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排序方式: 共有262条查询结果,搜索用时 15 毫秒
1.
Katerina Zaharieva Maya Shopska Ilyana Yordanova Sonia Damyanova 《Ceramics International》2018,44(1):326-332
Magnesium aluminate-based materials were prepared by applying different methods: (i) mechanochemical milling of the initial mixture of magnesium and aluminium nitrate powders (in appropriate stoichiometric amounts) followed by heat treatment at temperatures of 650 °C and 850 °C and (ii) melting of the mixture of nitrate precursors at 240 °C followed by thermal treatment at 650 °C, 750 °C and 850 °C. The effect of synthesis method on the structure and morphology of the obtained solids was studied by using various techniques such as: nitrogen adsorption-desorption isotherms, powder XRD, IR spectroscopy and SEM. It was shown that the mechanochemical milling performed before calcination procedure leads to obtaining of nanocrystalline magnesium aluminate spinel phase at lower temperature of 650 °C in comparison with the method using thermal treatment only (at 750 °C). The obtained nanomaterials exhibit mesoporous structure. 相似文献
2.
Vassilis P. Panoskaltsis Katerina D. Papoulia Saurabh Bahuguna Igor Korovajchuk 《Mechanics of Time-Dependent Materials》2007,11(3-4):217-230
We propose a generalization of the Kuhn model of linear viscoelasticity. This generalization, which has four material parameters, is able to provide a near frequency independent response over a wide range of frequencies. It is useful for highly dissipative materials such as asphalt concrete. It is derived by generalizing Lubliner and Panoskaltsis’s modified Kuhn model, but we also show that it is closely related to fractional derivative models. We show that the model admits a rheological approximation, that is, an approximation by classical springs and dashpots. The model and rheological representation are compared to experimental data. 相似文献
3.
Katerina Mangaroska Roberto Martinez-Maldonado Boban Vesin Dragan Gašević 《Journal of Computer Assisted Learning》2021,37(4):1030-1047
Multimodal data have the potential to explore emerging learning practices that extend human cognitive capacities. A critical issue stretching in many multimodal learning analytics (MLA) systems and studies is the current focus aimed at supporting researchers to model learner behaviours, rather than directly supporting learners. Moreover, many MLA systems are designed and deployed without learners' involvement. We argue that in order to create MLA interfaces that directly support learning, we need to gain an expanded understanding of how multimodal data can support learners' authentic needs. We present a qualitative study in which 40 computer science students were tracked in an authentic learning activity using wearable and static sensors. Our findings outline learners' curated representations about multimodal data and the non-technical challenges in using these data in their learning practice. The paper discusses 10 dimensions that can serve as guidelines for researchers and designers to create effective and ethically aware student-facing MLA innovations. 相似文献
4.
Katerina Philippou Christos N. Christou Vlad Socoliuc Ladislau Vekas Eugenia Tanasă Marinela Miclau Ioannis Pashalidis Theodora Krasia-Christoforou 《应用聚合物科学杂志》2021,138(15):50212
Magnetoactive electrospun fibrous membranes consisting of polyvinylpyrrolidone (PVP), chitosan (CS) and pre-fabricated, double-layer oleic acid-coated magnetite nanoparticles (OA.OA.Fe3O4) were fabricated and evaluated as new adsorbent materials for the removal and recovery of uranium (U(VI)) from aqueous solutions. The adsorption has been investigated by batch-type experiments and the solid material has been characterized by X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy/energy dispersive X-ray analysis (TEM/EDX) and vibration sample magnetometry (VSM) measurements prior and after uranium adsorption. The experimental adsorption data were found to be well fitted with the Langmuir isotherm and the pseudo-second order kinetic model. The results indicate that PVP/CS/OA.OA.Fe3O4 fibrous adsorbents exhibit good adsorption properties towards U(VI) in aqueous solutions, achieving a qmax value of 0.77 mol kg−1 (183.3 mg g−1) at pH 6.0. The experiments regarding the regeneration and reuse of the magnetoactive adsorbents were carried out using Na2CO3, at pH ~11. After four cycles, the percentage relative adsorption remained stable (~100%) whereas the desorption percentage decreased from 31.9% to 21.0%. Generally, the presented results demonstrate that the incorporation of the Fe3O4 NPs has a positive effect on the adsorption efficiency of U(VI) from aquatic environments. 相似文献
5.
6.
Chiara Braghin Natasha Sharygina Katerina Barone-Adesi 《Formal Aspects of Computing》2011,23(5):627-648
This article describes an approach for the automated verification of mobile systems. Mobile systems are characterized by the
explicit notion of location (e.g., sites where they run) and the ability to execute at different locations, yielding a number of security issues. To
this aim, we formalize mobile systems as Labeled Kripke Structures, encapsulating the notion of location net that describes the hierarchical nesting of the threads constituting the system. Then, we formalize a generic security-policy specification language that includes rules for expressing and manipulating the code location. In contrast to many other approaches, our technique
supports both access control and information flow specification. We developed a prototype framework for model checking of
mobile systems. It works directly on the program code (in contrast to most traditional process-algebraic approaches that can
model only limited details of mobile systems) and uses abstraction-refinement techniques, based also on location abstractions,
to manage the program state space. We experimented with a number of mobile code benchmarks by verifying various security policies.
The experimental results demonstrate the validity of the proposed mobile system modeling and policy specification formalisms
and highlight the advantages of the model checking-based approach, which combines the validation of security properties with
other checks, such as the validation of buffer overflows. 相似文献
7.
Lozenka Ivanova Katerina Rebok Maja Jordanova Zrinka Dragun Vasil Kostov Sheriban Ramani Damir Vali Nesrete Krasnii Vlatka Filipovi Mariji Damir Kapetanovi 《Microscopy research and technique》2020,83(9):1141-1152
Pigmented macrophage aggregates (MAs) are known to change under influence of various factors, such as aging, season, starvation, and/or pollution. In this study, changes in the pigment content of the MAs in the spleen of Vardar chub (Squalius vardarensis, Karaman) (n = 129) collected in spring and autumn, from three rivers with different pollution impact was examined: Zletovska River (metals), Kriva River (metals and municipal wastewater), and Bregalnica River (municipal wastewater). Collected data revealed increased relative volume and number of MAs containing hemosiderin under the influence of metals, significant in autumn (p < .05). In chub exposed to metals combined with municipal wastewater, significant increase of lipochrome accumulation in MAs in autumn, melanin in MAs in fish captured in the spring season, and number of splenic MAs containing combination of melanin and lipochrome was noted. Volumes and number of MAs containing combination of hemosiderin and lipochrome increased in spleen of fish captured in autumn from both Zletovska River and Kriva River, most likely due to the contribution of hemosiderin and lipochrome, respectively. Values measured for the various pigments in splenic MAs in fish captured from Bregalnica River, were overall closer to the values measured for fish captured from Kriva River. Notably, melanin and lipochrome are more likely to be found in fish from waters influenced by municipal wastewater (organic pollution) and hemosiderin in fish spleen from water influenced by mining activity (heavy metals pollution). 相似文献
8.
Jirina Tyleckova Rita Hrabakova Katerina Mairychova Petr Halada Lenka Radova Petr Dzubak Marian Hajduch Suresh J. Gadher Hana Kovarova 《International journal of molecular sciences》2012,13(12):15536-15564
A comprehensive proteome map of T-lymphoblastic leukemia cells and its alterations after daunorubicin, doxorubicin and mitoxantrone treatments was monitored and evaluated either by paired comparison with relevant untreated control and using multivariate classification of treated and untreated samples. With the main focus on early time intervals when the influence of apoptosis is minimized, we found significantly different levels of proteins, which corresponded to 1%–2% of the total amount of protein spots detected. According to Gene Ontology classification of biological processes, the highest representation of identified proteins for all three drugs belong to metabolic processes of proteins and nucleic acids and cellular processes, mainly cytoskeleton organisation and ubiquitin-proteasome pathway. Importantly, we observed significant proportion of changes in proteins involved in the generation of precursor metabolites and energy typical for daunorubicin, transport proteins participating in response to doxorubicin and a group of proteins of immune system characterising response to mitoxantrone. Both a paired comparison and the multivariate evaluation of quantitative data revealed daunorubicin as a distinct member of the group of anthracycline/anthracenedione drugs. A combination of identified drug specific protein changes, which may help to explain anti-cancer activity, together with the benefit of blocking activation of adaptive cancer pathways, presents important approaches to improving treatment outcomes in cancer. 相似文献
9.
10.
Robert Sevenich Elke Kleinstueck Colin Crews Warwick Anderson Celine Pye Katerina Riddellova Jaromir Hradecky Eliska Moravcova Kai Reineke Dietrich Knorr 《Journal of food science》2014,79(2):M230-M237
The benefits that high‐pressure thermal sterilization offers as an emerging technology could be used to produce a better overall food quality. Due to shorter dwell times and lower thermal load applied to the product in comparison to the thermal retorting, lower numbers and quantities of unwanted food processing contaminants (FPCs), for example, furan, acrylamide, HMF, and MCPD‐esters could be formed. Two spore strains were used to test the technique; Geobacillus stearothermophilus and Bacillus amyloliquefaciens, over the temperature range 90 to 121 °C at 600 MPa. The treatments were carried out in baby food puree and ACES‐buffer. The treatments at 90 and 105 °C showed that G. stearothermophilus is more pressure‐sensitive than B. amyloliquefaciens. The formation of FPCs was monitored during the sterilization process and compared to the amounts found in retorted samples of the same food. The amounts of furan could be reduced between 81% to 96% in comparison to retorting for the tested temperature pressure combination even at sterilization conditions of F0‐value in 7 min. 相似文献