全文获取类型
收费全文 | 89321篇 |
免费 | 9993篇 |
国内免费 | 7612篇 |
专业分类
电工技术 | 8589篇 |
技术理论 | 5篇 |
综合类 | 9145篇 |
化学工业 | 6908篇 |
金属工艺 | 1511篇 |
机械仪表 | 4454篇 |
建筑科学 | 5524篇 |
矿业工程 | 1264篇 |
能源动力 | 2816篇 |
轻工业 | 2499篇 |
水利工程 | 1556篇 |
石油天然气 | 2129篇 |
武器工业 | 1023篇 |
无线电 | 10208篇 |
一般工业技术 | 8837篇 |
冶金工业 | 2462篇 |
原子能技术 | 817篇 |
自动化技术 | 37179篇 |
出版年
2024年 | 239篇 |
2023年 | 1233篇 |
2022年 | 1585篇 |
2021年 | 2107篇 |
2020年 | 2758篇 |
2019年 | 2717篇 |
2018年 | 2477篇 |
2017年 | 3285篇 |
2016年 | 3686篇 |
2015年 | 3593篇 |
2014年 | 5282篇 |
2013年 | 7122篇 |
2012年 | 5597篇 |
2011年 | 6212篇 |
2010年 | 4569篇 |
2009年 | 5299篇 |
2008年 | 5248篇 |
2007年 | 5849篇 |
2006年 | 5183篇 |
2005年 | 4494篇 |
2004年 | 3708篇 |
2003年 | 3431篇 |
2002年 | 3045篇 |
2001年 | 2582篇 |
2000年 | 2378篇 |
1999年 | 1940篇 |
1998年 | 1637篇 |
1997年 | 1485篇 |
1996年 | 1234篇 |
1995年 | 1056篇 |
1994年 | 911篇 |
1993年 | 792篇 |
1992年 | 621篇 |
1991年 | 575篇 |
1990年 | 440篇 |
1989年 | 345篇 |
1988年 | 274篇 |
1987年 | 235篇 |
1986年 | 187篇 |
1985年 | 239篇 |
1984年 | 230篇 |
1983年 | 195篇 |
1982年 | 178篇 |
1981年 | 122篇 |
1980年 | 93篇 |
1979年 | 104篇 |
1978年 | 73篇 |
1977年 | 75篇 |
1976年 | 24篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
The perceived locations of paired auditory images, simulating direct sounds and their echoes, have been recently studied in budgerigars (Melopsittacus undulatus; M. L. Dent & R. J. Dooling, 2003a, 2003b). In this article, the authors extend those experiments to include measurements of the precedence effect using a discrimination paradigm in two additional bird species: canaries (Serinus canaria) and zebra finches (Taeniopygia guttata). Although time courses of summing localization, localization dominance, and echo thresholds were similar across all species, budgerigars had slightly higher overall levels of discrimination. The results from these experiments add further support that the precedence effect in birds is similar to that found in other animals and that the ability to suppress echoes that might degrade localization and auditory object perception may be a general property of the vertebrate auditory system. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
MAX1773/MAX1773A是用于双电池系统的电源选择器,它允许外部控制器去管理双电池组、适配器输入、电池充电器和系统负载所需的电源连接。文中介绍了MAX1773/1773A的特点、引脚功能、内部结构和工作原理,给出了MAX1773/MAX1773A的典型工作电路。 相似文献
105.
The focus of this paper lies in the practical aspects of voice over IP communication. VoIP configurations in the H.323 standard will be presented briefly. Following that, the fundamental protocol procedure of H.323 communication will be briefly explained. A further part of the paper will address the subject QoS (quality of service), and present the common measurement methods used in QoS. Results gained from experiments conducted in a VoIP environment will then follow. The investigations concentrate primarily on the load behavior of voice packets in relation to important parameters of this service. The results obtained are presented and evaluated in diagrams. The paper concludes with a summary. 相似文献
106.
107.
Many media processing applications create a load that varies significantly over time. Hence, if such an application is assigned a lower processing-time budget than needed in its worst-case load situation, deadline misses are likely to occur. This problem can be dealt with by designing media processing applications in a scalable fashion. A scalable media processing application can run in multiple qualities, leading to correspondingly different resource demands. The problem we consider is to find an accompanying quality control strategy, which minimizes both the number of deadline misses and the number of quality changes, while maximizing the quality of processing. We present an initial approach to the above problem by modeling it as a Markov decision process (MDP). Our model is based on measuring relative progress at milestones. Solving the MDP results in a quality control strategy that can be applied during runtime with only little overhead. We evaluate our approach by means of a practical example, which concerns a scalable MPEG-2 decoder. 相似文献
108.
Logistic模型的改进及在油藏可采储量预测中的应用 总被引:6,自引:2,他引:4
为了更准确地预测油气藏未来的经济可采储量,依据油气藏随开发必然要经历产量递减和生产收支平衡的实际。利用Logistic模型中技术可采储量、产量与时间的相互关系,经推导和改进后,再结合当前经济技术条件下的废弃产油量,预测油气藏的有效生产时间及其经济可呆储量。实践证实,改进后的Logistic模型预测结果更符合油气藏的生产实际,能为油气藏的储量管理提供可靠的依据。 相似文献
109.
110.