全文获取类型
收费全文 | 17382篇 |
免费 | 1904篇 |
国内免费 | 1130篇 |
专业分类
电工技术 | 570篇 |
综合类 | 1545篇 |
化学工业 | 3739篇 |
金属工艺 | 786篇 |
机械仪表 | 2036篇 |
建筑科学 | 860篇 |
矿业工程 | 394篇 |
能源动力 | 1064篇 |
轻工业 | 452篇 |
水利工程 | 413篇 |
石油天然气 | 498篇 |
武器工业 | 560篇 |
无线电 | 591篇 |
一般工业技术 | 3031篇 |
冶金工业 | 642篇 |
原子能技术 | 323篇 |
自动化技术 | 2912篇 |
出版年
2024年 | 107篇 |
2023年 | 405篇 |
2022年 | 717篇 |
2021年 | 819篇 |
2020年 | 741篇 |
2019年 | 652篇 |
2018年 | 566篇 |
2017年 | 727篇 |
2016年 | 762篇 |
2015年 | 756篇 |
2014年 | 1060篇 |
2013年 | 1239篇 |
2012年 | 1092篇 |
2011年 | 1347篇 |
2010年 | 820篇 |
2009年 | 986篇 |
2008年 | 912篇 |
2007年 | 1060篇 |
2006年 | 919篇 |
2005年 | 721篇 |
2004年 | 638篇 |
2003年 | 540篇 |
2002年 | 430篇 |
2001年 | 385篇 |
2000年 | 314篇 |
1999年 | 296篇 |
1998年 | 232篇 |
1997年 | 200篇 |
1996年 | 159篇 |
1995年 | 144篇 |
1994年 | 103篇 |
1993年 | 102篇 |
1992年 | 75篇 |
1991年 | 72篇 |
1990年 | 53篇 |
1989年 | 77篇 |
1988年 | 46篇 |
1987年 | 26篇 |
1986年 | 17篇 |
1985年 | 12篇 |
1984年 | 20篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1959年 | 8篇 |
1957年 | 2篇 |
1956年 | 2篇 |
1955年 | 5篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Ramon R. Costa Liu Hsu 《International Journal of Adaptive Control and Signal Processing》1992,6(1):19-33
A variable structure model reference adaptive controller (VS-MRAC) using only input and output measurements was recently proposed and shown to be globally asymptotically stable with superior transient behaviour and disturbance rejection properties. In this paper a singular perturbation approach is used in order to establish the robustness of the controller in the presence of unmodelled dynamics (parasitics) and disturbances. We develop a new Lyapunov-based technique to analyse the overall system and show that for sufficiently small parasitics the system remains stable and the output error is small in some sense. 相似文献
22.
23.
利用短周期地脉动推断深层地基S波速度 总被引:3,自引:0,他引:3
从二维随机波场的相关理论出发,提出了如何从短周期地脉动(频率>0.5Hz)时域信号中计算Rayleigh波弥散曲线,进而反演深层地基剪切波(S波)速度的理论方法和分析技术,并结合实测信号的分析结果,探讨了该方法的可行性和实用性。 相似文献
24.
研究了非晶Sm5Fe74.3Nb1.5Si11.7B4.5C2.5Cu0.5合金经400℃,保温10min预退火后的晶化动力学。结果表明;该合金的晶化相为α-Fe固溶体和Sm2Fe17Cx金属间化合物,两相的晶化表观激活能分别为557KJ/mol和514KJ/mol,当晶化体积分数为60%时,α-Fe相的晶化激活能达极大值;Sm2Fe17Cx相晶化激活能则随其晶化体积分数的增加而逐渐减小。 相似文献
25.
Analytical solution for the axisymmetric plane strain electroelastic dynamics of a special non-homogeneous piezoelectric hollow cylinder 总被引:1,自引:0,他引:1
By virtue of the introduction of a dependent variable and the separation of variables technique, the axisymmetric plane strain electroelastic dynamic problem of a special non-homogeneous piezoelectric hollow cylinder is transformed to a Volterra integral equation of the second kind about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solutions of displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow cylinder with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are finally presented. 相似文献
26.
Molecular dynamics simulation using a universal force field has been employed to determine the diffusion coefficients of O2 and Na2SO4 vapor into B2O3 and SiC from 700 K to 1273 K, respectively. Einstein diffusion was observed in a 250~300 ps simulation. 相似文献
27.
T. A. G. Langrish 《Drying Technology》2002,20(9):1789-1802
Progress in modelling air flow patterns in timber kilns using Computational Fluid Dynamics is reviewed in this work. These simulations are intended to predict the distribution of the flow in the fillet spaces between boards in a hydraulic model of a timber kiln. Here, the flow regime between the boards is transitional between laminar and turbulent flow, with Reynolds numbers of the order of 5000. Running the simulation as a transient calculation has shown few problems with convergence issues, reaching a mass residual of 0.2% of the total inflow after 40-100 iterations per time step for time steps of 0.01 s. Grid sensitivity studies have shown that non-uniform grids are necessary because of the sudden changes in flow cross section, and the flow simulations are insensitive to grid refinement for non-uniform grids with more than 300,000 cells. The best agreement between the experimentally-measured flow distributions between fillet spaces and those predicted by the simulation have been achieved for (effective) bulk viscosities between the laminar viscosity for water and ten times that value. This change in viscosity is not very large (less than an order of magnitude), given that effective turbulent viscosities are typically several orders of magnitude greater than laminar ones. This result is consistent with the transitional flows here. 相似文献
28.
We look at the task of computing the time-evolution of a non-linear system for a long time, in our case under random external
influences. Our specific example is the fatigue evaluation of a wind turbine. To facilitate such a computation, we look at
a reduction of the computational effort by projecting everything on a low-dimensional basis. In this case we take the Karhunen-Loève
basis generated from running the model a little while under the random loading. It is important that the error which is caused
by this reduction process can be controlled. We estimate the error by dual or adjoint methods. This in turn allows the process
of model reduction to be performed adaptively.
Dedicated to the memory of Prof. Mike Crisfield, for his cheerfulness and cooperation as a colleague and friend over many
years. 相似文献
29.
Liaqat A. Khan Edward A. Wicklein E. C. Teixeira 《Canadian Metallurgical Quarterly》2006,132(7):741-746
A three-dimensional (3D) computational fluid dynamics (CFD) model of a contact tank is presented in this paper. The model results are compared against 3D velocities and flow through curve (FTC) data, representing a tracer concentration profile, from a 1:8 scale physical model. The objective is to demonstrate that CFD models can simulate both the FTC and the 3D velocity field quite well. Simultaneous validation of velocities and FTC is important in ascertaining the predictive capabilities of CFD models, as physical model studies indicate that different baffle arrangements can lead to similar FTCs. Therefore, a good prediction of only FTC, as presented in previous 3D CFD model studies, does not necessarily imply a correct simulation of the flow field. 相似文献
30.
In this response to Jeffrey Stern's (2004) (see record 2004-21113-016) commentary on my article, "Giving the Devil His Due: Spite and the Struggle for Individual Dignity" (P. Shabad, 2000) (see record 2000-00917-004), I suggest that in emphasizing the conscious vindictiveness of explicit spite, Stern minimizes the perverse aspects of "cutting off one's nose to spite one's face" as a means of avenging oneself against powerful others. The underlying impetus of perverse spite is to break free from the prison of subtle developmental contingencies and unconscious seductions surrounding maternal possessiveness. When the child's self-assertive strivings are blocked because of the shame and fear of premature separateness, the inward obsessional churning of resentment becomes a fertile ground for perverse spite. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献