全文获取类型
收费全文 | 43149篇 |
免费 | 918篇 |
国内免费 | 180篇 |
专业分类
电工技术 | 530篇 |
综合类 | 630篇 |
化学工业 | 4567篇 |
金属工艺 | 588篇 |
机械仪表 | 885篇 |
建筑科学 | 842篇 |
矿业工程 | 391篇 |
能源动力 | 424篇 |
轻工业 | 2081篇 |
水利工程 | 612篇 |
石油天然气 | 54篇 |
武器工业 | 4篇 |
无线电 | 1870篇 |
一般工业技术 | 3420篇 |
冶金工业 | 21554篇 |
原子能技术 | 186篇 |
自动化技术 | 5609篇 |
出版年
2024年 | 55篇 |
2023年 | 192篇 |
2022年 | 117篇 |
2021年 | 112篇 |
2019年 | 56篇 |
2018年 | 468篇 |
2017年 | 680篇 |
2016年 | 1062篇 |
2015年 | 787篇 |
2014年 | 427篇 |
2013年 | 438篇 |
2012年 | 2141篇 |
2011年 | 2435篇 |
2010年 | 674篇 |
2009年 | 767篇 |
2008年 | 616篇 |
2007年 | 635篇 |
2006年 | 568篇 |
2005年 | 3348篇 |
2004年 | 2567篇 |
2003年 | 2048篇 |
2002年 | 846篇 |
2001年 | 731篇 |
2000年 | 281篇 |
1999年 | 619篇 |
1998年 | 6174篇 |
1997年 | 3816篇 |
1996年 | 2510篇 |
1995年 | 1463篇 |
1994年 | 1074篇 |
1993年 | 1113篇 |
1992年 | 252篇 |
1991年 | 307篇 |
1990年 | 304篇 |
1989年 | 279篇 |
1988年 | 297篇 |
1987年 | 226篇 |
1986年 | 203篇 |
1985年 | 171篇 |
1984年 | 71篇 |
1983年 | 85篇 |
1982年 | 133篇 |
1981年 | 180篇 |
1980年 | 195篇 |
1979年 | 60篇 |
1978年 | 104篇 |
1977年 | 616篇 |
1976年 | 1329篇 |
1975年 | 100篇 |
1971年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
991.
Oleksandr?PanchenkoEmail author Hasso?Plattner Alexander?B.?Zeier 《Information Systems Frontiers》2011,13(3):349-357
Enabling fast and detailed insights over large portions of source code is an important task in a global development ecosystem.
Numerous data structures have been developed to store source code and to support various structural queries, to help in navigation,
evaluation and analysis. Many of these data structures work with tree-based or graph-based representations of source code.
The goal of this project is to elaborate a data storage that enables efficient storing and fast querying of structural information.
The naive adjacency list method has been enhanced with the use of recent data compression approaches for column-oriented databases
to allow no-loss albeit compact storage of fine-grained structural data. The graph indexing has enabled the proposed data
model to expeditiously answer fine-grained structural queries. This paper describes the basics of the proposed approach and
illustrates its technical feasibility. 相似文献
992.
Maher El��Arbi Mohamed Koubaa Maha Charfeddine Chokri Ben Amar 《Multimedia Tools and Applications》2011,55(3):579-600
In this paper, we propose a video watermarking algorithm which embeds different parts of a single watermark into different shots of a video under the wavelet domain. Based on a Motion Activity Analysis, different regions of the original video are separated into perceptually distinct categories according to motion information and region complexity. Thus, the localizations of the watermark are adjusted adaptively in accordance with the human visual system and signal characteristics, which makes them perceptually invisible and less vulnerable to automated removal. In addition, contrary to traditional methods where the watermark remains at a fixed position on the screen, the watermark moves along with moving objects and thus motion artefacts can be avoid. The multi-frame based extraction strategy ensures that the watermark can be correctly recovered from a very short segment of video. Individual frames extracted from the video also contain watermark information. Experimental results show that the inserted watermark is not only less perceptible but also robust against common video processing attacks. 相似文献
993.
Radio frequency identification (RFID) is viewed as a technology that improves supply chain efficiency by enhancing inventory
efficiency, optimizing logistics, and coordinating the flow of materials. Although RFID has gained great attention in many
business applications, the financial gain that accrues over time from RFID adoption is not well understood. We examine the
effects of RFID on firm profits while adjusting for self-selection of adoption choice. We find that firms self-select into
a certain adoption mode on the basis of their organizational characteristics. Our results also show that RFID confers significant
benefits for firms that have adopted RFID. Interestingly, improved inventory ratio and sales efficiency begin to play a greater
role in shaping higher profitability over time for firms that have adopted RFID possibly due to time-consuming processes for
them to reap the benefits from RFID. However, we find that the values of RFID that accrue to firms are not universal across
firm. That is, our results suggest that RFID confers a significant value for certain firms while it does not for other firms
with unobservable disadvantages. In sum, our study sheds new light on what drives firms to adopt RFID and on which firms achieve
higher financial performance in a post-adoption period as a result of RFID adoption. 相似文献
994.
Jenq-Shiou?LeuEmail author Hui-Ching?Hsieh Yen-Chiu?Chen 《Multimedia Tools and Applications》2011,53(1):285-301
In the era of IP-based service, people expect a simple, cheap, and competent Voice over IP (VoIP) service as an alternative
of the traditional voice over PSTN. The introduction of the SIP protocol realizes the expectation. Following the cost saving
spirit of VoIP, we focus on studying inexpensive high availability solutions for the SIP-based VoIP Service. In this paper,
Peer-to-Peer (P2P) based and DN-LB based schemes are mainly compared in the paper. A P2P-based scheme enables an inexpensive
high availability solution to the VoIP service by the shared computation resources form P2P nodes. Such a P2P-based solution
may be appropriate for an individual VoIP user. However, a caller may take a large volume of messages to find out a callee
via the proxy nodes in the P2P network. This inherent property of a P2P network may induce the message overhead and long call
setup delay. Based on above, another inexpensive scheme, which is a probing-based name resolution solution, is proposed to
achieve high availability and load balancing for the VoIP service. We tag the probing mechanism onto the open source project
Domain Name Relay Daemon (DNRD) to become a domain name resolution based load balancer (DN-LB). With DN-LB, all request messages
from clients can be fairly distributed to all failure-proof proxy servers in the server farm without using any additional
costly intermediate network device and changing the standard SIP architecture. Such a DN-LB based solution may be a good choice
for a VoIP service provider. 相似文献
995.
Joan?CahillEmail author Nick?Mc?Donald Captain?Gabriel?Losa 《Cognition, Technology & Work》2011,13(1):43-66
A safe flight starts with effective performance of the pre-flight flight planning and briefing task. However, several problems
related to the execution of this task can be identified. Potentially, the introduction of an improved flight plan provides
an opportunity to improve the quality and availability of information provided to Flight Crew, thereby enhancing the quality
of crew briefings. The proposed risk-based, intelligent flight plan is designed from the perspective of the current operational
concept (e.g. fixed routes and ATC managerial role for separation), and associated airline Flight Planning and Dispatch functions.
In this case, the focus is sharing information across specific airline stakeholders (e.g. Flight Operations Management and
Safety functions) and Maintenance, to support a safe and efficient flight operation. Overall, the introduction of this new
flight plan will result in the definition of new operational and organisational processes, along with a new way of performing
the pre-flight, planning and briefing task. It is anticipated that this will impact positively on the operational and safety
outcome of the flight. 相似文献
996.
(O)mür (O)cal 《国际自动化与计算杂志》2011,8(2):254-261
The coefficient diagram method (CDM) is one of the most effective control design methods. It creates control systems that
are very stable and robust with responses without the overshoot and small settling time. Furthermore, all control parameters
of the control systems are changed by varying some adjustment parameters in CDM depending on the demands. The model reference
adaptive systems (MRAS) are the systems that follow and change the control parameters according to a given model reference
system. There are several methods to combine the CDM with MRAS. One of these is to use the MRAS parameters as a gain of the
CDM parameters. Another is to directly use the CDM parameters as the MRAS parameters. In the industrial applications, the
system parameters can be changed frequently, but if the controller, by self-tuning, recalculates and develops its own parameters
continuously, the system becomes more robust. Also, if the poles of the controlled systems approach the jw axis, the response of the closed-loop MRAS becomes more and more insufficient. In order to obtain better results, CDM is
combined with a self-tuning model reference adaptive system. Systems controlled by a model reference adaptive controller give
responses with small or without overshoot, have small settling times, and are more robust. Thus, in this paper, a hybrid combination
of MRAS and CDM is developed and two different control structures of the control signal are investigated. The two methods
are compared with MRAS and applied to real-time process control systems. 相似文献
997.
998.
Dragan Iveti? Author Vitae Author Vitae Branko Markoski Author Vitae 《Computers & Electrical Engineering》2010,36(1):169-179
This paper presents a novel video augmentation approach: a video recording of a real entity augmented by structured data. This augmented video is a self-contained entity integrating values of perceptible and non-perceptible attributes of the same real entity. It simplifies data search, storage and management. Streaming, sharing, collaboration and synchronization are also simplified by the fact that the structured data (so-called augmented data) are integrated in the video file and therefore only one file needs to be manipulated. Our approach was applied to address the issues which road engineers experience while using the ROad Measurement and Data Acquisition System (ROMDAS). The ROMDAS system collects and analyses the road-condition state through video recordings and the data corresponding acquired by specific measuring devices. Currently, however, road engineers have to search the videos manually in order to find details of interest provided by the analysis of the data measured due to the separation of the video from the data. The ROMDAS system manages a large collection of road-condition data. It does not offer history management of video recordings of the same road captured at different time. We present this hybrid video augmentation system: the Augmented Video stream Framework (AVF). It allows creation, search, history management and playback of such augmented video files for effective road surveying based on the discrete data recorded in parallel to the video recordings. The AVF provides road engineers with effective and more comfortable perceptible and non-perceptible data search, storage and history management to be used for (collaborative) road inspection and maintenance. 相似文献
999.
?pek Abas?kele? 《Computers & Electrical Engineering》2010,36(1):114-131
Recent advances in the development of optical technologies suggest the possible emergence of broadcast-based optical interconnects within cache-coherent distributed shared memory (DSM) multiprocessor architectures. It is well known that the cache-coherence protocol is a critical issue in designing such architectures because it directly affects memory latencies. In this paper, we evaluate via simulation the performance of three directory-based cache-coherence protocols; strict request-response, intervention forwarding and reply forwarding on the Simultaneous Optical Multiprocessor Exchange Bus (SOME-Bus), which is a low-latency and high-bandwidth broadcast-based fiber-optic interconnection network supporting DSM. The simulated system contains 64 nodes, each of which has a processor, a cache controller, a directory controller and an output channel. Simulations have been conducted for each protocol to measure average processor utilization, average network latency and average number of packets transferred over the network for varying values of the important DSM parameters such as the ratio of the mean channel service time to mean thread run time (T/R), probability of a cache block being in modified state {P(M)}, the fraction of write misses {P(W)} and home node contention rate. The results reveal that for all cases, except for low values of P(M), intervention forwarding gives the worst performance (lowest processor utilization and highest latency). The performance of strict request-response and reply forwarding is comparable for several values of the DSM parameters and contention rate. For a contention rate of 0%, the increase of P(M) makes reply forwarding perform better than strict request-response. The performance of all protocols decreases with the increase of P(W) and contention rate. However, the performance of strict request-response is the least affected among other protocols due to the negative impact of the increase of P(W) and contention rate. Therefore, for the full contention case (i.e. contention rate of 100%); for low values of P(M), or for mid values of P(M) and high values of P(W), strict request-response performs better than reply forwarding. These results are significant in the sense that they provide an insight to multiprocessor architecture designers for comparing the performance of different directory-based cache-coherence protocols on a broadcast-based interconnection network for different values of the DSM parameters and varying rates of contention. 相似文献
1000.
Explanation and reliability of prediction models: the case of breast cancer recurrence 总被引:1,自引:1,他引:0
Erik ?trumbelj Zoran Bosni? Igor Kononenko Branko Zakotnik Cvetka Gra?i? Kuhar 《Knowledge and Information Systems》2010,24(2):305-324
In this paper, we describe the first practical application of two methods, which bridge the gap between the non-expert user
and machine learning models. The first is a method for explaining classifiers’ predictions, which provides the user with additional
information about the decision-making process of a classifier. The second is a reliability estimation methodology for regression
predictions, which helps the users to decide to what extent to trust a particular prediction. Both methods are successfully
applied to a novel breast cancer recurrence prediction data set and the results are evaluated by expert oncologists. 相似文献