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   235篇
  免费   10篇
电工技术   3篇
化学工业   29篇
金属工艺   5篇
建筑科学   15篇
能源动力   19篇
轻工业   21篇
水利工程   2篇
无线电   20篇
一般工业技术   60篇
冶金工业   15篇
原子能技术   2篇
自动化技术   54篇
  2023年   2篇
  2020年   3篇
  2019年   4篇
  2018年   7篇
  2017年   5篇
  2016年   5篇
  2015年   7篇
  2014年   7篇
  2013年   16篇
  2012年   20篇
  2011年   12篇
  2010年   9篇
  2009年   12篇
  2008年   18篇
  2007年   13篇
  2006年   16篇
  2005年   4篇
  2004年   10篇
  2003年   6篇
  2002年   7篇
  2001年   8篇
  2000年   4篇
  1999年   5篇
  1998年   8篇
  1997年   11篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   2篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1975年   1篇
  1969年   1篇
  1939年   1篇
排序方式: 共有245条查询结果,搜索用时 234 毫秒
121.
A linguistic-engineering approach to large-scale requirements management   总被引:4,自引:0,他引:4  
For large software companies, the sheer number of textual requirements presents specific challenges. To find market opportunities, organizations must continuously elicit new requirements and reevaluate old ones as market needs evolve. Developing large, complex software products aimed at broad markets involves identifying and maintaining the link between product requirements and the massive inflow of customers' wishes. Automating this support through linguistic engineering could save considerable time and improve software quality.  相似文献   
122.
123.
Various methods were used to characterize avocado honey in Israel. Perseitol, a unique sugar present only in avocado honey, served as an indicator for the degree of purity of avocado honey. Low avocado pollen counts made the common melissopalynology method ineffective at predicting the contribution of avocado nectar to honey. It was also found that the levels of fructose, sucrose and glucose do not uniquely characterize avocado honey. Potassium content and eight other minerals were linearly highly correlated to perseitol content. Moreover, pH level, absorbance and degree of darkness were significantly correlated to perseitol content, and can therefore be used to characterize avocado honey.  相似文献   
124.
125.
The paper presents the wind shear stress on the sea surface as well as the velocity profile in stably stratified atmospheric boundary layer flow over wind waves by using similarity theory. For a given geostrophic velocity, Coriolis parameter, spectral peak period and stratification parameter, the sea surface shear stress is determined. Further, the direction of the sea surface shear stress and the velocity profile are given. Parameterizations of the results are also presented. Finally, the engineering relevance of the results is discussed, and, if the wind velocity at the 10 m elevation is available, a simplified method of calculating the sea surface shear stress is given.  相似文献   
126.
Dag Henning 《Energy》1997,22(12):1135-1150
MODEST, an energy-system optimisation model is described. It has been applied to a typical local Swedish electricity and district-heating utility and to the national power system. Present and potential installations and energy flows should be considered and their best combination can be obtained through optimisation. MODEST uses linear programming to minimise the capital and operation costs of energy supply and demand-side management. Seasonal, weekly, and diurnal variations of, for example, demand, costs, and capacities are considered. MODEST may be used to decide which investments to make, the dimensioning of new installations, and the operation of all system components. The municipal utility under study should now expand its heat production using woodchips. Electricity export or nuclear phase-out will probably raise the Swedish electricity prices. In this case, cost minimisation is achieved by introducing combined heat and power (CHP) production in the municipality. Fossil fuels should be used in the cogeneration plant at current taxation levels but biofuels are favourable if higher environmental fees are imposed for CO2 emissions. Biomass capacity expansion could decrease local CO2 emissions by 80%. Efficiency improvements for electricity use have robust profitability at high electricity prices. The Swedish electricity demand may be satisfied without nuclear power and fossil fuels through massive biomass use, wind-power supply, and energy conservation.  相似文献   
127.
This paper describes a novel noise-shaping Δ-Σ modulator for D/A-conversion which has no global feedback. The proposed topology is well suited for a pipelined clocking scheme allowing increased oversampling ratios for both first and higher order modulators. The maximum clock-frequency of the new modulator is limited only by the delay through one single accumulator regardless of modulator order, which represents a huge saving compared to the conventional modulator. The converter is very modular and scales easily to higher modulator orders. Still the proposed topology is mathematically equivalent to the classical Δ-Σ modulator. Theoretical analysis and circuit simulations for a first- and second-order modulator are presented. The first-order circuit has been implemented in a FPGA-circuit from Altera and measured results are presented.  相似文献   
128.
Extra virgin olive oils were extracted from six different major olive cultivars (Gemlik, Ayvalik, Domat, Akhisar, Memecik, Arbequina) cultivated in the Aegean region of Turkey. Fatty acid, sterol and tocopherol compositions were analyzed and the results were compared by multivariate statistical analysis. Olive samples were collected from the same orchard in order to limit the contribution of parameters such as climate, soil quality and agricultural practices to the total variance of chemical composition of olive oils. Principal component analysis (PCA) showed that cultivars can be clearly distinguished on the basis of fatty acid and sterol composition. It is of interest to note that palmitoleic acid content of Arbequina, a Spanish cultivar, is significantly (p < 0.05) higher than the local Turkish cultivars in question and it is the only olive sample whose palmitoleic acid concentration is higher than that of the stearic acid concentration, exhibiting a divergent composition from the local Turkish cultivars. β‐Sitosterol and Δ5‐avenasterol contents of the oils are significantly correlated (r = ?0.989, p < 0.05) and this results in a discriminative axis on the PCA loading plot. Tocopherol composition was relatively insufficient in discriminating the olive varieties. Regarding tocopherol compositions Gemlik cultivar is distinguished from other cultivars with its γ‐tocopherol content, which is in average two times higher than that of other cultivars. The result of the present compositional study provides important data which can be used for olive oil authenticity studies in Turkey.  相似文献   
129.
This study assessed the construct validity of the circumplex model of the Inventory of Interpersonal Problems (IIP-C) in Norwegian clinical and nonclinical samples. Structure was examined by evaluating the fit of the circumplex model to data obtained by the IIP-C. Observer-rated personality disorder criteria (DSM-IV, Axis II) were used as external correlates. The reliability of the IIP-C scales was acceptable and in the same range as in the original version. A multisample analysis strategy did not support an invariant circumplex model across the 2 groups. However, the estimated structures reflected mostly the same circular pattern of a quasi-circumplex model in the 2 groups. Departures from the ideal model were of negligible practical significance. The validity results examining personality disorder correlates of the IIP-C generally conformed to predictions, providing direct evidence for agreement between self-report and expert judgments of interpersonal problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
130.
BACKGROUND: Macronutrients play fundamental roles in processes affecting olive oil productivity and are expected to influence oil composition. A necessary step in optimal nutrient application management for olives is an understanding of the relationship between olive tree nutritional status and oil quality parameters. We studied the independent effects of N, P and K concentrations in irrigation solution on the oil quality of ‘Barnea’ olives by applying a wide range of macronutrient concentrations under highly controlled conditions. RESULTS: Oil composition was significantly influenced by P and N levels, while K levels had only a minor effect. Unsaturation levels were unaffected by the treatments but, within the unsaturated fatty acids, the levels of PUFA increased compared to those of MUFA. Specifically, levels of the MUFA C18:1, polyphenol content and peroxide values decreased while levels of the PUFA C18:3 increased in response to higher doses of N and P. CONCLUSION: Decreased MUFA and polyphenol levels coupled with increased omega‐3 levels demonstrated a potential negative influence on oil profile alongside increased nutritional benefits. The sum effects on oil yield and composition should be considered in designing of nutrient application management strategies for olive orchards. Copyright © 2009 Society of Chemical Industry  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