全文获取类型
收费全文 | 4926篇 |
免费 | 211篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 118篇 |
综合类 | 66篇 |
化学工业 | 1420篇 |
金属工艺 | 157篇 |
机械仪表 | 81篇 |
建筑科学 | 294篇 |
矿业工程 | 37篇 |
能源动力 | 157篇 |
轻工业 | 932篇 |
水利工程 | 46篇 |
石油天然气 | 37篇 |
武器工业 | 8篇 |
无线电 | 230篇 |
一般工业技术 | 654篇 |
冶金工业 | 213篇 |
原子能技术 | 52篇 |
自动化技术 | 670篇 |
出版年
2023年 | 43篇 |
2022年 | 65篇 |
2021年 | 122篇 |
2020年 | 85篇 |
2019年 | 74篇 |
2018年 | 119篇 |
2017年 | 106篇 |
2016年 | 161篇 |
2015年 | 128篇 |
2014年 | 158篇 |
2013年 | 245篇 |
2012年 | 184篇 |
2011年 | 200篇 |
2010年 | 192篇 |
2009年 | 200篇 |
2008年 | 178篇 |
2007年 | 172篇 |
2006年 | 137篇 |
2005年 | 113篇 |
2004年 | 111篇 |
2003年 | 95篇 |
2002年 | 146篇 |
2001年 | 136篇 |
2000年 | 94篇 |
1999年 | 101篇 |
1998年 | 101篇 |
1997年 | 84篇 |
1996年 | 68篇 |
1995年 | 72篇 |
1994年 | 67篇 |
1993年 | 43篇 |
1992年 | 58篇 |
1991年 | 60篇 |
1990年 | 44篇 |
1989年 | 52篇 |
1988年 | 36篇 |
1987年 | 42篇 |
1986年 | 37篇 |
1985年 | 34篇 |
1984年 | 39篇 |
1983年 | 33篇 |
1981年 | 35篇 |
1980年 | 31篇 |
1977年 | 29篇 |
1975年 | 27篇 |
1974年 | 30篇 |
1973年 | 28篇 |
1918年 | 29篇 |
1917年 | 30篇 |
1915年 | 34篇 |
排序方式: 共有5172条查询结果,搜索用时 15 毫秒
21.
Statistical Analysis of the Intergranular Film Thickness in Silicon Nitride Ceramics 总被引:1,自引:0,他引:1
Hans-Joachim Kleebe Michael K. Cinibulk Rowland M. Cannon Manfred Rüble 《Journal of the American Ceramic Society》1993,76(8):1969-1977
Silicon nitride materials typically reveal thin amorphous intergranular films along grain boundaries, with only the exception of special boundaries. It is known that such grainboundary films strongly affect the high-temperature properties of the bulk material. High-resolution electron microscopy (HREM) was used to study these amorphous films in different Si3 N4 ceramics. The observed film thicknesses at grain boundaries in these materials varied between 5and 15 Å. It was shown that the grain-boundary film thickness strongly depends on film chemistry. Careful inspections of film-thickness measurements across grain boundaries in a given material suggest that the film widths vary on the order of 1 Å. Therefore, a quantitative evaluation should allow for the determination of the standard deviation of the film thickness. The amorphous film widths along grain boundaries in four materials were measured over the entire length (up to 1 μm) of the grain boundary between two triple points. Forty to fifty data points were evaluated for each boundary, giving a Gaussian-like distribution of the film thickness around a median value, which corresponded well with the film width measured from single HREM micrographs. The accuracy achieved by the statistical method was better than ± 1 Å. 相似文献
22.
23.
Corrosion of oil-fired domestic boilers Depending on the surface temperature of the flue gas side the corrosion of oil fired domestic boilers proceeds either mainly by acid corrosion or by oxygen corrosion:
- – At surface temperatures of 60°C and higher the corrosion mechanism of acid corrosion prevails and the corrosion rates amount to 0.1–0.3 mm/year (values referred to continuous burner operation). The corrosion products consist of soluble iron(II)- and iron(III)sulfates. Higher corrosion rates can be attributed to an appreciable catalytic formation of sulfur trioxide on the corrosion products formed on the convective heating surfaces.
- – At surface temperatures of 40°C the mechanism of oxygen corrosion already dominates and the corrosion rates are about ten times higher (1.5–3 mm/year, referred to continous burner operation). The high portion of ioron oxide hydrates, especially goethit (α-FeOOH), makes the corrosion products difficult to remove.
- – Distinctly reduced service lives are also expected for the so called reduced temperature boilers (“Niedertemperaturkessel”) and low temperature boiers (“Tieftemperaturkessel”): According to the manufacturers these boilers may be operated at boiler water temperatures well below 60°C, as they are equipped with constructive measures to enhance the surface temperature on the flue gas side. However, these measures are only fully effective under stationary conditions.
24.
Johanna Nellen Kai Driessen Martin Neuhäußer Erika Ábrahám Benedikt Wolters 《Information Systems Frontiers》2016,18(5):927-952
In this paper we address the safety analysis of chemical plants controlled by programmable logic controllers (PLCs). We consider a specification of the control program of the PLCs, extended with the specification of the dynamic plant behavior. The resulting hybrid models can be transformed to hybrid automata, for which advanced techniques for reachability analysis exist. However, the hybrid automata models are often too large to be analyzed. We propose two counterexample-guided abstraction refinement (CEGAR) approaches to keep the size of the hybrid models moderate. 相似文献
25.
We present a novel physically‐based method to visualize stress tensor fields. By incorporating photoelasticity into traditional raycasting and extending it with reflection and refraction, taking into account polarization, we obtain the virtual counterpart to traditional experimental polariscopes. This allows us to provide photoelastic analysis of stress tensor fields in arbitrary domains. In our model, the optical material properties, such as stress‐optic coefficient and refractive index, can either be chosen in compliance with the subject under investigation, or, in case of stress problems that do not model optical properties or that are not transparent, be chosen according to known or even new transparent materials. This enables direct application of established polariscope methodology together with respective interpretation. Using a GPU‐based implementation, we compare our technique to experimental data, and demonstrate its utility with several simulated datasets. 相似文献
26.
Topology optimization of a cantilevered piezoelectric energy harvester using stress norm constraints
Fabian Wein Manfred Kaltenbacher Michael Stingl 《Structural and Multidisciplinary Optimization》2013,48(1):173-185
Vibrational piezoelectric energy harvesters are devices which convert ambient vibrational energy into electric energy. Here we focus on the common cantilever type in which an elastic beam is sandwiched between two piezoelectric plates. In order to maximize the electric power for a given sinusoidal vibrational excitation, we perform topology optimization of the elastic beam and tip mass by means of the SIMP approach, leaving the piezoelectric plates solid. We are interested in the first and especially second resonance mode. Homogenizing the piezoelectric strain distribution is a common indirect approach increasing the electric performance. The large design space of the topology optimization approach and the linear physical model also allows the maximization of electric performance by maximizing peak bending, resulting in practically infeasible designs. To avoid such problems, we formulate dynamic piezoelectric stress constraints. The obtained result is based on a mechanism which differs significantly from the common designs reported in literature. 相似文献
27.
Gorka Epelde Eduardo Carrasco Gottfried Zimmermann Jan Alexandersson Robert Neßelrath Markus Dubielzig 《Universal Access in the Information Society》2013,12(1):73-87
This paper presents a new approach to make current and future television universally accessible. The proposed approach provides a means of universal accessibility both for remotely operating the TV set and for interacting with online services delivered through the TV. This proposal is based on the ISO/IEC 24752 “Universal Remote Console” (URC) standard. This standard defines an abstract user interface layer called the “user interface socket” and allows the development of pluggable (plug-in) user interfaces for any type of user and any control device. The proposed approach lays the foundation for the development of advanced user interfaces that can be interacted within various modalities. Different prototypes have been developed based on this approach and tested with end users. The user tests have shown this approach to be a viable option for the proposed scenarios. Based on the experience gathered with the prototypes, recommendations and implementation options are suggested for commercial adoption. 相似文献
28.
Jolita Ralyt Manfred A. Jeusfeld Per Backlund Harald Kühn Nicolas Arni-Bloch 《Information Systems》2008,33(7-8):754
Interoperability is a key property of enterprise applications, which is hard to achieve due to the large number of interoperating components and semantic heterogeneity. The inherent complexity of interoperability problems implies that there exists no silver bullet to solve them. Rather, the knowledge about how to solve wicked interoperability problems is hidden in the application cases that expose those problems. The paper addresses the question of how to organise and use method knowledge to resolve interoperability problems. We propose the structure of a knowledge-based system that can deliver situation-specific solutions, called method chunks. Situational Method Engineering promotes modularisation and formalisation of method knowledge in the form of reusable method chunks, which can be combined to compose a situation-specific method. The method chunks are stored in a method chunk repository. In order to cater for management and retrieval, we introduce an Interoperability Classification Framework, which is used to classify and tag method chunks and to assess the project situation in which they are to be used. The classification framework incorporates technical as well as business and organisational aspects of interoperability. This is an important feature as interoperability problems typically are multifaceted spanning multiple aspects. We have applied the approach to analyse an industry case from the insurance sector to identify and classify a set of method chunks. 相似文献
29.
Andreas Ruh Adam-Mwanga Dieckmann Richard Heldele Volker Piotter Robert Ruprecht Christian Munzinger Jürgen Fleischer Jürgen Haußelt 《Microsystem Technologies》2008,14(12):1805-1811
In the field of micro-technology the production of metallic and ceramic micro-components by powder injection molding (PIM)
has become a more and more established fabrication method. But in order to fulfill the demand for more complex-shaped high-precision
micro-components further development work has to be performed. This is especially true if more efficient production routes
for multi-component-micro-assemblies consisting of different materials or sub-components are envisaged. To meet these challenges,
investigations are performed to realize and to establish two primary shape micro-processes. These are two-component micro-injection
molding (2C-MicroPIM) and sinter-joining. The realization of these technologies will lead to a markedly reduction of the efforts
for handling, adjustment, and assembling of metallic and ceramic micro-assemblies. Furthermore, an increased integration level
and functionality can be yielded. For an effective transfer of scientific results to industrial applications the whole process
chain must be considered, from development and construction of the tooling as well as of the components to the quality assurance
and determination of the properties of the assemblies after sintering. These primary shape processes shall enable the mutual
processing of different materials within the fabrication process, so avoiding separate mounting or assembling steps. Additionally
fixed and loose junctions between at least two components shall be realized. The progress in research and development will
be demonstrated especially by the implementation of shaft-to-collar connections between micro-gearwheels and corresponding
shafts. Regarding two-component micro-injection molding, the tool construction for shaft-to-collar connections will be presented
as well as first experimental results on the properties of selected ceramic powders and feedstocks for the special requirements
of the 2C-MicroPIM process. With the assembly step being performed outside the injection molding tool before sinter-joining
different parts and geometries can be combined quite easily. The presented article gives an overview on the concept and on
preliminary testing results for the fabrication of a shaft-to-collar-connection. Additionally, a solution for an automated
assembly of a shaft and a toothed wheel outside the injection molding tool is presented. 相似文献
30.
Scherer HU Wang J Toes RE van der Woude D Koeleman CA de Boer AR Huizinga TW Deelder AM Wuhrer M 《Proteomics. Clinical applications》2009,3(1):106-115
In several autoimmune disorders, including rheumatoid arthritis (RA), autoantibodies are thought to be the driving force of pathogenicity. Glycosylation of the Fc-part of human Igs is known to modulate biological activity. Hitherto, glycosylation of human IgG-Fc has been analyzed predominantly at the level of total serum IgG, revealing reduced galactosylation in RA. Given the pathogenic relevance of autoantibodies in RA, we wished, in the present study, to address the question whether distinct Fc-glycosylation features are observable at the level of antigen-specific IgG subpopulations. For this purpose, we have developed a method for the microscale purification and Fc-glycosylation analysis of anti-citrullinated peptide antibodies (ACPA). ACPA represent a group of autoantibodies that occur with unique specificity in RA patients. Their presence is associated with increased inflammatory disease activity and rapid joint destruction. Results indicate that ACPA of the IgG1 subclass vary considerably from total serum IgG1 with respect to Fc-galactosylation, with galactosylation being higher on ACPA than on serum IgG1 for some patients, while other patients show higher galactosylation on serum IgG1 than on ACPA. Using this method, studies can be performed on the biological and clinical relevance of ACPA glycosylation within RA patient cohorts. 相似文献