全文获取类型
收费全文 | 159883篇 |
免费 | 20578篇 |
国内免费 | 14168篇 |
专业分类
电工技术 | 20158篇 |
技术理论 | 12篇 |
综合类 | 18039篇 |
化学工业 | 13009篇 |
金属工艺 | 4093篇 |
机械仪表 | 9585篇 |
建筑科学 | 7918篇 |
矿业工程 | 4323篇 |
能源动力 | 7404篇 |
轻工业 | 2826篇 |
水利工程 | 7423篇 |
石油天然气 | 5850篇 |
武器工业 | 1607篇 |
无线电 | 22591篇 |
一般工业技术 | 9845篇 |
冶金工业 | 5197篇 |
原子能技术 | 1671篇 |
自动化技术 | 53078篇 |
出版年
2024年 | 1106篇 |
2023年 | 3001篇 |
2022年 | 5615篇 |
2021年 | 6264篇 |
2020年 | 6482篇 |
2019年 | 4978篇 |
2018年 | 4328篇 |
2017年 | 5224篇 |
2016年 | 5658篇 |
2015年 | 6200篇 |
2014年 | 10189篇 |
2013年 | 9951篇 |
2012年 | 11691篇 |
2011年 | 12366篇 |
2010年 | 9327篇 |
2009年 | 10066篇 |
2008年 | 10134篇 |
2007年 | 11400篇 |
2006年 | 9938篇 |
2005年 | 8899篇 |
2004年 | 7339篇 |
2003年 | 6543篇 |
2002年 | 5172篇 |
2001年 | 4438篇 |
2000年 | 3656篇 |
1999年 | 3031篇 |
1998年 | 2283篇 |
1997年 | 1879篇 |
1996年 | 1622篇 |
1995年 | 1331篇 |
1994年 | 1077篇 |
1993年 | 785篇 |
1992年 | 594篇 |
1991年 | 406篇 |
1990年 | 379篇 |
1989年 | 318篇 |
1988年 | 222篇 |
1987年 | 137篇 |
1986年 | 106篇 |
1985年 | 74篇 |
1984年 | 73篇 |
1983年 | 58篇 |
1982年 | 51篇 |
1981年 | 28篇 |
1980年 | 17篇 |
1979年 | 31篇 |
1975年 | 11篇 |
1963年 | 9篇 |
1959年 | 32篇 |
1951年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
J. L. Barron R. E. Mercer X. Chen P. Joe 《International journal of imaging systems and technology》2005,15(3):189-198
We present local least squares and regularization frameworks for computing 3D velocity (3D optical flow) from 3D radial velocity measured by a Doppler radar. We demonstrate the performance of our algorithms quantitatively on synthetic radial velocity data and qualitatively on real radial velocity data, obtained from the Doppler radar at Kurnell Radar station, Botany Bay, New South Wales, Australia. Radial velocity can be used to predict the future positions of storms in sequences of Doppler radar datasets.© 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 189–198, 2005 相似文献
112.
Average consensus in networks of dynamic agents with switching topologies and multiple time-varying delays 总被引:5,自引:0,他引:5
In this paper, we discuss average consensus problem in undirected networks of dynamic agents with fixed and switching topologies as well as multiple time-varying communication delays. By employing a linear matrix inequality method, we prove that all the nodes in the network achieve average consensus asymptotically for appropriate communication delays if the network topology is connected. Particularly, several feasible linear matrix inequalities are established to determine the maximal allowable upper bound of time-varying communication delays. Numerical examples are given to demonstrate the effectiveness and the sharpness of the theoretical results. 相似文献
113.
114.
Simonetta Balsamo Vittoria De Nitto Person Paola Inverardi 《Performance Evaluation》2003,51(2-4):269-288
A review is carried out on how queueing network models with blocking have been applied so far into the performance evaluation and prediction of Software Architectures (SA). Queueing network models with finite capacity queues and blocking have recently been introduced and applied as more realistic models of systems with finite capacity resources and population constraints. Queueing network models have been often adopted as models for the evaluation of software performance. Starting from our own experience, we observe the need of a more accurate definition of the performance models of SA to capture some features of the communication systems. We consider queueing networks with finite capacity and blocking after service (BAS) to represent some synchronization constraints that cannot be easily modeled with queueing network models with infinite capacity queues. We investigate the use of queueing networks with blocking as performance models of SA with concurrent components and synchronous communication. Queueing theoretic analysis is used to solve the queueing network model and study the synchronous communication and performance of concurrent software components. Our experience is supported by other approaches that also propose the use of queueing networks with blocking. Directions for future research work in the field are included. 相似文献
115.
介绍了一种基于人工神经网络(ANN)的声目标识别系统,概述了用MATLAB专用工具箱对神经网络权值进行训练及仿真的过程,叙述了ANN目标识别系统的数字信号处理器(DSP)实时实现过程,并着重分析定点实现过程中程序变量的定标、非线性运算的实现、溢出的处理等关键步骤.对不同字长的识别结果进行比较表明,基于定点实时实现的系统数据保持很高的精度,可以得到与浮点处理相同的识别率. 相似文献
116.
117.
In the present study a continuum model for one-dimensional plane Couette-Poiseuille flow is implemented to turbomolecular pumps in different flow regimes. Pumping performance of various turbomolecular pumps including 6 single rotors, a rotor-stator row, a rotor-stator-rotor row, and a multi-row with 13 alternative rotor-stator rows is considered here. The obtained results show that the model provides good quantitative values for pumping performance of turbomolecular pumps over the whole regimes ranging from molecular flow to transition to slip flow. 相似文献
118.
119.
Chouping Luo Marek Klisinski 《International journal for numerical methods in engineering》2004,61(2):159-188
The present study is a continuation of our previous work with the aim to reduce problems caused by standard higher order elements in contact problems. The difficulties can be attributed to the inherent property of the Galerkin method which gives uneven distributions of nodal forces resulting in oscillating contact pressures. The proposed remedy is use of piece‐wise linear weight functions. The methods to establish stiffness and/or mass matrix for 8‐node quadrilateral element in 2D are presented, i.e. the condensing and direct procedures. The energy and nodal displacement error norms are also checked to establish the convergence ratio. Interpretation of calculated contact pressures is discussed. Two new 2D 8‐node quadrilateral elements, QUAD8C and QUAD8D, are derived and tested in many examples, which show their good performance in contact problems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
120.
Friendship affects individual and organizational well-being through direct relations, social positions, and complex network structures. In this study, the authors use longitudinal data from 2 groups of master's of business administration students to increase understanding of how friendship networks develop. The authors propose and test a dynamic model in which attribute similarity facilitates dyadic friendship ties, as well as similar network centrality and social position; early friendship increases later similarity in structural position and centrality; and early structural similarity enhances the likelihood of future friendship. Findings largely supported the model, demonstrating how homophily and early social contacts can jointly shape maturing friendship networks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献