全文获取类型
收费全文 | 847篇 |
免费 | 45篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 9篇 |
综合类 | 8篇 |
化学工业 | 206篇 |
金属工艺 | 17篇 |
机械仪表 | 13篇 |
建筑科学 | 53篇 |
能源动力 | 37篇 |
轻工业 | 66篇 |
水利工程 | 7篇 |
石油天然气 | 4篇 |
无线电 | 63篇 |
一般工业技术 | 158篇 |
冶金工业 | 80篇 |
原子能技术 | 2篇 |
自动化技术 | 172篇 |
出版年
2023年 | 15篇 |
2022年 | 17篇 |
2021年 | 25篇 |
2020年 | 16篇 |
2019年 | 31篇 |
2018年 | 27篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 31篇 |
2014年 | 23篇 |
2013年 | 48篇 |
2012年 | 52篇 |
2011年 | 65篇 |
2010年 | 44篇 |
2009年 | 47篇 |
2008年 | 51篇 |
2007年 | 28篇 |
2006年 | 35篇 |
2005年 | 27篇 |
2004年 | 27篇 |
2003年 | 16篇 |
2002年 | 21篇 |
2001年 | 19篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有895条查询结果,搜索用时 15 毫秒
1.
A mixed mode digital/analog special purpose VLSI hardware implementation of an associative memory with neural architecture is presented. The memory concept is based on a matrix architecture with binary storage elements holding the connection weights. To enhance the processing speed analog circuit techniques are applied to implement the algorithm for the association. To keep the memory density as high as possible two design strategies are considered. First, the number of transistors per storage element is kept to a minimum. In this paper a circuit technique that uses a single 6-transistor cell for weight storage and analog signal processing is proposed. Second, the device precision has been chosen to a moderate level to save area as much as possible. Since device mismatch limits the performance of analog circuits, the impact of device precision on the circuit performance is explicitly discussed. It is shown that the device precision limits the number of rows activated in parallel. Since the input vector as well as the output vector are considered to be sparsely coded it is concluded, that even for large matrices the proposed circuit technique is appropriate and ultra large scale integration with a large number of connection weights is feasible. 相似文献
2.
Werner Baltes Gloria Bochmann 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1987,184(3):179-186
Summary From model roastings of mixtures containing serine, threonine and sucrose about 350 volatile compounds were separated and identified by GC/MS. Among them there were more than 100 monocyclic furans, 13 furanones and 8 bicyclic furans, the mass spectra and retention indices of which are recorded. The most important mass spectrometric fragmentation pathways are described. Spectra obtained from roasting coffee under identical conditions are compared with the spectra from model roastings.
Dissertation Gloria Bochmann, TU Berlin 1984 相似文献
Modell-Reaktionen zur Röstaroma-BildungII. Die massenspektrometrische Identifizierung von Furanen und Furanonen aus der Reaktion von Serin und Threonin mit Saccharose unter den Bedingungen der Kaffeeröstung
Zusammenfassung Aus Modellröstungen von Gemischen aus Serin, Threonin und Saccharose unter den Bedingungen der Kaffeeröstung wurden etwa 350 flüchtige Verbindungen mittels GC/MS getrennt und identifiziert. Unter ihnen befanden sich über 100 monocyclische Furane und 13 Furanone sowie 8 bicyclische Furane, deren Massenspektren und Retentions-indices angegeben werden. Die wichtigsten massenspektrometrischen Fragmentierungswege werden beschrieben. -Die aus einer gleich behandelten Röstung von Rohkaffee erhaltenen Spektren werden mit denen der Modellröstungen verglichen.
Dissertation Gloria Bochmann, TU Berlin 1984 相似文献
3.
4.
Ammoxidation of toluene over the perovskites YBa2Cu3O6.1, YBa2Cu2CoO6.7 and YBaCuCoO4.9 was investigated at 400 °C. At low partial pressures of O2 benzonitrile was selectively formed, while CO2 was the main product at high pressures of O2. Systematic differences in activity were observed for the three phases and are related to the crystal contents of Cu and Co. At low O2 pressures, Cu-sites are active for nitrile formation, while Co-sites give CO2. At high O2 pressures, the activity for CO2 of Cu-sites increases more than that of Co-sites due to filling of near-surface oxygen vacancies. 相似文献
5.
Arne Ketil Eidsvik Randi Karlsen Gordon Blair Paul Grace 《Journal of Computer and System Sciences》2008,74(2):158-169
Transaction execution in mobile environments needs to be flexible, not only to support typical mobile computing characteristics, like movement, disconnections and limited resources, but also to support the variety of transactional properties that might be required by different applications. Existing models for mobile transaction management solve different aspects of transaction execution, but are not flexible enough to solve all required aspects. Instead of designing a new transaction model, we propose a middleware (MobileTSe) which utilize existing transaction models to handle various requirements for mobile transaction execution. This paper presents an approach for flexible transaction processing in mobile applications, and describes how MobileTSe makes transaction services with different properties available on mobile units. We suggest a solution with transaction service discovery and control using UPnP. 相似文献
6.
Due to the increasing deployment of conversational real-time applications like VoIP and videoconferencing, the Internet is
today facing new challenges. Low end-to-end delay is a vital QoS requirement for these applications, and the best effort Internet
architecture does not support this natively. The delay and packet loss statistics are directly coupled to the aggregated traffic
characteristics when link utilization is close to saturation. In order to investigate the behavior and quality of such applications
under heavy network load, it is therefore necessary to create genuine traffic patterns. Trace files of real compressed video and audio are text files containing the number of bytes per video and audio frame. These can serve
as material to construct mathematical traffic models. They can also serve as traffic generators in network simulators since
they determine the packet sizes and their time schedule. However, to inspect perceived quality, the compressed binary content
is needed to ensure decoding of received media. The EvalVid streaming video tool-set enables this using a sophisticated reassembly
engine. Nevertheless, there has been a lack of research solutions for rate adaptive media content. The Internet community fears a congestion collapse if the usage of non-adaptive media content continues to
grow. This paper presents a solution named Evalvid-RA for the simulation of true rate adaptive video. The solution generates
real rate adaptive MPEG-4 streaming traffic, using the quantizer scale for adjusting the sending rate. A feedback based VBR
rate controller is used at simulation time, supporting TFRC and a proprietary congestion control system named P-AQM. Example
ns-2 simulations of TFRC and P-AQM demonstrate Evalvid-RA’s capabilities in performing close-to-true rate adaptive codec operation
with low complexity to enable the simulation of large networks with many adaptive media sources on a single computer. 相似文献
7.
Kirsten Bobzin Erich Lugscheider Felix Ernst Reimo Nickel Nazlim Bagcivan Daniel Parkot Arne Schlegel Stefania Ferrara Tatyana Kashko Noémi Leick 《Microsystem Technologies》2008,14(12):1887-1894
Nowadays, micro components have to fulfill rising optical requirements for different scientific and industrial fields like
astronomy, medicine or multimedia. For this purpose, advanced miniaturized chip-cameras are produced for the microsystems
engineering market. The assembly and joining technologies play a very important role in the production of these micro components.
Several challenges are associated with the joining of chip-cameras. In this study, the application of the soldering technology
has been considered in order to face these challenges. Two joining technologies have been investigated: active soldering and
transient liquid phase (TLP) bonding. Both soldering processes have shown a big potential for hybrid microsystems joining
in previous studies. For both processes, soldering alloys and parameters have been conceived in order to fulfill the joining
requirements of the micro camera components. For instance, the joining temperature represents a major challenge because the
chip-camera consists of a plastic material, polymethyl methacrylate (PMMA). Therefore, particular attention has been directed
to the soldering as well as to the coating temperature. The experimental investigations concerning the solders application
through physical vapor deposition (PVD) have been supported by finite element method (FEM) simulations. The analysis of the
temperature distribution in the micro components during the coating process was the focus of the calculations. Possible undesirable
local overheated areas of the chip-camera components can be detected through simulation.
相似文献
Tatyana KashkoEmail: |
8.
Dipl.-Ing. Dipl.-Wirt.?Ing. Arne Katzmarzik 《WIRTSCHAFTSINFORMATIK》2011,53(1):21-35
The market for the new provisioning type Software-as-a-Service (SaaS) has reached a significant size and still shows enormous growth rates. By varying size of SaaS products, providers can improve their market position and profits by successfully acting in the tension area of customer acquisition, pricing and costs. We first elaborate differences concerning product differentiation between classic software provisioning models and SaaS. Then, we introduce a micro-economic based decision model to maximize the return of a provider by finding an optimal granularity, i.e. by varying the size of services. This paper makes two contributions in this context: (1) it provides a conceptual foundation for product differentiation within the scope of SaaS and (2) it presents the first implementation of variable reproduction costs for web based software offers. The model is illustrated by a real world case with data from a SaaS provider. 相似文献
9.
This study investigated the effect of moving from small offices to a landscape environment for 19 Visual Display Unit (VDU) operators at Alcatel Denmark AS. The operators reported significantly improved lighting condition and glare situation. Further, visual discomfort was also significantly reduced on a Visual Analogue Scale (VAS). There was no significant correlation between lighting condition and visual discomfort neither in the small offices nor in the office landscape. However, visual discomfort correlated significantly with glare in small offices i.e. more glare is related to more visual discomfort. This correlation disappeared after the lighting system in the office landscape had been improved. There was also a significant correlation between glare and itching of the eyes as well as blurred vision in the small offices, i.e. more glare more visual symptoms. Experience of pain was found to reduce the subjective assessment of work capacity during VDU tasks. There was a significant correlation between visual discomfort and reduced work capacity in small offices and in the office landscape. When moving from the small offices to the office landscape, there was a significant reduction in headache as well as back pain. No significant changes in pain intensity in the neck, shoulder, forearm, and wrist/hand were observed.The pain levels in different body areas were significantly correlated with subjective assessment of reduced work capacity in small offices and in the office landscape.By careful design and construction of an office landscape with regard to lighting and visual conditions, transfer from small offices may be acceptable from a visual-ergonomic point of view. 相似文献
10.
The online computational burden of linear model predictive control (MPC) can be moved offline by using multi-parametric programming, so-called explicit MPC. The solution to the explicit MPC problem is a piecewise affine (PWA) state feedback function defined over a polyhedral subdivision of the set of feasible states. The online evaluation of such a control law needs to determine the polyhedral region in which the current state lies. This procedure is called point location; its computational complexity is challenging, and determines the minimum possible sampling time of the system. A new flexible algorithm is proposed which enables the designer to trade off between time and storage complexities. Utilizing the concept of hash tables and the associated hash functions, the proposed method solves an aggregated point location problem that overcomes prohibitive complexity growth with the number of polyhedral regions, while the storage–processing trade-off can be optimized via scaling parameters. The flexibility and power of this approach is supported by several numerical examples. 相似文献