全文获取类型
收费全文 | 110篇 |
免费 | 0篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 26篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 4篇 |
轻工业 | 13篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 4篇 |
一般工业技术 | 11篇 |
冶金工业 | 21篇 |
原子能技术 | 1篇 |
自动化技术 | 11篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2017年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 6篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 2篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有110条查询结果,搜索用时 0 毫秒
21.
Predicting pathogen risks to aid beach management: The real value of quantitative microbial risk assessment (QMRA) 总被引:2,自引:0,他引:2
There has been an ongoing dilemma for agencies that set criteria for safe recreational waters in how to provide for a seasonal assessment of a beach site versus guidance for day-to-day management. Typically an overall ‘safe’ criterion level is derived from epidemiologic studies of sewage-impacted beaches. The decision criterion is based on a percentile value for a single sample or a moving median of a limited number (e.g. five per month) of routine samples, which are reported at least the day after recreator exposure has occurred. The focus of this paper is how to better undertake day-to-day recreational site monitoring and management. Internationally, good examples exist where predictive empirical regression models (based on rainfall, wind speed/direction, etc.) may provide an estimate of the target faecal indicator density for the day of exposure. However, at recreational swimming sites largely impacted by non-sewage sources of faecal indicators, there is concern that the indicator-illness associations derived from studies at sewage-impacted beaches may be inappropriate. Furthermore, some recent epidemiologic evidence supports the relationship to gastrointestinal (GI) illness with qPCR-derived measures of Bacteroidales/Bacteroides spp. as well as more traditional faecal indicators, but we understand less about the environmental fate of these molecular targets and their relationship to bather risk. Modelling pathogens and indicators within a quantitative microbial risk assessment framework is suggested as a way to explore the large diversity of scenarios for faecal contamination and hydrologic events, such as from waterfowl, agricultural animals, resuspended sediments and from the bathers themselves. Examples are provided that suggest that more site-specific targets derived by QMRA could provide insight, directly translatable to management actions. 相似文献
22.
Critical design decisions are commonly made throughout the product development process assuming known material and process
behavior. However, stochastic variation during manufacture can inadvertently result in inferior or unacceptable product performance
and reduced production yields. Stochastic simulations have been developed to estimate the end-use performance distribution
prior to the commitment of hard tooling. This article proposes a definition for integrated product and process robustness,
and extends existing stochastic methods to model the important role of the manufacturing flexibility in elimination of defects
and product optimization. The goal is to enable the designer to understand and account for not only the negative effects of
manufacturing variation, but also the positive impact of manufacturing flexibility wherein instantaneous corrections in the
manufacturing process can frequently improve the product quality and eliminate flaws in the product design. Then, a methodology
is introduced and contrasted with conventional development methods in the evaluation of best practices for development of
a molded plastic component. 相似文献
23.
Virginia Funes-Collado Albert Morell-Garcia Roser Rubio José Fermín López-Sánchez 《Food chemistry》2013
Selenium is recognised as an essential micronutrient for humans and animals. One of the main sources of selenocompounds in the human diet is vegetables. Therefore, this study deals with the Se species present in different edible sprouts grown in Se-enriched media. We grew alfalfa, lentil and soy in a hydroponic system amended with soluble salts, containing the same proportion of Se, in the form of Se(VI) and Se(IV). Total Se in the sprouts was determined by acidic digestion in a microwave system and by ICP/MS. Se speciation was carried out by enzymatic extraction (Protease XIV) and measured by LC-ICP/MS. The study shows that the Se content of plants depends on the content in the growth culture, and that part of the inorganic Se was biotransformed mainly into SeMet. These results contribute to our understanding of the uptake of inorganic Se and its biotransformation by edible plants. 相似文献
24.
25.
Hydropower is considered an important form of renewable energy, often involving hydropeaking. While the effects of hydropeaking on aquatic communities in areas downstream the dam are well understood, there is a lack of studies investigating potential impacts on tributaries located further upstream. In this study, we tested the effects of hydropeaking operations on upstream tributaries in a restored area of the Danube River, with a focus on the periods of backlog and release of water (up-ramping and down-ramping, respectively) during the filling and release of the reservoir. We used brown trout egg and larval mortality, linked to hydraulic, sedimentary and physiochemical changes in spawning grounds as an indicator. We compared hydropeaking-affected versus non-affected sites in upstream tributaries using HydroEcoSedimentary Tools (HESTs) loaded with clean gravels and brown trout eggs. Egg and larval mortalities were significantly higher in the hydropeaking-affected site with more than 80% egg mortality and almost 100% larval mortality compared to values of 55–63% and 80–85%, respectively, in non-affected sites. Spawning ground quality was significantly altered in the hydropeaking-affected site, where the highest mortalities were observed. Overall, duration of time periods with flow velocities close to zero were a key variable, potentially decreasing oxygen supply for eggs and larvae. Such periods of close to zero flow velocities were driven by backlog periods during the filling of the reservoir, revealing that such events can severely impair ecological integrity of spawning sites in tributaries upstream of dams by slowing the flows in upstream tributaries. Such altered processes can reduce fish population recruitment and need to be considered in future restoration projects. 相似文献
26.
Werner Roser Gisela Hagberg Irina Mader Sophie Dellas Joachim Seelig Ernst W. Radue Wolfgang Steinbrich 《Magma (New York, N.Y.)》1997,5(3):179-183
This study presents a simple approach for the noninvasive assignment of glial brain tumors according to malignancy by single-voxel
proteon magnetic resonance spectroscopy at short echo times (TE≦50 milliseconds). Based on peak area ratios, a five-dimensional
data set was obtained for each investigated subject. This vector was then projected along metabolic coordinates in a two-dimensional
metabolic space. These coordinates had been determined in a previous study (Hagberg G et al., 1995,Magn Reson Med
34: 242–252). Tumor assignment was done without any knowledge of histology by comparing the location of the new cases to the
features of the previous study. All 11 investigated glioblastomas multiforme, as well as 4 of 5 astrocytomas grade II, could
easily be assigned to the groups of high- and low-grade tumors, respectively. Classification was more difficult in the case
of a cystic astrocytoma grade II and one astrocytoma grade III. Two spectra measured in normal-appearing matter of glioblastoma
patients were not classified as healthy. Using single-voxel proton magnetic resonance spectroscopy at short echo times with
the knowledge of a base study, a straightforward, fast, and noninvasive differential diagnosis of glial brain tumors is possible.
Supported by the Swiss National Science Foundation Research Grants No. 31-32533.91 (to J.S.) and 32.39773.93 (to W.S.).W.R.
and E.W.R. have been supported by the Krebsliga beider Basel.
A preliminary account of this work was given at the Third Annual Scientific Meeting of the International Society for Magnetic
Resonance in Medicine, Nice, France, August 1995, abstract 1719. 相似文献
27.
A continuous measure of gross primary production for the conterminous United States derived from MODIS and AmeriFlux data 总被引:2,自引:0,他引:2
Jingfeng Xiao Qianlai Zhuang Jiquan Chen David R. Cook Andrew D. Richardson Siyan Ma Shashi B. Verma Russell L. Scott Marcy Litvak Ge Sun Paul V. Bolstad Peter S. Curtis Matthias Falk David R. Foster Julian L. Hadley Roser Matamala Tilden P. Meyers Asko Noormets Kyaw Tha Paw U Gregory Starr Steven C. Wofsy 《Remote sensing of environment》2010,114(3):576-3101
The quantification of carbon fluxes between the terrestrial biosphere and the atmosphere is of scientific importance and also relevant to climate-policy making. Eddy covariance flux towers provide continuous measurements of ecosystem-level exchange of carbon dioxide spanning diurnal, synoptic, seasonal, and interannual time scales. However, these measurements only represent the fluxes at the scale of the tower footprint. Here we used remotely sensed data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to upscale gross primary productivity (GPP) data from eddy covariance flux towers to the continental scale. We first combined GPP and MODIS data for 42 AmeriFlux towers encompassing a wide range of ecosystem and climate types to develop a predictive GPP model using a regression tree approach. The predictive model was trained using observed GPP over the period 2000-2004, and was validated using observed GPP over the period 2005-2006 and leave-one-out cross-validation. Our model predicted GPP fairly well at the site level. We then used the model to estimate GPP for each 1 km × 1 km cell across the U.S. for each 8-day interval over the period from February 2000 to December 2006 using MODIS data. Our GPP estimates provide a spatially and temporally continuous measure of gross primary production for the U.S. that is a highly constrained by eddy covariance flux data. Our study demonstrated that our empirical approach is effective for upscaling eddy flux GPP data to the continental scale and producing continuous GPP estimates across multiple biomes. With these estimates, we then examined the patterns, magnitude, and interannual variability of GPP. We estimated a gross carbon uptake between 6.91 and 7.33 Pg C yr− 1 for the conterminous U.S. Drought, fires, and hurricanes reduced annual GPP at regional scales and could have a significant impact on the U.S. net ecosystem carbon exchange. The sources of the interannual variability of U.S. GPP were dominated by these extreme climate events and disturbances. 相似文献
28.
An approach based on local learning, relying on Nadaraya–Watson models (NWMs), is introduced for the problem of deriving an automatic controller able to exploit data collected during the operation of some complex plant or system by a reference teacher (e.g., a human operator). Such learning approach is particularly useful when the system is too complex to be modeled accurately and/or the task cannot be easily formalized by a cost function, a situation which rules out classic approaches based, e.g., on dynamic programming. Here it is proved that local models are a suitable solution for a real-time employment, since they allow to incorporate new information directly and efficiently without the need of offline training, and new data immediately reflect in improvement of performance. To this purpose, convergence analysis of the method is provided, also considering the case where the reference controller introduces random variations in the training data. Finally, a simulation test, concerning the control of a mechanical system, is provided to showcase the use of local models in an applicative scenario. 相似文献
29.
Kazuo Takayama Alberto Tun-Molina Alba Cano-Vicent Yukiko Muramoto Takeshi Noda Jos Luis Aparicio-Collado Roser Sabater i Serra Miguel Martí ngel Serrano-Aroca 《International journal of molecular sciences》2021,22(23)
The Coronavirus Disease (COVID-19) pandemic is demanding the rapid action of the authorities and scientific community in order to find new antimicrobial solutions that could inactivate the pathogen SARS-CoV-2 that causes this disease. Gram-positive bacteria contribute to severe pneumonia associated with COVID-19, and their resistance to antibiotics is exponentially increasing. In this regard, non-woven fabrics are currently used for the fabrication of infection prevention clothing such as face masks, caps, scrubs, shirts, trousers, disposable gowns, overalls, hoods, aprons and shoe covers as protective tools against viral and bacterial infections. However, these non-woven fabrics are made of materials that do not exhibit intrinsic antimicrobial activity. Thus, we have here developed non-woven fabrics with antimicrobial coatings of cranberry extracts capable of inactivating enveloped viruses such as SARS-CoV-2 and the bacteriophage phi 6 (about 99% of viral inactivation in 1 min of viral contact), and two multidrug-resistant bacteria: the methicillin-resistant Staphylococcus aureus and the methicillin-resistant Staphylococcus epidermidis. The morphology, thermal and mechanical properties of the produced filters were characterized by optical and electron microscopy, differential scanning calorimetry, thermogravimetry and dynamic mechanical thermal analysis. The non-toxicity of these advanced technologies was ensured using a Caenorhabditis elegans in vivo model. These results open up a new prevention path using natural and biodegradable compounds for the fabrication of infection prevention clothing in the current COVID-19 pandemic and microbial resistant era. 相似文献
30.