全文获取类型
收费全文 | 195904篇 |
免费 | 5698篇 |
国内免费 | 2736篇 |
专业分类
电工技术 | 5527篇 |
技术理论 | 3篇 |
综合类 | 3271篇 |
化学工业 | 31493篇 |
金属工艺 | 7989篇 |
机械仪表 | 7773篇 |
建筑科学 | 7984篇 |
矿业工程 | 1580篇 |
能源动力 | 5319篇 |
轻工业 | 19757篇 |
水利工程 | 1912篇 |
石油天然气 | 3687篇 |
武器工业 | 349篇 |
无线电 | 25563篇 |
一般工业技术 | 34179篇 |
冶金工业 | 25728篇 |
原子能技术 | 2892篇 |
自动化技术 | 19332篇 |
出版年
2022年 | 1584篇 |
2021年 | 2422篇 |
2020年 | 1775篇 |
2019年 | 1960篇 |
2018年 | 2300篇 |
2017年 | 2528篇 |
2016年 | 2526篇 |
2015年 | 2627篇 |
2014年 | 3848篇 |
2013年 | 9017篇 |
2012年 | 5701篇 |
2011年 | 7404篇 |
2010年 | 6023篇 |
2009年 | 6469篇 |
2008年 | 6992篇 |
2007年 | 7127篇 |
2006年 | 6715篇 |
2005年 | 6078篇 |
2004年 | 5435篇 |
2003年 | 5543篇 |
2002年 | 5829篇 |
2001年 | 5634篇 |
2000年 | 5048篇 |
1999年 | 5077篇 |
1998年 | 7625篇 |
1997年 | 6074篇 |
1996年 | 5319篇 |
1995年 | 4371篇 |
1994年 | 3932篇 |
1993年 | 3623篇 |
1992年 | 3089篇 |
1991年 | 2914篇 |
1990年 | 2802篇 |
1989年 | 2767篇 |
1988年 | 2615篇 |
1987年 | 2258篇 |
1986年 | 2168篇 |
1985年 | 2592篇 |
1984年 | 2339篇 |
1983年 | 2213篇 |
1982年 | 2090篇 |
1981年 | 2005篇 |
1980年 | 1870篇 |
1979年 | 1884篇 |
1978年 | 1770篇 |
1977年 | 2085篇 |
1976年 | 2563篇 |
1975年 | 1583篇 |
1974年 | 1430篇 |
1973年 | 1453篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
W Pf?rringer 《Canadian Metallurgical Quarterly》1997,135(4):Oa10-Oa11
92.
W. C. Kowalski 《Bulletin of Engineering Geology and the Environment》1994,50(1):51-57
It is pointed out that strength value of rock samples changes with time after sample excavation from a quarry. Three main stages of strength variability with time are distinguished: 1-the stage of hardening connected with increase in the compression strength; 2-stage of equilibrium of the antagonistic processes: hardening and mechanical fatigue; 3-stage of manifestation of mechanical fatigue. Mechanical fatigue is favorable to the manifestation latent weakness surface to new crack formation and at last to total disintegration in rock samples. 相似文献
93.
The management of innovation inevitably implies the management of uncertainty. Research and practise clearly indicate that judgements about the size and the nature of this are often inaccurate. This can result in poor performance against expectations and in some cases in complete failure. In this paper it is argued that prior analysis of the type of uncertainty can help to improve the success rate and/or reduce the time to completion. Early signs that discontinuation, or a significant change in direction, might be called for are also highlighted by this analysis. 相似文献
94.
Kerlavage A.R. FitzHugh W. Gladek A. Kelley J. Scott J. Shirley R. Sutton G. Man Wai-Chiu White O. Adams D. 《IEEE engineering in medicine and biology magazine》1995,14(6):710-717
The rapid advances in molecular biology have begun to shift many of the bottlenecks in genome research from the laboratory to the data analysis facility. The pace at which this has occurred creates a situation in which software development always has to catch up with the flow of data. Since such large-scale processes were not anticipated, the analysis infrastructure has not been fully established. Furthermore, most systems that have been built were designed by the biologists who collected the data. More recently, computer scientists, mathematicians, and engineers have taken an interest in this problem. This has had a positive effect, since it has created a tight synergy between the informatics and the biology. Several principles affected the design of the system developed at TIGR. Each of the sample preparation, sequencing, and analysis steps had to be managed, scheduled, and tracked. This information had to be made readily available to those who needed it for carrying out their tasks. Different skill levels of the users had to be taken into account. The degree of human intervention at each step had to be evaluated and built into the design. A mixed processing environment of Macintosh and Unix platforms had to be integrated. Most importantly, the system had to save time, reduce error, and ensure uniformity of the analysis and quality of the results. In the authors' experience, the tools they have built work well because of their early decisions as to which systems to use for development. The authors settled on a robust relational database management system (Sybase) and a portable development environment (C, C++) 相似文献
95.
Pulse oximetry is increasingly used to assess hypoxaemia in respiratory illnesses. Six children presenting with acute asthma and prolonged falls in oxygen saturation values after treatment with salbutamol are described who were subsequently shown to have pneumonic consolidation on chest radiography. 相似文献
96.
L. Palermo Jr.
M. Rachid
W. S. Venturini 《Engineering Analysis with Boundary Elements》1992,9(4):359-363In this article the direct boundary element formulations of stretching and bending plate problems are combined together to solve thin walled structures and other similar frames. The final system is obtained by assuming each individual plane structural element as a subregion. After the necessary transforms of these equations they can be combined together taking into account the displacement compatibility and equilibrium conditions. 相似文献
97.
W. Hein 《e & i Elektrotechnik und Informationstechnik》1998,115(11):605-607
The Kyoto Protocol to the United Nationsl Framework Convention on Climate Change gives a target for the reduction of greenhouse gases in the EU and most associated states of 8% from 1990 levels to 2010. The European Commissions Whitebook on Renewable Energy is setting a target of doubling the share of Renewable Energy from 6% now to 12% in 2010 for the European Union. There is no contradiction between these targets. 相似文献
98.
An improved accelerated cable life test is described. Through the use of programmable logic controllers (PLCs), very precise and consistent control of the accelerated aging process has been achieved. A computer has been utilized to make continuous real-time acquisition and storage of key operating parameters possible. This precise control and monitoring methodology has permitted the study of the synergistic effects of voltage and temperature on the accelerated aging of full-sized cables in the laboratory 相似文献
99.
100.
Diot C. Dabbous W. Crowcroft J. 《Selected Areas in Communications, IEEE Journal on》1997,15(3):277-290
Group communication supports information transfer between a set of participants. It is becoming more and more relevant in distributed environments. For distributed or replicated data, it provides efficient communication without overloading the network. For some types of multimedia applications, it is the only way to control data transmission to group members. This paper surveys protocol functions and mechanisms for data transmission within a group, from multicast routing problems up to end-to-end multipoint transmission control. We provide a bibliography which is organized by topic 相似文献