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排序方式: 共有451条查询结果,搜索用时 15 毫秒
21.
In this paper, a cost analysis of recovery block scheme has been presented. This study provides us the selection criterion for alternates and the software granularity under perfect acceptance tests. Two performance evaluation measures: a) cost-reliability index (CRI); b) cost of failure (COF) are studied and compared. CRI is shown to be a move restricted measure than COF. An experimental study has been carried out to supplement the analysis. Efficient placement of recovery blocks and the design of alternates has been discussed with reference to real-time applications.This work has been carried out under contract DOT-RC-92031. 相似文献
22.
Nanomechanical characterization of multilayered thin film structures for digital micromirror devices
The digital micromirror device (DMD), used for digital projection displays, comprises a surface-micromachined array of up to 2.07 million aluminum micromirrors (14 μm square and 15 μm pitch), which switch forward and backward thousands of times per second using electrostatic attraction. The nanomechanical properties of the thin-film structures used are important to the performance of the DMD. In this paper, the nanomechanical characterization of the single and multilayered thin film structures, which are of interest in DMDs, is carried out. The hardness, Young's modulus and scratch resistance of TiN/Si, SiO2/Si, Al alloy/Si, TiN/Al alloy/Si and SiO2/TiN/Al alloy/Si thin-film structures were measured using nanoindentation and nanoscratch techniques, respectively. The residual (internal) stresses developed during the thin film growth were estimated by measuring the radius of curvature of the sample before and after deposition. To better understand the nanomechanical properties of these thin film materials, the surface and interface analysis of the samples were conducted using X-ray photoelectron spectroscopy. The nanomechanical properties of these materials are analyzed and the impact of these properties on micromirror performance is discussed. 相似文献
23.
Thermal decomposition of powdered ammonium perchlorate (AP), polystyrene (PS) and propellant, catalysed by freshly-prepared CuCr2O4 and mixtures of CuCr2O4 and CuO, has been studied with a low concentration (1% by mass) of the catalysts. It appears that decomposition is increased due to heterogeneous catalysis. The kinetics of thermal decomposition of AP in the presence of CuCr2O4 in the orthorhombic region of AP have also been studied. 相似文献
24.
Bharat B. Panigrahi 《Materials Letters》2007,61(1):152-155
The effect of nickel powder additions (2 and 5 at.%) on the sintering behaviour of titanium powder has been investigated through the dilatometric sintering study. The sintering of titanium powder was found to be enhanced significantly and the activation energies were decreased with increasing nickel content. The sintering of Ti-2 at.% Ni system at lower temperature was found to be controlled by Ti-Ti and Ti-Ni solid state sintering, whereas inter-diffusion dominates in Ti-5 at.% Ni sintering. At higher temperatures, sintering was found to be controlled by mixed mechanisms, i.e. inter-diffusion, chemical reaction and transient liquid phase formation. 相似文献
25.
We present a method to obtain capacitive forces and dielectric constants of ultra-thin films on metallic substrates using multifrequency non-contact atomic force microscopy with amplitude feedback in air. Capacitive forces are measured via cantilever oscillations induced at the second bending mode and dielectric constants are calculated by fitting an analytic expression for the capacitance (Casuso et al 2007 Appl. Phys. Lett. 91 063111) to the experimental data. Dielectric constants for self-assembled monolayers of thiol molecules on gold (2.0±0.1) and sputtered SiO2 (3.6±0.07) were obtained under dry conditions, in good agreement with previous measurements. The high Q-factor of the second bending mode of the cantilever increases the accuracy of the capacitive measurements while the low applied potentials minimize the likelihood of variation of the dielectric constants at high field strength and of damage from dielectric breakdown of air. 相似文献
26.
Advanced high-energy plasma systems are being used to achieve the benefits of the high-velocity oxy-fuel (HVOF) system without
losing the inherent advantages of plasma for coating of gas turbine parts. MCrAlY coatings play a very important role in the
performance and reliability of gas turbine components. One of the important considerations for next generation of gas turbines,
which have more demanding conditions and need to withstand ever increasing operating temperatures, is that they should possess
very low oxygen content levels in the coating. Low oxygen content coatings are applied by the expensive low-pressure plasma
spray (LPPS)/vacuum plasma spray (VPS) technique for critical components in aero- and land-based gas turbines. This work deals
with the development of low-cost LPPS equivalent coatings (having low oxygen content) using the high-energy high-velocity
plasma spray (HEHVPS) gun and inert gas shroud. A comparison has also been made with CoNiCrAlY coatings by HVOF. 相似文献
27.
28.
Bharat K. Modhera Mousumi Chakraborty Hari C. Bajaj Parimal A. Parikh 《Catalysis Letters》2011,141(8):1182-1190
Abstract
Catalytic performance of Pt impregnated parent and desilicated nano-crystalline zeolites, ZSM-5 and Beta for n-hexane isomerization was studied. Difference in channel systems of the zeolites and absence/presence of mesopores therein were found to be reflected in product distributions. ZSM-5 was desilicated by NaOH and zeolite Beta with tetramethylammonium hydroxide (TMAOH.) Desilication was found to afford comparable catalytic performance to that of the parent counterpart at reaction temperature lower by 25 °C. Observed product distributions could be substantiated with characterizations such as ammonia TPD, surface area determination and SEM. Desilicated zeolite Beta was seen to be less prone to coking as deduced from the TGA study. Location of Pt with reference to proton sites within the channels and that inside the pores viz a viz external surface also have been discussed briefly. 相似文献29.
G. Seeta Rama Raju E. Pavitra L. Krishna Bharat Gattupalli Manikya Rao Tae-Joon Jeon Yun Suk Huh Young-Kyu Han 《Ceramics International》2018,44(12):13852-13857
Upconversion Sr2(Gd.98-xEr.02Ybx)8Si6O26 (SGSO:2Er3+/xYb3+) phosphor materials were synthesized using a citrate sol-gel process. X-ray diffraction patterns confirmed their hexagonal structure. Field emission scanning electron microscopy images of SGSO:2Er3+/xYb3+ phosphors depicted submicron particles. The enhanced upconversion luminescence properties of SGSO:2Er3+/xYb3+ phosphors were analysed as a function of Yb3+ ion concentration and laser power. The energy transfer induced enhanced emission of the Er3+/ Yb3+ ions co-doped SGSO phosphors was ascribed to multi-phonon relaxation. The calculated chromaticity coordinates of the SGSO:2Er3+/xYb3+ phosphors showed emissions could be tuned by changing Yb3+ ion concentration. Optimized sample exhibited the chromaticity coordinate values near to the ultra-high definition television standard green emission coordinates. 相似文献
30.
We discuss smart environments that identify and track their occupants using unobtrusive recognition modalities such as face, gait, and voice. In order to alleviate the inherent limitations of recognition, we propose spatio-temporal reasoning techniques based upon an analysis of the occupant tracks. The key idea underlying our approach is to determine the identity of a person based upon information from a track of events rather than a single event. We abstract a smart environment by a probabilistic state transition system in which each state records a set of individuals who are present in various zones of the smart environment. An event abstracts a recognition step, and the transition function defines the mapping between states upon the occurrence of an event. We express two forms of spatio-temporal reasoning in the form of transition functions: a track-based transition function and an error-correcting transition function. We also define the concepts of ‘precision’ and ‘recall’ to quantify the performance of the smart environment and provide experimental results to clarify the performance improvements from spatio-temporal reasoning. Our conclusion is that the state transition system is an effective abstraction of a smart environment and the application of spatial-temporal reasoning enhances the overall performance of a biometric recognition system. 相似文献