全文获取类型
收费全文 | 42010篇 |
免费 | 4960篇 |
国内免费 | 3819篇 |
专业分类
电工技术 | 4369篇 |
技术理论 | 7篇 |
综合类 | 6299篇 |
化学工业 | 1704篇 |
金属工艺 | 695篇 |
机械仪表 | 2355篇 |
建筑科学 | 9060篇 |
矿业工程 | 649篇 |
能源动力 | 671篇 |
轻工业 | 958篇 |
水利工程 | 591篇 |
石油天然气 | 898篇 |
武器工业 | 484篇 |
无线电 | 5190篇 |
一般工业技术 | 3395篇 |
冶金工业 | 508篇 |
原子能技术 | 366篇 |
自动化技术 | 12590篇 |
出版年
2024年 | 162篇 |
2023年 | 499篇 |
2022年 | 914篇 |
2021年 | 1027篇 |
2020年 | 1181篇 |
2019年 | 1097篇 |
2018年 | 1035篇 |
2017年 | 1378篇 |
2016年 | 1569篇 |
2015年 | 1684篇 |
2014年 | 2811篇 |
2013年 | 2913篇 |
2012年 | 3234篇 |
2011年 | 3455篇 |
2010年 | 2882篇 |
2009年 | 2911篇 |
2008年 | 2836篇 |
2007年 | 3118篇 |
2006年 | 2635篇 |
2005年 | 2220篇 |
2004年 | 1820篇 |
2003年 | 1517篇 |
2002年 | 1281篇 |
2001年 | 1100篇 |
2000年 | 1004篇 |
1999年 | 813篇 |
1998年 | 581篇 |
1997年 | 522篇 |
1996年 | 431篇 |
1995年 | 376篇 |
1994年 | 329篇 |
1993年 | 252篇 |
1992年 | 238篇 |
1991年 | 173篇 |
1990年 | 148篇 |
1989年 | 129篇 |
1988年 | 93篇 |
1987年 | 64篇 |
1986年 | 42篇 |
1985年 | 33篇 |
1984年 | 43篇 |
1983年 | 44篇 |
1982年 | 37篇 |
1981年 | 34篇 |
1980年 | 25篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1977年 | 19篇 |
1976年 | 7篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
CAO Wei-feng WANG Wen-boBeijing University of Posts Telecommunications Beijing P.R. China 《中国邮电高校学报(英文版)》2005,12(4)
1IntroductionCurrently,smart antenna technology can greatly en-hance system performance and i mprove the system ca-pacity so that it has been considered as a keytechnologyinthe third generation wireless communicationsystems .The researches on channel model , beamforming algo-rithms and receive algorithms have been widely carriedout and a great many of proposition have beensubmittedtothe 3th Generation Project Partner (3GPP) . Fromthe viewpoint of link-level and system-level research,many asp… 相似文献
72.
Many problems consist in splitting a set of objects into different groups so that each group verifies some properties. In practice, a partitioning is often encoded by an array mapping each object to its group numbering. In fact, the group number of an object does not really matter, and one can simply rename each group to obtain a new encoding. That is what we call the symmetry of the search space in a partitioning problem. This property may be prejudicial for optimization methods such as evolutionary algorithms (EA) which require some diversity during the search. 相似文献
73.
基于MATLAB在化工优化设计中的应用 总被引:2,自引:0,他引:2
结合化工优化计算的实例,着重介绍如何应用MATLAB7.0提供的优化工具箱来对线性规划及非线性规划模型进行求解。 相似文献
74.
In this work, we study dynamic provisioning of multicast sessions in a wavelength-routed sparse splitting capable WDM network
with an arbitrary mesh topology where the network consists of nodes with full, partial, or no wavelength conversion capabilities
and a node can be a tap-and-continue (TaC) node or a splitting and delivery (SaD) node. The objectives are to minimize the
network resources in terms of wavelength-links used by each session and to reduce the multicast session blocking probability.
The problem is to route the multicast session from each source to the members of every multicast session, and to assign an
appropriate wavelength to each link used by the session. We propose an efficient online algorithm for dynamic multicast session
provisioning. To evaluate the proposed algorithm, we apply the integer linear programming (ILP) optimization tool on a per
multicast session basis to solve off-line the optimal routing and wavelength assignment given a multicast session and the
current network topology as well as its residual network resource information. We formulate the per session multicast routing
and wavelength assignment problem as an ILP. With this ILP formulation, the multicast session blocking probability or success
probability can then be estimated based on solving a series of ILPs off-line. We have evaluated the effectiveness of the proposed
online algorithm via simulation in terms of session blocking probability and network resources used by a session. Simulation
results indicate that our proposed computationally efficient online algorithm performs well even when a fraction of the nodes
are SaD nodes. 相似文献
75.
A stochastic realization problem of a stationary stochastic process is re-visited, and a new stochastically balanced realization algorithm is derived in a Hilbert space generated by second-order stationary processes. The present algorithm computes a stochastically balanced realization by means of the singular value decomposition of a weighted block Hankel matrix derived by a “block LQ decomposition”. Extension to a stochastic subspace identification method explains how the proposed abstract algorithm is implemented in system identification. 相似文献
76.
Somsak Vanit-Anunchai Jonathan Billington Guy Edward Gallasch 《International Journal on Software Tools for Technology Transfer (STTT)》2008,10(1):29-56
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration
method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces
the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise
but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially
relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard,
the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we
introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the
peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP
to be analysed for larger parameter values.
Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree
University of Technology.
Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927). 相似文献
77.
78.
79.
Pedro Ribeiro 《International journal for numerical methods in engineering》2004,61(15):2696-2715
A p‐version, hierarchical finite element for curved, moderately thick, elastic and isotropic beams is introduced. The convergence properties of the element are analysed and some results are compared with results published elsewhere or calculated using a commercial finite element package. It is verified that, with the proposed element, shear locking does not affect the computation of the natural frequencies and that low dimensional, accurate models are obtainable. Geometrically non‐linear vibrations due to finite deformations, which occur for harmonic excitations with frequencies close to the first three natural frequencies of vibration, are investigated using Newmark's method. The influence of the thickness, longitudinal inertia and curvature radius on the dynamic behaviour of curved beams are studied. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
80.