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排序方式: 共有124条查询结果,搜索用时 15 毫秒
1.
Yttria-stabilized zirconia (NiO/YSZ) composites were prepared by the modified citrate–nitrate combustion synthesis. The citrate–nitrate combustion proceeded through several consecutive steps. Evolution of structure in the system and its changes were followed up by thermogravimetry-differential scanning calorimetry, X-ray powder diffraction, extended X-ray absorption fine structure, and high resolution transmission electron microscopy analyses of intermediate products prepared at distinct temperatures that correspond to different stages of the combustion process. It was shown that the crystalline structure developed gradually, first with crystallization of nano-sized NiO particles (400°–700°C), which was followed by crystallization of YSZ (800°–900°C). The final composite material after heat treatment at 1100°C comprised of nano-crystals with an average size of 6.5±2 nm.  相似文献   
2.
Organizing DNA origami building blocks into higher order structures is essential for fabrication of large structurally and functionally diverse devices and molecular machines. Unfortunately, the yields of origami building block attachment reactions are typically not sufficient to allow programed assembly of DNA devices made from more than a few origami building blocks. To investigate possible reasons for these low yields, a detailed single‐molecule fluorescence study of the dynamics of rectangular origami dimerization and origami dimer dissociation reactions is conducted. Reactions kinetics and yields are investigated at different origami and ion concentrations, for different ion types, for different lengths of bridging strands, and for the “sticky end” and “weaving welding” attachment techniques. Dimerization yields are never higher than 86%, which is typical for such systems. Analysis of the dynamic data shows that the low yield cannot be explained by thermodynamic instability or structural imperfections of the origami constructs. Atomic force microscopy and gel electrophoresis evidence reveal self‐dimerization of the origami monomers, likely via blunt‐end interactions made possible by the presence of bridging strands. It is suggested that this mechanism is the major factor that inhibits correct dimerization and means to overcome it are discussed.  相似文献   
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We describe a straightforward technique to synthesize pure Mo nanowires (NWs) from Mo6SyIz (8,2 <y + z ≤ 10) NWs as precursor templates. The structural transformations occur when Mo6SyIz NWs are annealed in Ar/H2 mixture leading to the formation of pure Mo NWs with similar structures as initial morphologies. Detailed microscopic characterizations show that large diameters (>15 nm) Mo NWs are highly porous, while small diameters (<7 nm) are made of solid nanocrystalline grains. We find NW of diameter 4 nm can carry up to 30 μA current without suffering structural degradation. Moreover, NWs can be elastically deformed over several cycles without signs of plastic deformation.  相似文献   
5.
建筑的前身是一个始建于20世纪50年代的电影院,由现代主义建筑师Franc Novak设计,一直被用作电影放映,年久失修。到21世纪,其陈旧的结构已无法满足一个新的建筑综合体的要求。  相似文献   
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This paper discusses current status and recent advancements of 3D graphics on mobile platforms and describes open issues concerning its usage in different applications. We have treated two particular application fields. Firstly, we deal with problems of visualization of complex data structures on mobile devices. The implementation of a 3D visualization renderer on the Symbian platform for mobile devices is written as a C++ application and based on the DieselEngine® as a rendering engine. 3D visualization of data is generated in the form of a Virtual Reality Modelling Language (VRML) file meaning that actually any kind of 3D content written in VRML file format can be rendered on such a device. It was the result of a project the objective of which was to provide a user interface on a mobile platform displaying visualization of hierarchical Grid monitoring data. Secondly, we describe the system that brings face animation to embedded platforms. Face animation is considered to be one of the toughest tasks in computer animation today and its delivery to mobile platforms brings possibilities for development of new innovative and attractive services for the mobile market.  相似文献   
7.
An Ontology for Virtual Organization Breeding Environments   总被引:1,自引:0,他引:1  
Companies and individuals connect into networks to share their resources with the purpose of achieving a common goal. The field of collaborative network organizations covers various types of organizational structures. Knowledge, which is stored in such networks, can be separated into two different levels. First, there is a common knowledge about the organizational structure itself that can be used and reused in any of such networks. The second level represents the domain-specific knowledge, which such networks cover and use to function. In this paper, we address both levels, first, by proposing an ontology representing the common vocabulary and identifying the actors and relationships in a specific type of network, namely virtual organization breeding environment (VBE), and second, by proposing a methodology for extracting network-specific knowledge related to competencies. The instantiation of the proposed VBE ontology and the developed approach to semiautomated construction of competencies have been applied to real problem scenarios of Virtuelle Fabrik, a Swiss-German cluster of companies in mechanical engineering.  相似文献   
8.
A novel, single-step, one-pot method for preparation of inorganic hollow particles is introduced. The concept is grounded on the classical theory of nucleation of growth and can be carried out entirely at room temperature. Starting from an appropriate solution, precipitation and selective dissolution of inorganic nanoparticles are triggered by continuous addition of a salt while carefully controlling the pH. The approach is demonstrated on the example of hollow calcium phosphate particles using calcium carbonate solid nanoparticles as a template. The proposed synthesis procedure is simple and cheap and can be extended to other biocompatible compounds. It also can be upgraded with an additional in situ step.  相似文献   
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Attachment of polysaccharide fucoidan to the polyethylene terephthalate (PET) polymer surface was studied by X-ray photoelectron spectroscopy (XPS). Fucoidan has antithrombogenic and anticoagulant properties and is therefore a promising coating for vascular graft implants for improving their hemocompatibility. Samples of PET polymer were first modified by nitrogen plasma treatment in order to change the surface wettability and to introduce amino groups to the surface, which act as a linker for further binding of fucoidan. Plasma treated samples were then incubated for 30 min in fucoidan solution. The presence of fucoidan layer on the polymer surface was demonstrated by appearance of S2p signal in the XPS spectra of the coated PET samples. The procedure for immobilization of fucoidan on PET surface was optimized by varying pH value of fucoidan solution from 5 to 7.4. The best results were obtained when using lower pH value pH = 5. At these conditions the thickness of the fucoidan coating was estimated to about 7 nm.  相似文献   
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