全文获取类型
收费全文 | 182793篇 |
免费 | 3375篇 |
国内免费 | 710篇 |
专业分类
电工技术 | 3445篇 |
综合类 | 215篇 |
化学工业 | 29333篇 |
金属工艺 | 6436篇 |
机械仪表 | 5535篇 |
建筑科学 | 6122篇 |
矿业工程 | 482篇 |
能源动力 | 4917篇 |
轻工业 | 19441篇 |
水利工程 | 1522篇 |
石油天然气 | 687篇 |
武器工业 | 9篇 |
无线电 | 22734篇 |
一般工业技术 | 34326篇 |
冶金工业 | 29831篇 |
原子能技术 | 2585篇 |
自动化技术 | 19258篇 |
出版年
2021年 | 1384篇 |
2019年 | 1424篇 |
2018年 | 1820篇 |
2017年 | 1789篇 |
2016年 | 2058篇 |
2015年 | 1753篇 |
2014年 | 2769篇 |
2013年 | 8792篇 |
2012年 | 4746篇 |
2011年 | 6533篇 |
2010年 | 5128篇 |
2009年 | 5595篇 |
2008年 | 6290篇 |
2007年 | 6519篇 |
2006年 | 5799篇 |
2005年 | 5410篇 |
2004年 | 5066篇 |
2003年 | 4908篇 |
2002年 | 4889篇 |
2001年 | 4616篇 |
2000年 | 4246篇 |
1999年 | 4243篇 |
1998年 | 7196篇 |
1997年 | 5723篇 |
1996年 | 4657篇 |
1995年 | 4162篇 |
1994年 | 3780篇 |
1993年 | 3598篇 |
1992年 | 3166篇 |
1991年 | 2901篇 |
1990年 | 2957篇 |
1989年 | 2894篇 |
1988年 | 2706篇 |
1987年 | 2413篇 |
1986年 | 2339篇 |
1985年 | 2882篇 |
1984年 | 2645篇 |
1983年 | 2426篇 |
1982年 | 2274篇 |
1981年 | 2207篇 |
1980年 | 2047篇 |
1979年 | 2076篇 |
1978年 | 1958篇 |
1977年 | 2243篇 |
1976年 | 2707篇 |
1975年 | 1718篇 |
1974年 | 1543篇 |
1973年 | 1582篇 |
1972年 | 1292篇 |
1971年 | 1164篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
Many cognitive tasks that are easy for humans to perform are proving difficult to emulate in computer systems. Combining the disciplines of psychology and engineering may offer a solution to some of these problems. A connectionist or neural network model of face recognition by humans which incorporates aspects of a model proposed by cognitive psychologists is presented. A comparative set of experiments has been performed using this simulation and human subjects for familiar face recognition. By employing the same stimuli for both humans and the computer model, it is possible to advance not only our understanding of human cognition but also to develop improved automated systems for face recognition 相似文献
992.
Transient fields of pulsed transducers in solids 总被引:1,自引:0,他引:1
The radiation and propagation of elastic waves in solid media are of fundamental importance in ultrasonic NDE. Due to the limitation of analytical approaches, numerical procedures are most appropriate for solving the governing equations. In this paper, the finite element method is used to predict the transient fields of pulsed transducers in a solid medium with axisymmetric geometry. Comparisons with other models are performed. The transducer field interactions with spherical voids are also presented. 相似文献
993.
994.
995.
The first magnetic resonance imaging profiles of chloride content in low- and high-permeability Portland cement mortar have been obtained using a novel material science imaging technique. The penetration of water as well as chloride and sodium ions, into mortar specimens was monitored for a period of 72 h. Marked differences in penetration depth were observed in low- and high-permeability mortar. These preliminary experiments show significant differences between the extent and nature in the penetration of chlorides compared to water and sodium. 相似文献
996.
997.
998.
Advances in instrumentation have made it possible in recent years to study the microstructure of inorganic materials at atomic resolution using the technique of high-resolution electron microscopy (HREM). Details of instrumentation have been described elsewhere [l], and applications and trends for HREM have recently been reviewed [2]. Although HREM is primarily a technique for studying bulk defects, it is increasingly also being applied in the profile-imaging mode to derive information about surfaces [3]. The high spatial resolution of the electron microscope makes it a valuable tool for the characterization of heterogeneous catalysts. This is evidenced by the growing number of studies wherein electron micrographs are being used to describe the morphology of a particular catalyst. Profile imaging is proving particularly useful in this regard for following changes in surface structure as a function of treatment conditions [4]. 相似文献
999.
W Samuel M Dryden M Sampson A Page H Shepherd 《Canadian Metallurgical Quarterly》1997,22(23):2763-2765
STUDY DESIGN: A case of paraspinal abscess formation from Haemophilus paraphrophilus is presented. OBJECTIVES: To describe a case of paraspinal abscess formation from H. paraphrophilus, a fastidious commensal organism of the mouth and pharynx. A precise bacteriologic identification can be difficult; techniques for such identification are discussed. SUMMARY OF BACKGROUND DATA: Spinal abscess caused by H. paraphrophilus is unusual and can be very difficult to diagnose. METHODS: The etiology, clinical presentation, technical examinations, and treatment are reviewed. RESULTS: Prolonged antibiotic treatment was curative, although surgery was considered. CONCLUSIONS: Bacteriologic diagnoses in these rare infections are difficult. Antibiotic therapy was curative in the patient described. 相似文献
1000.