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   293篇
  免费   12篇
电工技术   7篇
化学工业   32篇
金属工艺   4篇
机械仪表   4篇
建筑科学   9篇
能源动力   27篇
轻工业   47篇
水利工程   4篇
无线电   16篇
一般工业技术   32篇
冶金工业   94篇
原子能技术   1篇
自动化技术   28篇
  2023年   1篇
  2022年   6篇
  2021年   9篇
  2020年   2篇
  2019年   4篇
  2018年   7篇
  2017年   5篇
  2016年   8篇
  2015年   9篇
  2014年   11篇
  2013年   13篇
  2012年   11篇
  2011年   17篇
  2010年   11篇
  2009年   10篇
  2008年   15篇
  2007年   9篇
  2006年   7篇
  2005年   5篇
  2004年   6篇
  2003年   4篇
  2002年   9篇
  2001年   1篇
  2000年   1篇
  1999年   3篇
  1998年   19篇
  1997年   17篇
  1996年   7篇
  1995年   4篇
  1994年   8篇
  1993年   6篇
  1992年   1篇
  1991年   2篇
  1990年   5篇
  1989年   7篇
  1988年   6篇
  1987年   2篇
  1986年   1篇
  1985年   2篇
  1984年   4篇
  1983年   3篇
  1982年   3篇
  1980年   5篇
  1978年   1篇
  1977年   3篇
  1976年   12篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
排序方式: 共有305条查询结果,搜索用时 10 毫秒
91.
The problem of separating single-wall carbon nanotubes (CNTs) by diameter and/or chirality is one of the greatest impediments toward the widespread application of these promising materials in nanoelectronics. In this paper, we describe a novel physical-chemical method for diameter-selective CNT separation that is both simple and effective and that allows up-scaling to large volumes at modest cost. Separation is based on size-selective noncovalent matching of an appropriate anchor molecule to the wall of the CNT, enabling suspension of the CNTs in solvents in which they would otherwise not be soluble. We demonstrate size-selective separation in the 1-2 nm diameter range using easily synthesized oligo-acene adducts as a diameter-selective molecular anchor. CNT field effect transistors fabricated from diameter-selected CNTs show markedly improved electrical properties as compared to nonselected CNTs.  相似文献   
92.
The purpose of this paper is to test the evidence for spatial assimilation and straight-line assimilation in the transition of leaving home in Denmark. Based on data from the extensive Danish registers, the paper analyses the home-leaving patterns of Danes, Turkish immigrants, Turkish descendants and Somali immigrants. Two main findings emerged. First, while spatial segregation patterns of home-leavers were clear, inter-generational mobility did take place, supporting the notion of straight-line assimilation. Second, inter-generational effects were identified. While there was no indication that parental socio-economic situation affected the spatial segregation of home-leavers, substantial effects were found for the share of ethnic minorities in the parental neighbourhood: the higher the share of ethnic minorities, the higher the hazard for moving to an ethnic neighbourhood and the lower the hazard for moving to a non-ethnic neighbourhood. Similarity in the patterns of natives and the ethnic minority groups indicates that the processes taking place might be about more than assimilation between generations.  相似文献   
93.
94.
In this paper we aim to give insight to how manufacturing strategies, represented by manufacturing paradigms are linked to different approaches to knowledge. Strategies are closely related to the development of core competence and how to deal with knowledge in general. In this paper we focus on how the different manufacturing strategies represent different challenges when it comes to knowledge creation and knowledge transfer. Our discussion has references to suppliers in the automotive industry, represented by a Scandinavian case. In this case the focus is on lean principles, which in contrast to mass manufacturing, represents attention to the synthetic knowledge base and tacit knowledge. Mass manufacturing, which is also still relevant in the automotive industry, is more centralised in its approach to knowledge and is focusing more on the analytical knowledge base and explicit knowledge. Knowledge should be a central part of companies’ strategies, also functional such as within manufacturing, and should cover issues such as: what is crucial knowledge, how do we create it, and how to transfer it to meet our overall company goals?  相似文献   
95.
The effects of restrictive feeding strategies aimed at promoting a compensatory growth response were investigated with respect to tenderness improvement in pork M. longissimus thoracis. Compensatory growth response is defined by increased weight in pigs fed ad libitum after a period with restricted feeding compared to pigs fed ad libitum the entire fattening period. Specifically, the aim was to study the sensory textural characteristics after female and entire male pigs have been exposed to restrictions in either energy, protein or both in specific growth periods. It was found that textural differences were caused by feeding strategies and not related to variation in intramuscular fat, which did not vary significantly between genders. The female pigs demonstrated compensatory growth response and the texture was significantly (P<0.001) improved by low dietary level of energy from day 50 to 90 and normal dietary level of protein during the entire feeding period. For the entire male pigs, low level of protein in the late feeding period significantly (P<0.05) improved the texture. Also, low level of protein and normal level of energy in the early feeding period resulted in improved tenderness. However, these texture improvements were deemed not to be an effect of compensatory growth since the entire male pigs did not compensate for the feeding restriction in the early feeding period. The tenderness enhancement for the entire male pigs compromised the production results in terms of 7-15% lower carcass weight.  相似文献   
96.
97.
Participatory methods provide an increasingly accepted path to integrated assessment. This paper reflects on the role of two participatory modelling initiatives implemented in a highly conflictive setting: the Mancha Occidental aquifer, Spain. The methodologies are described within the context of the case study, examining their potential relevance to integrated assessment from a conceptual standpoint. The strengths and weaknesses of each approach are analysed in absolute and relative terms, attending to the different stages of the modelling process. The focus then shifts to explore the implications of this work within the context of participatory integrated assessment and scenario analysis. This serves the purpose of establishing the reasons why the tools have been useful in the eyes of stakeholders, and how the case-specific findings of this project may be relevant to other settings.  相似文献   
98.
Evidence of the causal role of marketing in the tobacco epidemic and the advent of the WHO Framework Convention on Tobacco Control have inspired more than half the countries in the world to ban some forms of tobacco marketing. This paper briefly describes the ways in which cigarette marketing is restricted and the tobacco industry's efforts to subvert restrictions. It reviews what is known about the impact of marketing regulations on smoking by adults and adolescents. It also addresses what little is known about the impact of marketing bans in relation to concurrent population-level interventions, such as price controls, anti-tobacco media campaigns and smoke-free laws. Point of sale is the least regulated channel and research is needed to address the immediate and long-term consequences of policies to ban retail advertising and pack displays. Comprehensive marketing restrictions require a global ban on all forms of promotion, elimination of packaging and price as marketing tools, and limitations on the quantity, type and location of tobacco retailers.  相似文献   
99.
The objective of the study was to evaluate a new pathogen inactivation concept that combines application of pressurized steam simultaneously with high-power ultrasound through a series of nozzles. On skin and meat surfaces of pork jowl samples, counts of total viable bacteria were reduced by 1.1 log CFU/cm(2) after treatment for 1 s and by 3.3 log CFU/cm(2) after treatment for 4 s. The mean reduction of 1.7 to 3.3 log CFU/cm(2) on the skin surface was significantly higher than the reduction of 1.1 to 2.5 log CFU/cm(2) on the meat surface. The inactivation of Salmonella Typhimurium, Salmonella Derby, Salmonella Infantis, Yersinia enterocolitica, and a nonpathogenic Escherichia coli was studied on inoculated samples that were treated for 0.5 to 2.0 s. With one exception, no significant differences in reduction were observed among the bacterial types. After treatment for 0.5 s, the 0.9-to 1.5-log reductions of E. coli were significantly higher than the 0.4- to 1.1-log reductions for Salmonella and Y. enterocolitica. Overall, reductions increased by increasing treatment time; reductions were 0.4 to 1.5 log CFU/cm(2) after treatment for 0.5 s and 2.0 to 3.6 log CFU/cm(2) after treatment for 2 s. Reductions on the skin (1 to 3.6 log CFU/cm(2)) were significantly higher than reductions on the meat surface (1 to 2.5 log CFU/cm(2)). The reduced effect on the meat surface may be explained by greater protection of bacteria in deep structures at the muscle surface. No significant difference in reduction was observed between samples inoculated with 10(4) CFU/cm(2) and those inoculated with 10(7) CFU/cm(2), and cold storage of samples for 24 h at 5°C after steam-ultrasound treatment did not lead to changes in recovery of bacteria.  相似文献   
100.
Increasing attention on extreme hydrological events has created considerable demand for real-time information on surface water, groundwater and the unsaturated zone. In the present study, we describe how to convert a national water resources model (DK-model) covering the entire freshwater cycle in Denmark to real-time application. We have engaged stakeholders in the process of designing a hydrological real-time system. The participatory approach has been supported by a web-based questionnaire survey and a participatory workshop. A system prototype presented to the stakeholders simulates groundwater levels, streamflow and water content in the root zone with a lead time of 48 h. The active engagement of stakeholders has provided very valuable insights and feedbacks regarding how model and data should be combined in a real-time to best supporting water resources management.  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