全文获取类型
收费全文 | 18630篇 |
免费 | 1615篇 |
国内免费 | 1126篇 |
专业分类
电工技术 | 949篇 |
综合类 | 1438篇 |
化学工业 | 1700篇 |
金属工艺 | 261篇 |
机械仪表 | 713篇 |
建筑科学 | 1070篇 |
矿业工程 | 240篇 |
能源动力 | 569篇 |
轻工业 | 441篇 |
水利工程 | 417篇 |
石油天然气 | 270篇 |
武器工业 | 120篇 |
无线电 | 1522篇 |
一般工业技术 | 1987篇 |
冶金工业 | 2084篇 |
原子能技术 | 112篇 |
自动化技术 | 7478篇 |
出版年
2024年 | 62篇 |
2023年 | 250篇 |
2022年 | 377篇 |
2021年 | 439篇 |
2020年 | 462篇 |
2019年 | 491篇 |
2018年 | 448篇 |
2017年 | 583篇 |
2016年 | 677篇 |
2015年 | 690篇 |
2014年 | 1000篇 |
2013年 | 1448篇 |
2012年 | 1010篇 |
2011年 | 1405篇 |
2010年 | 994篇 |
2009年 | 1199篇 |
2008年 | 1188篇 |
2007年 | 1210篇 |
2006年 | 1051篇 |
2005年 | 919篇 |
2004年 | 719篇 |
2003年 | 687篇 |
2002年 | 550篇 |
2001年 | 435篇 |
2000年 | 360篇 |
1999年 | 365篇 |
1998年 | 435篇 |
1997年 | 271篇 |
1996年 | 196篇 |
1995年 | 166篇 |
1994年 | 159篇 |
1993年 | 134篇 |
1992年 | 139篇 |
1991年 | 125篇 |
1990年 | 126篇 |
1989年 | 78篇 |
1988年 | 77篇 |
1987年 | 54篇 |
1986年 | 64篇 |
1985年 | 82篇 |
1984年 | 56篇 |
1983年 | 53篇 |
1982年 | 35篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Bruce C. Bunker R. James Kirkpatrick Richard K. Brow Gary L. Turner Carolyn Nelson 《Journal of the American Ceramic Society》1991,74(6):1430-1438
52.
53.
A semi-Markov model is constructed that describes an arbitrarily structured multicomponent technological system and takes
into account its calendar maintenance. Using an aggregation algorithm, approximate values of stationary reliability characteristics
and an optimal term of maintenance work are determined for the system.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 69–86, March–April 2006. 相似文献
54.
55.
Xi-Ren CaoAuthor Vitae Zhiyuan RenAuthor Vitae Shalabh BhatnagarAuthor Vitae Michael FuAuthor Vitae Steven MarcusAuthor Vitae 《Automatica》2002,38(6):929-943
We propose a time aggregation approach for the solution of infinite horizon average cost Markov decision processes via policy iteration. In this approach, policy update is only carried out when the process visits a subset of the state space. As in state aggregation, this approach leads to a reduced state space, which may lead to a substantial reduction in computational and storage requirements, especially for problems with certain structural properties. However, in contrast to state aggregation, which generally results in an approximate model due to the loss of Markov property, time aggregation suffers no loss of accuracy, because the Markov property is preserved. Single sample path-based estimation algorithms are developed that allow the time aggregation approach to be implemented on-line for practical systems. Some numerical and simulation examples are presented to illustrate the ideas and potential computational savings. 相似文献
56.
范忠礼 《电信工程技术与标准化》2002,(4):43-46
本提出了一种标准化的光控制平面。阐明了开了用于光传输网的控制平面所遇到的选择与挑战。光控制平面被分解成邻居发现、服务发现、连接控制和拓扑、资源发现等几个基本的过程。不同的网络组织和分割导致了几个不同的自动配置模型:软性持久链路模型、用户接口模型和对等模型。这是构成以IP为中心的光传输网的控制和管理基础。同时也介绍了基于SDH光交换的新一代CIENA公司智能光网络,它具有大容量光交换能力和网络拓扑结构自动发现、端对端电路配置、带宽动态分配等功能及特点,将大大提高数据、电路业务的服务质量,新一代智能光网络是干线和城域网络交换传输最佳的选择。 相似文献
57.
Jan A. Derecki 《Journal of Great Lakes research》1985,11(3):201-207
Periodic man-made changes in the outlet of Lake Huron through the St. Clair River date back to the middle of the last century. These artificial channel changes have been well documented during the present century. They consist of dredging for commercial gravel removal in the upper river during 1908–25 and uncompensated navigation improvements for the 7.6-m (25-ft) and 8.2-m (27-ft) projects completed in 1933 and 1962, respectively. The total effect of these changes on the levels of Lakes Michigan and Huron (hydraulically one lake) and on the upper St. Clair River profile was determined with dynamic flow models. The ultimate effect of the above dredging was a permanent lowering of the Lake Michigan-Huron levels 0.27 m (0.89 ft), which represents a tremendous loss of freshwater resource [32 km3 (7.7 mi3)]. 相似文献
58.
Damiana Chinese Antonella Meneghetti Gioacchino Nardin Patrizia Simeoni 《国际能源研究杂志》2007,31(9):829-848
A mixed integer linear programming model combined with a more traditional design by scenarios is proposed to optimize facilities size and operation mode of a municipal energy system involving significant civil centres and a hospital. Moving from the need of a new heat and power station for the local hospital due to the construction of new pavilions, the opportunity of involving other centres in the neighbourhood in a distributed cogeneration system is analysed, increasing system complexity step by step. Smaller cogeneration units tailored to hospital needs are rewarding ventures with relatively low risks but, in a country whose traditional power generation systems heavily rely on fossil fuels and where energy policy and market conditions can make it profitable to sell surplus power, district heating systems foster the installation of larger cogenerators and lead thereby to higher profits and to better performance as for primary energy savings and greenhouse gases emission reduction. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
59.
When a circuit is tested using random or pseudorandom patterns, it is essential to determine the amount of time (test length) required to test it adequately. We present a methodology for predicting different statistics of random pattern test length. While earlier methods allowed estimation only of upper bounds of test length and only for exhaustive fault coverage, the technique presented here is capable of providing estimates of all statistics of interest (including expected value and variance) for all coverage specifications.Our methodology is based on sampling models developed for fault coverage estimation [1]. Test length is viewed as awaiting time on fault coverage. Based on this relation we derive the distribution of test length as a function of fault coverage. Methods of approximating expected value and variance of test length are presented. Accuracy of these approximations can be controlled by the user. A practical technique for predicting expected test length is developed. This technique is based on clustering faults into equal detectability subsets. A simple and effective algorithm for fault clustering is also presented. The sampling model is applied to each cluster independently and the results are then aggregated to yield test lengths for the whole circuit. Results of experiments with several circuits (both ISCAS '85 benchmarks and other practical circuits) are also provided.This work was done while the author was with the Department of Electrical Engineering, Southern Illinois University, Carbondale, IL 62901. 相似文献
60.