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   261篇
  免费   0篇
电工技术   7篇
化学工业   36篇
金属工艺   11篇
机械仪表   1篇
建筑科学   27篇
能源动力   6篇
轻工业   43篇
水利工程   2篇
石油天然气   1篇
无线电   6篇
一般工业技术   47篇
冶金工业   42篇
原子能技术   3篇
自动化技术   29篇
  2022年   5篇
  2021年   7篇
  2020年   2篇
  2019年   8篇
  2018年   15篇
  2017年   11篇
  2016年   12篇
  2015年   6篇
  2014年   5篇
  2013年   24篇
  2012年   16篇
  2011年   14篇
  2010年   18篇
  2009年   26篇
  2008年   13篇
  2007年   9篇
  2006年   5篇
  2005年   6篇
  2004年   2篇
  2003年   1篇
  2002年   4篇
  2001年   1篇
  2000年   2篇
  1999年   2篇
  1998年   7篇
  1997年   5篇
  1996年   3篇
  1995年   4篇
  1994年   4篇
  1991年   1篇
  1990年   1篇
  1986年   1篇
  1984年   4篇
  1983年   2篇
  1982年   2篇
  1981年   3篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1972年   1篇
排序方式: 共有261条查询结果,搜索用时 546 毫秒
101.
European consumer willingness to purchase fat-modified foods was surveyed as part of the LIPGENE study. Representative samples of consumers (n = 5967) were interviewed in six countries (France, Great Britain, Portugal, Germany, Poland, and Italy). Of these 2025 were considered as “reporters” who indicated having at least one of: high cholesterol; high blood pressure; central obesity; and/or high blood sugar. Perceived risk from these conditions was also assessed on a 10-point scale. Principal component analysis suggested that those who perceived themselves at greater risk of conditions associated with metabolic syndrome, and those who were reporters, more frequently indicated willingness to purchase “healthy” fat-modified food products. The most preferred ‘vehicles’ for fat modification were fish and cheese. Acceptance of fat-modified fish, red meat and cheese product concepts, both standard and GM was positively associated with perceived risk of conditions associated with metabolic syndrome. Over 20% of reporters were willing to purchase GM fat-modified fish and cheese products. Our results indicate that if standard and GM fat-modified food products can be shown to ameliorate the risks presented by conditions associated with metabolic syndrome, there is a ready market for such foods.  相似文献   
102.
Brewers’ spent grain (BSG), a by-product of the brewing industry, contains high amounts of phenolic acids, which have antioxidant effects. The present study examined the ability of BSG extracts to protect against the genotoxic effects of oxidants, hydrogen peroxide (H2O2), 3-morpholinosydnonimine hydrochloride (SIN-1), 4-nitroquinoline 1-oxide (4-NQO) and tert-butylhydroperoxide (t-BOOH) in U937 cells. Four pale (P1–P4) and four black (B1–B4) BSG extracts were investigated. U937 cells were pre-incubated with BSG extracts, exposed to the oxidants and the DNA damage was measured by the Comet assay. The black BSG extracts (B1–B4) significantly protected against H2O2-induced DNA damage. Extract B2, which had the highest phenol content, provided the greatest protection. Extracts P2, B2, B3 and B4 provided significant protection against SIN-1-induced DNA damage. None of the extracts protected against DNA damage induced by t-BOOH and 4-NQO. The DNA protective effects of the BSG phenolic extracts may be related to iron chelation.  相似文献   
103.
Base metal (Cu, Fe, and Ni) and trace element (Ag, Au, Co, Pd, and Pt) distributions between low-iron nickel mattes with [Ni]:[Cu] = 4 (w/w) have been studied at 1623 K to 1723 K (1350 °C to 1450 °C). We equilibrated small slag–matte samples with CO–CO2–SO2–Ar atmospheres in pre-selected \( P_{{{\text{S}}_{2} }} \)\( P_{{{\text{O}}_{2} }} \) points, maintaining silica saturation by fused silica crucibles. The slags studied contained about 0 to 8.5 wt pct MgO. The matte–slag distribution coefficients L m/s[Me] were obtained from assays by electron probe X-ray microanalysis for the matte and by laser ablation-ICP-mass spectrometry for the slag. The measured L m/s[Me] values were clearly dependent on iron concentration of the matte and on MgO concentration of the slag, with values on the order of 104, 105, and 104 for gold, platinum, and palladium, respectively, in the 5 wt pct iron in matte experiments. The obtained data for silver were scattered, due to volatilization, resulting in depletion of most silver and its escape from matte to gas phase during the 3-hour equilibration period. The matte-to-slag distribution coefficient for silver was estimated to be L m/s[Ag] = 100 to 400. We also measured the distributions of the base metals Cu and Ni in the same conditions as the trace elements.  相似文献   
104.
The unique rumen of dairy cows allows them to digest fibrous forages and feedstuffs. Surprisingly, to date few attempts have been made to develop national methods to gain an understanding on the make-up of a dairy cow's diet, despite the importance of milk production. Consumer interest is growing in purchasing milk based on the composition of the cows' diet and the time they spend grazing. The goal of this research was to develop such a methodology using the national farm survey of Ireland as a data source. The analysis was completed for a 3-yr period from 2013 to 2015 on a nationally representative sample of 275 to 318 dairy farms. Trained auditors carried out economic surveys on farms 3 to 4 times per annum. The auditors collected important additional information necessary to estimate the diet of cows including the length of the grazing season, monthly concentrate feeding, type of forage(s) conserved, and milk production. Annual cow intakes were calculated to meet net energy requirements for production, maintenance, activity, pregnancy, growth, and live weight change using survey data and published literature. Our analysis showed that the average annual cow feed intake on a fresh matter basis ranged from 22.7 t in 2013 to 24.8 t in 2015 and from 4.8 to 5 t on a dry matter basis for the same period. Forage, particularly pasture, was the largest component of the Irish cow diet, typically accounting for 96% of the diet on a fresh matter basis and 82% of dry matter intake over the 3 yr. Within the cows' forage diet, grazed pasture was the dominant component and on average contributed 74 to 77% to the average annual cow fresh matter diet over the period. The proportion of pasture in the annual cow diet as fed was also identified as a good indicator of the time cows spend grazing (e.g., coefficient of determination = 0.85). Monthly, forage was typically the main component of the cow diet, but the average contribution of concentrate was substantial for the early spring months of January and February (30 to 35% of dry matter intake). Grazed pasture was the dominant source of forage from March to October and usually contributed 95 to 97% of the diet as fed in the summer period. Overall, the national farm survey from 2013 to 2015 shows that Irish dairy farms are very reliant on forage, particularly pasture, regardless of whether it is reported on a dry matter basis or as fed. There is potential to replicate this methodology in any regions or nations where representative farm surveys are conducted.  相似文献   
105.
106.
Planning has been widely vilified for the role it plays in disrupting the development process, hindering economic growth and creating the conditions for undersupply in housing markets, characterised by unaffordability. In this paper we hope to show that the analyses that support this view of planning are incomplete because of the theoretical limitations of the neoclassical tradition from which they emerge. By way of alternative we posit an account of planning that draws upon game theory and behavioural economics to explore those aspects of the activity that serve to animate the development process. This interpretation of planning as a “market maker” is explored through empirical case study research from three continental European contexts where planning is charged with playing an economically active role to control liquidity.  相似文献   
107.
Air kerma calibration coefficients for a reference class ionization chamber from narrow x-ray spectra and cesium 137 gamma-ray beams were compared between the National Institute of Standards and Technology (NIST) and the Kenya Bureau of Standards (KEBS). A NIST reference-class transfer ionization chamber was calibrated by each laboratory in terms of the quantity air kerma in four x-ray reference radiation beams of energies between 80 kV and 150 kV and in a cesium 137 gamma-ray beam. The reference radiation qualities used for this comparison are described in detail in the ISO 4037 publication.[1]The comparison began in September 2008 and was completed in March 2009. The results reveal the degree to which the participating calibration facility can demonstrate proficiency in transferring air kerma calibrations under the conditions of the said facility at the time of the measurements. The comparison of the calibration coefficients is based on the average ratios of calibration coefficients.  相似文献   
108.
A comparison has been made of the air-kerma standards for low-energy x rays at the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). The comparison involved a series of measurements at the PTB and the NIST using the air-kerma standards and two NIST reference-class transfer ionization chamber standards. Results are presented for the reference radiation beam qualities in the range from 25 kV to 50 kV for low energy x rays, including the techniques used for mammography dose traceability. The tungsten generated reference radiation qualities, between 25 kV and 50 kV used for this comparison, are new to NIST; therefore this comparison will serve as the preliminary comparison for NIST and a verification of the primary standard correction factors. The mammography comparison will repeat two previously unpublished comparisons between PTB and NIST. The results show the standards to be in reasonable agreement within the standard uncertainty of the comparison of about 0.4 %.  相似文献   
109.
One of the most frequently encountered causes of failure in engineering fasteners is fatigue. Typical locations for the fatigue of fasteners are the stress concentrations represented by the head to shank fillet, the first engaged thread and the thread runout. These locations are examined in relation to design rules known for over 60 years to be effective in reducing the stress concentration effect, but seldom used in engineering bolts, despite their relative simplicity. These design rules are also examined in relation to common fastener standards and their silence with regard to fatigue considerations.  相似文献   
110.
Confirmation bias is the tendency to bolster a hypothesis by seeking consistent evidence while minimizing inconsistent evidence. In criminal investigations, preferring hypothesis-consistent information could undermine accuracy by leading investigators to disregard evidence that challenges their theory of a case. Two studies examine factors that influence confirmation bias in criminal investigations. In Study 1 (N = 108), participants who articulated a hypothesis early in their review of a mock police file showed bias in seeking and interpreting evidence to favor that hypothesis. In Study 2 (N = 109), participants who considered why their hypothesis might be wrong showed less bias, but those who generated additional hypotheses did not. Implications for improving accuracy of investigations and suggestions for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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