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排序方式: 共有100条查询结果,搜索用时 11 毫秒
31.
Yuri B. Melnichenko Lilin He Richard Sakurovs Arkady L. Kholodenko Tomasz Blach Maria Mastalerz Andrzej P. Radliński Gang Cheng David F.R. Mildner 《Fuel》2012,91(1):200-208
Fluid–solid interactions in natural and engineered porous solids underlie a variety of technological processes, including geological storage of anthropogenic greenhouse gases, enhanced coal bed methane recovery, membrane separation, and heterogeneous catalysis. The size, distribution and interconnectivity of pores, the chemical and physical properties of the solid and fluid phases collectively dictate how fluid molecules migrate into and through the micro- and meso-porous media, adsorb and ultimately react with the solid surfaces. Due to the high penetration power and relatively short wavelength of neutrons, small-angle neutron scattering (SANS) as well as ultra small-angle scattering (USANS) techniques are ideally suited for assessing the phase behavior of confined fluids under pressure as well as for evaluating the total porosity in engineered and natural porous systems including coal. Here we demonstrate that SANS and USANS can be also used for determining the fraction of the pore volume that is actually accessible to fluids as a function of pore sizes and study the fraction of inaccessible pores as a function of pore size in three coals from the Illinois Basin (USA) and Bowen Basin (Australia). Experiments were performed at CO2 and methane pressures up to 780 bar, including pressures corresponding to zero average contrast condition (ZAC), which is the pressure where no scattering from the accessible pores occurs. Scattering curves at the ZAC were compared with the scattering from same coals under vacuum and analysed using a newly developed approach that shows that the volume fraction of accessible pores in these coals varies between ~90% in the macropore region to ~30% in the mesopore region and the variation is distinctive for each of the examined coals. The developed methodology may be also applied for assessing the volume of accessible pores in other natural underground formations of interest for CO2 sequestration, such as saline aquifers as well as for estimating closed porosity in engineered porous solids of technological importance. 相似文献
32.
Polyoxomolybdate [Mo_(36)O_(110)(NO)_4(H_2 O)_(14)]·52 H_2 O was synthesized by a simple one-pot procedure through reducing an acidified mixture of Na_2 MoO_4·2 H_2 O and NH_2 OH·HCl. In order to create a heterogeneous catalyst system, the polyoxomolybdate was pillared with MgAl-LDH-NO_3 by direct ion exchange. These novel materials were carefully analyzed by various chemico-physical methods. The catalytic degradation of methylene blue(MB) and rhodamine B(RB) as common dyes in the presence of MgAl-LDH-1 nanoparticles with aqueous hydrogen peroxide, H_2 O_2, as an oxidizing agent was studied in aqueous solution at room temperature. More importantly, the catalyst can be recovered and reused efficiently up to five consecutive cycles with negligible loss of catalytic activity. 相似文献
33.
Hanne Falsig Thomas Bligaard Jeppe Rass-Hansen Arkady L. Kustov Claus H. Christensen Jens K. Nørskov 《Topics in Catalysis》2007,45(1-4):117-120
The formation of NOx from combustion of fossil and renewable fuels continues to be a dominant environmental issue. We take one step towards rationalizing
trends in catalytic activity of transition metal catalysts for NO decomposition by combining microkinetic modelling with density
functional theory calculations. We show specifically why the key problem in using transition metal surfaces to catalyze direct
NO decomposition is their significant relative overbinding of atomic oxygen compared to atomic nitrogen. 相似文献
34.
The Expressive Power of Temporal Logic of Actions 总被引:1,自引:0,他引:1
35.
An infrastructure approach to support context-aware pervasive computing is advantageous for rapid prototyping of context-aware distributed applications and beneficial for unifying modelling of context and reasoning in uncertain conditions. This paper presents the ECORA framework for context-aware computing, which is designed with a focus on reasoning about context under uncertainty and addressing issues of heterogeneity, scalability, communication and usability. The framework follows an agent-oriented hybrid approach, combining centralized reasoning services with context-aware, reasoning capable mobile software agents. The use of a centralized reasoning engine provides powerful reasoning capabilities and deploying context-aware mobile agents enables agility and robustness of components in the pervasive system. The design and implementation of the framework at different levels, as well as three case studies, are presented. 相似文献
36.
Pervasive computing is a paradigm that focuses on the availability of computer resources anytime anywhere for any application and supports non-intrusive integration of computing services into everyday life. Context awareness is the core feature of pervasive computing. High-level context awareness can be enhanced by situation awareness that represents the ability to detect and reason about the real-life situations. In this article we propose, analyze and validate the formal verification method for situation definitions and demonstrate its feasibility and efficiency. Situations are often defined manually by domain experts and are, therefore, susceptible to definition inconsistencies and possible errors, which in turn can cause situation reasoning problems. The proposed method takes as an input properties of situations and dependencies among them as well as situation definitions in terms of low-level context features, and then either formally proves that the definitions do comply with the expected properties, or provides a complete set of counterexamples — context parameters that prove situation inconsistency. Evaluation and complexity analysis of the proposed approach are also presented and discussed. Examples and evaluation results demonstrate that the proposed approach can be used to verify real-life situation definitions, and detect non-obvious errors in situation specifications. 相似文献
37.
Talyzin AV Anoshkin IV Krasheninnikov AV Nieminen RM Nasibulin AG Jiang H Kauppinen EI 《Nano letters》2011,11(10):4352-4356
A novel material, graphene nanoribbons encapsulated in single-walled carbon nanotubes (GNR@SWNT), was synthesized using confined polymerization and fusion of polycyclic aromatic hydrocarbon (PAH) molecules. Formation of the GNR is possible due to confinement effects provided by the one-dimensional space inside nanotubes, which helps to align coronene or perylene molecules edge to edge to achieve dimerization and oligomerization of the molecules into long nanoribbons. Almost 100% filling of SWNT with GNR is achieved while nanoribbon length is limited only by the length of the encapsulating nanotube. The PAH fusion reaction provides a very simple and easily scalable method to synthesize GNR@SWNT in macroscopic amounts. First-principle simulations indicate that encapsulation of the GNRs is energetically favorable and that the electronic structure of the encapsulated GNRs is the same as for the free-standing ones, pointing to possible applications of the GNR@SWNT structures in photonics and nanoelectronics. 相似文献
38.
Mapping the myocardial fiber organization is important for assessing the electrical and mechanical properties of normal and diseased hearts. Current methods to determine the fiber organization have several limitations: histological sectioning mechanically distorts the tissue and is labor-intensive, while diffusion tensor imaging has low spatial resolution and requires expensive MRI scanners. Here, we utilized optical clearing, a fluorescent dye, and confocal microscopy to create three-dimensional reconstructions of the myocardial fiber organization of guinea pig and mouse hearts. We have optimized the staining and clearing procedure to allow for the nondestructive imaging of whole hearts with a thickness up to 3.5 mm. Myocardial fibers could clearly be identified at all depths in all preparations. We determined the change of fiber orientation across strips of guinea pig left ventricular wall. Our study confirms the qualitative result that there is a steady counterclockwise fiber rotation across the ventricular wall. Quantitatively, we found a total fiber rotation of 105.7+/-14.9 degrees (mean+/-standard error of the mean); this value lies within the range reported by previous studies. These results show that optical clearing, in combination with a fluorescent dye and confocal microscopy, is a practical and accurate method for determining myocardial fiber organization. 相似文献
39.
40.
Peter Spaeh Gaetano Aiello Robby Gessner Giovanni Grossetti Andreas Meier Theo Scherer Sabine Schreck Arkady Serikov Dirk Strauss Alessandro Vaccaro Bastian Weinhorst 《Fusion Engineering and Design》2013,88(6-8):878-881
After approval of the preliminary design of the ITER EC H&CD Upper Launcher, ECHUL-CA, a consortium of several European research institutes, was founded to pool resources for approaching the final design. At the end of 2011 the consortium has signed a 2 years contract with F4E to go ahead with the work on the launcher. The contract deals with design work on both the port plug, forming the structural system, and the mm-wave-system, which injects the RF-power into the plasma. Within the period of this contract all components being part of the Tritium confinement, of which the closure plate, the support flange, the diamond windows and the waveguide feed-throughs are the most outstanding ones, will get the status of the final design.Important steps to be done for the structural system are the optimization of the mechanical behavior of the launcher, leading to minimum deflections of the port plug during plasma disruptions and optimum seismic resistance. To reduce the effect of halo currents it was decided to recess the first wall of 100 mm compared to the regular blanket tangent. This recess requires substantial changes of the cooling system and the thermo-hydraulic design of the launcher. Also the layout of the shielding arrangement and the integration of the mm-wave system need significant revision. Moreover manufacturing aspects and enhanced remote handling capability are taken into account.For the final design also quality aspects must be considered; thus the design is elaborated with respect to applicable codes and standards, material specifications, risk analyses and the RAMI (reliability, availability, maintainability and inspectability) analysis to guarantee maximum performance of the device.This paper outlines the present status of the structural system of the EC H&CD upper launcher and represents the most recent steps towards its final design. 相似文献