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61.
Tohru Shiga Takeshi Narita Kazuyuki Tachi Akane Okada Hideroh Takahashi Toshio Kurauchi 《Polymer Engineering and Science》1997,37(1):24-30
This paper describes a new nondestructive technique for detecting internal stresses in coatings using time resolved fluorescence. The measurement principle is based upon an experimental result that the decay time of fluorescence from poly(3-octylthiophene), P3OT, dispersed in uniaxially-stretched polymer films decreases with increasing tensile stress acting on the films. Internal stresses in the clear coat and in the base coat of a multilayer structure, which was composed of electrodeposited coat, surface coat, base coat, and clear coat, were estimated from the decay time of fluorescence from P3OT in both coats. The order of internal stresses in the clear coat and base coat of the multilayer system was 1 MPa. When the coatings were piled up, the internal stress decreased as the distance from a metal substrate was increased. It was found that moisture and temperature influenced internal stresses in the clear coat rather than in the base coat. Internal stress in the clear coat, which was one layer coated on a metal substrate, was measured by the traditional bimetallic method or by the time resolved fluorescence technique. Comparing both methods, it was concluded that the time resolved fluorescence technique gave reliable values for internal stresses in coatings. 相似文献
62.
The adsorption properties of oxygen and methane on Ga-ZSM-5 and Cu-ZSM-5 catalysts were examined by a TPD method to clarify the extraordinary selectivity of HC-SCR using methane on Ga-ZSM-5. It was observed that Ga-ZSM-5 did not adsorb oxygen but adsorbed methane dissociatively, while on Cu-ZSM-5 oxygen was dissociatively adsorbed and reacted with adsorbed ethylene. 相似文献
63.
Takeshi Yagi Kazuo Shinozaki Nobuo Ishizawa Nobuyasu Mizutani Masanori Kato Akihiko Tsuge 《Journal of the American Ceramic Society》1988,71(7):334-C
The thermal diffusivity of AlN ceramics was significantly decreased by the addition of SiO2 . The AlN ceramics with 4 wt% SiO2 could not be densified by pressureless sintering in the temperature range 1400° to 1800°C. The thermal diffusivity of these samples was very low because of their porous structure. The AlN ceramics containing 2, 4, and 8 wt% SiO2 were densified by hot-pressing and also had low thermal diffusivity. In these samples, the grains of the 27R polytype that resulted from the reaction between AlN and SiO2 were dispersed, obstructing the conduction of heat. The relation between the amount of 27R polytype and the thermal diffusivity of the AlN ceramics was determined. 相似文献
64.
A physicochemical parameter, represented by the symbol Σs*, based on molar solubility in water and molar attraction constants of Small, has been developed to express quantitatively the relative hydrophobicity, or nonpolar character, of the hydrocarbon molecule. The value of Σs* can be calculated for a hydrocarbon from its chemical structure. The scale of Σs* is consistent within each group of aromatic, cyclic, and noncyclic hydrocarbons. Reverse osmosis data have been obtained at 250 psig for single-solute aqueous feed solution systems involving low concentrations of 39 different hydrocarbons (including 13 aromatics, 10 cyclic, and 16 noncyclic compounds) and several samples of cellulose acetate membranes of different surface porosities. The effect of operating pressure on membrane performance has also been studied for two aromatic hydrocarbon solutes. The values of Σs* for the solutes used were in the range of 425 to 924 for aromatic hydrocarbons, 521 to 931 for cyclic hydrocarbons, and 369 to 960 for noncyclic hydrocarbons. The reverse osmosis data have been correlated with Σs* for each group of hydrocarbons studied. In all cases, positive solute separations were obtained, and the ratio [PR]/[PWP] was less than 1. With respect to each film, solute separation increased with increase in Σs*, and decreased with increase in operating pressure. Also, solute separation decreased in the order aromatic hydrocarbon > cyclic hydrocarbon > noncyclic hydrocarbon at any given value of Σs*. At a given operating pressure, for low values of Σs* (~500 or less) solute separation increased with progressive decrease in average pore size on the membrane surface. For high values of Σs* (~800 or more), solute separation initially increased with decrease in average pore size, then passed through a maximum and minimum with further decrease in average pore size, and again increased with still further decrease in average pore size. The results are discussed on the basis of preferential sorption of solute at the membrane–solution interface under the experimental conditions studied. 相似文献
65.
Reverse osmosis separations of eight polyethylene glycol (PEG) solutes in the average molecular weight range of 200 to 6750 in single-solute dilute aqueous solutions have been studied using porous cellulose acetate membranes at the operating pressures of 50, 75, and 100 psig. Diffusivity data for the above PEG solutes have also been obtained from experimental data on intrinsic viscosities. From an analysis of all experimental data, numerical values for the parameters representing the polar (?ΔΔG/RT), steric (δ*ΣEs), and nonpolar (ω*Σs*) forces governing reverse osmosis separations of PEG solutes have been generated. These numerical values are useful for precise characterization of cellulose acetate membranes for whose specifications sodium chloride is not the appropriate reference solute because of its low or practically negligible separation under reverse osmosis operating conditions. This work also illustrates that solute separation in reverse osmosis can predictably increase or decrease with increase in operating pressure depending on experimental conditions. 相似文献
66.
Amorphous anodic titania, stabilised by incorporation of silicon species, is shown to grow to high voltages on sputter-deposited, single-phase Ti-Si alloys during anodizing at a constant current density in ammonium pentaborate electrolyte. The films comprise two main layers, with silicon species confined to the inner layers. An amorphous-to-crystalline transition occurs at ∼60 V on the Ti-6 at.% Si alloy, while the transition is suppressed to voltages above 140 V on alloys with 12 and 26 at.% silicon. The crystalline oxide, nucleated at a depth of ∼40% of the film thickness, is associated with the presence of a precursor of crystalline oxide in the pre-existing air-formed oxide. The modified structure of the air-formed oxide due to increased incorporation of silicon species suppresses the amorphous-to-crystalline transition until the onset of dielectric breakdown. The transport numbers of cations and anions during growth of the anodic oxides are independent of the concentration of silicon species in the inner layer, despite the marked change in the field strength. 相似文献
67.
68.
Cationic chitosan (CT) and anionic dextran sulfate (Dex) were layer-by-layer (LbL) assembled from aqueous solutions containing
1 M NaCl on a quartz crystal microbalance (QCM) substrate, and the original films ((CT-Dex)3-CT)) were end-capped with LbL assembly from CT solutions containing 1 M NaCl and Dex solutions without NaCl. The enzymatic
degradation of films by chitosanase was quantitatively analyzed by QCM in terms of numbers of end-capping steps. The degradation
of films end-capped with (Dex-CT)3 was considerably prolonged when compared to those end-capped with other end-capping steps. A mechanism for the prolonged
degradation was proposed by quantitative QCM data and zeta potential results. 相似文献
69.
In order to improve the fracture properties of p, p′-diaminodiphenylmethane-cured epoxy resin, various kinds of aromatic and aliphatic glycidyl compounds were investigated as a modifier at an amount of 30 wt %. Several compounds promoted the fracture toughness. In any glycidyl compounds, however, heat resistance was decreased by the modification. The dynamic mechanical properties of the modified epoxy resins were measured. The crosslinking density ρ was calculated from the theory of rubber elasticity, and the mechanical properties of the resins were discussed in regard to the crosslinking density. Tensile strength was scarcely affected by the crosslinking density. Elongation at break and Izod impact strength increased remarkably with decrease in crosslinking density. The fracture toughness KIc- increased with decrease in crosslinking density except at small ρ. 相似文献
70.
Summary Multi-step precipitation separation system was developed by using aqueous mixtures of some thermosensitive polymers. The following
three polymers were used here; poly(N-n-propylacrylamide), poly(N-isopropylacrylamide), and poly(N-isopropylmethacrylamide). A mixture of the three polymers showed three endothermic peaks, and the peak top temperatures were
almost consistent with that of the each polymer solution. The polymers were purified by thermal precipitation to obtain fractions
which can respond in narrow temperature ranges prior to use. In the case of the precipitation separation of two polymers mixtures,
purities of the obtained precipitate and supernatant fractions became high comparing with the case in which the unpurified
polymers were used. Parts of the polymers which were not the precipitation targets were also precipitated by the separation
procedures. This was caused not only by insolubilization of the non-targeted polymers due to their phase transitions but also
by their non-specific entanglement with the targeted polymers. The purities of the fractions also improved when the difference
of the phase transition temperature between two polymers was large enough to avoid the coprecipitation. In the case of the
precipitation separation of mixtures of the three polymers, purities of each fraction also improved when the purified polymers
were used. 相似文献