全文获取类型
收费全文 | 285701篇 |
免费 | 21799篇 |
国内免费 | 10891篇 |
专业分类
电工技术 | 15219篇 |
技术理论 | 33篇 |
综合类 | 17399篇 |
化学工业 | 49070篇 |
金属工艺 | 16741篇 |
机械仪表 | 18414篇 |
建筑科学 | 22611篇 |
矿业工程 | 9408篇 |
能源动力 | 7956篇 |
轻工业 | 16648篇 |
水利工程 | 4737篇 |
石油天然气 | 19969篇 |
武器工业 | 2238篇 |
无线电 | 31218篇 |
一般工业技术 | 34068篇 |
冶金工业 | 14829篇 |
原子能技术 | 2858篇 |
自动化技术 | 34975篇 |
出版年
2024年 | 836篇 |
2023年 | 4423篇 |
2022年 | 6684篇 |
2021年 | 10950篇 |
2020年 | 8299篇 |
2019年 | 7072篇 |
2018年 | 8015篇 |
2017年 | 9074篇 |
2016年 | 7897篇 |
2015年 | 11100篇 |
2014年 | 13719篇 |
2013年 | 16402篇 |
2012年 | 17786篇 |
2011年 | 19428篇 |
2010年 | 16752篇 |
2009年 | 15917篇 |
2008年 | 15454篇 |
2007年 | 15091篇 |
2006年 | 15986篇 |
2005年 | 14169篇 |
2004年 | 9068篇 |
2003年 | 7920篇 |
2002年 | 7327篇 |
2001年 | 6495篇 |
2000年 | 7106篇 |
1999年 | 8473篇 |
1998年 | 6813篇 |
1997年 | 5783篇 |
1996年 | 5422篇 |
1995年 | 4474篇 |
1994年 | 3727篇 |
1993年 | 2608篇 |
1992年 | 2111篇 |
1991年 | 1575篇 |
1990年 | 1142篇 |
1989年 | 909篇 |
1988年 | 738篇 |
1987年 | 487篇 |
1986年 | 357篇 |
1985年 | 234篇 |
1984年 | 161篇 |
1983年 | 104篇 |
1982年 | 125篇 |
1981年 | 83篇 |
1980年 | 67篇 |
1979年 | 24篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
991.
讨论了Web服务提供方的安全问题,通过对Web服务调用方式的分析,为Web服务的提供方设计了安全模型.所设计的模型不依赖于服务提供方选用的安全策略,方便策略的更改和安全检查机制的更新.该模型同样适用于Web服务的需求方. 相似文献
992.
引言
随着近年来数字处理电路电压的不断降低,电源功率密度的不断提高,对于电源次级整流的要求越来越高。整流器件已从最初的肖特基二极管整流,发展到用同步整流开关管替代二极管,以降低功耗。目前,控制同步整流开关管的方法主要有分立式和基于锁相环的控制芯片两种。用分立元件实现同步整流的缺点是响应过慢,系统可靠性相对差。单芯片同步整流是基于锁相环技术的,从初级取信号同步控制次级整流开关管,这种方法的缺点是不能保证在间隔模式(轻载或空载时发生)下可靠操作。 相似文献
993.
Energy efficiency is an important issue in wireless networks where the nodes are powered by batteries. In this work, we analyze the energy consumption in one-transmitter-multiple-receiver communication and develop scheduling schemes to improve energy efficiency at the transmitter. Our focus is on systems powered by a renewable energy source such as solar power. We consider an environment where both energy and time to access the wireless channel and transmit data are limited, and data destined for different receivers have different values and incur different energy costs. We present optimal scheduling algorithms that selectively transmit data at calculated rates so that the throughput or the total transmission value is maximized under given time limits and energy constraints. 相似文献
994.
新产品——钢带增强聚乙烯螺旋波纹管 总被引:1,自引:0,他引:1
钢带增强聚乙烯螺旋波纹管是一种创新的埋地排水管,把钢材的高刚度、高强度和聚乙烯的柔韧、耐腐结合在一起,突出的优点是环刚度高和节约原材料. 相似文献
995.
Hongxuan Zhang Venkatesha S. Minahan R. Sherman D. Oweis Y. Natarajan A. Thakor N.V. 《IEEE engineering in medicine and biology magazine》2006,25(4):39-45
Intraoperative neurological monitoring (INM) is the evaluation of the nervous system within the operating room (OR) environment. In this paper, the INM system is tested in a clinical setting in comparison with conventional somatosensory evoked potential (SEP) monitoring. The study results demonstrate the capability of the INM system in extracting clearer and more stable SEP signals. The high SNR of SEP signals collected in various clinical environments, including the OR, makes the INM system a robust platform for continuous monitoring. While the current use of EP monitoring is limited to intermittent analysis by a highly trained clinical neurophysiologist, the authors believe in changing this paradigm by developing continuous monitoring systems, such as the INM system, capable of automated quantitative EP analysis. This noninvasive monitoring modality will allow for a wider range of use in clinical practice. Based on volunteer and clinical patient studies, the INM monitoring system demonstrates much greater reliability and accuracy via the artifact rejection and denoising strategies. It provides more strategic filtering options for different situations under which the clinical SEP response signal could be greatly contaminated and distorted. Furthermore, the INM system offers a promising approach to signal extraction in real-time monitoring during SEP research. 相似文献
996.
Zhang Chi Jin Wen 《电气》2006,17(2):18-22
China's electric power reform has followed the western reform format, however, it doest not seem to have endorsed the liberalization ideology underlying the reform model. This raises the concern of whether and how a competitive power market may be established and reform objectives reached.
The new market competition model is easy to build in theory. The experience of many countries suggests that the market reform is extremely difficult because of the interruptions by different interest groups.
To transform a centrally planned power sector into a competitive power market is a daunting task. Policy makers need to take into consideration the transitional nature of the economy and power industry as they implement the competitive power market model. 相似文献
997.
Displacement Discontinuity Method for Fracture Mechanics Analysis of Reissner Plates: Static and Dynamic 总被引:1,自引:0,他引:1
This paper is concerned with the displacement discontinuity method applied to the shear deformable plates (Reissner’s and
Mindlin’s theories) with cracks subjected to static and dynamic loads. Fundamental solutions of dislocation are derived using
the Fourier transform method and the Laplace transformation technique. Boundary integral equations are presented in terms
of rotations/displacement on the crack surfaces. The Chebyshev polynomials of the second kind are used to evaluate the integral
equations with hypersingular kernels on the crack boundaries and determine the stress intensity factors at the crack tips.
Comparisons are made with other numerical solutions to demonstrate the proposed method is accurate both for static and dynamic
problems. 相似文献
998.
999.
多属性神经网络地震反演在NB油田水平井钻探中的应用 总被引:2,自引:0,他引:2
NB油田位于渤海海域,为新近系河流相稠油油田,储层横向分布不稳定,砂体厚度薄、连通性较差,油水关系复杂,开发设计部署了大量水平井。选择神经网络反演方法,建立地震属性与储层参数的非线性关系,进而根据其关系反演得到储层参数数据体,利用该数据体沿层切片提取储层预测信息,研究储层发育规律,指导该油田水平井的部署和钻探,取得了较好的效果,降低了钻探风险。用神经网络地震反演方法进行储层预测研究,指导水平井钻探,在渤海海域尚属首次。 相似文献
1000.