全文获取类型
收费全文 | 91篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 17篇 |
机械仪表 | 1篇 |
建筑科学 | 5篇 |
能源动力 | 6篇 |
轻工业 | 3篇 |
水利工程 | 3篇 |
无线电 | 4篇 |
一般工业技术 | 7篇 |
冶金工业 | 4篇 |
原子能技术 | 1篇 |
自动化技术 | 41篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 6篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1996年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有99条查询结果,搜索用时 296 毫秒
1.
Process-based models have been extensively applied to assess the impact of landuse change on water quantity and quality at landscape scales. However, the routine application of those models suffers from large computational efforts, lack of transparency and the requirement of many input parameters. Data-based models such as Feed-Forward Multilayer Perceptrons (MLP) and Classification and Regression Trees (CART) may be used as effective models, i.e. simple approximations of complex process-based models. These data-based approaches can subsequently be applied for scenario analysis and as a transparent management tool provided climatic boundary conditions and the basic model assumptions of the process-based models do not change dramatically. In this study, we apply MLP, CART and Multiple Linear Regression (LR) to model the spatially distributed and spatially aggregated percolation in soils using weather, groundwater and soil data. The percolation data is obtained via numerical experiments with Hydrus1D. Thus, the complex process-based model is approximated using simpler data-based approaches. The MLP model explains most of the percolation variance in time and space without using any soil information. This reflects the effective dimensionality of the process-based model and suggests that percolation in the study area may be modelled much simpler than using Hydrus1D. The CART model shows that soil properties play a negligible role for percolation under wet climatic conditions. However, they become more important if the conditions turn drier. The LR method does not yield satisfactory predictions for the spatially distributed percolation however the spatially aggregated percolation is well approximated. This may indicate that the soils behave simpler (i.e. more linear) when percolation dynamics are upscaled. 相似文献
2.
Luca AcetoTaolue Chen Anna IngolfsdottirBas Luttik Jaco van de Pol 《Theoretical computer science》2011,412(28):3035-3044
This paper contributes to the study of the equational theory of the priority operator of Baeten, Bergstra and Klop in the setting of the process algebra BCCSP. It is shown that, in the presence of at least two actions, the collection of process equations over BCCSP with the priority operator that are valid modulo bisimilarity, irrespective of the chosen priority order over actions, is not finitely based. This holds true even if one restricts oneself to the collection of valid process equations that do not contain occurrences of process variables. 相似文献
3.
We present a complete axiomatisation for four-valued sequential logic. It consists of nine axioms, from which all valid laws can be derived by equational reasoning. These nine axioms are independent of each other. 相似文献
4.
5.
6.
Eline Saenen Nele Horemans Nathalie Vanhoudt Hildegarde Vandenhove Geert Biermans May Van Hees Jean Wannijn Jaco Vangronsveld Ann Cuypers 《International journal of molecular sciences》2015,16(6):12405-12423
To evaluate the environmental impact of uranium (U) contamination, it is important to investigate the effects of U at ecologically relevant conditions. Since U speciation, and hence its toxicity, strongly depends on environmental pH, the present study aimed to investigate dose-dependent effects of U at pH 7.5. Arabidopsis thaliana plants (Mouse-ear Cress) were exposed for three days to different U concentrations at pH 7.5. In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress. However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed. In accordance with the roots, the ascorbate-glutathione cycle plays an important role in the antioxidative defence systems in A. thaliana leaves exposed to U at pH 7.5 as the ascorbate and glutathione biosynthesis were upregulated. In addition, small inductions of enzymes of the antioxidative defence system were observed at lower U concentrations to counteract the U-induced stress. However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed. 相似文献
7.
Cones and foci: A mechanical framework for protocol verification 总被引:1,自引:0,他引:1
We define a cones and foci proof method, which rephrases the question whether two system specifications are branching bisimilar in terms of proof obligations on relations between data objects. Compared to the original cones and foci method from Groote and Springintveld, our method is more generally applicable, because it does not require a preprocessing step to eliminate τ-loops. We prove soundness of our approach and present a set of rules to prove the reachability of focus points. Our method has been formalized and proved correct using PVS. Thus we have established a framework for mechanical protocol verification. We apply this framework to the Concurrent Alternating Bit Protocol.
相似文献
相似文献
8.
9.
Groundwater studies in several African countries show that the contamination of water-supply aquifers is mainly due to improper
placement of land-based activities such as agriculture, industries, waste disposal. In South Africa, groundwater pollution
is also of increasing concern due to fast population growth and accompanying development. Groundwater protection zoning is
a supplemental methodology for groundwater management that incorporates land use planning. The land is managed to minimize
the potential of groundwater contamination by human activities that occur on or below the land surface. The various benefits
associated with implementation of protection zoning are discussed for stakeholders such as communities, water supply companies,
ecosystems and policy makers. A South African case study is presented comparing the cost of protection with the cost incurred
due to the treatment of sick and dying people due to contaminated drinking water. These benefits must be communicated to the
stakeholders to start the implementation at all management levels. Implementation steps of groundwater protection zones are
discussed and can be tested even with low budgets and little data available. Monitoring and reassessment of protection zones
are important to test the effectiveness and prove to decision makers that the money was well spent. The legal framework for
implementation of groundwater protection zoning in a South African context is described, where the water law makes provision
for tools like differentiated protection, licensing and recovery of cost. Challenges regarding implementation of groundwater
protection are discussed with some action steps on how to move forward. 相似文献
10.
T Namitha Asokan K S Urmil Rajani Jaco Rachel Reena Philip G S Okram V Ganesan B Pradeep 《半导体学报》2014,35(5):052001-6
Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV-vis-NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9-300 K, which is explained on the basis of a phonon drag effect. 相似文献