全文获取类型
收费全文 | 1546篇 |
免费 | 36篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 83篇 |
综合类 | 1篇 |
化学工业 | 330篇 |
金属工艺 | 47篇 |
机械仪表 | 47篇 |
建筑科学 | 36篇 |
能源动力 | 56篇 |
轻工业 | 157篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 129篇 |
一般工业技术 | 287篇 |
冶金工业 | 236篇 |
原子能技术 | 62篇 |
自动化技术 | 115篇 |
出版年
2023年 | 8篇 |
2022年 | 10篇 |
2021年 | 23篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 24篇 |
2017年 | 27篇 |
2016年 | 23篇 |
2015年 | 25篇 |
2014年 | 34篇 |
2013年 | 107篇 |
2012年 | 63篇 |
2011年 | 92篇 |
2010年 | 61篇 |
2009年 | 58篇 |
2008年 | 63篇 |
2007年 | 58篇 |
2006年 | 48篇 |
2005年 | 60篇 |
2004年 | 58篇 |
2003年 | 52篇 |
2002年 | 50篇 |
2001年 | 37篇 |
2000年 | 44篇 |
1999年 | 23篇 |
1998年 | 105篇 |
1997年 | 78篇 |
1996年 | 42篇 |
1995年 | 32篇 |
1994年 | 24篇 |
1993年 | 28篇 |
1992年 | 12篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 24篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1969年 | 3篇 |
排序方式: 共有1593条查询结果,搜索用时 843 毫秒
101.
Fujimoto J Umeda Y Tamura T Tomiyama T Kimura F 《Environmental science & technology》2003,37(23):5398-5406
To achieve sustainability, resource consumption and waste generation must be drastically decreased. For societal acceptance, preservation of both quality of life and corporate profits are essential. One promising approach is to shift the source of value from the amount of product sold to the quality of services the product provides. This paper describes the need for redesigning recycling systems from a manufacturing perspective and then discusses the possibility of this "servicification" of products, describing our experience with prototype development. We discuss development of product prototypes and their business, using consumer facsimile machines as an example of "service-oriented products". Traditional thought presumes that only products comprising new materials and components are valuable. Consideration of a service-oriented product can serve as a stimulus to revise this mode of thought and to control delivery and quality of disposed products. This paper also provides a life cycle simulation of the developed service-oriented business. Simulation results indicate that service-oriented business can potentially reduce environmental impact while extending business opportunities from the viewpoint of whole product life cycles. 相似文献
102.
Purification and characterization of a novel glutamyl aminopeptidase from chicken meat 总被引:1,自引:0,他引:1
A novel glutamyl aminopeptidase (aminopeptidase A, EC 3.4.11.7) was purified from chicken meat by ammonium sulfate fractionation, ethanol fractionation, heat treatment, and successive column chromatographies of DEAE-Sepharose CL-6B and Sephadex G-200. The purified enzyme migrated as a single band on SDS-PAGE. The molecular weight of this enzyme was found to be 55,000 and 550,000 by SDS-PAGE and Sephadex G-200 column chromatographies, respectively. This enzyme hydrolyzed Glu- and Asp-, but not Leu-, Arg-, and Ala-2-naphthylamide (-2NA) at all. The optimum pH and temperature for hydrolysis of Glu-2NA was 7.5. and 70°C, respectively. Reducing agents such as cysteine and dithiothreitol inhibited the activity of this enzyme at concentrations of 1 mM. However, the activation by Ca(2+) and the inhibition by amastatin were not observed. 相似文献
103.
Berendse F Owens SM Serlemitsos PJ Tueller J Chan KW Soong Y Krimm H Baumgartner WH Ogasaka Y Tamura K Okajima T Tawara Y Yamashita K Misaki K Kunieda H 《Applied optics》2003,42(10):1856-1866
The International Focusing Optics Collaboration for microCrab Sensitivity (InFOCmicroS) balloonborne hard x-ray telescope incorporates graded Pt/C multilayers replicated onto segmented Al foils to obtain the significant effective area at energies previously inaccessible to x-ray optics. Reflectivity measurements of individual foils demonstrate our capability to produce a mass quantity of multilayered foils with a rms roughness of 0.5 nm. The effective area of the completed mirror is 78 and 22 cm2 at 20 and 40 keV, respectively. The measured half-power diameter is 2.0 +/- 0.6 are min (90% confidence). The successful completion of this mirror demonstrates its applicability to future x-ray telescopes such as Constellation-X. 相似文献
104.
Thanda Oo Hiroshi Kawasaki Yutaka Ohsawa Katsushi Ikeuchi 《Machine Vision and Applications》2007,18(1):17-24
This paper presents an optimal method for the separation of reflected and transparent layers from real-world scene images.
Whereas past research has been applied to indoor environments and static cameras, our technique can be used for outdoor scenes
and motion cameras. The method is based on spatio-temporal analysis, especially using epipolar plane images (EPI). The edge
and color information of EPI has been used to segment the areas on EPIs efficiently and separate the reflected and transparent
layers. This method can be used for refining building textures by removing reflections from captured images for the purpose
of city modeling. 相似文献
105.
Yasushi Sumi Yutaka Ishiyama Fumiaki Tomita 《Computer Vision and Image Understanding》2007,105(3):218-230
This paper presents a new robot-vision system architecture for real-time moving object localization. The 6-DOF (3 translation and 3 rotation) motion of the objects is detected and tracked accurately in clutter using a model-based approach without information of the objects’ initial positions. An object identification task and an object tracking task are combined under this architecture. The computational time-lag between the two tasks is absorbed by a large amount of frame memory. The tasks are implemented as independent software modules using stereo-vision-based methods which can deal with objects of various shapes with edges, including planar to smooth-curved objects, in cluttered environments. This architecture also leads to failure-recoverable object tracking, because the tracking processes can be automatically recovered, even if the moving objects are lost while tracking. Experimental results obtained with prototype systems demonstrate the effectiveness of the proposed architecture. 相似文献
106.
Chisachi Kato Yoshinobu Yamade Yang Guo Takehisa Takaishi Yasushi Takano 《Computers & Fluids》2007,36(1):53-68
Numerical computations of sound generated from flows with a low Mach number are presented based on Lighthill’s acoustic analogy with an assumption that sound does not alter the flow field from which it is generated. The source fluctuations of the flow field are computed by a large-eddy simulation (LES) with Dynamic Smagorinsky Model (DSM) and they are fed to the following acoustical computation as input data. An explicit/implicit finite element method with second order accuracy both in time and space is used for flow field discretization. The method is applied to the prediction of sound in three different classes of problems: far-field sound generated from flow around a bluff body, sound resulting from blade-stator interaction of turbomachinery and sound due to a turbulent boundary layer on an aerofoil. The computed frequency spectra of the sound show a fairly good agreement with the measured spectra for all the cases. 相似文献
107.
Tu-Bao Ho Canh-Hao Nguyen Saori Kawasaki Si-Quang Le Katsuhiko Takabayashi 《New Generation Computing》2007,25(3):247-262
Various data mining methods have been developed last few years for hepatitis study using a large temporal and relational database
given to the research community. In this work we introduce a novel temporal abstraction method to this study by detecting
and exploiting temporal patterns and relations between events in viral hepatitis such as “event A slightly happened before
event B and B simultaneously ended with event C”. We developed algorithms to first detect significant temporal patterns in
temporal sequences and then to identify temporal relations between these temporal patterns. Many findings by data mining methods
applied to transactions/graphs of temporal relations shown to be significant by physician evaluation and matching with published
in Medline. 相似文献
108.
A classical many-body potential for transition metal carbide cluster is developed in the form of the bond-order type potential function. The parameter sets between carbon atoms and several transition metal atoms (Fe, Co and Ni) are constructed by fitting binding energies from Density Functional Theory (DFT) calculations. Using the potential function, clustering process of carbon atoms to a small metal cluster is studied by classical molecular dynamics (MD) simulation. The number of hexagonal rings in the Co cluster increases about twice as fast as in the Fe cluster. This implies that the graphitic lattice interacts more strongly with Co atoms than with Fe atoms. A Co cluster has a crystal structure where metal atoms are regularly allocated and embedded in the hexagonal carbon network in the simulation. In contrast, carbon atoms cover the entire surface in case of the Fe cluster. Additionally, the potential energy surface that a carbon atom feels from a 2D closed-packed facet is examined using a hypothetical FCC(1 1 1) facet of several transition metals. The potential energy minima are distributed on the hexagonal network showing the 2D closed-packed facet can be a template where a graphene is formed. 相似文献
109.
110.
Since the beginning of the ‘Doi Moi’ policy in 1986, Hanoi has witnessed significant changes in its urban areas. Landsat and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scenes were used to identify built-up areas in Hanoi, and spatial metrics were used to characterize urban change patterns from 1975 to 2003. Firstly, a spatial metric called the ‘percentage of like adjacency’ was used to discern urban growth patterns, which were classified into three sub-patterns: expansion growth, infill growth and outlying growth. Secondly, the driving force underlying the urbanization of the city for the 1975–1984, 1984–1992, 1992–2001, 2001–2003 periods was investigated using a spatial metric analysis programme (FRAGSTATS). The expansion of urban areas along major transportation routes in the latter 1980s was identified as the main form of urbanization in Hanoi. This paper shows the potential application of spatial metrics as secondary sources of information for supporting remotely sensed data and their use to characterize urban growth patterns. 相似文献