全文获取类型
收费全文 | 543篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 98篇 |
金属工艺 | 8篇 |
机械仪表 | 8篇 |
建筑科学 | 48篇 |
能源动力 | 40篇 |
轻工业 | 42篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 43篇 |
一般工业技术 | 120篇 |
冶金工业 | 27篇 |
原子能技术 | 1篇 |
自动化技术 | 122篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 16篇 |
2015年 | 19篇 |
2014年 | 19篇 |
2013年 | 29篇 |
2012年 | 29篇 |
2011年 | 38篇 |
2010年 | 31篇 |
2009年 | 22篇 |
2008年 | 33篇 |
2007年 | 29篇 |
2006年 | 28篇 |
2005年 | 13篇 |
2004年 | 18篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 11篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 13篇 |
1996年 | 2篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1970年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有568条查询结果,搜索用时 203 毫秒
11.
Rabbits were fed diets enriched with cholestanol or cholestereol (3.5 g/wk) for 4–12 weeks. During cholestanol feeding, the
concentration of cholestanol in blood serum, liver, heart and aorta increased 15–30 times. In serum and liver, the concentration
of cholesterol also increased. Cholestanol-fed rabbits developed inflammatory changes in the liver, with proliferation of
small bile ducts. Liver tests were only slightly abnormal. Morphological atherosclerosis of the aorta was only occasionally
seen in rabbits receiving cholestanol for eight weeks or less.
During cholesterol feeding, the amounts of cholesterol in different tissues increased dramatically, most in the aorta. Morphological
atherosclerosis in the aorta was found in all rabbits fed cholesterol-enriched diets for more than four weeks. Brain cholestanol
was doubled in rabbits fed cholestanol for eight weeks, whereas brain sterols did not change significantly during cholesterol
feeding. After an additional regression period with cholestyramine for eight weeks, the increased content of cholestanol in
the brain was unchanged in cholestanol-fed rabbits. These observations are discussed in relation to the cholestanolosis of
the brain that develops in the rare inherited human disease cerebrotendinous xanthomatosis. 相似文献
12.
Ole Becker Peter Sopade Romain Bourdonnay Peter J. Halley George P. Simon 《Polymer Engineering and Science》2003,43(10):1683-1690
The effect of an organically surface modified layered silicate on the viscosity of various epoxy resins of different structures and different functionalities was investigated. Steady and dynamic shear viscosities of the epoxy resins containing 0–10 Wt% of the organoclay were determined using parallel plate rheology. Viscosity results were compared with those achieved through addition of a commonly used micronsized CaCO3 filler. It was found that changes in viscosities due to the different fillers were of the same order, since the layered silicate was only dispersed on a micron‐sized scale in the monomer (prior to reaction), as indicated by X‐ray diffraction measurements. Flow activation energies at a low frequency were determined and did not show any significant changes due to the addition of organoclay or CaCO3. Comparison between dynamic and steady shear experiments showed good agreement for low layered silicate concentrations below 7.5 wt%, i.e. the Cox‐Merz rule can be applied. Deviations from the Cox‐Merz rule appeared at and above 10 wt%, although such deviations were only slightly above experimental error. Most resin organoclay blends were well predicted by the Power Law model, only concentrations of 10 wt% and above requiring the Herschel‐Buckley (yield stress) model to achieve better fits. Wide‐angle X‐ray measurements have shown that the epoxy resin swells the layered silicate with an increase in the interlayer distance of approximately 15 Å, and that the rheology behavior is due to the lateral, micron‐size of these swollen tactoids. 相似文献
13.
Kenji Takizawa Yuri Bazilevs Tayfun E. Tezduyar Ming-Chen Hsu Ole Øiseth Kjell M. Mathisen Nikolay Kostov Spenser McIntyre 《Archives of Computational Methods in Engineering》2014,21(4):481-508
Flow problems with moving boundaries and interfaces include fluid–structure interaction (FSI) and a number of other classes of problems, have an important place in engineering analysis and design, and offer some formidable computational challenges. Bringing solution and analysis to them motivated the Deforming-Spatial-Domain/Stabilized Space–Time (DSD/SST) method and also the variational multiscale version of the Arbitrary Lagrangian–Eulerian method (ALE-VMS). Since their inception, these two methods and their improved versions have been applied to a diverse set of challenging problems with a common core computational technology need. The classes of problems solved include free-surface and two-fluid flows, fluid–object and fluid–particle interaction, FSI, and flows with solid surfaces in fast, linear or rotational relative motion. Some of the most challenging FSI problems, including parachute FSI, wind-turbine FSI and arterial FSI, are being solved and analyzed with the DSD/SST and ALE-VMS methods as core technologies. Better accuracy and improved turbulence modeling were brought with the recently-introduced VMS version of the DSD/SST method, which is called DSD/SST-VMST (also ST-VMS). In specific classes of problems, such as parachute FSI, arterial FSI, ship hydrodynamics, fluid–object interaction, aerodynamics of flapping wings, and wind-turbine aerodynamics and FSI, the scope and accuracy of the FSI modeling were increased with the special ALE-VMS and ST FSI techniques targeting each of those classes of problems. This article provides an overview of the core ALE-VMS and ST FSI techniques, their recent versions, and the special ALE-VMS and ST FSI techniques. It also provides examples of challenging problems solved and analyzed in parachute FSI, arterial FSI, ship hydrodynamics, aerodynamics of flapping wings, wind-turbine aerodynamics, and bridge-deck aerodynamics and vortex-induced vibrations. 相似文献
14.
Linear 1,2-polybutadiene, glass transition temperature (Tg) ?18°C, is crosslinked at ?10°C, to ?20°C by γ irradiation while strained in simple extension, with extension, ratios (λ0) from 1.2 to 2.7. After release, the sample retracts to a state of ease (λs) at room temperature. From equilibrium stress–strain measurements up to a stretch ratio relative to the state of ease (Λ) of 1.2, together with λ0 and λs, the concentration of network strands terminated by trapped entanglements (νN) is calculated. For this purpose, a three-constant Mooney–Rivlin formulation is used, in which the entanglement network is described by Mooney–Rivlin coefficients C1N and C2N, whereas the crosslink networks is described by the coefficient C1x only. The ratio ψN = C2N/(C1N + C2N) is estimated from parallel studies of nonlinear stress relaxation of the uncrosslinked polymer, taking into account the thermal history before and during irradiation. For substantial degrees of crosslinking, i.e., for R0′ = νx/νN > 0.4 (where νN is the concentration of network strands terminated by crosslinks), and for λ0 < 1.8, C2N agrees rather well with the value obtained from stress relaxation of the uncrosslinked polymer in the range of time scale where it is nearly independent of time (1.87 X 105 pascals). The corresponding value of νN is 2.3 × 10?4 moles/cm3, in good agreement with that obtained from viscoelastic measurements of the uncrosslinked polymer in the plateau zone (2.5 × 10?4). However, for R0′ ? 0.2, smaller values of C2N and νN are obtained, indicating that for low degrees of crosslinking the entanglements are not completely trapped. Also, for higher values of λ0, C2N and νN turn out to be somewhat smaller. Similar, less extensive results were obtained previously on a 1,2-polybutadiene with somewhat higher vinyl content and a higher Tg. Crosslinked samples of both these polymers were subjected to equilibrium stress–strain measurements in simple elongation from the state of ease at higher strains up to Λ = 1.7. The results agreed closely with calculations from the three-constant Mooney–Rivlin theory. 相似文献
15.
This paper investigates whether employees’ assessment of their primary task quality has a significant impact on their well‐being and job satisfaction, respectively. Furthermore, the paper hypothesizes that professional values and norms affect employees’ quality expectations on their work tasks and thus their assessment of primary task quality. The paper proposes a measure for primary task quality and uses it in the analyses of responses from 1,247 preschool teachers and teaching assistants in 94 public daycare centers in Denmark. The results indicate that an important factor for employees is their experience of quality in the job they perform. Moreover, quality expectations can differ between employees performing the same task due to, for example, difference in professional training. This leads us to propose a new research direction for job design theory that addresses employees’ assessment of the quality of their primary task job performance. 相似文献
16.
Rasmus E. Christiansen Boyan S. Lazarov Jakob S. Jensen Ole Sigmund 《Structural and Multidisciplinary Optimization》2015,52(4):737-754
Resonance and wave-propagation problems are known to be highly sensitive towards parameter variations. This paper discusses topology optimization formulations for creating designs that perform robustly under spatial variations for acoustic cavity problems. For several structural problems, robust topology optimization methods have already proven their worth. However, it is shown that direct application of such methods is not suitable for the acoustic problem under consideration. A new double filter approach is suggested which makes robust optimization for spatial variations possible. Its effect and limitations are discussed. In addition, a known explicit penalization approach is considered for comparison. For near-uniform spatial variations it is shown that highly robust designs can be obtained using the double filter approach. It is finally demonstrated that taking non-uniform variations into account further improves the robustness of the designs. 相似文献
17.
Morten Nobel-Jørgensen Niels Aage Asger Nyman Christiansen Takeo Igarashi J. Andreas Bærentzen Ole Sigmund 《Structural and Multidisciplinary Optimization》2015,51(6):1385-1391
This educational paper describes the implementation aspects, user interface design considerations and workflow potential of the recently published TopOpt 3D App. The app solves the standard minimum compliance problem in 3D and allows the user to change design settings interactively at any point in time during the optimization. Apart from its educational nature, the app may point towards future ways of performing industrial design. Instead of the usual geometrize, then model and optimize approach, the geometry now automatically adapts to the varying boundary and loading conditions. The app is freely available for iOS at Apple’s App Store and at http://www.topopt.dtu.dk/TopOpt3D for Windows and OSX. 相似文献
18.
Miche Jansen Boyan S. Lazarov Mattias Schevenels Ole Sigmund 《Structural and Multidisciplinary Optimization》2013,48(4):717-730
The aim of this paper is to incorporate a model for micro/nano lithography production processes in topology optimization. The production process turns out to provide a physical analogy for projection filters in topology optimization. Blueprints supplied by the designers cannot be directly used as inputs to lithographic processes due to the proximity effect which causes rounding of sharp corners and geometric interaction of closely spaced design elements. Therefore, topology optimization is applied as a tool for proximity effect correction. Furthermore, it is demonstrated that the robust projection filter can be used to account for uncertainties due to lithographic production processes which results in manufacturable blueprint designs and eliminates the need for subsequent corrections. 相似文献
19.
Thomas H. Langer Thorkil K. Iversen Ole Ø. Mouritsen Morten K. Ebbesen Michael R. Hansen 《Structural and Multidisciplinary Optimization》2013,47(4):621-630
Suspension systems on commercial vehicles have become an important feature meeting the requirements from costumers and legislation. The performance of the suspension system is often limited by available catalogue components. Additionally the suspension performance is restricted by the travel speed which highly influences the ride comfort. In this article a suspension system for an articulated dump truck is optimized in sense of reducing elapsed time for two specified duty cycles without violating a certain comfort threshold level. The comfort threshold level is here defined as a whole-body vibration level calculated by ISO 2631-1. A three-dimensional multibody dynamics simulation model is applied to evaluate the suspension performance. A non-gradient optimization routine is used to find the best possible combination of continuous and discrete design variables including the optimum operational speed without violating a set of side constraints. The result shows that the comfort level converges to the comfort threshold level. Thus it is shown that the operational speed and hence the operator input influences the ride comfort level. Three catalogue components are identified by the optimization routine together with a set of continuous design variables and two operational speeds one for each load case. Thus the work demonstrates handling of human factors in optimization of a mechanical system with discrete and continuous design variables. 相似文献
20.
Interactive topology optimization on hand-held devices 总被引:1,自引:1,他引:0
Niels Aage Morten Nobel-Jørgensen Casper Schousboe Andreasen Ole Sigmund 《Structural and Multidisciplinary Optimization》2013,47(1):1-6
This paper presents an interactive topology optimization application designed for hand-held devices running iOS or Android. The TopOpt app solves the 2D minimum compliance problem with interactive control of load and support positions as well as volume fraction. Thus, it is possible to change the problem settings on the fly and watch the design evolve to a new optimum in real time. The use of an interactive app makes it extremely simple to learn and understand the influence of load-directions, support conditions and volume fraction. The topology optimization kernel is written in C# and the graphical user interface is developed using the game engine Unity3D. The underlying code is inspired by the publicly available 88 and 99 line Matlab codes for topology optimization but does not utilize any low-level linear algebra routines such as BLAS or LAPACK. The TopOpt App can be downloaded on iOS devices from the Apple App Store, at Google Play for the Android platform, and a web-version can be run from www.topopt.dtu.dk. 相似文献