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   7170篇
  免费   464篇
  国内免费   488篇
电工技术   308篇
技术理论   8篇
综合类   770篇
化学工业   236篇
金属工艺   46篇
机械仪表   133篇
建筑科学   1335篇
矿业工程   214篇
能源动力   911篇
轻工业   229篇
水利工程   284篇
石油天然气   224篇
武器工业   16篇
无线电   543篇
一般工业技术   420篇
冶金工业   551篇
原子能技术   14篇
自动化技术   1880篇
  2024年   24篇
  2023年   74篇
  2022年   144篇
  2021年   137篇
  2020年   177篇
  2019年   152篇
  2018年   166篇
  2017年   181篇
  2016年   242篇
  2015年   252篇
  2014年   404篇
  2013年   606篇
  2012年   407篇
  2011年   554篇
  2010年   478篇
  2009年   484篇
  2008年   478篇
  2007年   546篇
  2006年   495篇
  2005年   412篇
  2004年   312篇
  2003年   287篇
  2002年   202篇
  2001年   174篇
  2000年   119篇
  1999年   108篇
  1998年   71篇
  1997年   59篇
  1996年   57篇
  1995年   39篇
  1994年   33篇
  1993年   22篇
  1992年   19篇
  1991年   16篇
  1990年   16篇
  1989年   15篇
  1988年   14篇
  1987年   8篇
  1986年   7篇
  1985年   23篇
  1984年   16篇
  1983年   9篇
  1982年   8篇
  1981年   9篇
  1979年   6篇
  1975年   6篇
  1972年   4篇
  1966年   6篇
  1956年   4篇
  1954年   3篇
排序方式: 共有8122条查询结果,搜索用时 281 毫秒
991.
An increasing number of social media and networking platforms have been widely used. People usually post the online comments to share their own opinions on the networking platforms with social media. Business companies are increasingly seeking effective ways to mine what people think and feel regarding their products and services. How to correctly understand the online customers’ reviews becomes an important issue. This study aims to propose a method with the aspect-oriented Petri nets (AOPN) to improve the examination correctness without changing any process and program. We collect those comments from the online reviews with Scrapy tools, perform sentiment analysis using SnowNLP, and examine the analysis results to improve the correctness. In this paper, we apply our method for a case of the online movie comments. The experimental results have shown that AOPN is helpful for the sentiment analysis and verifying its correctness.  相似文献   
992.
ABSTRACT

This paper studies open innovation practices in Russian state-owned enterprises (SOEs). In 2011, the Russian Government set ambitious goals in science, technology and innovation, and uses its large SOEs as channels to achieve these targets. These initiatives focus on the collaboration among innovation actors and introduce open innovation (OI) principles. Based on a large-scale innovation survey, we compare private enterprises to state-owned peers and present selected case studies. Our data support the claim that Russian SOEs are driving the demand for technology and mainly absorb incoming OI activities. Different to their peers, SOEs extend their OI activities to the country’s knowledge producers, such as research and technology organisations (RTOs), and leading universities. They work on incorporating scientific knowledge that could, indeed, hold the key to globally competitive technological innovations, but also have better capabilities to include business partners.

Abbreviation : OI: Open innovation; SOE: State-owned enterprise; RTO: Research and technology organisation; STI: Science, technology and innovation.  相似文献   
993.
We study the impact of product definition in electricity auctions. Recognizing the key role of the auction rules—pay as bid, uniform—the definition of the product itself emerges also as a critical step. Poorly designed products may impact both the market performance and the physical operation of the system. We investigate the impacts that the product definition can have on the market outcomes. A product definition implemented in some electricity markets is used to unveil critical aspects that must be considered when electricity products are defined. Our results provide guidelines for improving the product definition in electricity auctions.  相似文献   
994.
We conducted a randomized trial of portable HEPA air cleaners with pre-filters designed to also reduce NH3 in non-smoking homes of children age 6-12 with asthma in Yakima Valley (Washington, USA). Participants were recruited through the Yakima Valley Farm Workers Clinic asthma education program. All participants received education on home triggers while intervention families additionally received two HEPA cleaners (child's sleeping area, main living area). Fourteen-day integrated samples of PM2.5 and NH3 were measured at baseline and one-year follow-up. We fit ANCOVA models to compare follow-up concentrations in HEPA vs control homes, adjusting for baseline concentrations. Seventy-one households (36 HEPA, 35 control) completed the study. Most were single-family homes, with electric heat and stove, A/C, dogs/cats, and mean (SD) 5.3 (1.8) occupants. In the sleeping area, baseline geometric mean (GSD) PM2.5 was 10.7 (2.3) μg/m3 (HEPA) vs 11.2 (1.9) μg/m3 (control); in the living area, it was 12.5 (2.3) μg/m3 (HEPA) vs 13.6 (1.9) μg/m3 (control). Baseline sleeping area NH3 was 62.4 (1.6) μg/m3 (HEPA) vs 65.2 (1.8) μg/m3 (control). At follow-up, HEPA families had 60% (95% CI, 41%-72%; p < .0001) and 42% (19%-58%; p = .002) lower sleeping and living area PM2.5, respectively, consistent with prior studies. NH3 reductions were not observed.  相似文献   
995.
We conceptualized security-related stress (SRS) and proposed a theoretical model linking SRS, discrete emotions, coping response, and information security policy (ISP) compliance. We used an experience sampling design, wherein 138 professionals completed surveys. We observed that SRS had a positive association with frustration and fatigue, and these negative emotions were associated with neutralization of ISP violations. Additionally, frustration and fatigue make employees more likely to follow through on their rationalizations of ISP violations by decreased ISP compliance. Our findings provide evidence that neutralization is not a completely stable phenomenon but can vary within individuals from one time point to another.  相似文献   
996.
This article covers recent developments of material research in Thailand with a focus on environmental sustainability. Data on Thailand’s consumption and economic growth are briefly discussed to present a relevant snapshot of its economy. A selection of research work is classified into three topics, namely, (a) resource utilization, (b) material engineering and manufacturing, and (c) life cycle efficiency. Material technologies have been developed and implemented to reduce the consumption of materials, energy, and other valuable resources, thus reducing the burden we place on our ecological system. At the same time, product life cycle study allows us to understand the extent of the environmental impact we impart to our planet.  相似文献   
997.
ABSTRACT

The purpose of this study was to examine the influence of trust variables (trust: competence, trust: benevolence, trust: integrity) on leadership regarding the organization’s information security policy (ISP) compliance. An instrument with four constructs was used to collect data from 474 non-management subjects from various organizations in the USA. Collected data were analyzed through multiple regression procedure. Results revealed that all trust variables (trust: competence, trust: benevolence, trust: integrity) were influential in predicting the leadership regarding the organization’s ISP compliance. The findings are discussed and implications for practice are outlined. Conclusion, limitations, and recommendations for future research are drawn.  相似文献   
998.
Wave Energy Conversion (WEC) devices are at a pre-commercial stage of development with feasibility studies sensitive to uncertainties surrounding assumed input costs. This may affect decision making. This paper analyses the impact these uncertainties may have on investor, developer and policymaker decisions using an Irish case study. Calibrated to data present in the literature, a probabilistic methodology is shown to be an effective means to carry this out. Value at Risk (VaR) and Conditional Value at Risk (CVaR) metrics are used to quantify the certainty of achieving a given cost or return on investment. We analyse the certainty of financial return provided by the proposed Irish Feed-in Tariff (FiT) policy. The influence of cost reduction through bulk discount is also discussed, with cost reduction targets for developers identified. Uncertainty is found to have a greater impact on the profitability of smaller installations and those subject to lower rates of cost reduction. This paper emphasises that a premium is required to account for cost uncertainty when setting FiT rates. By quantifying uncertainty, a means to specify an efficient premium is presented.  相似文献   
999.
Policy goals to transition national energy systems to meet decarbonisation and security goals must contend with multiple overlapping uncertainties. These uncertainties are pervasive through the complex nature of the system, the long term consequences of decisions, and in the models and analytical approaches used. These greatly increase the challenges of informing robust decision making. Energy system studies have tended not to address uncertainty in a systematic manner, relying on simple scenario or sensitivity analysis. This paper utilises an innovative UK energy system model, ESME, which characterises multiple uncertainties via probability distributions and propagates these uncertainties to explore trade-offs in cost effective energy transition scenarios. A linked global sensitivity analysis is used to explore the uncertainties that have most impact on the transition. The analysis highlights the strong impact of uncertainty on delivering the required emission reductions, and the need for an appropriate carbon price. Biomass availability, gas prices and nuclear capital costs emerge as critical uncertainties in delivering emission reductions. Further developing this approach for policy requires an iterative process to ensure a complete understanding and representation of different uncertainties in meeting mitigation policy objectives.  相似文献   
1000.
Food waste is a significant problem and consumers’ tendency to reject misshapen produce has been identified as a key contributing factor. The current work investigates the implications of consumers incorporating aesthetic beauty into their prototypes—mental renderings—of fruits and vegetables. It is proposed that consumers have idealized prototypes for produce and this impacts the aversion to misshapen produce. The authors draw on prototype theory to predict that consumers’ personal experiences will influence the extent to which their prototypes for these foods have been biased towards aesthetic beauty and, consequently, how they respond to produce that is misshapen. Across three studies, the authors demonstrate that consumers who have direct experience with produce cultivation view produce that is low in aesthetic beauty as more prototypical, less disgusting, and more desirable. This work contributes to the food waste literature by offering novel insights into the psychological basis of the aversion to misshapen produce. These findings also present important implications for food policy.  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