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   217篇
  免费   4篇
  国内免费   2篇
电工技术   7篇
综合类   18篇
化学工业   10篇
机械仪表   20篇
建筑科学   47篇
矿业工程   1篇
能源动力   1篇
轻工业   12篇
水利工程   3篇
石油天然气   1篇
无线电   28篇
一般工业技术   5篇
冶金工业   47篇
原子能技术   1篇
自动化技术   22篇
  2023年   1篇
  2022年   1篇
  2021年   2篇
  2019年   1篇
  2017年   2篇
  2016年   1篇
  2015年   1篇
  2013年   3篇
  2012年   4篇
  2011年   4篇
  2010年   6篇
  2009年   10篇
  2008年   31篇
  2007年   30篇
  2006年   22篇
  2005年   19篇
  2004年   6篇
  2003年   15篇
  2002年   18篇
  2001年   45篇
  2000年   1篇
排序方式: 共有223条查询结果,搜索用时 29 毫秒
1.
For measuring trypsin inhibitor activity (TIA), there are two major official methods: American Oil Chemists Society (AOCS) method Ba 12a-2020 and International Organization for Standardization (ISO) 14902:2001. The former was recently approved. The two methods differ in sample preparation, extraction, colorimetric assay systems and TIA calculations. In this study, the two methods were symmetrically compared using three unique sets of samples: assorted protein products of soybeans, pulses, and grains; soybeans boiled for varied durations; and soy white flakes toasted for varied durations. For given samples, significant differences existed in TIA measured by the two methods, resulting from effects related to the assay systems and TIA calculations, not from the difference in sample preparation and extraction. When the same trypsin was used, TIA (in mg trypsin inhibited/g sample) measured by the two methods were highly correlated (r = 0.9973, n = 27), giving an equation of y = 0.5464x − 0.4887, where y represents ISO values and x for AOCS values. The line connecting ratios of ISO/AOCS in TIA and AOCS values remained relatively flat around 0.53 but started to curve down when TIA approached the lowest. Furthermore, for the same samples, TIA values measured by the ISO method decreased with increasing specific activity of trypsin used, while AOCS values remained consistent, leading to decreasing ratios of ISO/AOCS. Therefore, accurate and direct comparison of the two methods was impossible. It could not be resolved by simply changing ISO method's calculations as hypothesized earlier. Regardless, for most samples, ISO values were roughly about 55% of AOCS values.  相似文献   
2.
Xin-Na Geng  Danyu Bai 《工程优选》2019,51(8):1301-1323
This article addresses the no-wait flowshop scheduling problem with simultaneous consideration of common due date assignment, convex resource allocation and learning effect in a two machine setting. The processing time of each job can be controlled by its position in a sequence and also by allocating extra resource, which is a convex function of the amount of a common continuously divisible resource allocated to the job. The objective is to determine the optimal common due date, the resource allocation and the schedule of jobs such that the total earliness, tardiness and common due date cost (the total resource consumption cost) are minimized under the constraint condition that the total resource consumption cost (the total earliness, tardiness and common due date cost) is limited. Polynomial time algorithms are developed for two versions of the problem.  相似文献   
3.
The objectives of the present work were (1) to identify the cause of the linear bias in predictions of rumen-undegradable protein (RUP) content of feeds, and devise methods to remove the bias from prediction equations, and (2) to further explore the impact of rumen-degradable protein (RDP) on microbial N (MiN) outflow from the rumen. The kinetic model used by NRC (2001), which is based on protein fractionation and rates of degradation (Kd) and passage (Kp), displays considerable slope bias (?0.30 kg/kg), indicating parameter or structural problems. Regressing Kp by feed class and a static adjustment factor for the in situ–derived Kd on observed RUP flows completely resolved the slope bias problem, and the model performed significantly better than models using unadjusted Kd and marker-based Kp. The Kd adjustment was 3.82%/h, which represents approximately a 50% increase in rates of degradation over the in situ values, indicating that in situ analyses severely underestimate true rates of protein degradation. The Kp for concentrate-derived protein was 5.83%/h, which was slightly less than the marker-predicted rate of 6.69%/h. However, the derived forage protein rate was 0.49%/h, which was considerably less than the marker-based rate of 5.07%/h. Compartmental analysis of data from a single study corroborated the regression analysis, indicating that a 25% reduction in the overall passage rate and an 87% increase in the rate of degradation were required to align ruminal N pool sizes and the extent of protein degradation with the observed data. Therefore, one must conclude that both the in situ–derived degradation rates and the marker-based particle passage rates are biased relative to protein passage and cannot be used directly to predict RUP outflow from the rumen. The effects of RDP supply on microbial nitrogen (MiN) flow were apparent when intakes of individual nutrients were offered but not when DM intake and individual nutrient concentrations were offered, due to collinearity problems. Microbial N flow from the rumen was found to be linearly related to ruminally degraded starch, ruminally degraded neutral detergent fiber (NDF), RDP, and forage NDF intakes; and quadratically related to residual OM intake. More complicated models containing 2- and 3-way interactions among nutrients were also supported by the data. Independent MiN responses to RDP, ruminally degraded starch, and ruminally degraded NDF aligned with the expected responses to each of those nutrients. Nonlinear representations of MiN were found to be inferior to the linear models. Despite using unbiased predictions of RUP and MiN as drivers of AA flows, predictions of Arg, His, Ile, and Lys flow exhibited linear slope bias relative to the observed data, indicating that representations of the AA composition of the proteins may be biased or the observed data are biased. This is an improvement over the NRC (2001) predictions, where bias adjustments were required for all of the essential AA. Despite the bias for 4 AA flows, the revised prediction system was a substantial improvement over the prior work.  相似文献   
4.
中国可持续能源政策分析   总被引:2,自引:0,他引:2  
本文分析了21世纪第一个十年中国能源开发利用状况和2020年前中国能源发展的主要趋势。指出2001~2010期间,尽管中国能源支撑了中国经济的高速增长,中国经济增长的粗放型模式导致能源过度消费和能源系统本身的重碳化。作者认为中国能源"走出去"的战略是成功的。国际油气市场的变化提供了新的机遇,除了采取各种能源供应安全的防范措施和政策外,2020年前中国对外油气的依存度仍然快速增长。本文特别强调应对气候变化、节能和煤炭消费总量控制是中国能源可持续发展的三个关键问题。中国正在酝酿新一轮的改革,作者对能源机构的改革目标和内容提出了一些建议。  相似文献   
5.
This work evaluated the National Research Council (NRC) dairy model (2001) predictions of rumen undegradable (RUP) and degradable (RDP) protein compared with measured postruminal non-ammonia, nonmicrobial (NANMN) and microbial N flows. Models were evaluated using the root mean squared prediction error (RMSPE) as a percent of the observed mean, mean and slope biases as percentages of mean squared prediction error (MSPE), and concordance correlation coefficient (CCC). The NRC (2001) over-estimated NANMN by 18% and under-estimated microbial N by 14%. Both responses had large mean biases (19% and 20% of MSPE, respectively), and NANMN had a slope bias (22% of MSPE). The NRC NANMN estimate had high RMSPE (46% of observed mean) and low CCC (0.37); updating feed library A, B, and C protein fractions and degradation rate (Kd) estimates with newer literature only marginally improved fit. The re-fit NRC models for NANMN and microbial N had CCC of 0.89 and 0.94, respectively. When compared with a prediction of NANMN as a static mean fraction of N intake, the re-derived NRC approach did not have improved fit. A protein system of intermediate complexity was derived in an attempt to estimate NANMN with improved fit compared with the static mean NANMN model. In this system, postruminal appearance of A, B, and C protein fractions were predicted in a feed-type specific manner rather than from estimated passage and degradation rates. In a comparison to independent data achieved through cross-validation, the new protein system improved RMSPE (34 vs. 36% of observed mean) and CCC (0.42 vs. 0.30) compared with the static mean NANMN model. When the NRC microbial N equation was re-derived, the RDP term dropped from the model. Consequently, 2 new microbial protein equations were formulated, both used a saturating (increasing at a decreasing rate) form: one saturated with respect to TDN and the other saturated over increasing intakes of rumen degraded starch and NDF. Both equations expressed maximal microbial N production as a linear function of RDP intake. The function relating microbial N to intake of rumen degradable carbohydrate improved RMSPE (24 vs. 28% of the observed mean) and CCC (0.63 vs 0.30) compared with the re-derived NRC model. The newly derived equations showed modest improvements in model fit and improved capacity to account for known biological effects; however, substantial variability in NANMN and microbial N estimates remained unexplained.  相似文献   
6.
More than 3,000 individuals from 7 U.S. cities reported on their memories of learning of the terrorist attacks of September 11, as well as details about the attack, 1 week, 11 months, and/or 35 months after the assault. Some studies of flashbulb memories examining long-term retention show slowing in the rate of forgetting after a year, whereas others demonstrate accelerated forgetting. This article indicates that (a) the rate of forgetting for flashbulb memories and event memory (memory for details about the event itself) slows after a year, (b) the strong emotional reactions elicited by flashbulb events are remembered poorly, worse than nonemotional features such as where and from whom one learned of the attack, and (c) the content of flashbulb and event memories stabilizes after a year. The results are discussed in terms of community memory practices. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
试验结果表明,农地乐 52.25EC防治甜菜夜蛾速效性好于对照药剂抑太保和除尽,药后 1d的防效,1000、667倍液达 80%以上,500倍液达 90%以上。药后 7d的防效,1000、667倍液为 91.4%~93.3%,与抑太保 10%乳油 1000倍液相当;500倍液为 96.7%,与除尽相当。农地乐 52.25 EC防治甜菜夜蛾的持效期为 7~8天。农地乐对作物安全。示范面积2.1× 103hm2,平均防 效达 85%以上。农地乐 52.25 EC已成为冀东防治甜菜夜蛾的首选药剂。  相似文献   
8.
WPSC2 0 0 1对全球的规划教育工作者和规划师而言是一个巨大的成功。本文回顾了国际指导委员会和大会组织委员会为此作出的各种努力 ,并总结和分析了与会代表对大会、对中国规划教育和城市发展的评价  相似文献   
9.
The Award for Distinguished Scientific Applications of Psychology is presented to persons who, in the opinion of the Committee on Scientific Awards, have made distinguished theoretical or empirical advances leading to the understanding or amelioration of important practical problems. This document lists the winners of this award from 1973 to 2001, and provides the citation, biography, and selected bibliography for the 2001 recipient, David T. Lykken. Lykken's award address, entitled "Parental Licensure," is also included. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
10.
阐述了2001年中国石化集团公司的任务和主要工作,提出了具体的7项重点工作。并指出了集团公司“十五”计划的总体目标及发展方针。  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