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991.
Fatigue experiments were conducted on polycrystalline and monocrystalline samples of a high purity Al, 5.5 wt pct Zn, 2.5
wt pct Mg, 1.5 wt pct Cu alloy in the peak-hardened heat treatment condition. These experiments were conducted in dry laboratory
air and in 0.5N NaCl solutions at the corrosion potential and at applied potentials cathodic to the corrosion potential. It has been shown
that saline solutions severely reduce the fatigue resistance of the alloy, resulting in considerable amounts of intergranular
crack initiation and propagation under freely corroding conditions for polycrystalline samples. Applied cathodic potentials
resulted in still larger decreases in fatigue resistance and, for poly crystals, increases in the degree of transgranular
crack initiation and propagation. Increasing amounts of intergranular cracking were observed when applied cyclic stresses
were reduced (longer test times). The characteristics of cracking, combined with results obtained on tensile tests of deformed
and hydrogen charged samples, suggest that environmental cracking of these alloys is associated with a form of hydrogen embrittlement
of the process zones of growing cracks. Further, it is suggested that stress corrosion cracking and corrosion fatigue of these
alloys occurs by essentially the same mechanism, but that the often observed transgranular cracking under cyclic loading conditions
occurs due to enhanced hydrogen transport and/or concentrations associated with mobile dislocations at growing crack tips. 相似文献
992.
Investigated the stability of Minnesota Multiphasic Personality Inventory (MMPI) code types. Ss were 405 psychiatric patients (mean age 37 yrs) who had completed 2 valid MMPIs and some of whom had been rated twice on the Brief Psychiatric Rating Scale. Test–retest agreements for high-point, low-point, and 2-point codes were 42.72%, 43.95%, and 27.65%, respectively. Code types were somewhat more stable when scales in the codes had more extreme scores initially and when scores on the scales in the codes were considerably different from other scales in the profile. When MMPIs were classified as neurotic, psychotic, or characterological according to 2-point codes, many of the 2-point codes that changed from test to retest remained within the same diagnostic categories. For a subsample of 72 Ss, behavioral ratings of psychosis were compared with stability and change in 2-point code types. Results suggest that at least some changes in code types over time may be associated with meaningful behavioral changes. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
Dorothea F K Rawn Sue C Quade J Brian Shields Giacomo Conca Wing-Fung Sun Gladys M A Lacroix Mark Smith André Fouquet André Bélanger 《Food Additives & Contaminants》2007,24(2):149-155
Apple trees in an orchard in Quebec, Canada were treated, following label directions, with the fungicide captan (1,2,3,6-tetrahydro-N-(trichloromethylthio)phthalimide) during the 2003 agricultural season. A total of 142 apples from three rows of trees were selected for determination of captan by GC/MS. Individual apples were found to contain captan levels ranging from 16.9 to 6350 ng g-1. Only two individual apple samples exceeded the Canadian maximum residue limit (5000 ng g-1) for captan in apples. Six composite samples, comprising half portions of eight individual apples, were analysed from each of the three experimental rows. Composite samples ranged in concentration from 166 to 2620 ng g-1. The greatest uncertainty associated with the measured concentrations was due to variability among apples rather than the measurement of residue levels. 相似文献
994.
Warren Amye R.; Nunez Narina; Keeney Jennifer M.; Buck Julie A.; Smith Beverly 《Canadian Metallurgical Quarterly》2002,87(5):846
Hearsay testimony from children's interviewers is increasingly common in sexual abuse trials, but little is known about its effects on juries. In 2 studies, the authors examined college students' perceptions of 3 types of hearsay testimony (an actual interview with a child or an adult interviewer providing either the gist of what that child had said or a verbatim account of the interview). Interviewers were rated as more accurate and truthful than the children. The interview was rated as higher quality, and children's statements, including their false statements, were sometimes rated as more believable in the interviewer gist hearsay condition. Mock jurors reacted differently to various types of hearsay testimony, and interviewer gist testimony may favor a child's case. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
A rare case of the Ekman-Westborg-Julin syndrome in a 15-year-old boy is presented. The patient had general macrodontia with gigantic mandibular third molars. Other dental anomalies, such as peak-shaped cuspids, central cusps, dens in dente, multituberculism, and single conical molar roots, were also present. 相似文献
996.
Computer simulation of morphology and packing behaviour of irregular particles, for predicting apparent powder densities 总被引:2,自引:0,他引:2
This paper describes a methodology for prediction of powder packing densities which employs a new approach, designated as random sphere construction (RSC), for modelling the shape of irregular particles such as those produced by water atomization of iron. The approach involves modelling an irregular particle as a sphere which incorporates smaller corner spheres located randomly at its surface. The RSC modelling technique has been combined with a previously developed particle packing algorithm (the random build algorithm), to provide a computer simulation of irregular particle packings. Analysis of the simulation output data has allowed relationships to be established between the particle modelling parameters employed by the RSC algorithm, and the density of the simulated packings. One such parameter is η, which is the number of corner spheres per particle. A relationship was established between η (which was found to have a profound influence on packing density), and the fractional density of the packing, fd. Vision system techniques were used to measure the irregularity of the simulated particles, and this was also related to η. These two relationships were then combined to provide a plot of fractional density for a simulated packing against irregularity of the simulated particles. A comparison was made of these simulated packing densities and observed particle packing densities for irregular particles, and a correlation coefficient of 0.96 was obtained. This relatively good correlation indicates that the models developed are able to realistically simulate packing densities for irregular particles. There are a considerable number of potential applications for such a model in powder metallurgy (PM), process control. In combination with on-line particle image analysis, the model could be used to automatically predict powder densities from particle morphology. 相似文献
997.
The susceptibility of uninfected or Staphylococcus chromogenes-infected quarters to challenge with Staphylococcus aureus was measured. Seventeen S. chromogenes-infected quarters were challenged by infusion of S. aureus into the teat sinus; 47% (8 of 17) became infected and all 18 uninfected quarters challenged similarly with S. aureus became infected. No differences in daily milk yield were seen between uninfected quarters and S. chromogenes-infected quarters prior to S. aureus infusion. Postinfusion, milk yield for S. aureus-infected, S. chromogenes-infected, and S. chromogenes- and S. aureus-infected quarters differed. Somatic cell counts were elevated in S. chromogenes-infected quarters compared with uninfected quarters prior to S. aureus infusion. Somatic cell counts were not different between S. aureus- and S. chromogenes- and S. aureus-infected quarters postinfusion, but were different for S. chromogenes-infected quarters. Chloride concentrations in S. chromogenes- and S. aureus-infected quarters were different from either S. aureus-infected or S. chromogenes-infected quarters. Staphylococcus aureus colony forming units in quarters with preexisting S. chromogenes infections were lower than S. aureus colony-forming units in previously uninfected quarters. Possible protective mechanisms induced by S. chromogenes against superinfection by S. aureus are discussed. 相似文献
998.
Combining spatial and scale-space techniques for edge detection to provide a spatially adaptive wavelet-based noise filtering algorithm 总被引:4,自引:0,他引:4
New methods for detecting edges in an image using spatial and scale-space domains are proposed. A priori knowledge about geometrical characteristics of edges is used to assign a probability factor to the chance of any pixel being on an edge. An improved double thresholding technique is introduced for spatial domain filtering. Probabilities that pixels belong to a given edge are assigned based on pixel similarity across gradient amplitudes, gradient phases and edge connectivity. The scale-space approach uses dynamic range compression to allow wavelet correlation over a wider range of scales. A probabilistic formulation is used to combine the results obtained from filtering in each domain to provide a final edge probability image which has the advantages of both spatial and scale-space domain methods. Decomposing this edge probability image with the same wavelet as the original image permits the generation of adaptive filters that can recognize the characteristics of the edges in all wavelet detail and approximation images regardless of scale. These matched filters permit significant reduction in image noise without contributing to edge distortion. The spatially adaptive wavelet noise-filtering algorithm is qualitatively and quantitatively compared to a frequency domain and two wavelet based noise suppression algorithms using both natural and computer generated noisy images. 相似文献
999.
Eldek A.A. Elsherbeni A.Z. Smith C.E. Kai-Fong Lee 《Antennas and Propagation Magazine, IEEE》2002,44(5):146-155
Antenna designs are achieved for wideband operation by the use of a coplanar patch-slot antenna, fed by a coplanar waveguide. This design is easily tuned to operate at 2.45 and 5.75 GHz, with wide bandwidth for wireless systems. The operating frequency is controlled by modifying the patch dimensions. The return loss, input impedance, radiation pattern, directivity, gain, and efficiency of the proposed designs are computed and presented. A parametric study of the antenna is also introduced. 相似文献
1000.
Agnès Smith Gilles Gasgnier Pierre Abélard 《Journal of the American Ceramic Society》1990,73(4):1098-1099
This paper examines the effect of MgO addition on the structural and electrical characteristics of a ZnO varistor composition with few dopants. MgO acts as a grain-growth inhibitor. The electrical performances of the obtained varistors are improved. 相似文献