首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3413篇
  免费   102篇
  国内免费   50篇
电工技术   88篇
综合类   165篇
化学工业   131篇
金属工艺   17篇
机械仪表   86篇
建筑科学   521篇
矿业工程   103篇
能源动力   193篇
轻工业   224篇
水利工程   53篇
石油天然气   188篇
武器工业   16篇
无线电   91篇
一般工业技术   589篇
冶金工业   232篇
原子能技术   82篇
自动化技术   786篇
  2024年   2篇
  2023年   33篇
  2022年   62篇
  2021年   45篇
  2020年   78篇
  2019年   68篇
  2018年   77篇
  2017年   94篇
  2016年   131篇
  2015年   130篇
  2014年   214篇
  2013年   252篇
  2012年   206篇
  2011年   353篇
  2010年   207篇
  2009年   232篇
  2008年   206篇
  2007年   191篇
  2006年   209篇
  2005年   176篇
  2004年   115篇
  2003年   120篇
  2002年   73篇
  2001年   73篇
  2000年   39篇
  1999年   42篇
  1998年   28篇
  1997年   24篇
  1996年   14篇
  1995年   13篇
  1994年   5篇
  1993年   7篇
  1992年   7篇
  1991年   7篇
  1990年   3篇
  1989年   5篇
  1988年   6篇
  1987年   1篇
  1986年   1篇
  1985年   2篇
  1984年   4篇
  1983年   7篇
  1981年   1篇
  1977年   1篇
  1973年   1篇
排序方式: 共有3565条查询结果,搜索用时 15 毫秒
121.
《Ergonomics》2012,55(6):688-709
The present study developed risk assessment models for carpal tunnel syndrome (CTS) which can provide information of the likelihood of developing CTS for an individual having certain personal characteristics and occupational risks. A case-referent study was conducted consisting of two case groups and one referent group: (1) 22 work-related CTS patients (W-CTS), (2) 25 non-work related CTS patients (NW-CTS), and (3) 50 healthy workers (HEALTHY) having had no CTS history. The classification of CTS patients into one of the case groups was determined according to the type of insurance covering their medical costs. Personal characteristics, psychosocial stresses at work, and physical work conditions were surveyed by using a questionnaire tailor-designed to CTS (reliability of each scale ? 0.7). By contrasting the risk information of each case group to that of the referent group, three logistic regression models were developed: W-CTS/HEALTHY, NW-CTS/HEALTHY, and C-CTS/HEALTHY (C-CTS, the combined group of W-CTS and NW-CTS). ROC analysis indicated that the models have satisfactory discriminability (d′ = ;1.91 to 2.51) and high classification accuracy (overall accuracy = 83 – 89%). Both W-CTS/HEALTHY and C-CTS/HEALTHY include personal and physical factors, while NW-CTS/HEALTHY involves only personal factors. This suggests that the injury causation of NW-CTS patients should be attributable mainly to their ‘high’ personal susceptibility to the disorder rather than exposure to adverse work conditions, while that of W-CTS patients be attributable to improper work conditions and CTS-prone personal characteristics in combination.  相似文献   
122.
Food additives, such as food colours or sweeteners, play an important part in food supply. For a variety of reasons, some consumers might regard the use of food additives, especially artificial ones, with suspicion; food additives are considered unnatural, unhealthy or even a public health risk. The goal of this study was to investigate consumers’ perceptions and the most essential variables related to the acceptance of food additives. Two versions of a paper-and-pencil questionnaire, one investigating artificial food colours and the other investigating artificial sweeteners, were distributed to a large sample of Swiss German households. The final samples for artificial food colours and artificial sweeteners comprised 506 and 487 participants respectively. The questionnaires contained items on consumers’ acceptance, risk and benefit perception, trust in regulators, knowledge of regulation and their preference for natural products. The relationships between variables were investigated in a path model, which was constructed based on a review of previous literature. The path coefficients suggested that risk and benefit perceptions significantly influence the acceptance of the two selected food additives. The risk and benefit perceptions were influenced by consumers’ knowledge of regulation, their trust in regulators, and their preference for natural products. In the discussion, the study’s findings are examined in terms of their implications for further research and for the development of concrete communication materials.  相似文献   
123.
We examine the dependence structure of electricity spot prices across regional markets in Australia. One of the major objectives in establishing a national electricity market was to provide a nationally integrated and efficient electricity market, limiting market power of generators in the separate regional markets. Our analysis is based on a GARCH approach to model the marginal price series in the considered regions in combination with copulae to capture the dependence structure between the marginals. We apply different copula models including Archimedean, elliptical and copula mixture models. We find a positive dependence structure between the prices for all considered markets, while the strongest dependence is exhibited between markets that are connected via interconnector transmission lines. Regarding the nature of dependence, the Student-t copula provides a good fit to the data, while the overall best results are obtained using copula mixture models due to their ability to also capture asymmetric dependence in the tails of the distribution. Interestingly, our results also suggest that for the four major markets, NSW, QLD, SA and VIC, the degree of dependence has decreased starting from the year 2008 towards the end of the sample period in 2010. Examining the Value-at-Risk of stylized portfolios constructed from electricity spot contracts in different markets, we find that the Student-t and mixture copula models outperform the Gaussian copula in a backtesting study. Our results are important for risk management and hedging decisions of market participants, in particular for those operating in several regional markets simultaneously.  相似文献   
124.
The Iterated Prisoner’s Dilemma (IPD) game has been commonly used to investigate the cooperation among competitors. However, most previous studies on the IPD focused solely on maximizing players’ average payoffs without considering their risk preferences. By introducing the concept of income stream risk into the IPD game, this paper presents a novel evolutionary IPD model with agents seeking to balance between average payoffs and risks with respect to their own risk attitudes. We build a new IPD model of multiple agents, in which agents interact with one another in the pair-wise IPD game while adapting their risk attitudes according to their received payoffs. Agents become more risk averse after their payoffs exceed their aspirations, or become more risk seeking after their payoffs fall short of their aspirations. The aspiration levels of agents are determined based on their historical self-payoff information or the payoff information of the agent population. Simulations are conducted to investigate the emergence of cooperation under these two comparison methods. Results indicate that agents can sustain a highly cooperative equilibrium when they consider only their own historical payoffs as aspirations (called historical comparison) in adjusting their risk attitudes. This holds true even for the IPD with a short game encounter, for which cooperation was previously demonstrated difficult. However, when agents evaluate their payoffs in comparison with the population average payoff (called social comparison), those agents with payoffs below the population average tend to be dissatisfied with the game outcomes. This dissatisfaction will induce more risk-seeking behavior of agents in the IPD game, which will constitute a strong deterrent to the emergence of mutual cooperation in the population.  相似文献   
125.
Online networks using Web 2.0 technologies have proven useful for communication among all parties involved in managing crises. These networks rapidly disseminate information allowing for coordination among organizations responding to the needs of those whose safety and wellbeing are threatened by the crisis and its aftermath. This study provides a network analysis of official Twitter accounts activated during the Charleston, West Virginia, water contamination crisis in 2014. The city’s water supply was rendered unfit for drinking or bathing after 7500 gallons of a toxic chemical leaked into the Elk River. The network created by the 41 Twitter accounts associated with the West Virginia water contamination lacked density, contained several isolates, exchanged information quickly (geodesic distance diameter), and contained both national and local accounts. The lack of density indicates limited exchange of information, particularly between national and federal accounts. The rapid dissemination of the information that was shared and the fact that some accounts did bridge the local and national gap, however, show the positive potential for such networks in responding to crises.  相似文献   
126.
A. Rackes  M. S. Waring 《Indoor air》2016,26(4):642-659
We used existing data to develop distributions of time‐averaged air exchange rates (AER), whole‐building ‘effective’ emission rates of volatile organic compounds (VOC), and other variables for use in Monte Carlo analyses of U.S. offices. With these, we explored whether long‐term VOC emission rates were related to the AER over the sector, as has been observed in the short term for some VOCs in single buildings. We fit and compared two statistical models to the data. In the independent emissions model (IEM), emissions were unaffected by other variables, while in the dependent emissions model (DEM), emissions responded to the AER via coupling through a conceptual boundary layer between the air and a lumped emission source. For 20 of 46 VOCs, the DEM was preferable to the IEM and emission rates, though variable, were higher in buildings with higher AERs. Most oxygenated VOCs and some alkanes were well fit by the DEM, while nearly all aromatics and halocarbons were independent. Trends by vapor pressure suggested multiple mechanisms could be involved. The factors of temperature, relative humidity, and building age were almost never associated with effective emission rates. Our findings suggest that effective emissions in real commercial buildings will be difficult to predict from deterministic experiments or models.  相似文献   
127.
Hydrogen energy applications often require that systems are used indoors (e.g., industrial trucks for materials handling in a warehouse facility, fuel cells located in a room, or hydrogen stored and distributed from a gas cabinet). It may also be necessary or desirable to locate some hydrogen system components/equipment inside indoor or outdoor enclosures for security or safety reasons, to isolate them from the end-user and the public, or from weather conditions.Using of hydrogen in confined environments requires detailed assessments of hazards and associated risks, including potential risk prevention and mitigation features. The release of hydrogen can potentially lead to the accumulation of hydrogen and the formation of a flammable hydrogen-air mixture, or can result in jet-fires. Within Hyindoor European Project, carried out for the EU Fuel Cells and Hydrogen Joint Undertaking safety design guidelines and engineering tools have been developed to prevent and mitigate hazardous consequences of hydrogen release in confined environments. Three main areas are considered: Hydrogen release conditions and accumulation, vented deflagrations, jet fires and including under-ventilated flame regimes (e.g., extinguishment or oscillating flames and steady burns). Potential RCS recommendations are also identified.  相似文献   
128.
This paper identifies segments of Chinese consumers based on their perception of personal risk, how worried they are and their subjective knowledge about seven possible food-related hazards: additives, residues, counterfeit, inferior, genetically modified, deteriorated and nutritionally imbalanced food. Data were collected through a consumer survey conducted in Beijing (534 participants) and in Baoding (437 participants). Three clusters were identified: worried and knowledgeable consumers (60.1%), worried and ignorant consumers (21.7%) and moderately worried consumers (18.2%). The first two groups reported a high level of worry and high perception of personal risk about food-related hazards in China. The two hazards they were most worried about were counterfeit food and inferior quality food. Television, internet and personal communication were the three information channels most frequently used by participants to obtain information about food safety. Worried and ignorant consumers reported less frequent use of magazines, books and brochures compared with other consumers. Medical doctors, personal experience and research institutes were the three most trusted information sources for the first two groups of consumers. Moderately worried consumers only placed high levels of trust in medical doctors and themselves. Consumers' perceptions about the knowledge, honesty and concern of different information sources significantly and positively affected their trust in those sources. The study concludes by making recommendations as to how to improve communications with the different identified consumer segments and identifies future research required to expand its validity.  相似文献   
129.
《Ergonomics》2012,55(11):1531-1538
This paper discusses recent criticisms of the theory of risk homoeostasis which has been put forward to explain the spatial, temporal and per capita traffic accident risk in a given jurisdiction, as well as their pattern of interrelation. Four assumptions have recently been proposed in the literature as being necessary for the theory to be valid. These were viewed as wanting and, therefore, presented as a challenge to the theory in question. In the present discussion, these four assumptions are examined on their conceptual pertinence. It is concluded that, without some major and some seemingly minor-yet theoretically crucial—modifications, none of these assumptions appear to be essential to the validity of the theory under debate.  相似文献   
130.
Shared risks and opportunities set specific premises for risk management (RM) in temporary multi-organizations (TMOs). However, most project RM research is presented from the perspective of a single-organizational project delivery team or covers limited risk perceptions and RM approaches. This paper aims to address how well the body of knowledge on multi-organizational RM corresponds to a state-of-art understanding on project RM and to identify which gaps need to be addressed in future research. The review involves: 1) the preferred view of risk as threat and/or opportunity, 2) the nature of addressed risks as anticipated or unanticipated risks or unrealistic assumptions, 3) the role of the multi-organization as the source of risks and/or resources for risk management (RM), and 4) the allocation of risk responsibilities. The review covers research papers published between 2000 and 2012 in four journals: International Journal of Project Management (IJPM), Project Management Journal (PMJ), Journal of Construction Engineering and Management (JCEM), and IEEE Transactions on Software Engineering (TSE). 105 eligible research papers were identified. The results and conclusion outline the identified main gaps in multi-organizational RM research compared to the state-of-art RM research and TMO-specific characteristics. The results can be used to inform research agendas on more holistic and dynamic multi-organizational RM concepts.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号