全文获取类型
收费全文 | 7705篇 |
免费 | 682篇 |
国内免费 | 234篇 |
专业分类
电工技术 | 441篇 |
综合类 | 456篇 |
化学工业 | 826篇 |
金属工艺 | 242篇 |
机械仪表 | 415篇 |
建筑科学 | 301篇 |
矿业工程 | 119篇 |
能源动力 | 243篇 |
轻工业 | 2829篇 |
水利工程 | 63篇 |
石油天然气 | 664篇 |
武器工业 | 43篇 |
无线电 | 408篇 |
一般工业技术 | 479篇 |
冶金工业 | 145篇 |
原子能技术 | 81篇 |
自动化技术 | 866篇 |
出版年
2024年 | 59篇 |
2023年 | 164篇 |
2022年 | 280篇 |
2021年 | 324篇 |
2020年 | 345篇 |
2019年 | 282篇 |
2018年 | 288篇 |
2017年 | 302篇 |
2016年 | 323篇 |
2015年 | 347篇 |
2014年 | 440篇 |
2013年 | 461篇 |
2012年 | 517篇 |
2011年 | 585篇 |
2010年 | 392篇 |
2009年 | 370篇 |
2008年 | 349篇 |
2007年 | 390篇 |
2006年 | 339篇 |
2005年 | 322篇 |
2004年 | 262篇 |
2003年 | 240篇 |
2002年 | 195篇 |
2001年 | 154篇 |
2000年 | 133篇 |
1999年 | 126篇 |
1998年 | 128篇 |
1997年 | 100篇 |
1996年 | 59篇 |
1995年 | 55篇 |
1994年 | 44篇 |
1993年 | 43篇 |
1992年 | 28篇 |
1991年 | 23篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1959年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有8621条查询结果,搜索用时 0 毫秒
81.
H.S.J. Rashid C.S. Place G.R. Braithwaite 《International Journal of Industrial Ergonomics》2010,40(6):636-647
In this paper a statistical analysis of a sample of 58 helicopter maintenance-induced safety occurrences is conducted to study helicopter accidents and incidents’ survivability and the severity distribution of such occurrences. Analysis is also carried out to identify helicopter main and sub-systems mostly exposed to maintenance errors and to determine various types of such errors. Expected inherent relations between rotorcraft components affected and types of associated maintenance errors are investigated. Human factors-based triggers of these accidents and severe incidents are explored. The concept of Specific Failures (SFs) that immediately precede each of such occurrences is introduced for more detailed representation of the last breached individual and organizational safety barriers. Root causes of these safety occurrences were then sought utilizing the Human Factors Analysis and Classification System-Maintenance Extension (HFACS-ME) taxonomy with a refined focus on its third order categories’ list. The rotorcraft characteristics influencing individuals and organizational behaviours within Maintenance, Repair and Overhaul organizations (MROs) are discussed in the light of the root cause investigation results.
Relevance to industry
The study of human reliability within helicopter maintenance industry is waited to emphasise the understanding of causes and propagation mechanisms of maintainers' errors and their consequences on the overall aviation safety. Previous works often investigated maintenance errors and their roles in promoting aviation accidents of fixed-wing aircraft; this research is investigating the case of rotorcraft. 相似文献82.
83.
Shape optimized design of microwave dielectric resonators by level‐set and topology gradient methods
H. Khalil S. Bila M. Aubourg D. Baillargeat S. Verdeyme F. Jouve C. Delage T. Chartier 《国际射频与微波计算机辅助工程杂志》2010,20(1):33-41
The finite element method is coupled with the topology gradient (TG) and level‐set (LS) methods for optimizing the shape of microwave components using a computer‐aided design model. On the one hand, the LS approach is based on the classical shape derivative; while on the other hand, the TG method is precisely designed for introducing new perturbations in the optimization domain. These two approaches, which consist in minimizing a cost function related to the component behavior, are first described. Regarding given electrical specifications, these techniques are applied to optimize the distribution of ceramic parts of a dual‐mode resonator in order to improve its behavior. The optimized dielectric resonators result in a wide spurious‐free stop band. A comparison between classical and optimized dual mode resonator is presented. Theoretical results are then validated by careful measurements. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010. 相似文献
84.
85.
To allow efficient and user‐friendly development of a component‐based application, component systems have to provide a rather complex development infrastructure, including a tool for component composition, component repository, and a run‐time infrastructure. In this paper, we present and evaluate benefits of using meta‐modeling during the process of defining a component system and also during creation of the development and run‐time infrastructures. Most of the presented arguments are based on a broad practical experience with designing the component systems SOFA and SOFA 2; the former designed in a classical ad hoc ‘manual’ way, whereas the latter with the help of meta‐modeling. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
86.
站点计数是Web应用程序中一个最基本的功能,通过计数数据可以得知网站的受欢迎程度。构件是通过类代码来实现,设计的基本思路是:从存储站点计数数据的文件中读取数据,计数值增1,然后将数据写于文件。实际应用中,只要在需要计数的页面中加入一段代码就可以实现计数。 相似文献
87.
李云清 《计算机工程与应用》2001,37(23):136-138,156
对算法程序的功能规约进行等价变换,可以自然而且方便地得到求解问题设计思想的精确表达,即循环不变式。抽象算法又可以通过循环不变式获得。对算法程序中的算子进行提取、抽象就可以得到算法框架,而算法框架可以设计出可重用部件。文章通过对数组段极值问题的求解,展示了形式化推导不仅可以得到正确、高效的算法程序,而且具有软件重用的功能,并进一步给出了利用可重用部件求解数组段极值问题的C++实现。 相似文献
88.
Konstantinos Christodoulopoulos Vasileios Gkamas Emmanouel A. Varvarigos 《Journal of Grid Computing》2008,6(1):77-101
The existence of good probabilistic models for the job arrival process and the delay components introduced at different stages
of job processing in a Grid environment is important for the improved understanding of the Grid computing concept. In this
study, we present a thorough analysis of the job arrival process in the EGEE infrastructure and of the time durations a job
spends at different states in the EGEE environment. We define four delay components of the total job delay and model each
component separately. We observe that the job inter-arrival times at the Grid level can be adequately modelled by a rounded
exponential distribution, while the total job delay (from the time it is generated until the time it completes execution)
is dominated by the computing element’s register and queuing times and the worker node’s execution times. Further, we evaluate
the efficiency of the EGEE environment by comparing the job total delay performance with that of a hypothetical ideal super-cluster
and conclude that we would obtain similar performance if we submitted the same workload to a super-cluster of size equal to
34% of the total average number of CPUs participating in the EGEE infrastructure. We also analyze the job inter-arrival times,
the CE’s queuing times, the WN’s execution times, and the data sizes exchanged at the kallisto.hellasgrid.gr cluster, which is node in the EGEE infrastructure. In contrast to the Grid level, we find that at the cluster level the job
arrival process exhibits self-similarity/long-range dependence. Finally, we propose simple and intuitive models for the job
arrival process and the execution times at the cluster level. 相似文献
89.
90.
Roman Rosipal Mark Girolami Leonard J. Trejo Andrzej Cichocki 《Neural computing & applications》2001,10(3):231-243
In this paper, we propose the application of the Kernel Principal Component Analysis (PCA) technique for feature selection
in a high-dimensional feature space, where input variables are mapped by a Gaussian kernel. The extracted features are employed
in the regression problems of chaotic Mackey–Glass time-series prediction in a noisy environment and estimating human signal
detection performance from brain event-related potentials elicited by task relevant signals. We compared results obtained
using either Kernel PCA or linear PCA as data preprocessing steps. On the human signal detection task, we report the superiority
of Kernel PCA feature extraction over linear PCA. Similar to linear PCA, we demonstrate de-noising of the original data by
the appropriate selection of various nonlinear principal components. The theoretical relation and experimental comparison
of Kernel Principal Components Regression, Kernel Ridge Regression and ε-insensitive Support Vector Regression is also provided. 相似文献