全文获取类型
收费全文 | 893篇 |
免费 | 20篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 13篇 |
综合类 | 101篇 |
化学工业 | 133篇 |
金属工艺 | 11篇 |
机械仪表 | 17篇 |
建筑科学 | 190篇 |
矿业工程 | 7篇 |
能源动力 | 13篇 |
轻工业 | 26篇 |
水利工程 | 6篇 |
石油天然气 | 7篇 |
武器工业 | 1篇 |
无线电 | 41篇 |
一般工业技术 | 133篇 |
冶金工业 | 146篇 |
原子能技术 | 1篇 |
自动化技术 | 70篇 |
出版年
2023年 | 6篇 |
2022年 | 13篇 |
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 15篇 |
2017年 | 13篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 25篇 |
2013年 | 56篇 |
2012年 | 29篇 |
2011年 | 71篇 |
2010年 | 26篇 |
2009年 | 50篇 |
2008年 | 26篇 |
2007年 | 32篇 |
2006年 | 34篇 |
2005年 | 22篇 |
2004年 | 30篇 |
2003年 | 22篇 |
2002年 | 25篇 |
2001年 | 23篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 50篇 |
1997年 | 26篇 |
1996年 | 30篇 |
1995年 | 20篇 |
1994年 | 13篇 |
1993年 | 35篇 |
1992年 | 47篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有916条查询结果,搜索用时 375 毫秒
41.
Automata theory, algorithmic deduction and abstract interpretation provide the foundation behind three approaches to implementing program verifiers. This article is a first step towards a mathematical translation between these approaches. By extending Büchi’s theorem, we show that reachability in a control flow graph can be encoded as satisfiability in an extension of the weak, monadic, second-order logic of one successor. Abstract interpreters are, in a precise sense, sound but incomplete solvers for such formulae. The three components of an abstract interpreter: the lattice, transformers and iteration algorithm, respectively represent a fragment of a first-order theory, deduction in that theory, and second-order constraint propagation. By inverting the Lindenbaum–Tarski construction, we show that lattices used in practice are subclassical first-order theories. 相似文献
42.
43.
44.
SO–IL是一个概念设计工作室。工作室的业务遍及全球,拥有建筑界、学术界和艺术领域的丰富设计经验。Florian Idenburg和Jing Liu于2007年在布鲁克林成立了工作室,并将它设想为能涵盖不同规模的建筑和不同的建设阶段,成为一个具有创造性的触媒。 相似文献
45.
46.
Metamer density estimated color correction 总被引:1,自引:0,他引:1
Color correction is the transformation of response values of scanners or digital cameras into a device- independent color
space. In general, the transformation is not unique due to different acquisition and viewing illuminants and non-satisfaction
of the Luther–Ives condition by a majority of devices. In this paper we propose a method that approximates the optimal color
correction in the sense of a minimal mean error. The method is based on a representative set of reflectance spectra that is
used to calculate a special basic collection of device metameric blacks and an appropriate fundamental metamer for each sensor
response. Combining the fundamental metamer and the basic collection results in a set of reflectances that follows the density
distribution of metameric reflectances if calculated by Bayesian inference. Transforming only positive and bounded spectra
of the set into an observer’s perceptually uniform color space results in a point cloud that follows the density distribution
of device metamers within the metamer mismatch space of acqcuisition system and human observer. The mean value of this set
is selected for color correction, since this is the point with a minimal mean color distance to all other points in the cloud.
We present the results of various simulation experiments considering different acquisition and viewing illuminants, sensor
types, noise levels, and existing methods for comparison. 相似文献
47.
Wiklund U Akay M Morrison S Niklasson U 《IEEE transactions on bio-medical engineering》2002,49(7):651-661
In this paper, the discrete wavelet transform (DWT) was applied to analyze the fluctuations in RR interval and systolic arterial pressure (SAP) recorded from eight alpha-chloralose anesthetized pigs. Our aim was to characterize the autonomic modulation before and after cardiac autonomic blockade and during baroreflex function tests. The instantaneous power of decomposed low-frequency (LF) and high-frequency (HF) components was used for a time-variant spectral analysis. Our results suggested that transient events and changes in autonomic modulation were detected with high temporal resolution. A nonlinear relationship between RR interval and SAP during pharmacologically induced changes in blood pressure was found, when the superimposed effect of respiratory sinus arrhythmia was removed. In addition, the baroslopes were nearly linear when both the LF and HF components were removed using DWT decomposition. 相似文献
48.
Recently an electromagnetic hexapole system for the correction of the spherical aberration of the objective lens of a 200 kV transmission electron microscope has been constructed by Haider and coworkers. By appropriately exciting the hexapole elements it is possible to adjust specific values of the spherical aberration coefficient ranging from the value of the original uncorrected instrument over zero even to negative values. In the first part of the paper the consequences of the tunable spherical aberration are investigated. New imaging modes are available: By adjustment of an optimum value for the spherical-aberration coefficient, the point resolution of phase-contrast imaging can be extended to the information limit. Phase-contrast imaging can be improved by a reduced level of contrast delocalisation. For zero aberration contrast delocalisation does not occur. In this case high-resolution investigations are carried out under amplitude-contrast conditions, where the local image intensity of crystalline objects is controlled by electron diffraction channelling. The defocus and spherical aberration values related to the new imaging modes are given. In the second part novel applications of the instrument to semiconductor heterostructures and ceramic grain boundaries are examined. 相似文献
49.
Jana Urban Joemon M. Jose Cornelis J. van Rijsbergen 《Multimedia Tools and Applications》2006,31(1):1-28
We discuss an adaptive approach towards Content-Based Image Retrieval. It is based on the Ostensive Model of developing information needs—a special kind of relevance feedback model that learns from implicit user feedback and adds a temporal notion to relevance. The ostensive approach supports content-assisted browsing through visualising the interaction by adding user-selected images to a browsing path, which ends with a set of system recommendations. The suggestions are based on an adaptive query learning scheme, in which the query is learnt from previously selected images. Our approach is an adaptation of the original Ostensive Model based on textual features only, to include content-based features to characterise images. In the proposed scheme textual and colour features are combined using the Dempster-Shafer theory of evidence combination. Results from a user-centred, work-task oriented evaluation show that the ostensive interface is preferred over a traditional interface with manual query facilities. This is due to its ability to adapt to the user's need, its intuitiveness and the fluid way in which it operates. Studying and comparing the nature of the underlying information need, it emerges that our approach elicits changes in the user's need based on the interaction, and is successful in adapting the retrieval to match the changes. In addition, a preliminary study of the retrieval performance of the ostensive relevance feedback scheme shows that it can outperform a standard relevance feedback strategy in terms of image recall in category search. 相似文献
50.
结合土地利用再谈城市交通可持续发展 总被引:4,自引:1,他引:4
针对城市交通的现状分析了中国城市交通可持续发展的制约因素,论述了合理的土地利用规划是城市交通规划的前提,是解决21世纪我国城市交通面临的主要矛盾的根本方法,是实现我国城市交通可持续发展的有效途径. 相似文献