全文获取类型
收费全文 | 179262篇 |
免费 | 15651篇 |
国内免费 | 8434篇 |
专业分类
电工技术 | 11381篇 |
技术理论 | 13篇 |
综合类 | 11655篇 |
化学工业 | 29318篇 |
金属工艺 | 9914篇 |
机械仪表 | 11251篇 |
建筑科学 | 13709篇 |
矿业工程 | 5444篇 |
能源动力 | 5292篇 |
轻工业 | 12431篇 |
水利工程 | 3272篇 |
石油天然气 | 10720篇 |
武器工业 | 1403篇 |
无线电 | 21529篇 |
一般工业技术 | 21509篇 |
冶金工业 | 8736篇 |
原子能技术 | 1922篇 |
自动化技术 | 23848篇 |
出版年
2024年 | 901篇 |
2023年 | 3414篇 |
2022年 | 6346篇 |
2021年 | 8500篇 |
2020年 | 6399篇 |
2019年 | 5058篇 |
2018年 | 5725篇 |
2017年 | 6396篇 |
2016年 | 5703篇 |
2015年 | 7588篇 |
2014年 | 9396篇 |
2013年 | 11253篇 |
2012年 | 12243篇 |
2011年 | 12879篇 |
2010年 | 10992篇 |
2009年 | 10374篇 |
2008年 | 9900篇 |
2007年 | 9121篇 |
2006年 | 9298篇 |
2005年 | 7960篇 |
2004年 | 5310篇 |
2003年 | 4469篇 |
2002年 | 4001篇 |
2001年 | 3604篇 |
2000年 | 3533篇 |
1999年 | 4151篇 |
1998年 | 3454篇 |
1997年 | 2932篇 |
1996年 | 2741篇 |
1995年 | 2213篇 |
1994年 | 1798篇 |
1993年 | 1297篇 |
1992年 | 1044篇 |
1991年 | 785篇 |
1990年 | 567篇 |
1989年 | 465篇 |
1988年 | 367篇 |
1987年 | 252篇 |
1986年 | 209篇 |
1985年 | 129篇 |
1984年 | 116篇 |
1983年 | 86篇 |
1982年 | 86篇 |
1981年 | 68篇 |
1980年 | 62篇 |
1979年 | 29篇 |
1978年 | 25篇 |
1977年 | 24篇 |
1976年 | 26篇 |
1975年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Yang Xuejun Du Yunfei Wang Panfeng Fu Hongyi Jia Jia 《Parallel and Distributed Systems, IEEE Transactions on》2009,20(10):1471-1486
As the size of large-scale computer systems increases, their mean-time-between-failures are becoming significantly shorter than the execution time of many current scientific applications. To complete the execution of scientific applications, they must tolerate hardware failures. Conventional rollback-recovery protocols redo the computation of the crashed process since the last checkpoint on a single processor. As a result, the recovery time of all protocols is no less than the time between the last checkpoint and the crash. In this paper, we propose a new application-level fault-tolerant approach for parallel applications called the Fault-Tolerant Parallel Algorithm (FTPA), which provides fast self-recovery. When fail-stop failures occur and are detected, all surviving processes recompute the workload of failed processes in parallel. FTPA, however, requires the user to be involved in fault tolerance. In order to ease the FTPA implementation, we developed Get it Fault-Tolerant (GiFT), a source-to-source precompiler tool to automate the FTPA implementation. We evaluate the performance of FTPA with parallel matrix multiplication and five kernels of NAS Parallel Benchmarks on a cluster system with 1,024 CPUs. The experimental results show that the performance of FTPA is better than the performance of the traditional checkpointing approach. 相似文献
942.
Jae Kyeong Jeong Jong Han Jeong Hui Won Yang Tae Kyung Ahn Minkyu Kim Kwang Suk Kim Bon Seog Gu Hyun‐Joong Chung Jin‐Seong Park Yeon‐Gon Mo Hye Dong Kim Ho Kyoon Chung 《Journal of the Society for Information Display》2009,17(2):95-100
Abstract— A full‐color 12.1‐in.WXGA active‐matrix organic‐light‐emitting‐diode (AMOLED) display was, for the first time, demonstrated using indium‐gallium‐zinc oxide (IGZO) thin‐film transistors (TFTs) as an active‐matrix backplane. It was found that the fabricated AMOLED display did not suffer from the well‐known pixel non‐uniformity in luminance, even though the simple structure consisting of two transistors and one capacitor was adopted as the unit pixel circuit, which was attributed to the amorphous nature of IGZO semiconductors. The n‐channel a‐IGZO TFTs exhibited a field‐effect mobility of 17 cm2/V‐sec, threshold voltage of 1.1 V, on/off ratio >109, and subthreshold gate swing of 0.28 V/dec. The AMOLED display with a‐IGZO TFT array is promising for large‐sized applications such as notebook PCs and HDTVs because the a‐IGZO semiconductor can be deposited on large glass substrates (larger than Gen 7) using the conventional sputtering system. 相似文献
943.
Xiaohui Zhao Chengfei Liu Yun Yang Sadiq W. 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2009,39(6):1152-1164
Business collaboration encompasses the coordination of information flows among organizations as well as the composition of their business processes toward mutual benefits. While integrating business processes of different organizations seamlessly, it brings great challenges to keep participating organizations as autonomous entities. To address this issue, we propose a new perspective on modeling collaborative business processes with a novel concept called relative workflow (RWF). With its visibility control mechanism, the RWF model defines what a participating organization can perceive in collaboration and thereby allows each organization to customize its own collaboration process and behaviors. In this paper, we present a formal definition of RWFs and related algorithms for generating RWFs. A prototype is implemented on the Web service platform for the proof-of-concept purpose. 相似文献
944.
Soo-Yong Shin In-Hee Lee Young-Min Cho Kyung-Ae Yang Byoung-Tak Zhang 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2009,39(6):1606-1616
Probe design is one of the most important tasks in successful deoxyribonucleic acid microarray experiments. We propose a multiobjective evolutionary optimization method for oligonucleotide probe design based on the multiobjective nature of the probe design problem. The proposed multiobjective evolutionary approach has several distinguished features, compared with previous methods. First, the evolutionary approach can find better probe sets than existing simple filtering methods with fixed threshold values. Second, the multiobjective approach can easily incorporate the user's custom criteria or change the existing criteria. Third, our approach tries to optimize the combination of probes for the given set of genes, in contrast to other tools that independently search each gene for qualifying probes. Lastly, the multiobjective optimization method provides various sets of probe combinations, among which the user can choose, depending on the target application. The proposed method is implemented as a platform called EvoOligo and is available for service on the Web. We test the performance of EvoOligo by designing probe sets for 19 types of Human Papillomavirus and 52 genes in the Arabidopsis Calmodulin multigene family. The design results from EvoOligo are proven to be superior to those from well-known existing probe design tools, such as OligoArray and OligoWiz. 相似文献
945.
Yan Zhang Laurence T. Yang Jianhua Ma Jun Zheng 《Journal of Network and Computer Applications》2009,32(2):483-489
As a fundamental component in wireless networks, location management consists of two operations: location update and paging. These two supplementary operations enable the mobile user ubiquitous mobility. However, in case of failed location update, a significant consequence is the obsolete location identity in the network databases and thereafter the incapability in establishing the valid route for the potential call connection, which will seriously degrade the network quality-of-service (QoS). This issue is not theoretically studied in the literature. In this paper, we perform a quantitative analysis of the location management effect on QoS in the wireless networks. The metrics call blocking probability and the average number of blocked calls are introduced to reflect the QoS. For the sake of general applicability, the performance metrics are formulated with the relaxed tele-traffic parameters. Namely, the call inter-arrival time, cell residence time, location area residence time and location update inter-arrival time follow a general probability density function. The formulae are additionally specified in the static and several dynamic location management mechanisms. Numerical examples are presented to show the interaction between the performance metrics and location management schemes. The discussions on the sensitivity of tele-parameters are also given. 相似文献
946.
947.
Xiang-Bin Shi Xue Wang Jing Bi Fang Liu Dan Yang Xian-Yan Liu 《Multimedia Tools and Applications》2009,45(1-3):247-261
Considering player entity’s motion regularity into DR (Dead Reckoning) algorithm can improve its prediction accuracy in MMOG (Massively Multiplayer Online Games), a novel DR algorithm was proposed to solve this problem in this paper. First the artificial potential field model of player entities is created, and then the acceleration of player entities is weighted with the acceleration produced by the potential field force and the acceleration reckoned by the traditional DR algorithm. In order to calculate the weight, Q-Learning algorithm is used. The experiments show that the method can improve prediction accuracy and reduce the network traffic. 相似文献
948.
This paper is concerned with the problem of boosting social annotations using propagation, which is also called social propagation. In particular, we focus on propagating social annotations of web pages (e.g., annotations in Del.icio.us). Social annotations
are novel resources and valuable in many web applications, including web search and browsing. Although they are developing
fast, social annotations of web pages cover only a small proportion (<0.1%) of the World Wide Web. To alleviate the low coverage
of annotations, a general propagation model based on Random Surfer is proposed. Specifically, four steps are included, namely
basic propagation, multiple-annotation propagation, multiple-link-type propagation, and constraint-guided propagation. The
model is evaluated on a dataset of 40,422 web pages randomly sampled from 100 most popular English sites and ten famous academic
sites. Each page’s annotations are obtained by querying the history interface of Del.icio.us. Experimental results show that
the proposed model is very effective in increasing the coverage of annotations while still preserving novel properties of
social annotations. Applications of propagated annotations on web search and classification further verify the effectiveness
of the model. 相似文献
949.
Flexible decision tree for data stream classification in the presence of concept change, noise and missing values 总被引:1,自引:0,他引:1
In recent years, classification learning for data streams has become an important and active research topic. A major challenge
posed by data streams is that their underlying concepts can change over time, which requires current classifiers to be revised
accordingly and timely. To detect concept change, a common methodology is to observe the online classification accuracy. If
accuracy drops below some threshold value, a concept change is deemed to have taken place. An implicit assumption behind this
methodology is that any drop in classification accuracy can be interpreted as a symptom of concept change. Unfortunately however,
this assumption is often violated in the real world where data streams carry noise that can also introduce a significant reduction
in classification accuracy. To compound this problem, traditional noise cleansing methods are incompetent for data streams.
Those methods normally need to scan data multiple times whereas learning for data streams can only afford one-pass scan because
of data’s high speed and huge volume. Another open problem in data stream classification is how to deal with missing values.
When new instances containing missing values arrive, how a learning model classifies them and how the learning model updates
itself according to them is an issue whose solution is far from being explored. To solve these problems, this paper proposes
a novel classification algorithm, flexible decision tree (FlexDT), which extends fuzzy logic to data stream classification.
The advantages are three-fold. First, FlexDT offers a flexible structure to effectively and efficiently handle concept change. Second, FlexDT is robust to noise. Hence it can prevent noise
from interfering with classification accuracy, and accuracy drop can be safely attributed to concept change. Third, it deals
with missing values in an elegant way. Extensive evaluations are conducted to compare FlexDT with representative existing
data stream classification algorithms using a large suite of data streams and various statistical tests. Experimental results
suggest that FlexDT offers a significant benefit to data stream classification in real-world scenarios where concept change,
noise and missing values coexist. 相似文献
950.
Broadcasting scheme with low client buffers and bandwidths for video-on-demand applications 总被引:1,自引:1,他引:0
Hsiang-Fu Yu Hung-Chang Yang Yao-Tien Wang Ping-Lin Fan Chu-Yi Chien 《Multimedia Tools and Applications》2009,42(3):295-316
Efficient data broadcasting is independent of request arrivals, and is thus highly promising when transmitting popular videos.
A conventionally adopted broadcasting method is periodic broadcasting, which divides a popular video into segments, which
are then simultaneously broadcast on different data channels. Once clients want to watch the video, they download the segments
from these channels. The skyscraper broadcasting (SkB) scheme supports clients with small bandwidths. An SkB client requires
only two-channel bandwidths to receive video segments. This work proposes a reverse SkB (RSkB) scheme, which extends SkB by
reducing buffering spaces. The RSkB is mathematically shown to achieve on-time video delivery and two-channel client bandwidths.
A formula for determining the maximum number of segments buffered by an RSkB client is presented. Finally, an analysis of
RSkB reveals that its client buffer requirements are usually 25–37% lower than SkB. Extensive simulations of RSkB further
demonstrate that RSkB yields lower client buffer demand than other proposed systems.
相似文献
Hsiang-Fu YuEmail: |