全文获取类型
收费全文 | 19164篇 |
免费 | 2421篇 |
国内免费 | 1419篇 |
专业分类
电工技术 | 1962篇 |
综合类 | 2379篇 |
化学工业 | 1244篇 |
金属工艺 | 474篇 |
机械仪表 | 1295篇 |
建筑科学 | 1331篇 |
矿业工程 | 436篇 |
能源动力 | 323篇 |
轻工业 | 2949篇 |
水利工程 | 378篇 |
石油天然气 | 610篇 |
武器工业 | 117篇 |
无线电 | 1899篇 |
一般工业技术 | 1155篇 |
冶金工业 | 600篇 |
原子能技术 | 108篇 |
自动化技术 | 5744篇 |
出版年
2024年 | 122篇 |
2023年 | 283篇 |
2022年 | 580篇 |
2021年 | 653篇 |
2020年 | 710篇 |
2019年 | 588篇 |
2018年 | 580篇 |
2017年 | 624篇 |
2016年 | 726篇 |
2015年 | 813篇 |
2014年 | 1234篇 |
2013年 | 1197篇 |
2012年 | 1457篇 |
2011年 | 1487篇 |
2010年 | 1146篇 |
2009年 | 1182篇 |
2008年 | 1265篇 |
2007年 | 1499篇 |
2006年 | 1327篇 |
2005年 | 1090篇 |
2004年 | 972篇 |
2003年 | 828篇 |
2002年 | 657篇 |
2001年 | 519篇 |
2000年 | 380篇 |
1999年 | 266篇 |
1998年 | 175篇 |
1997年 | 118篇 |
1996年 | 98篇 |
1995年 | 94篇 |
1994年 | 76篇 |
1993年 | 46篇 |
1992年 | 40篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1971年 | 3篇 |
1965年 | 5篇 |
1964年 | 4篇 |
1963年 | 3篇 |
1961年 | 5篇 |
1960年 | 4篇 |
1959年 | 3篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
61.
This paper presents an output only damage diagnostic algorithm based on frequency response functions and the principal components for health monitoring of laminated composite structures. The principal components evaluated from frequency response data, are employed as dynamical invariants to handle the effects of operational/environmental variability on the dynamic response of the structure. Finite element models of a laminated composite beam and plate are used to generate vibration data for healthy and damaged structures. Three numerical examples include a laminated composite beam, cantilever plate made of carbon–epoxy and a laminated composite simply supported plate. Varied levels of delamination of laminated composite plies and matrix cracking at varied locations in the plies are simulated at different spatial locations of the structure. Numerical investigations have been carried out to identify the spatial location of damage using the proposed principal component analysis (PCA) based algorithm. In order to limit the number of sensors on the structure, an optimal sensor placement algorithm based on PCA is employed in the present work and the effectiveness of the proposed algorithm with a limited number of sensors is also investigated. Finally, the inverse problem associated with the detection of delamination and matrix cracking is formulated as an optimization problem and is solved using the newly developed dynamic quantum particle swarm optimization (DQPSO) algorithm. Studies carried out and presented in this paper clearly indicate that the proposed SHM scheme can robustly identify the instant of damage, spatial location, the extent of delamination and matrix cracking even with limited sensor measurements and also with noisy data. 相似文献
62.
ContextThe artifact-centric methodology has emerged as a new paradigm to support business process management over the last few years. This way, business processes are described from the point of view of the artifacts that are manipulated during the process.ObjectiveOne of the research challenges in this area is the verification of the correctness of this kind of business process models where the model is formed of various artifacts that interact among them.MethodIn this paper, we propose a fully automated approach for verifying correctness of artifact-centric business process models, taking into account that the state (lifecycle) and the values of each artifact (numerical data described by pre and postconditions) influence in the values and the state of the others. The lifecycles of the artifacts and the numerical data managed are modeled by using the Constraint Programming paradigm, an Artificial Intelligence technique.ResultsTwo correctness notions for artifact-centric business process models are distinguished (reachability and weak termination), and novel verification algorithms are developed to check them. The algorithms are complete: neither false positives nor false negatives are generated. Moreover, the algorithms offer precise diagnosis of the detected errors, indicating the execution causing the error where the lifecycle gets stuck.ConclusionTo the best of our knowledge, this paper presents the first verification approach for artifact-centric business process models that integrates pre and postconditions, which define the behavior of the services, and numerical data verification when the model is formed of more than one artifact. The approach can detect errors not detectable with other approaches. 相似文献
63.
ContextA component-based software (CBS) system is a typical example of a composite component, which is composed of two or more atomic components. In the test of a CBS system, it is necessary to automatically generate expected results because they are compared with the actual results.ObjectiveThis paper proposes an automatic generation algorithm of expected results for the testing of a CBS system.MethodThe algorithm analyzes Input/Output (I/O) relationships of a CBS system to identify inputs that influence its outputs. Then, the algorithm uses test cases of atomic components for each input and automatically generates expected results. To evaluate the proposed approach, we compare the proposed approach with the other I/O relationship based approach via two case studies which are the CBS systems for guide robot. The comparison shows the effectiveness of our approach.ResultsTo verify effectiveness of the proposed approach, we measure the cost of manual generation of expected results for each case study. The costs are from 0.001 to 0.015 in the first case study, and are from 0.590 to 0.998 in the second case study.ConclusionThis proposed approach reduces the time-consuming and error-prone task which manually generates expected results for the testing of a CBS system. 相似文献
64.
利用高强度聚焦超声对新鲜的离体猪肉进行辐射,并通过B超获取辐射前后的超声图像。采用二维离散Walsh变换法,从辐射前后的超声图像的差图像中分离出低频分量,作为反映温度信息的参数。选取确定系数作为衡量误差的参数,通过曲线拟合,发现二维离散Walsh变换直流分量与温度呈近似线性关系,且多组数据的斜率非常接近,与传统的灰度均值测温法相比,实验结果表明,该方法误差更小,温度分辨率更高,使用正交矩阵变换,符合计算机语言的逻辑,仿真检测时间较短,在实际应用中能为超声无损测温提供准确可靠的依据。 相似文献
65.
66.
针对传统RBAC模型无法满足业务审批系统要求的权限可分级、能动态管理的新需求,提出一种改进后的基于角色的控制访问模型。该模型能够动态地创造权限、分配权限、撤销权限,达到资源分离、多级权限管理的目的。结合一个实际项目,采用脚本语言JS (JavaScript)和主流的SSH框架,给出该模型的实现过程,增强各类角色对权限的分级、动态管理,该模型的可行性由此得到验证。 相似文献
67.
针对复杂化工过程具有的非线性、非高斯性和动态特征,提出了基于核独立成分分析(KICA)的模式匹配方法,用于动态过程监控和诊断。首先,利用滑动窗建立基准集与测试集的KICA模型,提取各自的核独立元:其次,融合余弦函数绝对值度量和距离度量,提出新的不相似度监控指标,识别训练与测试操作期间的相似模式,进行故障检测:最后,基于两类数据的核子空间之间的差异子空间,获得每个过程变量方向与该差异子空间之间的互信息,并定义新的非线性非高斯贡献度指标,进行故障诊断。基于污水处理过程的仿真结果表明,与主成分分析不相似度因子的方法、标准的独立成分分析(ICA)统计指标方法及标准的ICA T~2/SPE指标融合的贡献度方法相比,本文提出的方法具有更好的检测能力与故障诊断效果。 相似文献
68.
针对Android存在的特权提升攻击问题,提出了基于动态权限集的Android强制访问控制模型DP_ManDroid。该模型首先分析强连通分支的权限分布特性,构建动态的权限集划分;然后在信息流与权限集耦合的基础上,抽象权限提升路径;最后提出线性时间的访问控制算法,并通过动态追踪权限集,实现了细粒度的决策控制。与现有 安全模型的对比,以及在原型系统上的仿真结果表明,所提出的安全模型很好地抵御了特权提升攻击,同时降低了时间复杂度。 相似文献
69.
70.