全文获取类型
收费全文 | 20403篇 |
免费 | 2428篇 |
国内免费 | 1790篇 |
专业分类
电工技术 | 3310篇 |
技术理论 | 4篇 |
综合类 | 2580篇 |
化学工业 | 1131篇 |
金属工艺 | 371篇 |
机械仪表 | 1146篇 |
建筑科学 | 2232篇 |
矿业工程 | 571篇 |
能源动力 | 927篇 |
轻工业 | 784篇 |
水利工程 | 474篇 |
石油天然气 | 670篇 |
武器工业 | 226篇 |
无线电 | 1773篇 |
一般工业技术 | 1516篇 |
冶金工业 | 707篇 |
原子能技术 | 136篇 |
自动化技术 | 6063篇 |
出版年
2024年 | 185篇 |
2023年 | 458篇 |
2022年 | 675篇 |
2021年 | 843篇 |
2020年 | 861篇 |
2019年 | 682篇 |
2018年 | 605篇 |
2017年 | 792篇 |
2016年 | 833篇 |
2015年 | 943篇 |
2014年 | 1580篇 |
2013年 | 1321篇 |
2012年 | 1560篇 |
2011年 | 1630篇 |
2010年 | 1311篇 |
2009年 | 1273篇 |
2008年 | 1240篇 |
2007年 | 1312篇 |
2006年 | 1288篇 |
2005年 | 1035篇 |
2004年 | 860篇 |
2003年 | 737篇 |
2002年 | 567篇 |
2001年 | 460篇 |
2000年 | 387篇 |
1999年 | 257篇 |
1998年 | 193篇 |
1997年 | 145篇 |
1996年 | 114篇 |
1995年 | 106篇 |
1994年 | 93篇 |
1993年 | 49篇 |
1992年 | 50篇 |
1991年 | 33篇 |
1990年 | 29篇 |
1989年 | 26篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1962年 | 3篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
针对传统FCM(Fuzzy C-means)算法中初始聚类中心选取的随机性以及对初始值敏感的问题,提出一种基于进化策略的色彩空间加权的FCM聚类算法.通过在RGB(Red Green Blue)色彩空间矢量中设置加权矩阵来补偿各色彩的非均匀性,并采用一种类内最小距离最大的统计聚类算法来初始化聚类中心.实验结果表明,该算法能有效减少颜色量化后的均方差值,保持重建图像的整体层次和局部特征细节,对研究图像处理技术有较强的实际意义.Abstract: Aiming at a defect on randomness of the initial clustering center choosing and sensitivity of initial value in tradition FCM(fuzzy C-means) algorithm, a clustering algorithm about FCM of weighted color space based on evolutionary strategy is proposed. By interposing weighted matrix in RGB(Red Green Blue) color space, the color's inhomogeneous is compensated. And by using a statistics clustering algorithm of minimal maximal distance, clustering center is initiated. The experimental results show that the algorithm can decrease effectively the mean square deviation of color quantization, keep overall arrangement of ideas and part characteristic detail in image reconstruction, and has practical value to the study of the image process technology. 相似文献
33.
为了帮助顾客从众多对症的非处方药中选出最满意的药品,提出了开发1个基于Web的非处方药满意度评价系统。系统根据顾客提供的典型症状,采用疾病与症状相结合的选药策略,查找出所有对症的非处方药,并以药品安全性、疗效、稳定性、易用性、价格作为评价因素,根据顾客的关注角度和关注程度确定各因素权重,用模型b=W·R对对症药品进行满意度评价,按满意度高低依次推荐。经实际应用,系统推荐准确度在70%以上。 相似文献
34.
35.
结构性测试中,进化测试是一种高效的自动生成高质量测试用例的技术.然而,当程序中出现非结构化特征时,在面向节点的测试标准下,其效率极其低下甚至不及随机测试生成方法.在考虑循环体内部出现跳转(goto、retum)语句的情况下,提出了一种适应度计算方法.该方法在结合传统进化测试适应度计算的基础上,充分考虑了循环次数对于进化搜索的影响.实验结果表明,本适应度函数可以很好地引导进化搜索,并以较小的代价生成测试用例. 相似文献
36.
37.
不确定系统的稳定广义预测控制 总被引:2,自引:0,他引:2
针对一类有界不确定线性离散被控对象,采用Min-Max优化方法,提出一种新的稳定广义预测控制(MMSGPC)算法.引入内模控制结构,将干扰和不确定性从被控对象中分离出来,并利用局部反环节对其进行补偿;采用Min-Max优化方法,将终端约束条件转化为有界不确定性最差情况时应的线性方程;通过引入矩阵的Moore-Penrose逆,得到了终端约束线性方程的通解,并结合性能指标函数求得了最优控制律.通过仿真实例验证了该方法的稳定效果. 相似文献
38.
Lin Lin Mitsuo Gen 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2009,13(2):157-168
Genetic Algorithms (GAs) and other Evolutionary Algorithms (EAs), as powerful and broadly applicable stochastic search and
optimization techniques have been successfully applied in the area of management science, operations research and industrial
engineering. In the past few years, researchers gave lots of great idea for improvement of evolutionary algorithms, which
include population initialization, individual selection, evolution, parameter setting, hybrid approach with conventional heuristics
etc. However, though lots of different versions of evolutionary computations have been created, all of them have turned most
of its attention to the development of search abilities of approaches. In this paper, for improving the search ability, we
focus on how to take a balance between exploration and exploitation of the search space. It is also very difficult to solve
problem, because the balance between exploration and exploitation is depending on the characteristic of different problems.
The balance also should be changed dynamically depend on the status of evolution process. Purpose of this paper is the design
of an effective approach which it can correspond to most optimization problems. In this paper, we propose an auto-tuning strategy
by using fuzzy logic control. The main idea is adaptively regulation for taking the balance among the stochastic search and
local search probabilities based on the change of the average fitness of parents and offspring which is occurred at each generation.
In addition, numerical analyses of different type optimization problems show that the proposed approach has higher search
capability that improve quality of solution and enhanced rate of convergence. 相似文献
39.
Yuan Deng Yihai Yang Yuanhang Xiao He-Lou Xie Ruochen Lan Lanying Zhang Huai Yang 《Advanced functional materials》2023,33(35):2301319
Switchable passive radiative cooling (PRC) smart windows can modulate sunlight transmission and spontaneously emit heat to outer space through atmospheric transparent window, presenting great potential in building energy conservation. However, realizing stable and on-demand control of the cooling efficiency for PRC materials is still challenging. Herein, an electro-controlled polymer-dispersed liquid crystal (PDLC) smart window showing PRC property is designed and prepared by adding mid-infrared emitting reactive monomers into the conventional PDLC matrix. It is found that not only the electro-optical properties but also the PRC efficiency of PRC PDLC film are tunable by regulating the content of the mid-infrared emitting components, film thickness, and micromorphology. This advanced PRC PDLC material achieves a near/sub-ambient temperature when the solar irradiance is below 400 W m−2 and can dynamically manage daytime cooling efficiency. Importantly, its PRC efficiency is capable of being tuned in an on-demand and ultrafast millisecond-scale way, whose controllable transparency enables multistage heat regulation. This study is hoped to provide new inspiration in the preparation of advanced optical devices and energy-efficient equipment. 相似文献
40.
In today's Internet routing infrastructure, designers have addressed scaling concerns in routing constrained multiobjective optimization problems examining latency and mobility concerns as a secondary constrain. In tactical Mobile Ad-hoc Network (MANET), hubs can function based on the work plan in various social affairs and the internally connected hubs are almost having the related moving standards where the topology between one and the other are tightly coupled in steady support by considering the touchstone of hubs such as a self-sorted out, self-mending and self-administration. Clustering in the routing process is one of the key aspects to increase MANET performance by coordinating the pathways using multiple criteria and analytics. We present a Group Adaptive Hybrid Routing Algorithm (GAHRA) for gathering portability, which pursues table-driven directing methodology in stable accumulations and on-request steering strategy for versatile situations. Based on this aspect, the research demonstrates an adjustable framework for commuting between the table-driven approach and the on-request approach, with the objectives of enhancing the output of MANET routing computation in each hub. Simulation analysis and replication results reveal that the proposed method is promising than a single well-known existing routing approach and is well-suited for sensitive MANET applications. 相似文献