全文获取类型
收费全文 | 1535篇 |
免费 | 142篇 |
国内免费 | 109篇 |
专业分类
电工技术 | 151篇 |
综合类 | 123篇 |
化学工业 | 68篇 |
金属工艺 | 320篇 |
机械仪表 | 120篇 |
建筑科学 | 23篇 |
矿业工程 | 13篇 |
能源动力 | 58篇 |
轻工业 | 14篇 |
水利工程 | 55篇 |
石油天然气 | 19篇 |
武器工业 | 15篇 |
无线电 | 178篇 |
一般工业技术 | 171篇 |
冶金工业 | 35篇 |
原子能技术 | 54篇 |
自动化技术 | 369篇 |
出版年
2024年 | 7篇 |
2023年 | 20篇 |
2022年 | 20篇 |
2021年 | 31篇 |
2020年 | 38篇 |
2019年 | 39篇 |
2018年 | 47篇 |
2017年 | 56篇 |
2016年 | 50篇 |
2015年 | 68篇 |
2014年 | 86篇 |
2013年 | 105篇 |
2012年 | 95篇 |
2011年 | 120篇 |
2010年 | 92篇 |
2009年 | 90篇 |
2008年 | 84篇 |
2007年 | 101篇 |
2006年 | 104篇 |
2005年 | 77篇 |
2004年 | 57篇 |
2003年 | 67篇 |
2002年 | 40篇 |
2001年 | 39篇 |
2000年 | 38篇 |
1999年 | 43篇 |
1998年 | 23篇 |
1997年 | 21篇 |
1996年 | 19篇 |
1995年 | 14篇 |
1994年 | 17篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1973年 | 2篇 |
1965年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有1786条查询结果,搜索用时 31 毫秒
1.
River Bifurcation Analysis by Physical and Numerical Modeling 总被引:1,自引:0,他引:1
Gianluca Zanichelli Elpidio Caroni Virgilio Fiorotto 《Canadian Metallurgical Quarterly》2004,130(3):237-242
In the framework of a river regulation design of the Po River Delta (Northern Italy), a study on a large physical model of the bifurcation Po di Goro-Po di Venezia was conducted with the main objective of determining the discharge subdivision rate at the river node, in order to assess the inflow conditions in the Po di Goro River for flood risk analysis. In this context, a two-dimensional depth averaged numerical model was tested against measured values, with reference to the prototype. In this paper a comprehensive analysis and discussion of the results is reported in order to highlight the applicability of numerical models in comparison with physical ones in river engineering applications. 相似文献
2.
CHEN Yong-ping LI Chi-wai ZHANG Chang-kuang 《水动力学研究与进展(B辑)》2006,18(2):148-155
1. INTRODUCTION When wastewater is discharged into rivers, lakes or oceans, it usually leads to the formulation of turbulent jet with a free surface. If the ambient water depth is shallow, the jet will impinge on the water surface and the confinement of f… 相似文献
3.
应用统计控制图法,选用平均值——标准差、平均值——极差控制图法,控制24^#坝粘土填筑干密度值及施工偶然异常波动,早期提出警报,以保证土坝的施工质量。 相似文献
4.
Shu‐Li Sun Jing Ma Nan Lv 《International Journal of Adaptive Control and Signal Processing》2008,22(10):932-948
Based on the optimal fusion estimation algorithm weighted by scalars in the linear minimum variance sense, a distributed optimal fusion Kalman filter weighted by scalars is presented for discrete‐time stochastic singular systems with multiple sensors and correlated noises. A cross‐covariance matrix of filtering errors between any two sensors is derived. When the noise statistical information is unknown, a distributed identification approach is presented based on correlation functions and the weighted average method. Further, a distributed self‐tuning fusion filter is given, which includes two stage fusions where the first‐stage fusion is used to identify the noise covariance and the second‐stage fusion is used to obtain the fusion state filter. A simulation verifies the effectiveness of the proposed algorithm. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
5.
NUMERICAL ANALYSIS AND EXPERI- MENT OF UNSTEADY THERMAL FIELD OF ROTOR PLATE FOR EDDY CURRENT RETARDER 总被引:3,自引:0,他引:3
LIU Chengye HE Ren 《机械工程学报(英文版)》2008,21(4):71-75
The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are also defined. The finite element governing equation is derived by Galerkin method. The time differential item is discrete based on Galerkin format that is stable at any condition. And a new style of varying time step method is used in iteration process. The thermal field on the rotor plate at the radial and axle directions is analyzed and varying temperature at appointed points on two side-surfaces is measured. The testing and analytical data are uniform approximately. Finite element method can be used for estimating thermal field of the rotor plate at initial design stage of eddy current retarder. 相似文献
6.
7.
8.
WU YuWei MA Bo & LI Pei Beijing Laboratory of Intelligent Information Technology 《中国科学:信息科学(英文版)》2012,(11):2635-2645
This paper presents a novel formulation for contour tracking.We model the second-order statistics of image regions and perform covariance matching under the variational level set framework.Specifically,covariance matrix is adopted as a visual object representation for partial differential equation(PDE) based contour tracking.Log-Euclidean calculus is used as a covariance distance metric instead of Euclidean distance which is unsuitable for measuring the similarities between covariance matrices,because the matrices typically lie on a non-Euclidean manifold.A novel image energy functional is formulated by minimizing the distance metric between the candidate object region and a given template,and maximizing the one between the background region and the template.The corresponding gradient flow is then derived according to a variational approach,enabling partial differential equations(PDEs) based contour tracking.Experiments on several challenging sequences prove the validity of the proposed method. 相似文献
9.
传统基于干扰噪声协方差矩阵(interference-plus-noise covariance matrix,INCM)重构的鲁棒自适应波束形成(robust adaptive beamformer,RAB)算法在多种样本数据协方差矩阵误差和信号导向向量误差的失配环境中具有较强的鲁棒性,但目前主流的INCM重构法都是对信号和干扰的导向向量通过建立凸优化模型来估计,这带来了很高的计算复杂度。为了解决这个问题,提出了一种低复杂度的基于INCM重构的RAB算法。该算法首先将干扰信号的导向向量分解为对应标称项和误差项的和,然后通过一种子空间方法估计得到误差项的单位向量。接下来对一个Capon空间谱功率最大问题进行求解,得到误差项的模值,以此得到重构的INCM。同时利用Capon空间谱中残差噪声的存在,使用交替投影法估计得到期望信号的导向向量,最后得到所提算法的权重向量。仿真实验表明所提算法在多种误差环境下具有较强鲁棒性的同时,还具有较低的计算复杂度。 相似文献
10.
对于采用星敏感器的航天器姿态确定问题,提出了一种快速的姿态优化估计方法;首先,根据Rodrigues参数和观测向量之间的线性关系,引入四元数,构造了不同的非奇异的优化准则;其次,借助四元数,求解了基于该准则的姿态优化算法;误差协方差分析和数值仿真结果表明,该算法与著名的QUaternion ESTmation(QUEST)算法相比,在相同的操作系统环境下,具有相同的姿态估计精度,但计算速度更快,对两种算法选取间隔为2000次的仿真步长,统计数据长度为100个采样点,最后对结果加权求平均值,统计结果显示仅为QUEST的三分之一;这种姿态优化估计方法具有一定的工程应用价值。 相似文献