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排序方式: 共有877条查询结果,搜索用时 13 毫秒
81.
82.
Kaupo Kukli Mikko Ritala Teet Uustare Jaan Aarik Katarina Forsgren Timo Sajavaara Markku Leskel Anders Hrsta 《Thin solid films》2002,410(1-2):53-60
ZrO2 films of thicknesses varied in the range of 3–30 nm were atomic layer deposited from ZrI4 and H2O–H2O2 on p-Si(100) substrates. The effects of film thickness and deposition temperature on the structure and dielectric properties of ZrO2 were investigated. At 272 and 325 °C, the growth of ZrO2 started with the formation of the cubic polymorph and continued with the formation of the tetragonal polymorph. The ratio between the lattice parameters increased with the film thickness and growth temperature. The effective permittivity, determined from the accumulation capacitance of Hg/ZrO2/Si capacitors, increased with the film thickness, reaching 15–17 in 25-nm-thick films. The permittivity decreased with the increasing growth temperature. The hysteresis of the capacitance–voltage curves was the narrowest for the films deposited at 325 °C, and increased towards both lower and higher deposition temperatures. 相似文献
83.
Matthias Holl Timo Rogge Stefan Loehnert Peter Wriggers Raimund Rolfes 《Computational Mechanics》2014,53(1):173-188
This work presents a new multiscale technique to investigate advancing cracks in three dimensional space. This fully adaptive multiscale technique is designed to take into account cracks of different length scales efficiently, by enabling fine scale domains locally in regions of interest, i.e. where stress concentrations and high stress gradients occur. Due to crack propagation, these regions change during the simulation process. Cracks are modeled using the extended finite element method, such that an accurate and powerful numerical tool is achieved. Restricting ourselves to linear elastic fracture mechanics, the $J$ -integral yields an accurate solution of the stress intensity factors, and with the criterion of maximum hoop stress, a precise direction of growth. If necessary, the on the finest scale computed crack surface is finally transferred to the corresponding scale. In a final step, the model is applied to a quadrature point of a gas turbine blade, to compute crack growth on the microscale of a real structure. 相似文献
84.
Timo P. J. Mikkola Heikki Raiko 《International Journal of Pressure Vessels and Piping》1992,52(3):357-377
A program system for fracture assessment of nuclear power plant structures has been developed. The system consists of an easy-to-use program for engineering analysis and an automated finite element (FE) program system for more accurate analysis with solid three-dimensional (3D) models. The VTTSIF (SIF stress intensity factor) program for engineering fracture assessment applies either the weight function method or superposition method in calculating the stress intensity factor, and the fatigue crack growth analysis is based on the Paris equation. The structural geometry cases of the VTTSIF program are organized in an extendable subroutine database. The generation of a 3D FE model of a cracked structure is automated by the ACR program (automatic finite element model generation for part through cracks). The FE analyses are created with generally accepted commercial programs, and the virtual crack extension method (VCE) is used for fracture parameter evaluation by the VTTVIRT postprocessor program (program for J-integral evaluation using virtual crack extension method). The several test cases have demonstrated that the accuracy of the present system is satisfactory for practical applications. 相似文献
85.
Although Finland's forest resources have been utilized intensively, the size of the total volume of the growing stock has increased since the mid-1960s, and hence increasing amounts of carbon have been sequestered by forests. The net sequestration by forests has also been substantial when compared with the CO2 emissions resulting from energy generation and consumption based on fossil fuels and peat. It is also important, from the point of view of mitigating the effects of climate change, to assess how the sequestration capacity of forests may change under changing climatic conditions. This paper presents the results of a study assessing the development of the forest and wood-product carbon budget for Finland, based on regionally measured data, detailed dynamic models, and recent predictions concerning the changing climate. At the starting point for the simulation (1990), nearly 90% of the forest sector's carbon storage was found in the forest. Regular management transferred carbon from forests to wood products. Under the current climatic conditions, the simulated forest carbon storage increased 45% by the year 2100, and the wood-product storage by 320%, as a consequence of continuous production. Under changing climate conditions, the forest carbon storage increased, but started to decline when the temperature increase exceeded 2.5°C within 40 years. 相似文献
86.
Jari MalmElina Sahramo Juho PeräläTimo Sajavaara Maarit Karppinen 《Thin solid films》2011,519(16):5319-5322
Low-temperature atomic layer deposition (ALD) processes are intensely looked for to extend the usability of the technique to applications where sensitive substrates such as polymers or biological materials need to be coated by high-quality thin films. A preferred film orientation, on the other hand, is often required to enhance the desired film properties. Here we demonstrate that smooth, crystalline ZnO thin films can be deposited from diethylzinc and water by ALD even at room temperature. The depositions were carried out on Si(100) substrates in the temperature range from 23 to 140 °C. Highly c-axis-oriented films were realized at temperatures below ~ 80 °C. The film crystallinity could be further enhanced by post-deposition annealing under O2 or N2 atmosphere at 400-600 °C while keeping the original film orientation intact. 相似文献
87.
Xiuqin Shang Fei-Yue Wang Gang Xiong Timo R. Nyberg Yong Yuan Sheng Liu Chao Guo Sen Bao 《IEEE/CAA Journal of Automatica Sinica》2018,5(2):489-500
Social manufacturing (SM), a novel distributed, collaborative and intelligent manufacturing mode, is proposed and developed for high-end apparel customization. The main components of SM cloud are designed, and its research topics are summarized. Then, SM's key technologies are studied. 3D technologies for apparel customization, like 3D modeling, 3D fitting mirror and 3D customization, are developed to improve the customization precision and user experience. Information based collaborative management is realized to share, communicate, and handle the information efficiently among all groups and individuals of SM cloud. Suppliers' evaluation mechanism is designed to support the optimal decisions making. Next, SM cloud is constructed in five layers for high-end apparel customization. By using SM cloud based crowd-sourcing, social resources can be allocated rationally and utilized efficiently, consumer can customize the product in any processes like innovation, design, making, marketing and service, and traditional apparel enterprise can be upgraded into SM mode for keeping it competitive in the future customization markets. 相似文献
88.
Timo Ropinski Jennis Meyer-Spradow Stefan Diepenbrock Jörg Mensmann Klaus Hinrichs 《Computer Graphics Forum》2008,27(2):567-576
We propose a method for rendering volumetric data sets at interactive frame rates while supporting dynamic ambient occlusion as well as an approximation to color bleeding. In contrast to ambient occlusion approaches for polygonal data, techniques for volumetric data sets have to face additional challenges, since by changing rendering parameters, such as the transfer function or the thresholding, the structure of the data set and thus the light interactions may vary drastically. Therefore, during a preprocessing step which is independent of the rendering parameters we capture light interactions for all combinations of structures extractable from a volumetric data set. In order to compute the light interactions between the different structures, we combine this preprocessed information during rendering based on the rendering parameters defined interactively by the user. Thus our method supports interactive exploration of a volumetric data set but still gives the user control over the most important rendering parameters. For instance, if the user alters the transfer function to extract different structures from a volumetric data set the light interactions between the extracted structures are captured in the rendering while still allowing interactive frame rates. Compared to known local illumination models for volume rendering our method does not introduce any substantial rendering overhead and can be integrated easily into existing volume rendering applications. In this paper we will explain our approach, discuss the implications for interactive volume rendering and present the achieved results. 相似文献
89.
Summary The purpose of this study is to quantify and compare the publication and citation output of the biggest faculties of economics and social sciences in Germany. Various publication and citation measures based upon Social Science Citation Index (SSCI) data are used to explore the comparative strengths and weaknesses of ten academic fields at the named faculties. To reflect the varying size of the fields and faculties, output measures as well as productivity measures are explicitly considered. From a bibliometric perspective empirical results demonstrate that various measures are necessary to adequately identify the comparative strengths and weaknesses of entire faculties and of selected disciplines within faculties. 相似文献
90.
Incremental constraint modelling in a feature modelling system 总被引:1,自引:0,他引:1
The techniques of constraint propagation have recently been successfully applied to feature-based design. Because of their speed, constraint propagation methods allow incremental design and rapid local modifcations of the part. However, cyclic constraints cause serious problems to current constraint propagation algorithms. Variational geometric design systems can, in principle, manage these cases. Unfortunately, this typically requires complete re-evaluation of the underlying set of constraint equations, making the method unsuitable for interactive use. The proposed system aims to localize the problem of constraint solving and maintenance. The constraint graph of the part or assembly is divided into several independent partial graphs, subsystems. Afterwards, each subsystem is handled separately using a selected constraint solving technique for the subsystem. 相似文献