全文获取类型
收费全文 | 44220篇 |
免费 | 4523篇 |
国内免费 | 2414篇 |
专业分类
电工技术 | 3354篇 |
技术理论 | 2篇 |
综合类 | 3552篇 |
化学工业 | 6898篇 |
金属工艺 | 2588篇 |
机械仪表 | 2775篇 |
建筑科学 | 3586篇 |
矿业工程 | 1277篇 |
能源动力 | 1175篇 |
轻工业 | 3785篇 |
水利工程 | 871篇 |
石油天然气 | 2348篇 |
武器工业 | 489篇 |
无线电 | 5281篇 |
一般工业技术 | 4576篇 |
冶金工业 | 1819篇 |
原子能技术 | 773篇 |
自动化技术 | 6008篇 |
出版年
2024年 | 262篇 |
2023年 | 853篇 |
2022年 | 1779篇 |
2021年 | 2257篇 |
2020年 | 1721篇 |
2019年 | 1392篇 |
2018年 | 1513篇 |
2017年 | 1622篇 |
2016年 | 1458篇 |
2015年 | 1920篇 |
2014年 | 2386篇 |
2013年 | 2639篇 |
2012年 | 2995篇 |
2011年 | 3106篇 |
2010年 | 2809篇 |
2009年 | 2712篇 |
2008年 | 2685篇 |
2007年 | 2495篇 |
2006年 | 2439篇 |
2005年 | 2069篇 |
2004年 | 1384篇 |
2003年 | 1296篇 |
2002年 | 1364篇 |
2001年 | 1227篇 |
2000年 | 975篇 |
1999年 | 816篇 |
1998年 | 491篇 |
1997年 | 498篇 |
1996年 | 447篇 |
1995年 | 313篇 |
1994年 | 288篇 |
1993年 | 217篇 |
1992年 | 200篇 |
1991年 | 116篇 |
1990年 | 92篇 |
1989年 | 82篇 |
1988年 | 67篇 |
1987年 | 45篇 |
1986年 | 29篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1959年 | 6篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
71.
A new variational framework of geometric active contours to track multiple non-rigid moving objects in the clutter background is presented. Incorporating motion edge information, it consists of motion detection and tracking stages. The results of experiments are promising and demonstrate the validity of the proposed framework 相似文献
72.
Failure analysis and a study of the wear mechanism were performed on a heavily loaded carburized gear with some unusual features. The analysis showed that the different failure forms on the tooth surface of the gear were dependent on the sub-surface shearing stress, the lubrication conditions and the surface roughness. Delaminations formed on the addendum surface were the main reason for the gear failure. A suggestion for improvement has been tried, and a desirable result has been obtained. 相似文献
73.
Jieping Ye Janardan R. Qi Li Haesun Park 《Knowledge and Data Engineering, IEEE Transactions on》2006,18(10):1312-1322
High-dimensional data appear in many applications of data mining, machine learning, and bioinformatics. Feature reduction is commonly applied as a preprocessing step to overcome the curse of dimensionality. Uncorrelated Linear Discriminant Analysis (ULDA) was recently proposed for feature reduction. The extracted features via ULDA were shown to be statistically uncorrelated, which is desirable for many applications. In this paper, an algorithm called ULDA/QR is proposed to simplify the previous implementation of ULDA. Then, the ULDA/GSVD algorithm is proposed, based on a novel optimization criterion, to address the singularity problem which occurs in undersampled problems, where the data dimension is larger than the sample size. The criterion used is the regularized version of the one in ULDA/QR. Surprisingly, our theoretical result shows that the solution to ULDA/GSVD is independent of the value of the regularization parameter. Experimental results on various types of data sets are reported to show the effectiveness of the proposed algorithm and to compare it with other commonly used feature reduction algorithms. 相似文献
74.
75.
航天产品可靠性信息的来源多样,可靠性信息的时间性、随机性、有价性、时效性和可追溯性等特征,决定了可靠性数据收集应满足真实性、连续性、完整性等基本要求。同时,对多源信息的收集应遵循先进行需求分析,再确定数据收集点并制定数据收集表格的程度进行。给出了信息的适用性准则和信息分类的三维模型。最后结合具体型号航天产品的可靠性工作的要求,给出了可靠性信息数据库系统的整体方案设计。 相似文献
76.
用浸渍法制备了一系列氧化锆担载的含稀土Ⅷ族金属催化剂,对其在二氧化碳甲烷化过程中的催化活性作了研究,并用漫反射紫外可见光谱,FTIR等手段对催化剂作了表征。结果表明,含稀土新型催化剂具有催化活性高,目标产物选择性好等优点;稀土主要以氧化物形式存在于催化剂表面,参与对氢及表面含碳物种的吸附及活化;含稀土三组份催化剂的活性与所添加稀土三价离子的4f电子数有关。 相似文献
77.
丁苯嵌段共聚物与醋酸乙烯酯本体接枝物表征的研究 总被引:1,自引:0,他引:1
本文主要对接枝共聚物SBS-g-VAC的红外光谱(IR)、核磁共振潜(NMR)、透射电镜(TEM)、扫描电镜(SEM)的表征工作进行了讨论,表明了接枝物SBS-g-VAC的存在及其结构特征。 相似文献
78.
作战管理语言(Battle Management Language,BML)是一种无歧义的语言规范,用于解决指控和仿真系统间的互操作问题。针对BML命令缺乏语义信息,难以被计算机理解和自动处理的问题,分析了BML的五视图体系结构,引入了BNF形式化语法,并在此基础上提出了一种语义标注方法,对命令中的对象、时间和地理位置等要素进行标注,然后整合各要素来表达整条命令的语义,系统通过解析标注文档可以实现对命令的无歧义理解,最后给出实例予以说明。论文为表达BML命令的语义提出了一种借鉴思路。 相似文献
79.
Qi Zhao Xuanzhe Liu Xingrun Chen Jiyu Huang Gang Huang Hong Mei 《Service Oriented Computing and Applications》2012,6(2):99-116
Facilitated by the SOA and new Web technologies, Service-Oriented Rich Clients (SORCs) compose various Web-delivered services in Web browser to create new applications. The SORCs support client-side data storage and manipulation and provide more features than traditional thin clients. However, the SORCs might suffer from data access issues, mainly due to both client-side incompatible data sources and server-side improper or even undesirable cache strategies. Addressing the data access issues, this paper proposes a data access framework for SORCs. The main contributions of this paper are as follows. First, the framework makes the SORCs accommodate heterogeneous local storage solutions and diverse Web browsers properly. The framework abstracts the underlying details of different local storages and selects the most proper data sources for current SORC in use. Secondly, the framework provides a cache mechanism, which supports client-side customized cache strategies. An adaptive technique for the strategies is also proposed to adjust cache strategies based on users?? historical actions to achieve better performance. 相似文献
80.
In most priority scheduling algorithms, the number of priority levels is assumed to be unlimited. However, if a task set requires more priority levels than the system can support, several jobs must in practice be assigned the same priority level. To solve this problem, a novel group priority earliest deadline first (GPEDF) scheduling algorithm is presented. In this algorithm, a schedulability test is given to form a job group, in which the jobs can arbitrarily change their order without reducing the schedulability. We consider jobs in the group having the same priority level and use shortest job first (SJF) to schedule the jobs in the group to improve the performance of the system. Compared with earliest deadline first (EDF), best effort (BE), and group-EDF (gEDF), simulation results show that the new algorithm exhibits the least switching, the shortest average response time, and the fewest required priority levels. It also has a higher success ratio than both EDF and gEDF. 相似文献