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   74篇
  免费   2篇
化学工业   9篇
机械仪表   1篇
能源动力   6篇
轻工业   2篇
水利工程   1篇
无线电   9篇
一般工业技术   9篇
冶金工业   23篇
原子能技术   3篇
自动化技术   13篇
  2022年   1篇
  2021年   3篇
  2020年   3篇
  2018年   5篇
  2017年   3篇
  2016年   2篇
  2014年   2篇
  2013年   4篇
  2011年   1篇
  2009年   2篇
  2006年   3篇
  2003年   1篇
  2002年   1篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   3篇
  1996年   5篇
  1995年   2篇
  1994年   2篇
  1993年   2篇
  1991年   2篇
  1989年   1篇
  1984年   3篇
  1983年   6篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
  1976年   3篇
  1975年   1篇
  1974年   2篇
  1972年   1篇
  1970年   1篇
  1968年   1篇
  1948年   1篇
排序方式: 共有76条查询结果,搜索用时 468 毫秒
41.
Experiments were conducted on sandy loam soils of Tirupati campus of Andhra Pradesh Agricultural University for two rainy seaons of 1980 and 1981 to study the effect of split application of NPK fertilizers on Spanish bunch groundnut. The fertilizer doses were 40 N, 20 P and 40 K kg ha–1 in 1980 and 30 N, 10 P and 25 K kg ha–1 in 1981.In 1980, uptake of N (48 kg ha–1), P (7 kg ha–1) and K (37 kg ha–1) was maximum with the application of 10 N, 5 P and entire 40 K kg ha–1 as basal and 30 N and 15 P kg ha–1 at 30 days after sowing, leading to highest pod yield (0.76 t ha–1). In 1981, application of 20 N, 10 P and 25 K kg ha–1 as basal dose and 20 N kg ha–1 at 30 days after seeding resulted in highest uptake of N (114 kg ha–1), P (17 kg ha–1) and K (58 kg ha–1) and hence the pod yield (2.36 t ha–1).Differences in the uptake of NPK and pod yield in 1980 and 1981 was due to variation in total rainfall and its distribution during the crop period. Rainfall was equally distributed throughout the crop period in 1981, whereas there were two prolonged dry spells of more than 40 days in 1980.  相似文献   
42.
Transient faults are emerging as a critical concern in the reliability of general-purpose microprocessors. As architectural trends point toward multicore designs, there is substantial interest in adapting such parallel hardware resources for transient fault tolerance. This paper presents process-level redundancy (PLR), a software technique for transient fault tolerance, which leverages multiple cores for low overhead. PLR creates a set of redundant processes per application process and systematically compares the processes to guarantee correct execution. Redundancy at the process level allows the operating system to freely schedule the processes across all available hardware resources. PLR uses a software-centric approach to transient fault tolerance, which shifts the focus from ensuring correct hardware execution to ensuring correct software execution. As a result, many benign faults that do not propagate to affect program correctness can be safely ignored. A real prototype is presented that is designed to be transparent to the application and can run on general-purpose single-threaded programs without modifications to the program, operating system, or underlying hardware. The system is evaluated for fault coverage and performance on a four-way SMP machine and provides improved performance over existing software transient fault tolerance techniques with a 16.9 percent overhead for fault detection on a set of optimized SPEC2000 binaries.  相似文献   
43.
  1. Freshly milled rice bran has been extracted with commercial hexane and the recovered oil and extracted meal examined for their respective content of wax. The oils were refined and bleached by standards as well as several special methods. The crude, caustic soda refined, and several refined and bleached oils were examined spectrophotometrically.
  2. When freshly milled rice bran of good quality is extracted with commercial hexane, an oil of relatively low free fatty acid content is obtained. This oil possesses good color and is as stable as other similar types of crude oils.
  3. If the oils is extracted from the brain at a temperature below about 10°C. and the extraction is discontinued at the right time, the extracted oil represents 90–95% of the total lipids in the brain and contains very little wax. This wax, which is readily extracted with hot commercial hexane as well as other types of solvents, amounts to about 3–9% of the total extractable lipids.
  4. When subjected to ordinary caustic soda refining methods, good rice brain oils behave much like cottonseed oils of comparable free fatty acid content. Both caustic soda refining in a hydrocarbon solvent and refining with sodium carbonate result in refining losses approximating the absolute or Wesson loss.
  5. Some of the refined oils when bleached according to usual practice produce products acceptable for use in the edible trade. However, refined rice bran oil has a definitely greenish cast resulting from the presence of chlorophyll, but this color can be removed by bleaching with a small amount of activated acidic clay.
  相似文献   
44.
The cost of hydrogen in early fuel cell electric vehicle (FCEV) markets is dominated by the cost of refueling stations, mainly due to the high cost of refueling equipment, small station capacities, lack of economies of scale, and low utilization of the installed refueling capacity. Using the hydrogen delivery scenario analysis model (HDSAM), this study estimates the impacts of these factors on the refueling cost for different refueling technologies and configurations, and quantifies the potential reduction in future hydrogen refueling cost compared to today's cost in the United States. The current hydrogen refueling station levelized cost, for a 200 kg/day dispensing capacity, is in the range of $6–$8/kg H2 when supplied with gaseous hydrogen, and $8–$9/kg H2 for stations supplied with liquid hydrogen. After adding the cost of hydrogen production, packaging, and transportation to the station's levelized cost, the current cost of hydrogen at dispensers for FCEVs in California is in the range of $13–$15/kg H2. The refueling station capacity utilization strongly influences the hydrogen refueling cost. The underutilization of station capacity in early FCEV markets, such as in California, results in a levelized station cost that is approximately 40% higher than it would be in a scenario where the station had been fully utilized since it began operating. In future mature hydrogen FCEV markets, with a large demand for hydrogen, the refueling station's levelized cost can be reduced to $2/kg H2 as a result of improved capacity utilization and reduced equipment cost via learning and economies of scale.  相似文献   
45.
The cost of hydrogen delivery for transportation accounts for most of the current H2 selling price; delivery also requires substantial amounts of energy. We developed harmonized techno-economic and life-cycle emissions models of current and future H2 production and delivery pathways. Our techno-economic analysis of dispensed H2 costs guided our selection of pathways for the life-cycle analysis. In this paper, we present the results of market expansion scenarios using existing capabilities (for example, those that use H2 from steam methane reforming, chlor-alkali, and natural gas liquid cracker plants), as well as results for future electrolysis plants that use nuclear, solar, and hydroelectric power. Reductions in greenhouse gas emissions for fuel cell electric vehicles compared to conventional gasoline pathways vary from 40% reduction for fossil-derived H2 to 20-fold for clean H2. Supplemental tables with greenhouse gas emissions data for each step in the H2 pathways enable readers to evaluate additional scenarios.  相似文献   
46.
An operation strategy known as two-tier “pressure consolidation” of delivered tube-trailers (or equivalent supply storage) has been developed to maximize the throughput at gaseous hydrogen refueling stations (HRSs) for fuel cell electric vehicles (FCEVs). The high capital costs of HRSs and the consequent high investment risk are deterring growth of the infrastructure needed to promote the deployment of FCEVs. Stations supplied by gaseous hydrogen will be necessary for FCEV deployment in both the near and long term. The two-tier pressure consolidation method enhances gaseous HRSs in the following ways: (1) reduces the capital cost compared with conventional stations, as well as those operating according to the original pressure consolidation approach described by Elgowainy et al. (2014) [1], (2) minimizes pressure cycling of HRS supply storage relative to the original pressure consolidation approach; and (3) increases use of the station's supply storage (or delivered tube-trailers) while maintaining higher state-of-charge vehicle fills.  相似文献   
47.
The net retention volumes, VN, of n‐alkanes and five polar probes are determined on cellulose acetate phthalate–polycaprolactonediol blend column by inverse gas chromatography in the temperature range 323.15–363.15 K. The dispersive surface energy, $\gamma _{\bf S}^{\bf d}$ , of the blend has been calculated using the VN values of n‐alkanes and the $\gamma _{\bf S}^{\bf d}$ at 333.15 K is 12.6 mJ/m2. The $\gamma _{\bf S}^{\bf d}$ values are decreasing linearly with increase of temperature. The VN values of the five polar solutes are used to calculate the specific component of the enthalpy of adsorption, ${\Delta }{H}_{\bf a}^{\bf S}$ . The Lewis acid–base parameters, Ka and Kb, are derived using ${\bf \Delta }{H}_{\bf a}^{\bf S}$ values and are found to be 0.019 and 0.403, respectively. The Ka and Kb values indicate that the blend surface contain more basic sites and interact strongly with the acidic probes. The acid–base parameters have been used to analyze the preferential interaction of the solid surface with acidic and basic probes. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers  相似文献   
48.
49.
50.
AIMS: A low level of response (LR) to alcohol is a characteristic of sons of alcoholics and predicts an elevated future alcoholism risk. A 12-question Self-Rating of the Effects (SRE) of alcohol form has been shown to correlate cross-sectionally with a designation of a low LR determined by alcohol challenges. DESIGN: This study evaluates the potential usefulness of the SRE as a retrospective measure of both the response to alcohol and of subsequent alcoholism in two samples. SETTING: All subjects were studied in the United States, most in California. PARTICIPANTS: First, 94 sons of alcoholics and controls completed the SRE 15 years after an alcohol challenge, and SRE values were compared to their prior LR results and their alcoholic outcomes. Secondly, the relationship between SRE results and alcoholic status was determined in 551 men and women alcoholics, their relatives, and controls. MEASUREMENTS: Subjects were evaluated with face-to-face interviews. FINDINGS: Despite the interval of 15 years, the correlation between the SRE and the subjective high feelings on the alcohol challenge was between -0.3 and -0.4. For those 94 subjects the full SRE correlated with a diagnosis of alcohol dependence at 0.5, a figure that remained at 0.3 even when only the estimates related to the earliest drinking experiences were considered. For the 551 men and women, the correlation between the SRE and alcohol dependence diagnoses was 0.6, including 0.3 for the estimates of the first five times of drinking. All major findings in both samples remained robust when the recent drinking history or the number of items endorsed was considered, or when the most severe alcohol problem, passing out, was deleted from the analysis. CONCLUSIONS: When alcohol challenges are not possible, these retrospective reports indicate that the SRE is a potentially useful surrogate for determining a subgroup of people who might carry a low level of response to alcohol and a subsequent elevated risk for alcoholism.  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