全文获取类型
收费全文 | 5399篇 |
免费 | 437篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 75篇 |
综合类 | 11篇 |
化学工业 | 1440篇 |
金属工艺 | 286篇 |
机械仪表 | 282篇 |
建筑科学 | 105篇 |
矿业工程 | 4篇 |
能源动力 | 249篇 |
轻工业 | 456篇 |
水利工程 | 15篇 |
石油天然气 | 14篇 |
无线电 | 889篇 |
一般工业技术 | 1133篇 |
冶金工业 | 242篇 |
原子能技术 | 66篇 |
自动化技术 | 586篇 |
出版年
2024年 | 8篇 |
2023年 | 84篇 |
2022年 | 136篇 |
2021年 | 193篇 |
2020年 | 149篇 |
2019年 | 161篇 |
2018年 | 200篇 |
2017年 | 212篇 |
2016年 | 253篇 |
2015年 | 154篇 |
2014年 | 237篇 |
2013年 | 325篇 |
2012年 | 410篇 |
2011年 | 482篇 |
2010年 | 310篇 |
2009年 | 296篇 |
2008年 | 274篇 |
2007年 | 230篇 |
2006年 | 207篇 |
2005年 | 163篇 |
2004年 | 145篇 |
2003年 | 144篇 |
2002年 | 144篇 |
2001年 | 105篇 |
2000年 | 107篇 |
1999年 | 84篇 |
1998年 | 104篇 |
1997年 | 67篇 |
1996年 | 82篇 |
1995年 | 60篇 |
1994年 | 25篇 |
1993年 | 33篇 |
1992年 | 27篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1977年 | 6篇 |
1976年 | 11篇 |
1975年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有5853条查询结果,搜索用时 0 毫秒
91.
Christoph Weigel Valeriya Cherkasova Mathias Holz Hai Binh Phi Christian Görner Tenorio Björn Wilbertz Leonard Voßgrag Thomas Fröhlich Steffen Strehle 《Advanced Engineering Materials》2023,25(9):2201873
Ultralow expansion (ULE) glasses are of special interest for temperature stabilized systems for example in precision metrology. Nowadays, ULE materials are mainly used in macroscopic and less in micromechanical systems. Reasons for this are a lack of technologies for parallel fabricating high-quality released microstructures with a high accuracy. As a result, there is a high demand in transferring these materials into miniaturized application examples, realistic system modeling, and the investigation of microscopic material properties. Herein, a technological base for fabricating released micromechanical structures and systems with a structure height above 100 μm in ULE 7972 glass is established. Herein, the main fabrication parameters that are important for the system design and contribute thus to the introduction of titanium silicate as material for glass-based micromechanical systems are discussed. To study the mechanical properties in combination with respective simulation models, microcantilevers are used as basic mechanical elements to evaluate technological parameters and other impact factors. The implemented models allow to predict the micromechanical system properties with a deviation of only ±5% and can thus effectively support the micromechanical system design in an early stage of development. 相似文献
92.
Study on the solidification cracking behaviour of high strength aluminum alloy welds: Effects of alloying elements and solidification behaviours 总被引:1,自引:0,他引:1
The solidification cracking susceptibility of the 7000 series Al-Zn-Mg high strength aluminum alloy has been studied. The cracking behaviour of the specimens were evaluated by a Tig-a-Ma-Jig Varestraint test process under various augmented strain conditions. It has been experimentally observed that the addition of copper decreased the solidification cracking resistivity of the high strength aluminum alloy weld metal by increasing the total crack length (TCL). The effect of the addition of manganese on the solidification cracking behaviour is found to be beneficial by markedly decreasing the solidification cracking susceptibility as the manganese content increases from 0.3 to 0.7%. This enhancement by manganese is understood to be attributed to the reduction of the mushy zone size during the solidification process. The effects of chromium and zirconium additions are also investigated. The weld metal containing zirconium is less sensitive to the solidification cracking than the weld metal containing chromium. In addition, the solidification behaviours of the tested alloys are also investigated and it is found that as the solidification temperature range (T) becomes narrow, the solidified structure becomes more dendritic in its features which is believed to create higher solidification cracking resistance. 相似文献
93.
This study presents a method that uses a standing surface acoustic wave (SSAW) to continuously separate particles in a size-gradient
manner in a microchannel flow. The proposed method was applied to a colloidal suspension containing poly dispersed particles
with three different sizes (1, 5, and 10 μm) but the same density and compressibility. Particle suspension was focused hydrodynamically
at an entrance region, and particles were forced actively toward the side wall where SSAW-pressure nodes were generated by
two interdigital transducers (IDTs) across the channel. The particles placed in the middle stream, in which the shear rate
was minimized, were separated successfully in a size-gradient manner by acoustic force. In addition, this study further developed
an analytical model to predict the displacement of particles in microchannel flow by considering viscous, acoustic, and diffusive
forces. The predicted values of particle displacement showed excellent agreement with the experimental results, and diffusion
was found to be important and not negligible. The advantage of this method is to minimize the shear rate on particles, which
would be useful for potential applications of shear-dependent cells such as platelets. 相似文献
94.
Ohad Gur Manav Bhatia William H. Mason Joseph A. Schetz Rakesh K. Kapania Taewoo Nam 《Structural and Multidisciplinary Optimization》2011,44(2):277-298
The paper describes the development of a multidisciplinary design optimization framework for conceptual design of truss-braced
wing configurations. This unconventional configuration requires specialized analysis tools supported by a modular and flexible
framework to accommodate different configurations. While the previous framework developed at Virginia Tech was a monolithic
Fortran-77 code, the need for more flexibility for complex truss-braced wing configurations was addressed by the development
of this new framework, which is based on Phoenix Integration ModelCenterTM environment. The framework uses updated structural and aerodynamic design modules that enable a more general geometry definition.
The new framework, thus, provides a foundation for future design concepts, especially multi-member truss-braced wing configurations.
The fuel saving potential of these truss-braced wing configurations is presented by comparing different truss designs with
gradually increased level of complexity. 相似文献
95.
Tien Van Do 《Acta Informatica》2010,47(1):67-75
In this paper we introduce the new M/M/1 retrial queue with working vacations which is motivated by the performance analysis
of a Media Access Control function in wireless systems. We give a condition for the stability of the model, which has an important
impact on setting the retrial rate for such systems. We derive the closed form solution in equilibrium for the retrial M/M/1
queue with working vacations, and we also show that the conditional stochastic decomposition holds for this model as well. 相似文献
96.
Yong‐Kyu Jang Seong Jun Lee Jae Young Lee Yi Li Jae Hoon Hwang Sang Woo Kim Chang Woo Shim Ju Yeon Seo Nam Jin Kim Yi Joon Ahn Nam Hee Kim Seon Hong Ahn Seong Ryong Lee Dae Hee Park Chi Woo Kim 《Journal of the Society for Information Display》2011,19(3):253-257
Abstract— A novel pixel design for vertical‐alignment LCDs with superior transmittance has been developed. The new liquid‐crystal mode, refered to as the hole‐induced vertical‐alignment mode (Hi‐VA), uses a via hole of an organic layer on a TFT substrate to achieve multi‐domain alignment. Compared to the conventional design, the Hi‐VA mode has a transmittance of up to 135% with a contrast ratio of 2000:1. Moreover, the new structure is free from ITO patterning or protrusion on the color‐filter side, which makes the fabrication process simple and low cost. 相似文献
97.
Beomseok Nam Minho Shin Henrique Andrade Alan Sussman 《Journal of Parallel and Distributed Computing》2010
In distributed query processing systems, load balancing plays an important role in maximizing system throughput. When queries can leverage cached intermediate results, improving the cache hit ratio becomes as important as load balancing in query scheduling, especially when dealing with computationally expensive queries. The scheduling policies must be designed to take into consideration the dynamic contents of the distributed caching infrastructure. In this paper, we propose and discuss several distributed query scheduling policies that directly consider the available cache contents by employing distributed multidimensional indexing structures and an exponential moving average approach to predicting cache contents. These approaches are shown to produce better query plans and faster query response times than traditional scheduling policies that do not predict dynamic contents in distributed caches. We experimentally demonstrate the utility of the scheduling policies using MQO, which is a distributed, Grid-enabled, multiple query processing middleware system we developed to optimize query processing for data analysis and visualization applications. 相似文献
98.
This article addresses the issue of visual landmark recognition in autonomous robot navigation along known routes, by intuitively
exploiting the functions of the human visual system and its navigational ability. A feedforward–feedbackward architecture
has been developed for recognising visual landmarks in real time. It integrates the theoretical concepts from the pre-attentive
and attentive stages in the human visual system, the selective attention adaptive resonance theory neural network and its
derivatives, and computational approaches towards object recognition in computer vision. The architecture mimics the pre-attentive
and attentive stages in the context of object recognition, embedding neural network processing paradigm into a computational
template-matching approach in computer vision. The real-time landmark recognition capability is achieved by mimicking the
pre-attentive stage, where it models a selective attention mechanism for optimal computational resource allocation, focusing
only on the regions of interest to address the computational restrictive nature of current computer processing power. Similarly,
the recognition of visual landmarks in both clean and cluttered backgrounds is implemented in the attentive stage by developing
a memory feedback modulation (MFM) mechanism that enables knowledge from the memory to interact and enhance the efficiency
of earlier stages in the architecture. Furthermore, it also incorporates both top-down and bottom-up facilitatory and inhibition
pathways between the memory and the earlier stages to enable the architecture to recognise a 2D landmark, which is partially
occluded by adjacent features in the surroundings. The results show that the architecture is able to recognise objects in
cluttered backgrounds using real-images in both indoor and outdoor scenes. Furthermore, the architecture application in autonomous
robot navigation has been demonstrated through a number of real-time trials in both indoor and outdoor environments. 相似文献
99.
Martijn H. A. Bonte Lionel Fourment Tien-tho Do A. H. van den Boogaard J. Huétink 《Structural and Multidisciplinary Optimization》2010,42(5):797-810
During the last decades, simulation software based on the Finite Element Method (FEM) has significantly contributed to the
design of feasible forming processes. Coupling FEM to mathematical optimization algorithms offers a promising opportunity
to design optimal metal forming processes rather than just feasible ones. In this paper Sequential Approximate Optimization (SAO) for optimizing forging processes is discussed. The algorithm
incorporates time-consuming nonlinear FEM simulations. Three variants of the SAO algorithm—which differ by their sequential
improvement strategies—have been investigated and compared to other optimization algorithms by application to two forging
processes. The other algorithms taken into account are two iterative algorithms (BFGS and SCPIP) and a Metamodel Assisted
Evolutionary Strategy (MAES). It is essential for sequential approximate optimization algorithms to implement an improvement
strategy that uses as much information obtained during previous iterations as possible. If such a sequential improvement strategy
is used, SAO provides a very efficient algorithm to optimize forging processes using time-consuming FEM simulations. 相似文献
100.
We present a new rapid prototyping method designed for simple fabrication of 3D microfluidics using a maskless direct writing technique on polymer substrates. The entire process is enabled by a commercial cutter plotter with 10 μm resolution precision and high speed. A CAD design of top and bottom microstructures is directly written on a polymer substrate using a cutter plotter after setting up the suitable force. The smallest channel width of 20 μm was obtained with the minimum force and 100 μm from the maximum. Also the written depth increased linearly with force from 30 to 130 μm. Several 3D microfluidic devices are demonstrated using a maskless writing technique. The entire fabrication process from CAD layout to a final 3D device can be completed in 30 min outside the clean room facilities. 相似文献