全文获取类型
收费全文 | 8825篇 |
免费 | 475篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 121篇 |
综合类 | 38篇 |
化学工业 | 2263篇 |
金属工艺 | 238篇 |
机械仪表 | 186篇 |
建筑科学 | 612篇 |
矿业工程 | 20篇 |
能源动力 | 283篇 |
轻工业 | 844篇 |
水利工程 | 87篇 |
石油天然气 | 43篇 |
武器工业 | 1篇 |
无线电 | 665篇 |
一般工业技术 | 1473篇 |
冶金工业 | 560篇 |
原子能技术 | 58篇 |
自动化技术 | 1819篇 |
出版年
2023年 | 85篇 |
2022年 | 202篇 |
2021年 | 333篇 |
2020年 | 187篇 |
2019年 | 201篇 |
2018年 | 271篇 |
2017年 | 233篇 |
2016年 | 316篇 |
2015年 | 233篇 |
2014年 | 342篇 |
2013年 | 632篇 |
2012年 | 487篇 |
2011年 | 615篇 |
2010年 | 432篇 |
2009年 | 497篇 |
2008年 | 459篇 |
2007年 | 411篇 |
2006年 | 343篇 |
2005年 | 292篇 |
2004年 | 276篇 |
2003年 | 260篇 |
2002年 | 190篇 |
2001年 | 140篇 |
2000年 | 139篇 |
1999年 | 114篇 |
1998年 | 132篇 |
1997年 | 128篇 |
1996年 | 98篇 |
1995年 | 79篇 |
1994年 | 82篇 |
1993年 | 87篇 |
1992年 | 58篇 |
1991年 | 62篇 |
1990年 | 61篇 |
1989年 | 68篇 |
1988年 | 49篇 |
1987年 | 47篇 |
1986年 | 50篇 |
1985年 | 53篇 |
1984年 | 62篇 |
1983年 | 44篇 |
1982年 | 40篇 |
1981年 | 38篇 |
1980年 | 39篇 |
1979年 | 32篇 |
1978年 | 35篇 |
1977年 | 34篇 |
1976年 | 45篇 |
1975年 | 41篇 |
1973年 | 37篇 |
排序方式: 共有9311条查询结果,搜索用时 31 毫秒
271.
Hole Kjell J. Netland Lars-Helge Espelid Yngve Klingsheim Andr N. Helleseth Hallvar Henriksen Jan B. 《Security & Privacy, IEEE》2008,6(4):14-20
Open wireless networks raise privacy issues and entail increased risk of malicious attacks and illegal downloading activities. Such networks are nonetheless attractive—particularly to universities—because they enhance usability and thus expand access to nonsensitive system resources. At universities, such access brings numerous benefits to students, faculty, and the surrounding community alike. Here, the authors describe the challenges of removing individual user authentication requirements at the perimeter of a university network in which mobile device users access system resources over wireless links to the wired infrastructure. The authors discuss how to mitigate the security and privacy risks entailed in an open network of this sort, and also describe how IT departments can vary the network's degree of openness. 相似文献
272.
273.
Sacchi M Spezzani C Carpentiero A Prasciolu M Delaunay R Lüning J Polack F 《The Review of scientific instruments》2007,78(4):043702
We have developed a setup for measuring holographically formed interference patterns using an integrated sample-mask design. The direct space image of the sample is obtained via a two-dimensional Fourier transform of the X-ray diffraction pattern. We present the details of our setup, commenting on the influence of geometrical parameters on the imaging capabilities. As an example, we present and discuss the results of test experiments on a patterned Co film. 相似文献
274.
A self-analysis of the NASA-TLX workload measure 总被引:2,自引:0,他引:2
Computer use and, more specifically, the administration of tests and materials online continue to proliferate. A number of subjective, self-report workload measures exist, but the National Aeronautics and Space Administration-Task Load Index (NASA-TLX) is probably the most well known and used. The aim of this paper is to consider the workload costs associated with the computer-based and paper versions of the NASA-TLX measure. It was found that there is a significant difference between the workload scores for the two media, with the computer version of the NASA-TLX incurring more workload. This has implications for the practical use of the NASA-TLX as well as for other computer-based workload measures. 相似文献
275.
In this paper a reusable multi-agent architecture for intelligent Websites is presented and illustrated for an electronic department store. The architecture has been designed and implemented using the compositional design method for multi-agent systems DESIRE. The agents within this architecture are based on a generic information broker agent model. It is shown how the architecture can be exploited to design an intelligent Website for insurance, developed in co-operation with the software company Ordina Utopics and an insurance company. 相似文献
276.
Jan O. Borchers 《AI & Society》2001,15(4):359-376
To create successful interactive systems, user interface designers need to cooperate with developers and application domain experts in an interdisciplinary team. These groups, however, usually lack a common terminology to exchange ideas, opinions and values. This paper presents an approach that uses pattern languages to capture this knowledge in software development, human-computer interaction (HCI) and the application domain. A formal, domain-independent definition of design patterns allows for computer support without sacrificing readability, and pattern use is integrated into the usability engineering life cycle. As an example, experience from building an award-winning interactive music exhibit was turned into a pattern language, which was then used to inform follow-up projects and support HCI education.An earlier version of this paper appeared in theProceedings of the DIS 2000 International Conference on Designing Interactive Systems (16–19 August 2000, New York) and appears by permission of the ACM Press. 相似文献
277.
When artists portray human faces, they generally endow their portraits with properties that render the faces esthetically more pleasing. To obtain insight into the changes introduced by artists, we compared Fourier power spectra in photographs of faces and in portraits by artists. Our analysis was restricted to a large set of monochrome or lightly colored portraits from various Western cultures and revealed a paradoxical result. Although face photographs are not scale-invariant, artists draw human faces with statistical properties that deviate from the face photographs and approximate the scale-invariant, fractal-like properties of complex natural scenes. This result cannot be explained by systematic differences in the complexity of patterns surrounding the faces or by reproduction artifacts. In particular, a moderate change in gamma gradation has little influence on the results. Moreover, the scale-invariant rendering of faces in artists' portraits was found to be independent of cultural variables, such as century of origin or artistic techniques. We suggest that artists have implicit knowledge of image statistics and prefer natural scene statistics (or some other rules associated with them) in their creations. Fractal-like statistics have been demonstrated previously in other forms of visual art and may be a general attribute of esthetic visual stimuli. 相似文献
278.
Hoyer D Friedrich H Frank B Pompe B Baranowski R Zebrowski JJ Schmidt H 《Computer methods and programs in biomedicine》2006,81(3):246-255
Heart rate variability (HRV) represents the cardiovascular control mediated by the autonomic nervous system and other mechanisms. In the established task force HRV monitoring different cardiovascular control mechanisms can approximately be identified at typical frequencies of heart rate oscillations by power spectral analysis. HRV measures assessing complex and fractal behavior partly improved clinical risk stratification. However, their relationship to (patho-)physiology is not sufficiently explored. Objective of the present work is the introduction of complexity measures of different physiologically relevant time scales. This is achieved by a new concept of the autonomic information flow (AIF) analysis which was designed according to task force HRV. First applications show that different time scales of AIF improve the risk stratification of patients with multiple organ dysfunction syndrome and cardiac arrest patients in comparison to standard HRV. Each group's significant time scales correspond to their respective pathomechanisms. 相似文献
279.
Free binary decision diagrams (FBDDs) are graph-based data structures representing Boolean functions with the constraint (additional
to binary decision diagram) that each variable is tested at most once during the computation. The function EARn is the following Boolean function defined for n × n Boolean matrices: EARn(M) = 1 iff the matrix M contains two equal adjacent rows. We prove that each FBDD computing EARn has size at least
and we present a construction of such diagrams of size approximately
. 相似文献
280.
A polynomial time computable metric between point sets 总被引:4,自引:0,他引:4
Measuring the similarity or distance between sets of points in a metric space is an important problem in machine learning
and has also applications in other disciplines e.g. in computational geometry, philosophy of science, methods for updating
or changing theories, . Recently Eiter and Mannila have proposed a new measure which is computable in polynomial time. However, it is not a distance
function in the mathematical sense because it does not satisfy the trian gle inequality. We introduce a new measure which
is a metric while being computable in polynomial time. We also present a variant which computes a normalised metric and a
variant which can associate different weights with the points in the set.
Received: 18 October 1999 / 8 January 2001 相似文献