全文获取类型
收费全文 | 1606篇 |
免费 | 25篇 |
专业分类
电工技术 | 18篇 |
化学工业 | 329篇 |
金属工艺 | 14篇 |
机械仪表 | 33篇 |
建筑科学 | 69篇 |
矿业工程 | 13篇 |
能源动力 | 47篇 |
轻工业 | 174篇 |
水利工程 | 10篇 |
石油天然气 | 6篇 |
无线电 | 69篇 |
一般工业技术 | 257篇 |
冶金工业 | 462篇 |
原子能技术 | 14篇 |
自动化技术 | 116篇 |
出版年
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 20篇 |
2013年 | 76篇 |
2012年 | 25篇 |
2011年 | 43篇 |
2010年 | 34篇 |
2009年 | 41篇 |
2008年 | 51篇 |
2007年 | 45篇 |
2006年 | 56篇 |
2005年 | 39篇 |
2004年 | 35篇 |
2003年 | 42篇 |
2002年 | 41篇 |
2001年 | 21篇 |
2000年 | 24篇 |
1999年 | 46篇 |
1998年 | 106篇 |
1997年 | 69篇 |
1996年 | 50篇 |
1995年 | 30篇 |
1994年 | 33篇 |
1993年 | 33篇 |
1992年 | 20篇 |
1991年 | 10篇 |
1990年 | 25篇 |
1989年 | 25篇 |
1988年 | 27篇 |
1987年 | 29篇 |
1986年 | 21篇 |
1985年 | 23篇 |
1984年 | 36篇 |
1983年 | 25篇 |
1982年 | 25篇 |
1981年 | 27篇 |
1980年 | 34篇 |
1979年 | 23篇 |
1978年 | 20篇 |
1977年 | 24篇 |
1976年 | 29篇 |
1975年 | 18篇 |
1974年 | 14篇 |
1973年 | 19篇 |
1972年 | 12篇 |
1968年 | 10篇 |
排序方式: 共有1631条查询结果,搜索用时 15 毫秒
31.
Uniaxial time-dependent creep and cycled stress behavior of a standard and toughened film adhesive were studied experimentally. Both adhesives exhibited progressive accumulation of strain from an applied cycled stress. Creep tests were fit to a viscoelastic power law model at three different applied stresses which showed nonlinear response in both adhesives. A third order nonlinear power law model with a permanent strain component was used to describe the creep behavior of both adhesives and to predict creep recovery and the accumulation of strain due to cycled stress. Permanent strain was observed at high stress but only up to 3% of the maximum strain. Creep recovery was under predicted by the nonlinear model, while cycled stress showed less than 3% difference for the first cycle but then over predicted the response above 1000 cycles by 4–14% at high stress. The results demonstrate the complex response observed with structural adhesives, and the need for further analytical advancements to describe their behavior. 相似文献
32.
M. A. Wells I. V. Samarasekera J. K. Brimacombe E. B. Hawbolt D. J. Lloyd 《Metallurgical and Materials Transactions B》1998,29(3):611-620
A comprehensive mathematical model of the hot tandem rolling process for aluminum alloys has been developed. Reflecting the
complex thermomechanical and microstructural changes effected in the alloys during rolling, the model incorporated heat flow,
plastic deformation, kinetics of static recrystallization, final recrystallized grain size, and texture evolution. The results
of this microstructural engineering study, combining computer modeling, laboratory tests, and industrial measurements, are
presented in three parts. In this Part I, laboratory measurements of static recrystallization kinetics and final recrystallized
grain size are described for AA5182 and AA5052 aluminum alloys and expressed quantitatively by semiempirical equations. In
Part II, laboratory measurements of the texture evolution during static recrystallization are described for each of the alloys
and expressed mathematically using a modified form of the Avrami equation. Finally, Part III of this article describes the
development of an overall mathematical model for an industrial aluminum hot tandem rolling process which incorporates the
microstructure and texture equations developed and the model validation using industrial data. The laboratory measurements
for the microstructural evolution were carried out using industrially rolled material and a state-of-the-art plane strain
compression tester at Alcan International. Each sample was given a single deformation and heat treated in a salt bath at 400
°C for various lengths of time to effect different levels of recrystallization in the samples. The range of hot-working conditions
used for the laboratory study was chosen to represent conditions typically seen in industrial aluminum hot tandem rolling
processes, i.e., deformation temperatures of 350 °C to 500 °C, strain rates of 0.5 to 100 seconds and total strains of 0.5 to 2.0. The semiempirical
equations developed indicated that both the recrystallization kinetics and the final recrystallized grain size were dependent
on the deformation history of the material i.e., total strain and Zener-Hollomon parameter (Z), where
and time at the recrystallization temperature. 相似文献
33.
R. PearceAuthor Vitae T. IakimovM. AnderssonAuthor Vitae L. HultmanAuthor VitaeA. Lloyd SpetzAuthor Vitae R. YakimovaAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(2):451-455
Epitaxially grown single layer and multi layer graphene on SiC devices were fabricated and compared for response towards NO2. Due to electron donation from SiC, single layer graphene is n-type with a very low carrier concentration. The choice of substrate is demonstrated to enable tailoring of the electronic properties of graphene, with a SiC substrate realising simple resistive devices tuned for extremely sensitive NO2 detection. The gas exposed uppermost layer of the multi layer device is screened from the SiC by the intermediate layers leading to a p-type nature with a higher concentration of charge carriers and therefore, a lower gas response. The single layer graphene device is thought to undergo an n-p transition upon exposure to increasing concentrations of NO2 indicated by a change in response direction. This transition is likely to be due to the transfer of electrons to NO2 making holes the majority carriers. 相似文献
34.
Christian Bur Peter Reimann Mike Andersson Anita Lloyd Spetz Andreas Schütze 《Microsystem Technologies》2012,18(7-8):1015-1025
A silicon carbide based enhancement type metal insulator field effect transistor with porous gate metallization has been investigated as a total NO x sensor operated in a temperature cycling mode. This operating mode is quite new for gas sensors based on the field effect but promising results have been reported earlier. Based on static investigations we have developed a suitable T-cycle optimized for NO x detection and quantification in a mixture of typical exhaust gases (CO, C2H4, and NH3). Significant features describing the shape of the sensor response have been extracted and evaluated with multivariate statistics (e.g. linear discriminant analysis) allowing quantification of NO x . Additional cleaning-cycles every 30?min improve the stability of the sensor further. With this kind of advanced signal processing the influence of sensor drift and cross sensitivity to ambient gases can be reduced effectively. Measurements have proven that different concentrations of NO x can be detected even in a changing mixture of other typical exhaust gases under dry and humid conditions. In addition to that, unknown concentrations of NO x can be detected based on a small set of training data. It can be concluded that the performance of GasFETs for NO x determination can be enhanced considerably with temperature cycling and appropriate signal processing. 相似文献
35.
Bubble formation and stability in the film blowing processing of in situ polymerized and melt-compounded polyamide 6-based layered silicate nanocomposites (LSNs) are correlated to their underlying rheology, structure, and crystallization behavior. The layered silicates enhance melt elasticity, induce γ -form crystallinity, and increase crystallization rates without having any significant effect on the extent of crystallinity. A bubble stability quantification method employed to assess the level of instability during the film blowing process finds the in situ polymerized LSNs to be more stable than PA6, while melt-compounded LSNs do not display such an improved processability. All of the LSN films produced by film blowing possess superior mechanical properties compared to neat nylon 6, despite their relatively rougher film surfaces. 相似文献
36.
Thomas Manke Lloyd Demetrius Martin Vingron 《Journal of the Royal Society Interface》2006,3(11):843-850
The structure of molecular networks is believed to determine important aspects of their cellular function, such as the organismal resilience against random perturbations. Ultimately, however, cellular behaviour is determined by the dynamical processes, which are constrained by network topology. The present work is based on a fundamental relation from dynamical systems theory, which states that the macroscopic resilience of a steady state is correlated with the uncertainty in the underlying microscopic processes, a property that can be measured by entropy. Here, we use recent network data from large-scale protein interaction screens to characterize the diversity of possible pathways in terms of network entropy. This measure has its origin in statistical mechanics and amounts to a global characterization of both structural and dynamical resilience in terms of microscopic elements. We demonstrate how this approach can be used to rank network elements according to their contribution to network entropy and also investigate how this suggested ranking reflects on the functional data provided by gene knockouts and RNAi experiments in yeast and Caenorhabditis elegans. Our analysis shows that knockouts of proteins with large contribution to network entropy are preferentially lethal. This observation is robust with respect to several possible errors and biases in the experimental data. It underscores the significance of entropy as a fundamental invariant of the dynamical system, and as a measure of structural and dynamical properties of networks. Our analytical approach goes beyond the phenomenological studies of cellular robustness based on local network observables, such as connectivity. One of its principal achievements is to provide a rationale to study proxies of cellular resilience and rank proteins according to their importance within the global network context. 相似文献
37.
This two-part paper presents modelling and scheduling approaches of flexible manufacturing systems using Petri nets (PNs) and artificial intelligence (AI)-based heuristic search methods. In Part I, PN-based modelling approaches and basic AI-based heuristic search algorithms were presented. In Part II, a new heuristic function that exploits PN information is proposed. Heuristic information obtained from the PN model is used to dramatically reduce the search space. This heuristic is derived from a new concept, the resource cost reachability matrix, which builds on the properties of B-nets proposed in Part I. Two hybrid search algorithms, (1) an approach to model dispatching rules using analysis information provided by the PN simulation and (2) an approach of the modified stage-search algorithm, are proposed to reduce the complexity of large systems. A random problem generator is developed to test the proposed methods. The experimental results show promising results. 相似文献
38.
Peter Lloyd Woodfield Andrew Seagar Wayne Hall 《International Journal of Thermophysics》2012,33(2):259-278
Vibrating wire viscometers rely on the principle that the viscosity of the fluid surrounding the wire provides the dominant
damping action on the motion of the wire. However, some residual damping is always present due to other effects such as internal
friction of the wire (anelastic relaxation), losses through the wire supports, and magnetic damping. Magnetic damping is a
physical mechanism that has received relatively less attention than internal friction in the context of viscometers. The phenomenon
arises because the current induced by the motion of the wire contributes to the magnetic field in such a way as to oppose
its own motion. For a test circuit using a 40 μm diameter tungsten wire in a 0.3 T magnetic field, surprisingly, the effect
of magnetic damping was found to be of a similar order of magnitude to other non-viscous damping effects. The effect can be
accounted for by including the internal impedance of the oscillating voltage source in the model and it disappears completely
for a perfect oscillating current source. 相似文献
39.
40.
C.W. Chan I. Hussain D.G. Waugh J. Lawrence H.C. Man 《Materials science & engineering. C, Materials for biological applications》2013,33(3):1344-1354
The biocompatibility of NiTi after laser welding was studied by examining the in vitro (mesenchymal stem cell) MSC responses at different sets of time varying from early (4 to 12 h) to intermediate phases (1 and 4 days) of cell culture. The effects of physical (surface roughness and topography) and chemical (surface Ti/Ni ratio) changes as a consequence of laser welding in different regions (WZ, HAZ, and BM) on the cell morphology and cell coverage were studied. The results in this research indicated that the morphology of MSCs was affected primarily by the topographical factors in the WZ: the well-defined and directional dendritic pattern and the presence of deeper grooves. The morphology of MSCs was not significantly modulated by surface roughness. Despite the possible initial Ni release in the medium during the cell culture, no toxic effect seemed to cause to MSCs as evidenced by the success of adhesion and spreading of the cells onto different regions in the laser weldment. The good biocompatibility of the NiTi laser weldment has been firstly reported in this study. 相似文献