全文获取类型
收费全文 | 58615篇 |
免费 | 3102篇 |
国内免费 | 70篇 |
专业分类
电工技术 | 403篇 |
综合类 | 49篇 |
化学工业 | 12119篇 |
金属工艺 | 1095篇 |
机械仪表 | 1080篇 |
建筑科学 | 1856篇 |
矿业工程 | 112篇 |
能源动力 | 1537篇 |
轻工业 | 8739篇 |
水利工程 | 517篇 |
石油天然气 | 285篇 |
武器工业 | 6篇 |
无线电 | 3063篇 |
一般工业技术 | 9581篇 |
冶金工业 | 12925篇 |
原子能技术 | 343篇 |
自动化技术 | 8077篇 |
出版年
2023年 | 475篇 |
2022年 | 895篇 |
2021年 | 1506篇 |
2020年 | 1067篇 |
2019年 | 1113篇 |
2018年 | 1934篇 |
2017年 | 1931篇 |
2016年 | 2053篇 |
2015年 | 1537篇 |
2014年 | 2041篇 |
2013年 | 3871篇 |
2012年 | 3324篇 |
2011年 | 3527篇 |
2010年 | 2737篇 |
2009年 | 2567篇 |
2008年 | 2638篇 |
2007年 | 2300篇 |
2006年 | 1821篇 |
2005年 | 1546篇 |
2004年 | 1423篇 |
2003年 | 1280篇 |
2002年 | 1135篇 |
2001年 | 770篇 |
2000年 | 764篇 |
1999年 | 926篇 |
1998年 | 4256篇 |
1997年 | 2606篇 |
1996年 | 1766篇 |
1995年 | 1024篇 |
1994年 | 881篇 |
1993年 | 859篇 |
1992年 | 308篇 |
1991年 | 321篇 |
1990年 | 287篇 |
1989年 | 306篇 |
1988年 | 265篇 |
1987年 | 236篇 |
1986年 | 235篇 |
1985年 | 281篇 |
1984年 | 228篇 |
1983年 | 168篇 |
1982年 | 201篇 |
1981年 | 214篇 |
1980年 | 186篇 |
1979年 | 149篇 |
1978年 | 139篇 |
1977年 | 267篇 |
1976年 | 531篇 |
1975年 | 107篇 |
1973年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Sébastien Ambellouis Fran?ois Cabestaing Jack-Gérard Postaire 《IEEE transactions on image processing》2006,15(6):1601-1609
Energy-based methods for motion estimation in image sequences process the input data either in the spatiotemporal or in the frequency domain. In both cases, the algorithms already described in the literature often require a huge number of elementary operations. In this paper, we describe a class of velocity selective filters which yield an accurate detection of the edges moving in the sequence. We first present a filtering scheme based on a convolution operation computed on a finite size neighborhood and describe its properties in the spatiotemporal and frequency domains. Then, we show that filters with similar properties can be implemented recursively, i.e., as convolutions computed on infinite-size neighborhoods. As an example, we finally show the filters' responses in the case of two superimposed translational motions. 相似文献
92.
93.
J. Gutirrez J. M. Barandiarn Z. Kaczkowski 《Materials Science and Engineering: A》2004,370(1-2):392-395
The change of magnetoelastic properties after thermal treatments has been investigated for two groups of metallic glasses. (Fe79Co21)75+xSi15−1.4xB10+0.4x (x (at.%)=0, 2, 4, 6, 8, 10) has been studied both in the as-prepared state and after thermal annealing in an applied magnetic field, to achieve a particular domain structure, at temperatures well below the crystallization temperatures. Changes in the ΔE effect, magnetomechanical coupling (k) and internal friction coefficient (Q−1) are reported, reaching values of about 60% of the saturation value ES. Fe64Ni10Nb3Cu1Si13B9 alloys annealed in vacuum for 1 h in the temperature range 350–550 °C showed maximum values of the ΔE effect and k of 61% and 0.85, respectively, accompanied by a minimum value of Q of around 2 for the sample annealed at 460 °C. These variations are related to the progress of nanocrystalization. The properties achieved are among the best reported for magnetomechanical applications. 相似文献
94.
Quality of service has become today a major concern for operators of mobile communication networks. The massive development of networks and strong competition between operators has lead to the necessary and daily follow-up of network quality of service, a key factor for its subscriber’s fidelity. This article aims at presenting the optimization methodology and proposes its illustration with a case of RNO (Radio Network Optimisation) software usage, one of the Alcatel optimization toolchain component. After a short presentation of cellular network, the optimization basic principles are described. RNO software and its main functionnalities are then detailed before a last part dedicated to a real case of optimization done with RNO software. 相似文献
95.
Responds to Gauthier (see record 2004-17185-003) who commented on the two articles by Koerner et al (see record 2004-17185-001) and by Roberge et al (see record 2004-17185-002. The purpose of this response is to discuss the issue of limited availability of mental health services for anxiety disorders in Canada. From a public health perspective, the authors emphasize the importance of gathering Canadian empirical data on the organization of mental health services for anxiety disorders. Specifically more research is needed on care requirements, and the financial and structural barriers that restrict access to mental health services at the regional, provincial and national levels. The authors also discuss the role of psychologists in improving mental health care in Canada. Cost-effectiveness studies conducted in interdisciplinary practice environments could demonstrate the value added by psychology in the organization of mental health care for anxiety disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
96.
D. Vignolles D. Smirnov G. Rikken B. Raquet H. Rakoto C. Proust M. Nardone J. Léotin F. Lecouturier M. Goiran O. Drachenko J. M. Broto L. Brossard A. Audouard 《Journal of Low Temperature Physics》2003,133(1-2):97-120
An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned. 相似文献
97.
Three different vanadium-modified Pd/Al2O3 catalysts were prepared and tested as catalysts for the deep oxidation of methane. Vanadium was added to the palladium catalyst by incipient wetness of palladium catalyst in order to modify its properties and improve its thermal stability and thioresistance. The behaviour of vanadium-modified catalysts depends on the concentration of this compound, being 0.5 wt.% the optimum amount. However, when strong catalyst poisons are present in the gas (SO2), these modified catalysts do not show a better performance than unmodified catalyst. Bimetallic catalysts were tested with and without further reduction, being observed that reduced bimetallic catalysts perform worse than the non-reduced ones. 相似文献
98.
Désiré Lara; Veissier Isabelle; Després Gérard; Boissy Alain 《Canadian Metallurgical Quarterly》2004,118(4):363
Appraisal theories provide a framework that gives insight into emotions and could allow comparisons across species. According to these theories, events are first evaluated on their suddenness, novelty, and unpredictability. The authors examined the ability of lambs (Ovis aries) to evaluate an event according to these 3 criteria through 3 tests. The lambs responded to suddenness with a startle response coupled with an increase in heart rate and to novelty with an orientation response coupled with an increase of vagal activity. There was no clear evidence that lambs can detect the predictability of an event. Those results support the usefulness of appraisal theories to assess emotion in animals. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
99.
Rossato Janine I.; Bonini Juliana S.; Coitinho Adriana S.; Vianna Monica R. M.; Medina Jorge H.; Cammarota Martín; Izquierdo Iván 《Canadian Metallurgical Quarterly》2004,118(3):563
The gamma aminobutyric acid-A (GABAA) agonist, muscimol, the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist, D-2-amino-5-phosphonopentanoic acid (AP5), and the inhibitor of the extracellularly regulated kinases (ERKs), UO 126, cause retrograde amnesia when administered to the hippocampus. In the present study, the authors found that they all cause retrograde amnesia for 1-trial inhibitory avoidance, not only when infused into the dorsal CA1 region of the hippocampus, but also when infused into the basolateral amygdala or the entorhinal, parietal, and posterior cingulate cortices. The posttraining time course of the effect of each drug was, however, quite different across brain structures. Thus, in all of them, NMDA receptors and the ERK pathway are indispensable for memory consolidation, and GABAA receptor activation inhibits memory consolidation: but in each case, their influence is interwoven differently. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
100.