration of these foams. It was also found that sound insulation performance of these cellular composites did not improve significantly. Unlike foam composites, addition of silica aerogel into elastomeric PU improved its thermal and acoustic insulation properties. Because of the more promising properties of elastomeric PU composites, further examinations including measurements of compression strength and water contact angle of silica aerogel/PU composites were also taken. Final results showed a significant improvement in general properties of PU coatings by adding little amounts of silica aerogel (1–4 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44521. 相似文献
70.