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排序方式: 共有1025条查询结果,搜索用时 593 毫秒
71.
T.M. Razykov G. Contreras-Puente G.C. Chornokur M. Dybjec Yu. Emirov B. Ergashev A. Hubbimov K.M. Kouchkarov D. Morel S. Ostapenko E. Sanchez-Meza E. Stefanakos H.M. Upadhyaya O. Vigil-Galan Yu.V. Vorobiev 《Solar Energy》2009,83(1):90-2290
CdTe films with different compositions (Cd-rich, Te-rich and stoichiometric) were fabricated by a novel and low cost chemical molecular beam deposition method (CMBD) in atmospheric pressure hydrogen flow. Cd and Te granules were used as precursors. The films were deposited on ceramic (SiO2:Al2O3) substrates at 580 °C and 600 °C. The growth rate was varied in the range of 9-30 Å/s. The composition (Cd/Te) of the samples was changed by controlling the molecular beam intensity (MBI) ratio. Three samples fabricated at MBI ratios Cd/Te = 0.5, 1.0 and 1.16 were investigated by XRD, AFM, EDX, SEM, photoluminescence (PL) and Hall methods. 相似文献
72.
GH Posner MH Parker J Northrop JS Elias P Ploypradith S Xie TA Shapiro 《Canadian Metallurgical Quarterly》1999,42(2):300-304
In only three chemical operations, natural trioxane lactone artemisinin (1) was converted into a series of C-10 carbon-substituted 10-deoxoartemisinin compounds 4-9. The three steps involved lactone reduction, replacement of the anomeric lactol OH by F using diethylaminosulfur trifluoride, and finally boron trifluoride-promoted substitution of F by aryl, heteroaryl, and acetylide nucleophiles. All of these C-10 nonacetal, chemically robust, enantiomerically pure compounds 4-9 have high antimalarial potencies in vitro against Plasmodium falciparum malaria parasites, and furans 5a and 5b and pyrrole 7a are antimalarially potent also in vivo even when administered to rodents orally. 相似文献
73.
Elias Pentti Juho Rysti Anssi Salmela Alexander Sebedash Juha Tuoriniemi 《Journal of Low Temperature Physics》2011,165(3-4):132-165
We present results of low-temperature experiments on dilute mixtures of 3He in 4He and on pure 3He, obtained by means of two kinds of mechanical oscillators immersed in the liquid sample: vibrating wires and quartz tuning forks. The helium sample was cooled either by adiabatic demagnetization of an immersed copper nuclear stage or by adiabatic melting of 4He in superfluid 3He. The measured effect of the surrounding fluid on the mechanical resonance of the oscillators is compared with existing theories. We also discuss resonances of second sound and the state of supersaturation, both observed by a tuning fork in helium mixtures. 相似文献
74.
Elias Penelope K.; Elias Merrill F.; Robbins Michael A.; Gage Paulette 《Canadian Metallurgical Quarterly》1987,2(4):340
A total of 45 subjects in three age groups (younger, middle-age, older) were trained to word process on microcomputers using a commercial training program and an experimenter-designed test and evaluation protocol. Although all of the subjects mastered the essentials of word processing, the older group took significantly longer to complete the training and evaluation procedures and performed more poorly on a review examination that tested their knowledge of the word-processing commands and techniques. The results are discussed in relation to requirements for trainer assistance, motivational factors, and the need to design training protocols that meet the needs of older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
C. Santos L.H.P. Teixeira J.K.M.F. Daguano S.O. Rogero K. Strecker C.N. Elias 《Ceramics International》2009,35(2):709-718
The influence of Al2O3 addition and sintering parameters on the mechanical properties and cytotoxicity of tetragonal ZrO2–3 mol% Y2O3 ceramics was evaluated. Samples containing 0, 10, 20 and 30 wt.% of Al2O3 particles were prepared by cold uniaxial pressing (80 MPa) and sintered in air at 1500, 1550 and 1600 °C for 120 min. The effects of the sintering conditions on the microstructure were analyzed by X-ray diffraction analysis and scanning electron microscopy. Hardness and fracture toughness were determined by the Vickers indentation method and the mechanical resistance by four-point bending tests. As a preliminary biological evaluation, “in vitro” cytotoxicity tests were realized to determine the cytotoxic level of the ZrO2–Al2O3 composites, using the neutral red uptake method with NCTC clones L929 from the American Type Culture Collection (ATCC) bank. Fully dense ceramic materials were obtained with a hardness ranging between 1340 HV and 1585 HV, depending on the amount of Al2O3 in the ZrO2 matrix. On the other hand, no significant influence of the Al2O3 addition on fracture toughness was observed, exhibiting values near 8 MPa m1/2 for all compositions and sintering conditions studied. The non-cytotoxic behavior, the elevated fracture toughness, the good bending strength (σf = 690 MPa) and the elevated Weibull's modulus (m = 11) exhibited by the material, show that these ceramic composites are highly suitable biomaterials for dental implant applications. 相似文献
76.
George Z. Voyiadjis Babur Deliktas Elias C. Aifantis 《Canadian Metallurgical Quarterly》2001,127(7):636-645
Thermodynamically consistent constitutive equations are derived here in order to investigate size effects on the strength of composite, strain, and damage localization effects on the macroscopic response of the composite, and statistical inhomogeneity of the evolution-related damage variables associated with the representative volume element. This approach is based on a gradient-dependent theory of plasticity and damage over multiple scales that incorporates mesoscale interstate variables and their higher order gradients at both the macro- and mesoscales. This theory provides the bridging of length scales. The interaction of the length scales is a paramount factor in understanding and controlling material defects such as dislocation, voids, and cracks at the mesoscale and interpreting them at the macroscale. The behavior of these defects is captured not only individually, but also the interaction between them and their ability to create spatiotemporal patterns under different loading conditions. The proposed work introduces gradients at both the meso- and macroscales. The combined coupled concept of introducing gradients at the mesoscale and the macroscale enables one to address two issues simultaneously. The mesoscale gradients allow one to address issues such as lack of statistical homogeneous state variables at the macroscale level such as debonding of fibers in composite materials, cracks, voids, and so forth. On the other hand, the macroscale gradients allow one to address nonlocal behavior of materials and interpret the collective behavior of defects such as dislocations and cracks. The capability of the proposed model is to properly simulate the size-dependent behavior of the materials together with the localization problem. Consequently, the boundary-value problem of a standard continuum model remains well-posed even in the softening regime. The enhanced gradient continuum results in additional partial differential equations that are satisfied in a weak form. Additional nodal degrees of freedom are introduced that leads to a modified finite-element formulation. The governing equations can be linearized consistently and solved within the incremental iterative Newton-Raphson solution procedure. 相似文献
77.
Lazaros Elias Mavromatidis Pierre Michel Mohamed El Mankibi Mat Santamouris 《Building Simulation》2010,3(4):279-294
This paper reports on a numerical and experimental study of heat transfer phenomena through two different multilayer fibrous
insulations for building applications. The investigated samples were composed of different layers of fibrous materials and
aluminium foils, placed between one or two air gaps in the vertical dimension. An experimental apparatus (a guarded hot box)
has been used to measure heat transfer through the samples, while a finite volume numerical model combined radiation/conduction
heat transfer was developed to predict the temperature distribution and heat transfer in such insulation systems comprised
of the materials separated by multiple reflective foils. The model takes into account the coupling between the solid conduction
of the fibrous system and the gaseous conduction and radiation. The radiation heat transfer through the insulation system
has been modelled via the two flux approximation. The numerical results were compared with the experimental data from the
guarded hot box for model validation, as well as to assess the effectiveness of the reflective foils in changing the resistance
of the insulations. The comparative verification of the model showed that the numerical results were consistent with the experimental
data through the environmental conditions under examination. 相似文献
78.
José D. Ambrósio Nelson M. Larocca Luiz A. Pessan Elias Hage Jr 《Polymer Engineering and Science》2010,50(12):2382-2391
In this research, it was studied the effects of the processing parameters applied to a twin screw extruder on the morphology and impact strength of poly(butylene terephthalate)/acrylonitrile‐butadiene‐styrene blends with and without a reactive compatibilizer. It was found that the increase of the feed rate highly decreased the ductile brittle transition temperature (DBTT) and slightly increased the room temperature impact strength (RTIS) of the compatibilized blends. Besides the influence of the feed rate, it was also found that the compatibilized blends could reach high RTIS and low DBTT values by an appropriate combination of the compatibilizer feeding position in the extruder, the screw rotation speed and the width of the kneading discs of the screw. The DBTT was found to be at least partially controlled by the spatial distribution of the rubbery particles, which was quantified by finite body tessellation, a method applied for the first time in polymer blends. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers 相似文献
79.
Wardah Fatimah Mohammad Yusoff Elias Salleh Nor Mariah Adam Abdul Razak Sapian Mohamad Yusof Sulaiman 《Building and Environment》2010
In the hot and humid climate, stack ventilation is inefficient due to small temperature difference between the inside and outside of naturally ventilated buildings. Hence, solar induced ventilation is a feasible alternative in enhancing the stack ventilation. This paper aims to investigate the effectiveness of a proposed solar induced ventilation strategy, which combines a roof solar collector and a vertical stack, in enhancing the stack ventilation performance in the hot and humid climate. The methodology selected for the investigation is physical experimental modelling which was carried out in the actual environment. The results are presented and discussed in terms of two performance variables: air temperature and air velocity. The findings indicate that the proposed strategy is able to enhance the stack ventilation, both in semi-clear sky and overcast sky conditions. The highest air temperature difference between the air inside the stack and the ambient air (Ti−To) is achieved in the semi-clear sky condition, which is about 9.9 °C (45.8 °C–35.9 °C). Meanwhile, in the overcast sky condition, the highest air temperature difference (Ti−To) is 6.2 °C (39.3 °C–33.1 °C). The experimental results also indicate good agreement with the theoretical results for the glass temperature, the air temperature in the roof solar collector’s channel and the absorber temperature. The findings also show that wind has significant effect to the induced air velocity by the proposed strategy. 相似文献
80.