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71.
Large amounts of water containing-ammonium nitrogen(NH4+-N)have attracted increasing attention.Catalytic ozonation technology,involving the generation of hydroxyl radical(OH)with strong oxidation ability,was originally utilized to degrade organic-containing wastewater.In this paper,Ce/MnOx composite metal oxide catalysts prepared with different preparation conditions were used to degrade wastewater containing inorganic pollutant(NH4+-N).The as-prepared catalyst features were characterized using X-ray diffraction(XRD),Brunauer-Emmett-Teller method(BET),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and H2-temperature programmed reduction(H2-TPR)techniques.The results show that the catalyst,prepared by conditions with precipitant Na2CO3 and Ce/Mn molar ratio 1:2 calcined at 400℃for 3 h in pH 11.0,displays the optimal performance,with the removal rate of NH4+-N and selectivity to gaseous nitrogen,88.14 wt%and 53.67 wt%,respectively.The effects of several operating factors including solution pH,initial NH4+-N concentrations and scavengers were evaluated.In addition,XRD patterns of catalyst with the best performance and the comparative study on decontamination of NH4+-N by various processes(O3,catalyst and catalyst/O3)show that the primary metal oxides are CeO2 and MnO2 in Ce/MnOx composite metal oxide catalysts,which have a synergistic effect on the catalytic ozonation of NH4+-N,and the new phase MnO2 plays a great role.After 5 consecutive use cycles,the degradation efficiency is declined slightly,and can still achieve better than 70 wt%over 1 h reaction.Additionally,the application of catalytic ozonation for actual wastewater on the removal rate of NH4+-N was investigated.Possible mechanism and degradation pathway of NH4+-N were also proposed.In a word,the application of CeO2-MnO2 composite metal oxide catalysts in catalytic ozonation can be regarded as an effective,feasible and promising method for the treatment of NH4+-N. 相似文献
72.
73.
Ability of the direct wave of radar ground-coupled antenna for NDT of concrete structures 总被引:1,自引:0,他引:1
The research work presented in this paper aims at evaluating the potential of the direct wave of radar ground-coupled antennas for the on site physical characterization of concrete. According to studies highlighting the ability of radar reflected waves to characterize concrete, the potential of the direct wave is studied by systematic comparison of direct and reflected wave attenuations. Among the various features of electromagnetic waves propagating through concrete, attenuation is the most sensitive to moisture and chloride contents. In order to study the sensitivity of the direct wave to the physical condition of the concrete, laboratory experiments were conducted on concrete slabs with various porosities, water contents and chloride contamination levels.The results of this study show very satisfactory correlations between attenuations of direct and reflected waves, indicating that both waves provide similar information regarding the physical state of concrete. This correlation was confirmed on two bridges by comparison of direct wave attenuation maps with reflection attenuation maps. Therefore, radar interpretation method based on the direct wave attenuation should be able to detect, in a very fast way, physical contrasts in concrete structures and, consequently, identify probable pathological areas. 相似文献
74.
研究了Ce对Al—16%Si合金熔体粘滞性的影响。结果表明:Ce的加入增加了合金熔体的粘度,且随着Ce含量的增加粘度值也增加。结合加入Ce的Al—16%Si合金氢含量的变化、凝固组织和DSC曲线研究了熔体结构的变化,分析了粘度与液态结构变化之间的关系。 相似文献
75.
T. Nguyen I. Zarudi L.C. Zhang 《International Journal of Machine Tools and Manufacture》2007,47(1):97-106
This paper studies an innovative development of a steel grinding–hardening technology using an inert cryogen—liquid nitrogen. It was found that phase transformations took place during grinding with the application of liquid nitrogen and resulted in hardened surface layer in a ground component. The layer had a fine laths martensite structure which gave rise to a remarkably high hardness. It was also shown that the treatment can produce superior surface integrity, with compressive surface residual stresses and without surface oxidation. Due to the inert nature of the liquid nitrogen, the grinding process becomes environmentally conscious. 相似文献
76.
77.
多元酚——甲醛树脂中游离酚,游离醛含量的测定 总被引:6,自引:0,他引:6
多元酚--甲醛树脂是本院开发的热固粘接剂新产品,本文给出了这一产品技术指标中游离酚、游离醛含量的测定方法,并对方法进行了讨论。 相似文献
78.
Simulation of nitrogen dynamics and biomass production in winter wheat using the Danish simulation model DAISY 总被引:14,自引:0,他引:14
S. Hansen H. E. Jensen N. E. Nielsen H. Svendsen 《Nutrient Cycling in Agroecosystems》1991,27(2-3):245-259
A dynamic simulation model for the soil plant system is described. The model includes a number of main modules, viz., a hydrological model including a submodel for soil water dynamics, a soil temperature model, a soil nitrogen model including a submodel for soil organic matter dynamics, and a crop model including a submodel for nitrogen uptake. The soil part of the model has a one-dimensional vertical structure. The soil profile is divided into layers on the basis of physical and chemical soil characteristics. The simulation model was used to simulate soil nitrogen dynamics and biomass production in winter wheat grown at two locations at various levels of nitrogen fertilization. The simulated results were compared to experimental data including concentration of inorganic nitrogen in soil, crop yield, and nitrogen accumulated in the aboveground part of the crop. Based on this validation it is concluded that the overall performance of the model is satisfactory although some minor adjustments of the model may prove to be necessary. 相似文献
79.
Polyurethanes were prepared from toluene diisocyanate (TDI), 1-4-butane diol (BDO) and polycaprolactone-based triols with varying molecular weights. Among each molecular weight triol-based urethane, hard segment content was varied from 20% to 70%. Differential scanning calorimetry, tensile testing, and Iosipescu shear testing were done on all the various urethanes prepared. Thermal characterization data revealed the dependence of phase separation on hard segment content as well as on the triol molecular weight. Tensile data and Iosipescu shear data further confirmed the observations made from the DSC data. The data further indicated that phase separation can greatly improve the modulus of cross-linked segmented urethanes. Adhesion of these urethanes to glass surface was evaluated using soda-lime float glass plate. Urethane samples were cast on the air side of the glass plates and adhesion was measured in shear mode. Adhesion data indicated that in addition to hard segment content, modulus, cross-link density, and molecular weight of the triols, phase separation seems to be a major factor in controlling adhesion. Surfaces of the failed adhesion samples were also analyzed and the failure mode was found to be cohesive, in varying degree, with the different urethane systems. 相似文献
80.
Two different methods of producing bi‐ and trimodal latices of a mixture of methyl methacrylate, butyl acrylate, and small amounts of acrylic acid were tested. It is shown that a combination of concentrating blends of seed particles by semibatch reaction, followed by a nucleation of small particles plus a second semibatch phase allowed us to obtain stable latices with solids contents over 65% and viscosities of below 2500 mPa s?1 with little coagulum formation. The key parameter in determining latex stability, coagulum formation, and viscosity appears to be the the particle size distribution, and especially its modification attributed to secondary nucleation. Because it is not possible to eliminate water‐soluble monomers from the polymerization recipe, secondary (homogeneous) nucleation must be minimized by careful addition of the free‐radical initiator and choice of monomer feed flow rates. The nucleation of the third population in the trimodal latices is best accomplished with a mixed surfactant system because renucleation by anionic surfactant alone leads to detrimental changes in the particle size distribution (PSD) resulting from excessive flocculation of particles. In addition, it was found that the viscosity of the final products was not sensitive to small changes in the ionic strength of the latex, although neutralization to a pH of 6 effectively doubles the final latex viscosity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1916–1934, 2002; DOI 10.1002/app.10513 相似文献