全文获取类型
收费全文 | 76篇 |
免费 | 2篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 32篇 |
金属工艺 | 2篇 |
建筑科学 | 1篇 |
轻工业 | 4篇 |
水利工程 | 1篇 |
无线电 | 14篇 |
一般工业技术 | 5篇 |
冶金工业 | 9篇 |
原子能技术 | 1篇 |
自动化技术 | 8篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 9篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 5篇 |
2007年 | 6篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2002年 | 4篇 |
2001年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有78条查询结果,搜索用时 31 毫秒
1.
Jennifer G. Winter M. Catherine Eimers Peter J. Dillon Lem D. Scott Wolfgang A. Scheider Campbell C. Willox 《Journal of Great Lakes research》2007,33(2):381-396
Total phosphorus (TP) inputs to Lake Simcoe have led to hypolimnetic dissolved oxygen (DO) depletion and loss of cold water fish habitat. Since 1990, efforts have been made to reduce the total TP input to the lake below a defined target of 75 t/year, which was predicted to lead to reductions in spring TP concentration and improvements in end-of-summer hypolimnetic DO concentrations. The total TP load to the lake during the most recent period of record (1998/99-2003/04) ranged from 53 to 76 t/yr and averaged 67 t/yr, compared to an average of 114 t/yr estimated between 1990/91 and 1997/98 (range 85-157 t/yr). Reductions in TP loads from the catchment via tributary discharge (∼26 t) accounted for the majority of the decrease in total load between the two time periods. Total P concentrations decreased significantly in four out of six long-term monitored tributaries; however, concentrations in all six tributaries remain above the level recommended to avoid nuisance plant growth (30 μg/L). Although TP loads to the lake are currently below the target 75 t/yr, excessive growths of filamentous algae and macrophytes continue to be a problem in the nearshore zone. End-of-summer minimum hypolimnetic DO concentrations (average 4.3 mg/L, 1998/99-2003/04) remain substantially below the level (7 mg/L) that is considered protective of lake trout. Efforts to reduce TP loads to the lake therefore need to continue. 相似文献
2.
Erika Nassar Chris Mulligan Lem Taylor Chad Kerksick Melyn Galbreath Mike Greenwood Richard Kreider Darryn S Willoughby 《Journal of the International Society of Sports Nutrition》2007,4(1):14-13
Melatonin and resistance exercise alone have been shown to increase the levels of growth hormone (GH). The purpose of this
study was to determine the effects of ingestion of a single dose of melatonin and heavy resistance exercise on serum GH, somatostatin
(SST), and other hormones of the GH/insulin-like growth factor 1 (IGF-1) axis. Physically active males (n = 30) and females
(n = 30) were randomly assigned to ingest either a melatonin supplement at 0.5 mg or 5.0 mg, or 1.0 mg of dextrose placebo.
After a baseline blood sample, participants ingested the supplement and underwent blood sampling every 15 min for 60 min,
at which point they underwent a single bout of resistance exercise with the leg press for 7 sets of 7 reps at 85% 1-RM. After
exercise, participants provided additional blood samples every 15 min for a total of 120 min. Serum free GH, SST, IGF-1, IGFBP-1,
and IGFBP-3 were determined with ELISA. Data were evaluated as the peak pre- and post-exercise values subtracted from baseline
and the delta values analyzed with separate three-way ANOVA (p < 0.05). In males, when compared to placebo, 5.0 mg melatonin
caused GH to increase (p = 0.017) and SST to decrease prior to exercise (p = 0.031), whereas both 0.5 and 5.0 mg melatonin
were greater than placebo after exercise (p = 0.045) and less than placebo for SST. No significant differences occurred for
IGF-1; however, males were shown to have higher levels of IGFBP-1 independent of supplementation (p = 0.004). The 5.0 mg melatonin
dose resulted in higher IGFBP-3 in males (p = 0.017). In conclusion, for males 5.0 mg melatonin appears to increase serum
GH while concomitantly lowering SST levels; however, when combined with resistance exercise both melatonin doses positively
impacts GH levels in a manner not entirely dependent on SST. 相似文献
3.
There are different ventilation control methods for outdoor air quantity in air-conditioned spaces to reduce the energy consumed in cooling the outdoor air. Demand controlled ventilation (DCV) is an important strategy to control the outdoor air quantity. However, the current practice in DCV systems creates several problems for air-conditioned office buildings. Although metabolic carbon dioxide (CO2) concentration is mainly used as a surrogate indicator for ventilation adequacy, the conventional DCV system does not seriously consider the placement location of the CO2 sensor, and it does not take into account the adverse effects of the consequential increase in pollutant concentrations in the indoor space when the fresh airflow rate is reduced. In this study, a long period of subjective and objective measurements were conducted in an occupied office to examine its suitability for conversion to a new demand controlled ventilation system (nDCV). After the feasibility investigation, an nDCV system was developed to optimize the energy consumed for outdoor air ventilation while providing the desirable thermal comfort and indoor air quality. The true optimization of this nDCV is achieved by a new concept of the optimized indoor air quality window which determines the most representative locations for the indicator sensors. A minimum ventilation rate is determined by a calibration procedure for the pollutant inventory of a building, taking into account the infiltration characteristics. Radon gas, which is a notorious carcinogenic indoor pollutant, is used as a reference to determine the minimum fresh airflow rate. The findings show that this nDCV system reduced 16% of fresh air cooling energy consumption without jeopardizing the thermal comfort and indoor air quality. 相似文献
4.
Kwok-Wai Cheung Kwok-Ching Tsui Jiming Liu 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2004,34(1):143-148
With the advent of the World Wide Web, providing just-in-time personalized product recommendations to customers now becomes possible. Collaborative recommender systems utilize correlation between customer preference ratings to identify "like-minded" customers and predict their product preference. One factor determining the success of the recommender systems is the prediction accuracy, which in many cases is limited by lacking adequate ratings (the sparsity problem). Recently, the use of latent class model (LCM) has been proposed to alleviate this problem. In this paper, we first study how the LCM can be extended to handle customers and products outside the training set. In addition, we propose the use of a pair of LCMs (called dual latent class model-DLCM), instead of a single LCM, to model customers' likes and dislikes separately for enhancing the prediction accuracy. Experimental results based on the EachMovie dataset show that DLCM outperforms both LCM and the conventional correlation-based method when the available ratings are sparse. 相似文献
5.
Richard B Kreider Colin D Wilborn Lem Taylor Bill Campbell Anthony L Almada Rick Collins Mathew Cooke Conrad P Earnest Mike Greenwood Douglas S Kalman Chad M Kerksick Susan M Kleiner Brian Leutholtz Hector Lopez Lonnie M Lowery Ron Mendel Abbie Smith Marie Spano Robert Wildman Darryn S Willoughby Tim N Ziegenfuss Jose Antonio 《Journal of the International Society of Sports Nutrition》2010,7(1):1-43
Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients. 相似文献
6.
Kwok-Wai Cheung Dit-Yan Yeung Chin R.T. 《IEEE transactions on pattern analysis and machine intelligence》2002,24(8):1133-1139
To achieve integrated segmentation and recognition in complex scenes, the model-based approach has widely been accepted as a promising paradigm. However, the performance is still far from satisfactory when the target object is highly deformed and the level of outlier contamination is high. In this paper, we first describe two Bayesian frameworks, one for classifying input patterns and another for detecting target patterns in complex scenes using deformable models. Then, we show that the two frameworks are similar to the forward-reverse setting of Hausdorff matching and that their matching and discriminating properties are complementary to each other. By properly combining the two frameworks, we propose a new matching scheme called bidirectional matching. This combined approach inherits the advantages of the two Bayesian frameworks. In particular, we have obtained encouraging empirical results on shape-based pattern extraction, using a subset of the CEDAR handwriting database containing handwritten words of highly varying shape. 相似文献
7.
The rheological properties and curing kinetics of a general-purpose polyester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone-and-plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). It was found that, as cure progresses, the steady shear viscosity increases very rapidly with cure time at all shear rates investigated, and normal forces show negative values at low shear rates and positive values at high shear rates. The observed negative normal forces are believed to result from material shrinkage during cure, and positive normal forces from the deformation of large molecules, formed by crosslinking reactions during cure. Note that, in a cone-and-plate rheometer, the shrinkage force acts in the direction opposite to that of normal forces. It is, therefore, concluded that extreme caution is needed in the interpretation of normal force measurements with thermosetting resins, subjected to steady shearing flow. Dynamic measurements seem to offer some insight on the onset of gel formation. More specifically, we have found that, when the unsaturated polyester resin was cured at a fast rate, the time at which a maximum in the loss modulus G” occurs coincides reasonably well with the time tη∞ at which the steady shear viscosity η approaches infinity. However, at a slow rate of cure, the time at which tan δ equals unity agrees fairly well with tη∞. DSC measurement has permitted us to determine the degree of cure as a function of cure time and the kinetic parameters in an empirical expression for the curing kinetics advanced by Kamal and co-workers. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various values of isothermal curing temperature. 相似文献
8.
Lemâne Delva Renée Goodrich‐Schneider 《International Journal of Food Science & Technology》2013,48(5):1048-1056
The antioxidant activity and antimicrobial property of phenolic extracts from acerola (Malpighia emarginata DC) fruit were assessed. The contribution of ascorbic acid and phenolic compounds in the total antioxidant capacity of the extracts was also evaluated. The extracts showed high total phenolic values and possessed high antioxidant activity as expressed by 2,2′‐diphenylpicrylhydrazyl (DPPH) and oxygen radical absorbance capacity assays (ORAC). The ascorbic acid content ranged from 405 to 1744 mg/100 g of fruit on a fresh weight basis. The antioxidant capacity of the phenolic fractions was in the following order: anthocyanins<phenolic acids<flavonoids. The phenolic fractions contributed 7.1–36.5% of the antioxidant activity expressed by ORAC, whereas the contribution of ascorbic accounted for 18–39% of the total activity. Selected extracts from the flavonoids fraction showed some activity against Staphylococcus aureus. 相似文献
9.
P Bourges MH Lemée-Cailleau P Launois C Ecolivet H Cailleau F Moussa A Mierzejewski 《Canadian Metallurgical Quarterly》1996,54(21):15002-15015
10.
The rheological properties and curing kinetics of a vinyl ester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone-and-plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). Also determined were the rheological properties and curing kinetics of the resin when it had been thickened using magnesium oxide (MgO), in the presence of calcium carbonate (CaCO3) as filler and polyvinyl acetate (PVAc) as low-profile additive. The steady shearing flow behavior observed with the vinyl ester resin was found to be very similar to that observed with a general-purpose polyester resin, reported in Paper I of this series [C. D. Han and K. W. Lem, J. Appl. Polym. Sci., 28 , 3155 (1983)]. However, a significant difference in the oscillatory shearing flow behavior was found between the two resins. We have concluded that dynamic measurement is much more sensitive to variations in resin chemistry than steady shearing flow measurement. DSC measurement has permitted us to determine the degree of cure as a function of cure time. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various isothermal curing temperatures. 相似文献