全文获取类型
收费全文 | 37038篇 |
免费 | 2858篇 |
国内免费 | 1413篇 |
专业分类
电工技术 | 1945篇 |
综合类 | 2129篇 |
化学工业 | 6555篇 |
金属工艺 | 1821篇 |
机械仪表 | 2117篇 |
建筑科学 | 3565篇 |
矿业工程 | 719篇 |
能源动力 | 1164篇 |
轻工业 | 2240篇 |
水利工程 | 586篇 |
石油天然气 | 2030篇 |
武器工业 | 254篇 |
无线电 | 4449篇 |
一般工业技术 | 4752篇 |
冶金工业 | 1911篇 |
原子能技术 | 555篇 |
自动化技术 | 4517篇 |
出版年
2024年 | 114篇 |
2023年 | 515篇 |
2022年 | 863篇 |
2021年 | 1317篇 |
2020年 | 1026篇 |
2019年 | 843篇 |
2018年 | 933篇 |
2017年 | 1080篇 |
2016年 | 968篇 |
2015年 | 1284篇 |
2014年 | 1640篇 |
2013年 | 2127篇 |
2012年 | 2236篇 |
2011年 | 2447篇 |
2010年 | 2040篇 |
2009年 | 2016篇 |
2008年 | 1964篇 |
2007年 | 1920篇 |
2006年 | 1974篇 |
2005年 | 1755篇 |
2004年 | 1225篇 |
2003年 | 1090篇 |
2002年 | 1050篇 |
2001年 | 907篇 |
2000年 | 993篇 |
1999年 | 1067篇 |
1998年 | 1017篇 |
1997年 | 844篇 |
1996年 | 816篇 |
1995年 | 664篇 |
1994年 | 528篇 |
1993年 | 474篇 |
1992年 | 332篇 |
1991年 | 237篇 |
1990年 | 242篇 |
1989年 | 168篇 |
1988年 | 132篇 |
1987年 | 94篇 |
1986年 | 74篇 |
1985年 | 54篇 |
1984年 | 45篇 |
1983年 | 32篇 |
1982年 | 32篇 |
1981年 | 19篇 |
1980年 | 23篇 |
1979年 | 10篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1973年 | 8篇 |
1970年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
在等离子体动力学、电磁学理论等物理问题的数值模拟中,各类数值模拟程序产生了大量复杂结构的科学数据.一方面,计算程序需要以高效率的I/O方式存储数据,另一方面,数据需要在各类程序间很容易地交换与共享.随着数据的规模与复杂度不断增加,传统数据管理方式的局限性日益突出.为此,设计了面向计算物理领域的数据存储模型--数值模拟网格数据模型(JAD),引入元数据管理机制,对数值模拟程序数据对象进行抽象与封装,在HDF5软件库基础上实现了高层I/O函数库(JADLib),集成先进的数据存储技术,提供直观、易用的应用程序编程接口(API),使得数值模拟数据以统一格式高效率地存储.目前,JADLib已推广应用于高功率微波、惯性约束聚变等领域多个数值模拟程序中,与元数据管理系统(JADIS)、并行可视化系统(JaVis)建立了耦合,使得用户可以直接利用这些系统进行数据的浏览、分析及可视化,促进了应用程序间的数据共享. 相似文献
982.
随着Web数据库数量和其蕴含数据量飞速的增长,对Deep Web数据的集成越来越成为研究领域关注的问题.然而由于Web上的信息以半结构化及无结构化的数据信息居多,导致了抽取的结果中包含诸多的不确定性.如有噪音数据、重复字符、简写与全称混合等问题.这给识别重复记录带来了很大不便,导致传统的去重算法无法达到很好的效果.为此,提出了一种面向deep Web结果整合的重复记录识别模型.在该模型中,提出了一种基于编辑距离的改进算法,基于该算法实现字符串匹配;通过构建属性匹配图,并采用二次确认机制实现识别重复记录.应用该模型,既提高了识别效率又保证了识别精确度,并通过实验证明了提出的算法和模型的可行性. 相似文献
983.
984.
985.
针对当前可靠性预测模型的预测精度问题,提出一种增强贝叶斯组合的短期软件可靠性预测模型。该模型以基于小波分解的单个可靠性预测模型作为基本预测模型, 根据当前相邻几个失效时间间隔的预测精度,更新组合模型中各个基本预测模型的权重,解决了贝叶斯组合模型权重计算采用全部历史数据而导致某个基本预测模型权值占主导地位的缺陷,提高了贝叶斯组合模型对软件可靠性的预测精度。实验结果表明,增强贝叶斯组合预测模型的预测精度不仅优于单一的预测方法,而且也优于传统的软件组合预测模型,能显著提高软件可靠性预测的精度和模型对数据的适应性。 相似文献
986.
This paper provides a new approach referred to as pseudo-predictor feedback (PPF) for stabilisation of linear systems with multiple input delays. Differently from the traditional predictor feedback which is from the model reduction appoint of view, the proposed PPF utilises the idea of prediction by generalising the corresponding results for linear systems with a single input delay to the case of multiple input delays. Since the PPF will generally lead to distributed controllers, a truncated pseudo-predictor feedback (TPPF) approach is established instead, which gives finite dimensional controllers. It is shown that the TPPF can compensate arbitrarily large yet bounded delays as long as the open-loop system is only polynomially unstable. The proposed TPPF approach is then used to solve the consensus problems for multi-agent systems characterised by linear systems with multiple input delays. Numerical examples show the effectiveness of the proposed approach. 相似文献
987.
Yukang Cui James Lam Zhiguang Feng Jun Shen 《International journal of systems science》2016,47(15):3720-3729
This paper is concerned with the characterisation of robust admissibility and admissibilisation for uncertain discrete-time singular system with interval time-varying delay. Considering the norm-bounded uncertainty and the interval time-varying delay, a new comparison model is introduced to transform the original singular system into two connected subsystems. After this transformation, a singular system without uncertainty and delay can be handled by the Lyapunov–Krasovskii functional method. By virtue of the scaled small gain theorem, an admissibility condition of the original singular system is proposed in terms of linear matrix inequalities. Moreover, the problem of robust admissibilisation of uncertain discrete singular time-varying system is also studied by iterative linear matrix inequality algorithm with initial condition optimisation. Several numerical examples are used to illustrate that the results are less conservative than existing ones. 相似文献
988.
989.
In this paper, we address the containment control problem for multi-agent systems under heterogeneous unbounded communication delays with emphasis on the convergence rate analysis. Different from most works on multi-agent systems, we resort to a viewpoint from the area of positive delay systems. We first cast the containment control problem into the stability analysis of an associated error system. In order to capture the convergence rate, we introduce a nondecreasing positive function whose reciprocal represents the decay rate of the associated error system. Under the assumption that each follower has access to at least one leader and some mild hypotheses on the communication delays, an explicit condition is given to characterise the decay rate of the associated error system in terms of linear programming. In addition, we provide several special cases when the communication delays are restricted by linear, sublinear and logarithmic growth rates, respectively. Finally, through numerical examples, it is shown that the convergence rate is dominated by the delays being the highest order infinitely large quantity. 相似文献
990.
PolSAR anisotropic diffusion filter with a refined similarity measure and an adaptive fidelity constraint 总被引:1,自引:0,他引:1
Xiaoshuang Ma Huanfeng Shen Liangpei Zhang 《International journal of remote sensing》2016,37(24):5988-6011
The presence of speckle complicates the tasks of interpreting and analysing polarimetric synthetic aperture radar (PolSAR) images. The nonlinear anisotropic diffusion (AD) method has been found to perform well in removing image noise. In this article, we propose a new AD method for PolSAR speckle reduction. An iterative refinement method is employed to measure the similarity between pixels and construct the diffusion coefficient in the iteration process, by considering both information in the original speckled image and the restored image of the last iteration. In addition, to alleviate the over-smoothing problem the conventional AD methods often encounter, an adaptive fidelity constraint is added into the diffusion equation by considering local heterogeneity information and the amount of noise. Experiments on both simulated and real PolSAR images confirm the ability of the proposed method to both suppress speckle and retain image details. 相似文献