全文获取类型
收费全文 | 502篇 |
免费 | 27篇 |
专业分类
电工技术 | 8篇 |
综合类 | 2篇 |
化学工业 | 122篇 |
金属工艺 | 4篇 |
机械仪表 | 11篇 |
建筑科学 | 29篇 |
能源动力 | 21篇 |
轻工业 | 74篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 37篇 |
一般工业技术 | 61篇 |
冶金工业 | 69篇 |
原子能技术 | 2篇 |
自动化技术 | 86篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 11篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 20篇 |
2015年 | 18篇 |
2014年 | 21篇 |
2013年 | 28篇 |
2012年 | 23篇 |
2011年 | 27篇 |
2010年 | 34篇 |
2009年 | 22篇 |
2008年 | 30篇 |
2007年 | 25篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 12篇 |
1998年 | 23篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1944年 | 1篇 |
1931年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有529条查询结果,搜索用时 640 毫秒
1.
Astrid Heidemann Lassen Frank Gertsen Jens Ove Riis 《Creativity & Innovation Management》2006,15(4):359-372
This paper explores the linkage between the entrepreneurial orientation of established firms and the development of radical innovation. Through five case studies in firms involved in radical innovation, three propositions are developed, suggesting that proactiveness, risk‐taking and autonomy stimulate the development of radical innovation, whereas competitive aggressiveness does not necessarily do so, as radical innovations are directed towards the creation of entirely new arenas of business, where existing competitors are not present. 相似文献
2.
Astrid Labidi Marie-Christine Salon Alessandro Gandini Hervé Cheradame 《Polymer Bulletin》1985,14(3-4):271-278
Summary 2-Furyl vinyl ketone was polymerised using anionic, cationic and free-radical initiators. Yields and molecular weights varied with the type of activation. Whereas radical polymerisation gave a product possessing a regular vinylic structure, other kinds of units were detected in the polymers prepared with anionic and cationic catalysts. 相似文献
3.
4.
Directed diffusion for wireless sensor networking 总被引:25,自引:0,他引:25
Intanagonwiwat C. Govindan R. Estrin D. Heidemann J. Silva F. 《Networking, IEEE/ACM Transactions on》2003,11(1):2-16
Advances in processor, memory, and radio technology enable small and cheap nodes capable of sensing, communication, and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. We explore the directed diffusion paradigm for such coordination. Directed diffusion is data-centric in that all communication is for named data. All nodes in a directed-diffusion-based network are application aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network (e.g., data aggregation). We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network analytically and experimentally. Our evaluation indicates that directed diffusion can achieve significant energy savings and can outperform idealized traditional schemes (e.g., omniscient multicast) under the investigated scenarios. 相似文献
5.
The development of verbal and spatial working memory was investigated with an interference paradigm. Memory spans were obtained from 3 groups (8-, 10-, and 19-yr olds) under 6 different conditions: Two primary memory tasks (1 verbal, 1 spatial) were administered in isolation and in conjunction with 2 versions of a secondary task. The primary tasks required recalling a series of visually presented digits and recalling the locations of Xs in a series of visually presented grids. The secondary tasks required reporting the color of the stimuli as they were presented using either a verbal or a spatial response. Analyses revealed that all age groups showed domain-specific interference (i.e., interference by a secondary task from the same domain as the primary task), but only the 8-yr-olds also showed nonspecific interference (i.e., interference by a secondary task from a domain different than the primary memory task), suggesting that at least some executive functions do not reach adult levels of efficiency until approximately age 10. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
A new method for characterization of stratified thermal energy stores (TES) that integrates both the first law and the second law concerns is presented here. The first law concern is incorporated into a quantity called energy response factor and the second law concern into an entropy generation ratio. A product of these two quantities is at the heart of the TES efficiency definitions. This approach removes the overemphasis of the existing methods either on the first or the second law of thermodynamics which often biases the characterization results. The information about the evolution of the temperature field of the system in time is the prerequisite of the new method. It may be obtained from experiments or from suitable numerical simulations. The current method can be easily integrated into computational fluid dynamic (CFD) simulations and thus facilitate CFD-based design analysis. As an example of such CFD-integrated analysis, a large-scale hot water seasonal heat store is numerically studied to identify the effects of aspect ratio, containment shape, internal structures, and containment size on their efficiency. The results suggest the effectiveness of the new method in deriving useful design insights. 相似文献
7.
An executable subset of VDM-SL in an SA/RT framework 总被引:2,自引:2,他引:0
In this article we present the executable specification language IPTES Meta-IV based on the formal specification language VDM-SL. The language has been fitted to work in an SA/RT framework and the article presents how it supports the specification of the data transformation part of SA/RT. Furthermore we present some of the advanced constructs of the language seen as an executable specification language in its own right. Finally we present how an IPTES Meta-IV interpreter is used in combination with a high-level timed Petri net executor to execute SA/RT models. 相似文献
8.
The frequency modulation response and tuning dynamics of a two-section DFB laser are determined by carrier and thermal modulation of the active layer refractive index. In response to a step change in the injection current for switching between channels in a wavelength division multiplexed system, the optical frequency changes rapidly due to the carrier effect, and then slowly drifts toward a steady state value due to the thermal effect. For wavelength switched applications with heterodyne detection, the drifting of the optical frequency broadens the spectrum of the IF signal and may impose a limit on the time that the signal remains within the IF passband (residency time). The IF spectral broadening and residency time are investigated theoretically and experimentally. Based upon a minimum mean square error fit between experimental and theoretical FM responses, the dependence of the spectral broadening and residency time on the bias condition of the laser and the optical frequency switching interval is characterized 相似文献
9.
The authors present a new traveling wave method for calculating the linewidth, the frequency tuning efficiency, and a mode stability parameter for a general class of laser-diode structures. The method leads to simple semianalytic expressions which allow an easy numerical determination of the three parameters 相似文献
10.
Martin Gneiser Julia Heidemann Mathias Klier Andrea Landherr Florian Probst 《Information Systems and E-Business Management》2012,10(1):61-84
Online social networks have been gaining increasing economic importance in light of the rising number of their users. Numerous
recent acquisitions priced at enormous amounts have illustrated this development and revealed the need for adequate business
valuation models. The value of an online social network is largely determined by the value of its users, the relationships
between these users, and the resulting network effects. Therefore, the interconnectedness of a user within the network has
to be considered explicitly to get a reasonable estimate for its economic value. Established standard business valuation models,
however, do not account for these aspects sufficiently. Thus, we propose an economic model for the valuation of online social
networks, which takes into account the users’ interconnectedness within the network. Furthermore, we analyze different centrality
measures, which can be used to quantify users’ interconnectedness in online social networks and propose a measure which is
based on the PageRank-algorithm. Finally, the practical application of the model is illustrated by an example of the European
online social network XING.com. 相似文献