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21.
《Cement and Concrete Composites》2000,22(1):17-27
Infrastructures in Japan suffered severe damage in the Hyogoken–Nambu earthquake that occurred on 17 January 1995. The expressway bridges operated by Japan Highway Public Corporation (JH) also had serious damage. According to the lessons from experience of the earthquake, JH has been constructing highway networks having higher seismic reliability as an emergency transporting lifeline, and has been urgently implementing seismic retrofit work. This paper consists of two chapters. First, the outline of seismic retrofit of reinforced concrete piers is described. Second, the seismic retrofit of high hollow circular reinforced concrete piers having cut-off of longitudinal reinforcement and changed wall thickness along the height with carbon fiber sheets is indicated. 相似文献
22.
《Engineering Analysis with Boundary Elements》2005,29(2):161-165
In the present paper, a simple mushy zone model is used to track the moving boundaries in an evaporation problem in which the vapor is removed upon formation. Two main parameters for the mushy zone model are analyzed as well as their effect on the movement of the moving boundaries and the thickness of the mushy zone. A new approximate method is developed for analysis and tracking the moving boundaries appears throughout the process. The proposed method mainly based on applying the boundary integral equation corresponding to each phase in such a way that the associated boundary and initial conditions as well as energy equations at the moving boundaries achieved with minimum error and low number of iterations. The results of the present paper seem to be good because there are neither analytical or numerical solutions available. 相似文献
23.
《Engineering Analysis with Boundary Elements》2001,25(2):141-145
In this paper Poisson's equation in two dimensions is studied and different solutions with a BEM are outlined depending on whether the source function is harmonic or not. When the Laplacian of the source function is zero or a constant, the Galerkin vector and the multiple-reciprocity method are applied. When the Laplacian of the source function is no longer zero, the source function is approximated by Lagrange polynomials. This method is then improved by subtracting a parabola from the source function. 相似文献
24.
《Engineering Analysis with Boundary Elements》2001,25(4-5):363-376
The dynamic responses of fluid-saturated semi-infinite porous continua to transient excitations such as seismic waves or ground vibrations are important in the design of soil-structure systems. Biot's theory of porous media governs the wave propagation in a porous elastic solid infiltrated with fluid. The significant difference to an elastic solid is the appearance of the so-called slow compressional wave. The most powerful methodology to tackle wave propagation in a semi-infinite homogeneous poroelastic domain is the boundary element method (BEM). To model the dynamic behavior of a poroelastic material in the time domain, the time domain fundamental solution is needed. Such solution however does not exist in closed form. The recently developed ‘convolution quadrature method’, proposed by Lubich, utilizes the existing Laplace transformed fundamental solution and makes it possible to work in the time domain. Hence, applying this quadrature formula to the time dependent boundary integral equation, a time-stepping procedure is obtained based only on the Laplace domain fundamental solution and a linear multistep method. Finally, two examples show both the accuracy of the proposed time-stepping procedure and the appearance of the slow compressional wave, additionally to the other waves known from elastodynamics. 相似文献
25.
《Water research》1996,30(3):541-550
The feasibility of using free-settling test for estimating activated sludge floc density was discussed in the present work. Some usually applied models or correlations, such as for the primary particle density, the drag coefficient, the correction factor for advection flow through the floc and the estimation for floc permeability, are examined. The results show that floc permeability depends strongly on the models or parameter sets applied. However, the effective floc density, and also the fractal dimension, is insensitive to the floc permeability estimation, but is strongly dependent on the drag coefficient expression employed. Possible valid experimental range is proposed. 相似文献
26.
《Construction and Building Materials》2000,14(6-7):311-315
A case of of long-term and frequent highway pavement failure induced by poor soil properties, at a locality along the F209 highway at Ado-Ekiti was investigated. Visual observation revealed an extensive pavement failure right down to the subgrade level. Laboratory test results of the disturbed soil samples, collected from the failed sections of the road showed that the natural soil moisture ranged from 2.5% to 8.3%, the liquid limit from 43% to 60.50%, the linear shrinkage from 1 to 10.10 and the specific gravity values from 2.57 to 2.67. X-Ray diffraction analysis confirmed the presence of abundant kaolinite and illite in the soil sample. A CBR value of 20% indicated a strong reduction in the strength of the soil materials used in the construction of the road. Excess fines and very high liquid limit values combined with a very low CBR value to instigate the failure of the pavement at this locality. The geotechnical properties indicated substandard paving properties for Nigerian roads. Therefore, some method of soil improvement, such as soil stabilisation is required to improve the strength of the soil and prolong the useful life and durability of the road. 相似文献
27.
《Acta Metallurgica》1983,31(11):1849-1860
We study the segregation process in quenched binary alloys by analyzing and comparing the time evolution of the structure function and of the grain distribution obtained from computer simulations on a model system. We find good agreement between cluster sizes and densities determined directly on the computer sample and ones obtained by the Guinier method from the structure function. We then describe a graphical method for determining the scaling behaviour of the structure function S(k, t) which gives good statistics because the whole curve S(k, t) vs k is used. This yields very good agreement between the scaling function (scaled with the Guinier radius) obtained from the computer simulations and from a variety of real experiments. This function shows a universal behaviour independent of the alloy composition, the temperature and even the substance investigated. Our results are also not consistent with the more recent theoretical work (Binder et al., Furukawa et al.) which give alternate derivations and extensions of the Guinier formulas. 相似文献
28.
《International Journal of Impact Engineering》2002,27(2):161-177
An analysis of the spall bar test as a reliable method of determining the dynamic tensile strength of brittle materials is presented. The method is based on the propagation and reflection of elastic waves in bars. Failure occurs when compressive waves are reflected into tensile ones on reaching a free end. The study analyses the hypotheses needed to obtain the true tensile strength with this experimental technique, referring to the requirements of the material and of the experimental procedure. The analysis is complemented with numerical simulations of the testing procedure. The correct way to determine the true dynamic tensile strength of ceramic materials is outlined. Finally, the results of tests of some ceramic materials, three different aluminium oxides, an alumina reinforced with zirconia, silicon carbide and boron carbide are presented. 相似文献
29.
《International Journal of Engineering Science》1986,24(5):649-673
The flow of an incompressible, viscous, electrically conducting fluid with a suspension of inert particles over a rotating disk in the presence of a circular magnetic field is investigated. The governing equations of motion are reduced to a set of nonlinear ordinary differential equations by similarity transformations, and solved numerically by using least squares finite element method. The radial velocity of the panicles attains its maximum on the surface of the disk and the particles slip in the tangential direction. The flow boundary layer is thickened and the axial flow field is reduced as a result of the magnetic field. The particle density is maximum near the surface of the disk. 相似文献
30.
利用半直线和全直线上的Legendre有理配置点和相应的微分矩阵,结合矩阵分解方法,建立了一种求解三维无界规则区域问题的快速有理谱配点算法,发展了三维无界区域谱方法的数值求解方法.数值结果显示了方法的有效性和高精度性. 相似文献