全文获取类型
收费全文 | 1807篇 |
免费 | 88篇 |
专业分类
电工技术 | 4篇 |
综合类 | 1篇 |
化学工业 | 435篇 |
金属工艺 | 32篇 |
机械仪表 | 25篇 |
建筑科学 | 73篇 |
矿业工程 | 2篇 |
能源动力 | 17篇 |
轻工业 | 268篇 |
水利工程 | 24篇 |
石油天然气 | 6篇 |
无线电 | 60篇 |
一般工业技术 | 268篇 |
冶金工业 | 437篇 |
原子能技术 | 3篇 |
自动化技术 | 240篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 63篇 |
2021年 | 62篇 |
2020年 | 29篇 |
2019年 | 47篇 |
2018年 | 57篇 |
2017年 | 44篇 |
2016年 | 50篇 |
2015年 | 51篇 |
2014年 | 58篇 |
2013年 | 102篇 |
2012年 | 104篇 |
2011年 | 156篇 |
2010年 | 126篇 |
2009年 | 98篇 |
2008年 | 132篇 |
2007年 | 113篇 |
2006年 | 70篇 |
2005年 | 67篇 |
2004年 | 58篇 |
2003年 | 42篇 |
2002年 | 48篇 |
2001年 | 41篇 |
2000年 | 27篇 |
1999年 | 29篇 |
1998年 | 17篇 |
1997年 | 20篇 |
1996年 | 21篇 |
1995年 | 12篇 |
1994年 | 19篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1895条查询结果,搜索用时 15 毫秒
131.
Exploratory spatial data analysis of the distribution of regional per capita GDP in Europe, 1980−1995 总被引:9,自引:0,他引:9
The aim of this paper is to study the space-time dynamics of European regional per capita GDP. A sample of 138 European regions
over the 1980–1995 period provides clear evidence of global and local spatial autocorrelation as well as spatial heterogeneity
in the distribution of regional per capita GDP. The detection of spatial clusters of high and low per capita GDP throughout
the period is an indication of the persistence of spatial disparities among European regions. The dynamism of European regions
is investigated by exploring the spatial pattern of regional growth. Implications for applied econometric work on the convergence
of European regions are then suggested.
Received: 11 September 2000 / Accepted: 11 March 2002
RID="*"
ID="*"Previous versions of this article were presented at the 6th RSAI World Congress 2000 “Regional Science in a Small World”,
Lugano, Switzerland, May 16–20, 2000 and the 40th ERSA Congress “European Monetary Union and Regional Policy”, Barcelona,
Spain, August 29 – September 1, 2000. We would like to thank L. Anselin, R.J.G.M. Florax, A. Getis, C. Baumont, an and suggestions.
We would also like to thank Eurostat: G. Decand and A. Behrens from the regional statistics section (division E4) as well
as J. Recktenwald and I. Dennis for the help they provided on the Eurostat-Regio database. The usual disclaimer applies. 相似文献
132.
The respective influences of exposure and inborn neural networks on conspecific and nonconspecific face processing remain unclear. Although the importance of exposure in the development of object and face recognition in general is well documented, studies explicitly comparing face recognition across species showed a species-specific effect. For instance, laboratory monkeys exposed daily to human faces were better at discriminating monkeys than humans, suggesting that the role of exposure may not be the only factor affecting cross-species recognition. In the present study, the authors investigated conspecific and nonconspecific face recognition in chimpanzees (Pan troglodytes) from 2 primate centers that provided different exposure to chimpanzee and human faces. The authors showed that the chimpanzees from the center providing more exposure to human faces than to chimpanzee faces were better at discriminating human faces than they were at discriminating chimpanzee faces. The chimpanzees from the other center did not show the same effect. A computational simulation was developed to evaluate the average similarities among human pictures and among chimpanzee pictures. Both categories were comparable. Chimpanzees' scores were significantly correlated with the similarity coefficients. Overall, the results show that exposure is a critical determinant in conspecific and nonconspecific face recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
133.
The use of manufacturing system reconfiguration in conjunction with maintenance operations has not been previously reported in the literature. This research attempts to incorporate reconfiguration into Preventive Maintenance (PM) actions for improved system performance in terms of reduced total cost. This paper presents an Integrated Reconfiguration and Age-Based Maintenance (IRABM) policy and applies it to a parallel-serial manufacturing system. The expected total cost of implementing the IRABM policy is estimated and minimized through a simulation-based heuristic optimization procedure. Using this method, it is possible to systematically identify the conditions under which the integration of reconfiguration into maintenance is cost effective. In addition, numerical examples demonstrate that the manufacturing system could have a higher probability of fulfilling production requirements at a lower cost under the IRABM policy compared to the conventional age-based PM policy. The influences of the input parameters associated with reconfiguration, production, and reliability on the performance of IRABM policy also are studied. 相似文献
134.
Research on aggression from organizational outsiders (customers, clients or patients) has ignored insider-instigated aggression, and has been limited to employees in emotional labor jobs (e.g., social work and customer services). The authors argue that customer-employee interactions have distinct characteristics from organizational insider interactions, and provide two studies to compare the frequency and strain of verbal abuse from customers, supervisors and coworkers. Furthermore, they assess whether customer verbal abuse is only a critical issue for employees in jobs requiring emotional labor, measured with both O*NET job codes and self-reported display rules. With a national random sample of U.S. employees (n = 2446) and a convenience sample of U.S. employees who have customer contact (n = 121), the authors find that verbal abuse from outsiders (1) occurs more frequently than insider verbal abuse, particularly for those with higher emotional labor requirements, and (2) predicts emotional exhaustion over and above insider verbal abuse, regardless of emotional labor requirements. The authors conclude that better integration of customer aggression and insider aggression research is needed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
135.
136.
Scheduling schemes play a key role in the system performance of broadband wireless systems such as WLANs/WMANs. Maximal SNR and round robin are two conventional scheduling strategies that emphasize efficiency and fairness, respectively. The proportional fair scheme provides a trade-off between efficiency and fairness, and has been well studied in TDMA and CDMA systems. In this article we extended the PF scheduling scheme to OFDM-based BWSs (OPF). In addition, we propose three variations: adaptive OPF (AOPF), multimedia AOPF (MAOPF), and normalized MAOPF (NMAOPF) in order to meet the QoS requirements for multirate services in multimedia systems. The adaptive modulation and coding schemes in time varying and frequency selective fading are considered. The system performances of the algorithms are compared in terms of efficiency (throughput and mean packet delay) and fairness (user satisfaction rate and average user rate). Joint physical and media access control layer simulation results show that AOPF and MAOPF can improve throughput at the cost of fairness, and NMAOPF can provide the highest throughput without losing fairness. 相似文献
137.
Emmanuel Defaÿ David Wolozan Jean-Pierre Blanc Emmanuelle Serret Pierre Garrec Sophie Verrun Denis Pellissier Philippe Delpech Julie Guillan Bernard Andr Laurent Ulmer Marc Aïd Pascal Ancey 《Solid-state electronics》2007,51(11-12):1624
This paper describes realization and characterization of SrTiO3 (STO) high K MIM capacitors above BiCMOS integrated circuit (IC). These capacitances are connected to IC and are used as coupling capacitors in order to realize a high pass filter. Surface capacitance achieved is 10 nF/mm2 with capacitance value of 1.2 nF. The process for STO MIM fabrication does not exceed 400 °C, which is compatible with interconnections. Typical K and dielectric losses values obtained are, respectively 110% and 2%. Yield obtained reaches 83% for capacitors. A functional high pass filter using these STO capacitors was realized in this study. It exhibits a cut-off frequency at 6.5 kHz and a constant gain at higher frequencies of −1.3 dB. 相似文献
138.
This study uses social capital theory and social network analysis to explore how relations in an online academic communication network impact the overall structure of that network. Social network analysis is a particularly advantageous methodological tool for linking changes in microlevel choices to macrolevel structural alterations. Results indicate the online communication network’s structure exists independent of changes in communication ties. Specifically degree centrality, betweenness centrality, and clique formation indicated communication ties are initiated and discontinued over a 7-month timeframe. However, the dynamic nature of the microlevel communication choices does not mirror the quasi-stable structure of the online network. Results provide avenues for future research. 相似文献
139.
We explore the problem of budgeted machine learning, in which the learning algorithm has free access to the training examples’ class labels but has to pay for each attribute that is specified. This learning model is appropriate in many areas, including medical applications. We present new algorithms for choosing which attributes to purchase of which examples, based on algorithms for the multi-armed bandit problem. In addition, we also evaluate a group of algorithms based on the idea of incorporating second-order statistics into decision making. Most of our algorithms are competitive with the current state of art and performed better when the budget was highly limited (in particular, our new algorithm AbsoluteBR2). Finally, we present new heuristics for selecting an instance to purchase after the attribute is selected, instead of selecting an instance uniformly at random, which is typically done. While experimental results showed some performance improvements when using the new instance selectors, there was no consistent winner among these methods. 相似文献