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71.
The dynamic effects of the motion of single bubbles entrained in a liquid are investigated. Extensive original experimental results are presented on the pressures associated with the motion of large, isolated spherical cap air bubbles rising both freely and through constricting orifices in a vertical cylindrical pipe filled with quiescent water. The pressures, measured at the pipe wall, were found to be as high as the dynamic bubble pressure for translational bubble motion, and an order of magnitude larger for oscillatory bubble motion following bubble formation. 相似文献
72.
Cyril Stanley Smith 《Metallurgical and Materials Transactions A》1975,6(3):603-623
The entire history of materials is examined with emphasis upon the structural differences at stages of discovery, development
and mature adjustment in analogy with the S-curve of a phase change. The earliest discovery of almost all useful materials
or techniques occurred in making decorative objects. Alloying, shaping and welding techniques began in jewelry and sculpture;
crystallization, spinodal transformation, and interface energy equilibrium were sensitively used in ceramic glazes; oriental
lacquer and celluloid trinkets are precursors of the plastic industry. Far from being an applied science, practice in materials
was far in advance of physical and chemical theory until less than a century ago, and even today intuitive understanding cannot
be disregarded. The alchemists built their mystic concepts upon the coloring techniques of ancient artisans. Chemistry came
from dying, pot making and particularly the quantitative separatory reactions of the assayer. But, once developed, science
became highly effective in controlling and improving industrial practice. The discovery of electricity gave a new type of
property to be studied, and the richness of today’s approach to materials came from the subsequent joining of the physicist’s
approach with the other threads that had been maturing through the ages. Technological change alters the patterns of human
interaction and it underlies most social upheavals. Technology is a rich part of the human experience and it deserves far
more attention than it has hitherto received by historians. 相似文献
73.
The latest developments in the chemical reprocessing of spent nuclear fuels are reviewed with particular accent on operating plants. Trends in the development of multi-purpose headends for a range of enrichments, geometries, and alloy components are given. The general design features of small- and large-scale plants are compared, and their significance to commercial application is reviewed. Progress in nonaqueous and pyrometallurgical reprocessing methods is reported. Research and development are reported for headend processes for new fuel compositions and fuel claddings. 相似文献
74.
The electroreduction of a series of 3-phenyl-2,3-dioxopropionanilide 2-arylhydrazones (III) on the dropping mercury electrode (dme) was investigated in ethanolic Britton-Robinson buffers. In each case, the polarographic curves showed two waves, A and B, corresponding to a four- and a two-electron process, respectively. The E1/2 values for the wave A at pH 8.0 were shown to be a linear function of the Hammett substituent constant σ; -(E1/2)A(V) = 0.982 + 0.145 σ (r = 0.989). A mechanism for the polarographic reduction of III is proposed. 相似文献
75.
76.
77.
Cyril Portmann Cora Prestinari Theresa Myers Judith Scharte Dr. Karl Gademann Prof. Dr. 《Chembiochem : a European journal of chemical biology》2009,10(5):889-895
Out of the green! Precursor‐directed biosynthesis allowed for the production of new nostocarboline derivatives that display phytotoxic and algicidal properties—in a phototrophic organism. The mechanism of action includes downregulation of photosynthesis, as demonstrated by chlorophyll‐a fluorescence imaging.
78.
Xiaohong Gu Lipiin Sung Bouchra Kidah Mounira Oudina Cyril Clerici Haiqing Hu Debbie Stanley Walter E. Byrd Jerry Y. C. Jean Tinh Nguyen Jonathan W. Martin 《Journal of Coatings Technology and Research》2009,6(1):67-79
Surface topography and gloss are two related properties affecting the appearance of a polymeric coating system. Upon exposure
to ultraviolet (UV) radiation, the surface topography of a coating becomes more pronounced and, correspondingly, its gloss
generally decreases. However, the surface factors affecting gloss and appearance are difficult to ascertain. In this article,
atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM) measurements have been performed on an amine-cured
epoxy coating system exposed to outdoor environments in Gaithersburg, Maryland. The formation of the protuberances is observed
at the early degradation stages, followed by the appearance of circular pits as exposure continues. At long exposure times,
the circular features enlarge and deepen, resulting in a rough surface topography and crack formation. Fourier Transform Infrared
Spectroscopy (FTIR) study indicates that the oxidation and chain scission reactions are likely the origins of the surface
morphological changes. The relationship between changes in surface roughness and gloss has been analyzed. The root mean square
(RMS) roughness of the coating is related to nanoscale and microscale morphological changes in the surface of the coating
as well as to the gloss retention. A near-linear dependence of RMS roughness with the measurement length scale (L) is found on a double logarithmic scale, i.e., RMS ∼ L
f. The scaling factor, f, decreases with exposure time. The relationship between surface topography, on nano- to microscales,
and the macroscale optical properties such as gloss retention is discussed. Moreover, a recent development in using an angle-resolved
light scattering technique for the measurement of the specular and off-specular reflectance of the UV-exposed specimens is
also demonstrated, and the optical scattering data are compared to the gloss and the roughness results.
相似文献
Xiaohong GuEmail: |
79.
Chen-Chen Peng Sheng-Yi Yang Hong-Cheng Li Guo-Hua Xie Lin-Song Cui Sheng-Nan Zou Cyril Poriel Zuo-Quan Jiang Liang-Sheng Liao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(48):2003885
In this work, two novel thermally activated delayed fluorescence (TADF) emitters, 2tDMG and 3tDMG, are synthesized for high-efficiency organic light-emitting diodes (OLEDs), The two emitters have a tilted face-to-face alignment of donor (D)/acceptor (A) units presenting intramolecular noncovalent interactions. The two TADF materials are deposited either by an evaporation-process or by a solution-process, both of them leading to high OLED performance. 2tDMG used as the emitter in evaporation-processed OLEDs achieves a high external quantum efficiency (EQE) of 30.8% with a very flat efficiency roll-off of 7% at 1000 cd m−2. The solution-processed OLEDs also display an interesting EQE of 16.2%. 3tDMG shows improved solubility and solution processability as compared to 2tDMG, and thus a high EQE of 20.2% in solution-processed OLEDs is recorded. The corresponding evaporation-processed OLEDs also reach a reasonably high EQE of 26.3%. Encouragingly, this work provides a novel strategy to address the imperious demands for OLEDs with high EQE and low roll-off. 相似文献
80.
A popular approach for computing photorealistic images of virtual objects requires applying reflectance profiles measured from real surfaces, introducing several challenges: the memory needed to faithfully capture realistic material reflectance is large, the choice of materials is limited to the set of measurements, and image synthesis using the measured data is costly. Typically, this data is either compressed by projecting it onto a subset of its linear principal components or by applying non‐linear methods. The former requires many components to faithfully represent the input reflectance, whereas the latter necessitates costly extrapolation algorithms. We learn an underlying, low‐dimensional non‐linear reflectance manifold amenable to rapid exploration and rendering of real‐world materials. We can express interpolated materials as linear combinations of the measured data, despite them lying on an inherently non‐linear manifold. This allows us to efficiently interpolate and extrapolate measured BRDFs, and to render directly from the manifold representation. We exploit properties of Gaussian process latent variable models and use our representation for high‐performance and offline rendering with interpolated real‐world materials. 相似文献