全文获取类型
收费全文 | 2028篇 |
免费 | 76篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 36篇 |
综合类 | 6篇 |
化学工业 | 627篇 |
金属工艺 | 54篇 |
机械仪表 | 45篇 |
建筑科学 | 125篇 |
矿业工程 | 9篇 |
能源动力 | 46篇 |
轻工业 | 132篇 |
水利工程 | 5篇 |
无线电 | 133篇 |
一般工业技术 | 363篇 |
冶金工业 | 114篇 |
原子能技术 | 28篇 |
自动化技术 | 386篇 |
出版年
2023年 | 20篇 |
2022年 | 35篇 |
2021年 | 67篇 |
2020年 | 34篇 |
2019年 | 35篇 |
2018年 | 37篇 |
2017年 | 38篇 |
2016年 | 72篇 |
2015年 | 54篇 |
2014年 | 63篇 |
2013年 | 93篇 |
2012年 | 113篇 |
2011年 | 144篇 |
2010年 | 113篇 |
2009年 | 95篇 |
2008年 | 111篇 |
2007年 | 94篇 |
2006年 | 109篇 |
2005年 | 75篇 |
2004年 | 76篇 |
2003年 | 49篇 |
2002年 | 42篇 |
2001年 | 40篇 |
2000年 | 33篇 |
1999年 | 37篇 |
1998年 | 38篇 |
1997年 | 33篇 |
1996年 | 25篇 |
1995年 | 22篇 |
1994年 | 24篇 |
1993年 | 20篇 |
1992年 | 22篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 14篇 |
1974年 | 16篇 |
1973年 | 7篇 |
排序方式: 共有2109条查询结果,搜索用时 15 毫秒
101.
End of life management (EOL) is currently a hot topic in the electronics industry. Currently, mostly IT equipment and goods of consumer electronics are considered. In the nearest future automation equipment has also to be taken into account. There are three possibilities depending on the age and kind of the device: resell–reuse–recycle, called the “3Rs”. For recycling fully or semi-automated disassembly will gain in importance in the nearest future also for robots. Producers of robots have to take into account EoL because of regulations and laws as well as according to ethical codes contributing to protection of the environment. Based on previous works a real example will be presented and discussed. 相似文献
102.
Bernd Oberwinkler 《Materials Science and Engineering: A》2011,528(18):5983-5992
Ti-6Al-4V is a commonly used titanium base alloy in aerospace applications. The increasing demand for damage-tolerant designs of such components necessitates a detailed knowledge of its crack growth behavior. The aim of this research was the characterization and phenomenological modeling of long crack growth behavior with respect to microstructure and stress ratio. Therefore, the long crack propagation was characterized for eight different heat treatment conditions and four stress ratios. For comparison, physically short crack growth tests were also performed. The long crack growth threshold was found to be dominated by roughness-induced crack closure, and the fracture surface roughness is controlled by the primary α-grain size. The reason for this correlation is a near-threshold crack propagation mode, which is dominated by the transcrystalline fracture of α-grains. This correlation was used to model the crack growth threshold with respect to microstructure. A linear relation was determined between the stress ratio and the threshold value, which was also found in this approach. Further presented models cover the crack growth behavior in the near-threshold (Stage I) and mid-growth rate regions (Stage II). 相似文献
103.
Marcel Müri Bernd Gotsmann Yann Leroux Marius Trouwborst Emanuel Lörtscher Heike Riel Marcel Mayor 《Advanced functional materials》2011,21(19):3706-3714
Due to the increasing importance of modified electrodes for many applications in nanotechnology, including molecular electronics, bioelectronics, and sensors, there is a need to find ways to chemically attach suitable molecular films onto the electrodes. Combining the electroreduction of aryl diazonium salts with the Sonogashira cross‐coupling reaction, a new modular technique to modify electrodes is presented. The new technique allows a wide range of functional groups to be introduced onto electrode surfaces with high surface coverage by the functional subunit. Various organic subunits, including redox chromophores, are successfully attached to platinum electrodes. The corresponding films are characterized using cyclic voltammetry, X‐ray photoelectron spectroscopy, atomic force microscopy, and contact‐angle measurements. The electroreduction of diazonium salts is successfully achieved on a broad variety of conducting and semiconducting surfaces, which shows that the technique is applicable to a broad variety of substrates. 相似文献
104.
Marek Vančo Bernd Hamann Oliver Kreylos Magali I. Billen Margarete A. Jadamec 《Computing and Visualization in Science》2011,14(4):143-156
The three-dimensional shapes of tectonic plates that sink into the Earth’s mantle (slabs) are the starting point for a range
of geoscience studies, from determining the forces driving the motion of tectonic plates, to potential seismic and tsunami
hazards, to the sources of magmas beneath active volcanos. For many of these applications finite element methods are used
to model the deformation or fluid flow, and therefore the input model parameters, such as feature geometries, temperature
or viscosity, must be defined with respect to a smooth, continuous distance field around the slab. In this paper we present
a framework for processing sparse and noisy seismic data (earthquake locations), defining the shape of the slab and computing
a continuous distance function on a mesh with variable node spacing. Due to the inhomogeneous volumetric distribution of earthquakes
within the slab and significant inaccuracies in the locations of earthquakes occurring hundreds of kilometers below the Earth’s
surface, the seismicity data set is extremely noisy and incomplete. Therefore, the preprocessing is the major part of the
framework consisting of several steps including a point based smoothing procedure, a powerful method to use other observational
constraints on slab location (e.g., seismic tomography or geologic history) to extend of the slab shape beyond earthquake
data set and continuous resampling using moving least squares method. For the preprocessed point data we introduce approaches
for finding the three-dimensional boundary of the slab and a subdivision of the slab into quadric implicit polynomials. The
resulting distance field is then compiled from distances to the piecewise continuous approximation of the slab and distances
to slab boundary. 相似文献
105.
Die Geschichte des Internets ist eine Erfolgsgeschichte. Dieser Erfolg beruht u.a. auf einer neutralen Datenübermittlung,
die dadurch gekennzeichnet ist, dass Netzbetreiber Datenpakete von und an ihre Kunden unver?ndert und gleichberechtigt übertragen,
unabh?ngig davon, woher diese stammen und welche Anwendungen die Pakete generiert haben. In jüngster Zeit werden Forderungen
nach Verkehrsregelungen im Internet lauter. Begründet wird diese Initiative mit einer drohenden Netzüberlastung, die durch
die wachsende Popularit?t von Videoangeboten wie YouTube oder Streaming-Angeboten wie Hulu entsteht. Kritiker befürchten,
dass durch den Einsatz neuer Netzwerkmanagementtechniken die Innovationsoffenheit und die freie Kommunikation im Internet
gef?hrdet werden. Der Beitrag analysiert die M?glichkeiten und Grenzen der Gew?hrleistung von Netzneutralit?t durch das deutsche
Telekommunikations- und Medienrecht. 相似文献
106.
Rainer Dudek Ralf Doering Christine Bombach Bernd Michel 《Microelectronics Reliability》2009,49(8):839-845
Secondary effects on thermal fatigue of solder joints, which frequently have been neglected, were studied by means of the finite element method (FEM). Based on a semi-empirical approach to predict fatigue life by evaluating the cyclic accumulated equivalent creep strain or energy density, effects of organic boards intrinsic properties on solder joint fatigue were investigated. Aspects of more realistic FR-4 board modelling were studied, in particular concerning its in-plane anisotropy and intrinsic warpage behaviour. Intrinsic board warpage was measured on test board level as well as for boards from series production. High intrinsic warpage was in particular found for several test boards. The effects for the worst case scenario observed so far were analysed for both first level and second level interconnects. The change in predicted fatigue life varied between 30% and 500%, the latter most critical effects were found at large QFN components. Another secondary effect studied was to include the frequently neglected interfacial intermetallics into FEM. It turned out that for components with relatively large standoff like LFBGAs the effects were actually negligible, but for the highly miniaturized components like chip resistors CR0201 they are the decisive factor. 相似文献
107.
The topic of this paper is minimum cost operative planning of pressurized water supply networks over a finite horizon and
under reliable demand forecast. Since this is a very hard problem, it is desirable to employ sophisticated mathematical algorithms,
which in turn calls for carefully designed models with suitable properties. The paper develops a nonlinear mixed integer model
and a nonlinear programming model with favorable properties for gradient-based optimization methods, based on smooth component
models for the network elements. In combination with further nonlinear programming techniques (Burgschweiger et al. in ZIB
Report ZR-05-31, Zuse Institute Berlin, 2005), practically satisfactory near-optimum solutions even for large networks can be generated in acceptable time using standard
optimization software on a PC workstation. Such an optimization system is in operation at Berliner Wasserbetriebe. 相似文献
108.
Environmental chemistry of aminopolycarboxylate chelating agents 总被引:1,自引:0,他引:1
Nowack B 《Environmental science & technology》2002,36(19):4009-4016
Aminopolycarboxylate chelating agents are under scrutiny due to their influence on metal availability and mobility and in particular due to their persistence in the environment. In this review chelate adsorption, metal-mobilization, metal-exchange, mineral dissolution, reactive transport, photodegradation, and chemical degradation are all shown to be substantially affected by the chelated metal ion. The different reactivities of the metal-complexes have to be considered when assessing the reactions of chelating agents in the environment because they occur in natural waters predominantly in the form of metal complexes. Knowing the speciation of chelating agents in natural waters is therefore crucial for predicting their environmental fate. Despite this importance, only a few speciation measurements have been reported for natural waters, and model calculations have been frequently used instead. These calculations are, however, complicated by slow metal-exchange reactions that result in a nonequilibrium speciation and by the presence of naturally occurring ligands that compete with the chelating agents for available metals. The basis for a refined risk assessment of aminocarboxylate chelates should be the actual speciation in the natural water directly determined by analytical methods. The discussion of the influence of chelates on metal availability and fate also has to include the potential presence of other aminopolycarboxylate chelating agents besides the well-known EDTA and NTA. 相似文献
109.
A combination of a Hartmann-Shack sensor and a standard far-field measurement on one single detector is proposed. The technique is fast and operates without movable parts, thus permitting a compact design. It is not only suited for characterization of the wave-front distribution but may also be considered for determination of the important parameters of beam width, beam divergence, and beam propagation ratio M2 of partially coherent laser beams. First results indicate that a fairly thorough beam characterization, including spatial coherence, propagation characteristics, and beam quality, can be achieved with this method. 相似文献
110.
Prof. Dr. Hans Ulrich Buhl Dr. Bernd Heinrich Prof. Dr. Peter Loos Prof. Dr. Ulrich Frank Visiting Prof. Daniel L. Moody PhD Prof. Jeffrey Parsons PhD Prof. Dr. Michael Rosemann Prof. Dr. Elmar J. Sinz Prof. Ron Weber PhD Achim Kindler Dr. Prof. Dr. Claus Rautenstrauch Dipl.-Wirt.-Inf. Peter Fettke 《WIRTSCHAFTSINFORMATIK》2005,47(2):152-161