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1.
Phase transformations in particles of ultrafine powders of graphite, hexagonal boron nitride, and quartz during rapid heating and cooling by passage through a laser beam were investigated. A continuous infrared laser with a wavelength of 10.6 μm was used as a heat source through which the powders were recycled several times. Methods of concentrating the product phases are described. Particles of diamond, carbides, cubic boron nitride, koesite and stishovite were obtained in the mixed products. 相似文献
2.
Published data on the preparation procedures, stability, and complexation of U(III) in aqueous solutions are summarized and correlated. Reactions with inorganic and organic free radicals studied by the flash radiolysis method, the spectroscopic properties, the extraction and ion-exchange behavior of U(III), and methods for isolation of solid U(III) compounds from aqueous solutions are discussed. 相似文献
3.
N. E. Shchepina V. V. Avrorin G. A. Badun V. M. Fedoseev S. E. Ukhanov S. B. Lewis 《Radiochemistry》2007,49(6):630-632
Ion-molecule reactions of free phenyl cations with six-membered nitrogen-containing heterocyclic compounds: α-, β-, and γ-picolines, were studied. Phenyl cations were generated by tritium β-decay in double-labeled benzene. The mechanism of competing reactions of electrophilic addition to the nitrogen heteroatom in the ring and electrophilic substitution of the C-H bond in the pyridine ring was examined. The effect of methyl substituent in the pyridine molecule on the reaction pathway was evaluated. A one-step procedure for nuclear-chemical synthesis of tritium-labeled N-phenylpicolinium salts and phenyl-substituted picolines was developed. 相似文献
4.
Behavior of hydrated 238-242Pu(IV) oxide in 0.09-0.9 M NaOH containing 1 ×10-
3 M Na2SiO3 and in 0.1-0.2 M NaClO4 containing 1×10-
3-0.09 M Na2SiO3 (pH 11 and 9) was studied radiometrically with the aid of a scintillation counter. In alkaline solutions with pH 13.8-11 and high Na2SiO3 content, the Pu(IV) solubility increases owing to the reaction Pu(IV) + nSiO3
2
- = PuI
V(SiO3
2
-)
n
. At pH 9, Na2SiO3 has virtually no effect on the Pu(IV) solubility. 相似文献
5.
V. M. Vodolazkin V. A. Sorokin Yu. G. Fedoseev 《Soil Mechanics and Foundation Engineering》1989,26(5):207-209
Conclusions Frozen clayey soils of semi-hard and hard consistency and sandy soils of medium density have a structural strength equal to the value of the actual pressure under complete saturation, and, consequently, the suspending effect of water, and their deformation is determined by the presence of ice striations and the extent to which the macropores that form after their complete thawing are interconnected.
From The Editorial Office: Problems that are extremely interesting from the scientific and practical standpoint are touched upon in the paper. The authors, however, do not always adequately substantiate their own assumptions. Making note of the influence exerted by the suspending action of water on the settlement of frozen soils, the authors fail to cite data on comparison of the results of settlement computation with allowance for and with disregard of the suspending effect of water and actual settlement; this would impart greater persuasiveness to their assumptions. The authors' conclusions on the structural strength of soils are also insufficiently founded — neither physicomechanical characteristics of the soils under consideration nor geologic sections are cited, and there is no comparison made between computed and actual settlements.By publishing the paper "in order of discussion," therefore, the editorial office hopes that other specialists will participate in the solution of these critical problems.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 17–18, September–October, 1989. 相似文献
6.
A new integrated method is described for measuring the transverse diffusion and thermal conductivity coefficients of a parallel turbulent liquid stream. The method differs from other methods in a number of ways: the location of the temperature or impurity-concentration sensors outside and not inside the medium under study; simplicity of implementation; speed of measurements; and applicability to finely divided porous media as well as to large bundles of tubes, lattices, and charges, and to free turbulent streams. On the basis of experimental data we establish a limiting law of mixing of a liquid in porous media and the previously known interrelation of turbulent diffusion and thermal conductivity with the hydraulic resistance of the porous medium.Translated from Izmeritel'naya Tekhnika, No. 7, pp. 51–53, July, 1994. 相似文献
7.
The stability of Np(VI) in 5–200 mM iminodiacetic acid (H2IDA) solutions at 23.5–55°С was studied by spectrophotometry. In a solution with pH 2 and excess Np(VI), 1 mol of H2IDA reduces 2 mol of Np(VI) to Np(V). In 1 and 0.5 M HClO4 solutions containing 200 mM H2IDA and 1 mM Np(VI), no more than 36 and 65% of Np(VI), respectively, is reduced at 44.5°С. Complete reduction of Np(VI) is observed in solutions containing 0.2 M HClO4 and less. In the examined ranges of H2IDA concentrations and temperatures, Np(VI) is consumed in accordance with the first-order rate law. The reduction mechanism involves formation of a Np(VI) iminodiacetate complex, which is followed by intramolecular charge transfer. The generated radical reduces Np(VI). The activation energy is 107 ± 3 kJ mol–1. 相似文献
8.
A. G. Cherniavsky V. I. Gulyayev V. V. Gaidaichuk A. I. Fedoseev 《Canadian Metallurgical Quarterly》2005,18(3):139-145
This paper describes large space antenna projects based on application of a closed polygonal pantograph truss used for transforming, deploying, and prestressing the reflector structure. Their reflecting surfaces represent a flexible mesh fabric. Two means of maintaining the surface are discussed herein. The first technique is associated with employment of forces of the gravity field gradient. The second is based on the use of a flexible carcass prestressed by internal forces applied to the pantograph. Reflectors of the second kind have a rather complicated mechanical structure depending on the way of their attachment to a carrier. Provisions are made for supporting the reflector by an articulated arm linked with its central interface and through the use of tube beams, supporting the reflector periphery structures. During the design of the reflectors, special attention was paid to the problems of their structural simulations at the stages of their launching, deployment, and orbital motion. The deployable antennas considered can be enabling elements for many space missions ranging from communications to other satellite systems, including radar, remote sensing, interferometry, wireless power transmission, etc. They exhibit an enhanced stiffness of structure, required for the digit tele- and radio-communication and navigation, which makes it possible to diminish ray scattering, to raise the power of the accepted signals, and to prevent frequency losses. 相似文献
9.
Zlotnikov A. O. Shustin M. S. Fedoseev A. D. 《Journal of Superconductivity and Novel Magnetism》2021,34(12):3053-3088
Journal of Superconductivity and Novel Magnetism - The review is aimed at highlighting the aspects of topological superconductivity in the absence of spin–orbit interaction in two-dimensional... 相似文献
10.
Oxidation of Np(IV) with hydrogen peroxide in NaHCO3-Na2CO3 solutions was studied by spectrophotometry. In NaHCO3 solution, Np(IV) is oxidized to Np(V) and partially to Np(VI). It follows from the electronic absorption spectra that Np(IV) in 1 M Na2CO3 forms with H2O2 a mixed peroxide-carbonate complex. Its stability constant β is estimated at 25–30. The Np(IV) bound in the mixed complex disappears in a first-order reaction with respect to [Np(IV)]. The first-order rate constant k’ is proportional to [H2O2] in the H2O2 concentration range 2.5–11 mM, but further increase in [H2O2] leads to a decrease in k′. The bimolecular rate constant k = k′/[H2O2] in solutions containing up to 11 mM H2O2 increases in going from 1 M NaHCO3 to 1 M Na2CO3 and significantly decreases with a further increase in the carbonate content. The activated complex is formed from Np(IV) peroxide-carbonate and carbonate complexes. Synchronous or successive electron transfer leads to the oxidation of Np(IV) to Np(V). Large excess of H2O2 oxidizes Np(V) to Np(VI), which is then slowly reduced. As a result, Np(V) is formed in carbonate solutions at any Np(IV) and H2O2 concentrations. 相似文献