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41.
An approach to improve the accuracy of the incremental solutions to a nonlinear problem, through a strategy to control the size of the increment, based on stationary of an argumented energy functional, is presented. The problem of control of an optimum step size in the incremental theory is formulated for a fixed number of increments. The variables in this argumented functional are: (i) the incremental displacement vector, (ii) the scalar parameters
i
which characterize the size of each of the increments, i = 1,..., N, and (iii) a Lagrange multiplier which enforces the constraint that the sum of all the normalized increments, i. e., i is equal to 1. The optimality condition provides us a rigorous approach which gives rise to an iterative procedure because of nonlinearity of the stationary condition. If the number of increments is not prescribed, a noniterative procedure can be obtained, where the incremental sequence is controlled adaptively with less computational effort. The extension of the proposed method to non-selfadjoint problems, where a potential energy function does not exist, is also discussed. Numerical examples demonstrate the remarkable improvement in the accuracy of the solution by optimizing the incremental sequence, as well as the effectiveness of the adaptive control procedure proposed.Paper presented at The 16th International Congress of Theoretical and Applied Mechanics, Lyngby, Denmark, August 19–25, 1984 相似文献
42.
K. Nagaoka Y. Tanaka H. Kubota T. Makita 《International Journal of Thermophysics》1986,7(5):1023-1031
A new generalized correlation is presented for the low-pressure gaseous viscosity of fluorocarbon refrigerants. The following empirical equation is obtained based on the most reliable experimental data for 16 fluorocarbons: $$\eta \xi = \left( {0.5124T_r - 0.0517} \right)^{0.82} Z_c ^{ - 0.81}$$ where η is the viscosity in μPa·s and ξ is the viscosity parameter defined using the critical temperature T c in K, the critical pressure P c in MPa, and the molar mass M in g·mol?1 as follows: $$\xi = T_c ^{1/6} M^{ - 1/2} P_c ^{ - 2/3}$$ The applicable ranges are 0.6<T r<1.8 and 0.253<Z c<0.282. The availability of the correlating equation for both pure fluorocarbons and their mixtures has been investigated based on the experimental data of these authors and those in the literature. It is found that the present correlation is useful for the prediction of the viscosity of pure fluorocarbons and their binary mixtures at atmospheric pressure with mean deviations less than 1.6%. 相似文献
43.
Strengthening mechanisms of nickel-base superalloys have been discussed with the background of the Japanese research and development activities in this field. As candidates for materials of intermediate heat exchangers which will be used for a future programme of nuclear steelmaking systems, two kinds of alloys have successfully been developed in Japan. The designs of these alloys have been reviewed from metallurgical aspects including their composition and creep properties. In addition to the conventional methods to strengthen these alloys, such as solid solution hardening or particle precipitation hardening, a grain-boundary precipitation strengthening due to tungsten-rich 2 phase in the Ni-Cr-W system, would be expected as a further advanced method. 相似文献
44.
Using a Debye function analysis, the presence of icosahedral and face centered cuboctahedral gold in a 1 1 ratio has been found in freshly prepared Au/Mg(OH)2 catalyst. The results support earlier studies which suggest the icosahedral form to be more stable at small nanometer sizes. Interactions between the gold and the Mg(OH)2 support appear to be weak, with the gold rapidly coagulating over a period of three months. Re-analysis of the aged sample shows the gold to be mainly in the form of truncated decahedra. 相似文献
45.
高速气流冲击式粉体表面改性装置——HYBRIDIZATION系统及应用 总被引:4,自引:0,他引:4
利用高速气流冲击法进行粉体/粉体系表面改性技术,是迄今为止各种粉体材料开发中最为引人注目的技术之一。HYBRIDIZATION(下称HYB)系统是利用高速气流冲击法对微粉体进行干式/机械化处理,是使材料复合化的最实用的装置,可对各类有机物、无机物、金属等进行广泛组合,通用性很强,适用于许多行业领域。从本文所述的系统构成、型式,有关的典型球形化处理的运转特性,利用复合化高温粉体测定被处理粉体表面温度,利用颜料改变色调等的处理特点及该系统的适用性等(一部分是从已发表的学术论文及专利上摘录的),可以说明HYB系统的概况。 相似文献
46.
47.
Masahiro Tatsumisago Tsutomu Minami Masami Tanaka 《Journal of the American Ceramic Society》1981,64(7):97-C-
A new technique combining a thermal-image furnace and a twin roller is described for quenching the melt to form glass. The technique was applied to the simple system Li2 O-SiO2 , since its fundamental parameters in the estimation of critical cooling rate are available. Glass flakes were obtained in the composition Li4 SiO4 , for which a very large critical cooling rate (∼109 K·s−1 ) was needed for glass formation. 相似文献
48.
Polytetramethylene glycol (molecular weight range 1000–8000) was prepared by the polymerization of tetrahydrofuran (THF) using a binary catalyst system of fuming sulfuric acid and perchloric acid. When 28% fuming sulfuric acid alone was used as the catalyst, the average molecular weight of polymer was low, the maximum value being 1000–1100. By the combination of fuming sulfuric acid with a small amount of perchloric acid, the average molecular weight of the polymer was increased to about 8000. Furthermore, the molecular weight was readily controlled in the range of 1000 to 8000 by varying the amount of the binary catalyst. 相似文献
49.
A computerized thermodynamics-oriented procedure for reaction system synthesis is proposed. First, hierarchy structure of chemical reactions is discussed and the reaction system is categorized into three types; (1) combination with a heat source or sink, (2) combination with a reaction donor, and (3) decomposition of target reaction into subtargets. Then, the algorithm to find subtarget reactions and/or donor reactions is presented. 相似文献
50.
The minimum sequence lengths (nc) of vinyl acetate (VAc) units necessary to form a colored iodine complex were determined to be 4 and 17 for radically polymerized VAc/vinyl propionate (VPr) and VAc/isopropenyl acetate (IPAc) copolymers, respectively. The iodine affinities (I/VAc) of VAc/VPr copolymers (SP-series) obtained by propionylation of partially saponified polyvinyl acetate (PVAc) were remarkably affected by the saponification conditions. An increase of the water content in acetone/water mixture as saponification solvent brought about a decrease of the iodine affinities of the SP-series. The dependence of the iodine affinity on the saponification of monomer units in the SP-series was compared with that in the radically polymerized VAc/VPr copolymers by taking the sequence probability as the measure of monomer unit distribution. The results strongly supported an occurence of the slide fastener reaction at high degrees of saponification, which was well-known in the saponification of PVAc. Furthermore, it was found that the saponification mode of PVAc at low degrees of saponification was influenced uniquely by the water content in saponification solvents and the saponification temperature. 相似文献