全文获取类型
收费全文 | 117879篇 |
免费 | 10246篇 |
国内免费 | 4968篇 |
专业分类
电工技术 | 7068篇 |
技术理论 | 7篇 |
综合类 | 7599篇 |
化学工业 | 20373篇 |
金属工艺 | 6467篇 |
机械仪表 | 7317篇 |
建筑科学 | 9642篇 |
矿业工程 | 3440篇 |
能源动力 | 3514篇 |
轻工业 | 7672篇 |
水利工程 | 2098篇 |
石油天然气 | 7283篇 |
武器工业 | 877篇 |
无线电 | 13452篇 |
一般工业技术 | 14274篇 |
冶金工业 | 5510篇 |
原子能技术 | 1308篇 |
自动化技术 | 15192篇 |
出版年
2024年 | 551篇 |
2023年 | 2027篇 |
2022年 | 3520篇 |
2021年 | 4845篇 |
2020年 | 3728篇 |
2019年 | 3141篇 |
2018年 | 3382篇 |
2017年 | 3916篇 |
2016年 | 3299篇 |
2015年 | 4687篇 |
2014年 | 5707篇 |
2013年 | 6783篇 |
2012年 | 7428篇 |
2011年 | 7987篇 |
2010年 | 6980篇 |
2009年 | 6650篇 |
2008年 | 6433篇 |
2007年 | 6101篇 |
2006年 | 6351篇 |
2005年 | 5525篇 |
2004年 | 3774篇 |
2003年 | 3288篇 |
2002年 | 3079篇 |
2001年 | 2805篇 |
2000年 | 2952篇 |
1999年 | 3159篇 |
1998年 | 2672篇 |
1997年 | 2274篇 |
1996年 | 2097篇 |
1995年 | 1825篇 |
1994年 | 1473篇 |
1993年 | 1056篇 |
1992年 | 860篇 |
1991年 | 677篇 |
1990年 | 491篇 |
1989年 | 436篇 |
1988年 | 353篇 |
1987年 | 245篇 |
1986年 | 167篇 |
1985年 | 97篇 |
1984年 | 65篇 |
1983年 | 49篇 |
1982年 | 63篇 |
1981年 | 39篇 |
1980年 | 35篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1965年 | 3篇 |
1959年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
首先说明西方国家通信网近年发展变迁情况,然后对IP与WDM的结合使用、光数据网的发展、密集波分多路的应用和光网中通路的保护4个主要方面作了具体说明。 相似文献
242.
A wavelet-based multisensor data fusion algorithm 总被引:7,自引:0,他引:7
Lijun Xu Jian Qiu Zhang Yong Yan 《IEEE transactions on instrumentation and measurement》2004,53(6):1539-1545
This paper presents a wavelet transform-based data fusion algorithm for multisensor systems. With this algorithm, the optimum estimate of a measurand can be obtained in terms of minimum mean square error (MMSE). The variance of the optimum estimate is not only smaller than that of each observation sequence but also smaller than the arithmetic average estimate. To implement this algorithm, the variance of each observation sequence is estimated using the wavelet transform, and the optimum weighting factor to each observation is obtained accordingly. Since the variance of each observation sequence is estimated only from its most recent data of a predetermined length, the algorithm is self-adaptive. This algorithm is applicable to both static and dynamic systems including time-invariant and time-varying processes. The effectiveness of the algorithm is demonstrated using a piecewise-smooth signal and an actual time-varying flow signal. 相似文献
243.
244.
In this paper, we present a static load balancing method for mapping production rules in an expert system onto processors of a message-passing multicomputer. The method uses simulated annealing to achieve a nearly optimal allocation of production rules onto processor nodes. The approach balances the initial rule distribution to avoid higher communication demand among processor nodes at run time. A formal mapping model is developed and a new cost function is defined for the annealing process. New heuristic swap functions and cooling policies are provided to ensure the quality of the annealing process. A software load balancing package, SIMAL, was implemented on a SUN workstation to carry out the benchmark experiments. The overhead associated with this mapping method is O(m In m), where m is the number of rules in the production system. Two benchmark production systems, Toru-waltz and Tourney, are mapped onto a hypercube computer with 32 nodes. Experimental benchmark results verify the effectiveness of the rule mapping method. The method can be applied for distributed artificial intelligence processing or for the parallel execution of cooperating expert systems on a message-passing multicomputer. 相似文献
245.
Chuanju Xu 《Journal of scientific computing》2006,27(1-3):495-505
A stabilization method for the spectral element computation of incompressible flow problems is investigated. It is based on a filtering procedure which consists in filtering the velocity field by a spectral vanishing Helmholtz-type operator at each time step. Relationship between this filtering procedure and SVV-stabilization method, introduced recently in [JCP, 2004, 196(2), p680], is established. A number of numerical examples are presented to show the accuracy and stabilization capability of the method. 相似文献
246.
247.
The noise of aerodynamics nature from modern transonic fan is examined from its sources with the perspective of noise reduction through aero-acoustics design using advanced Computational Fluid Dynamics (CFD) tools. In particular the problems associated with the forward propagating noise in the front is addressed. It is identified that the shock wave spillage from the leading edge near the fan tip is the main source of the tone noise. Two different approaches have been studied to reduce the forward arc tone noise and two state-of-art transonic fans are designed using the strategies developed. The following rig tests show that while the fans exhibit other noise problems, the primary goals of noise reduction have been achieved through both fans and the novel noise reduction concept vindicated. 相似文献
249.
250.