全文获取类型
收费全文 | 1877篇 |
免费 | 62篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 38篇 |
综合类 | 1篇 |
化学工业 | 466篇 |
金属工艺 | 68篇 |
机械仪表 | 31篇 |
建筑科学 | 14篇 |
矿业工程 | 3篇 |
能源动力 | 92篇 |
轻工业 | 71篇 |
水利工程 | 15篇 |
石油天然气 | 17篇 |
无线电 | 258篇 |
一般工业技术 | 408篇 |
冶金工业 | 217篇 |
原子能技术 | 2篇 |
自动化技术 | 249篇 |
出版年
2023年 | 13篇 |
2022年 | 36篇 |
2021年 | 42篇 |
2020年 | 29篇 |
2019年 | 40篇 |
2018年 | 62篇 |
2017年 | 45篇 |
2016年 | 42篇 |
2015年 | 32篇 |
2014年 | 65篇 |
2013年 | 160篇 |
2012年 | 78篇 |
2011年 | 94篇 |
2010年 | 71篇 |
2009年 | 65篇 |
2008年 | 73篇 |
2007年 | 84篇 |
2006年 | 47篇 |
2005年 | 53篇 |
2004年 | 41篇 |
2003年 | 54篇 |
2002年 | 45篇 |
2001年 | 30篇 |
2000年 | 33篇 |
1999年 | 25篇 |
1998年 | 72篇 |
1997年 | 53篇 |
1996年 | 32篇 |
1995年 | 30篇 |
1994年 | 28篇 |
1993年 | 36篇 |
1992年 | 23篇 |
1991年 | 30篇 |
1990年 | 35篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 16篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 19篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1973年 | 6篇 |
排序方式: 共有1950条查询结果,搜索用时 15 毫秒
41.
Detecting spatio-temporal clusters, i.e. clusters of objects similar to each other occurring together across space and time, has important real-world applications such as climate change, drought analysis, detection of outbreak of epidemics (e.g. bird flu), bioterrorist attacks (e.g. anthrax release), and detection of increased military activity. Research in spatio-temporal clustering has focused on grouping individual objects with similar trajectories, detecting moving clusters, or discovering convoys of objects. However, most of these solutions are based on using a piece-meal approach where snapshot clusters are formed at each time stamp and then the series of snapshot clusters are analyzed to discover moving clusters. This approach has two fundamental limitations. First, it is point-based and is not readily applicable to polygonal datasets. Second, its static analysis approach at each time slice is susceptible to inaccurate tracking of dynamic cluster especially when clusters change over both time and space. In this paper we present a spatio-temporal polygonal clustering algorithm known as the Spatio-Temporal Polygonal Clustering (STPC) algorithm. STPC clusters spatial polygons taking into account their spatial and topological properties, treating time as a first-class citizen, and integrating density-based clustering with moving cluster analysis. Our experiments on the drought analysis application, flu spread analysis and crime cluster detection show the validity and robustness of our algorithm in an important geospatial application. 相似文献
42.
Non-Parametric Mixture Model Based Evolution of Level Sets and Application to Medical Images 总被引:1,自引:0,他引:1
We present a novel region-based curve evolution algorithm which has three primary contributions: (i) non-parametric estimation
of probability distributions using the recently developed NP windows method; (ii) an inequality-constrained least squares
method to model the image histogram with a mixture of nonparametric probability distributions; and (iii) accommodation of
the partial volume effect, which is primarily due to low resolution images, and which often poses a significant challenge
in medical image analysis (our primary application area). We first approximate the image intensity histogram as a mixture
of non-parametric probability density functions (PDFs), justifying its use with respect to medical image analysis. The individual
densities in the mixture are estimated using the recent NP windows PDF estimation method, which builds a continuous representation
of discrete signals. A Bayesian framework is then formulated in which likelihood probabilities are given by the non-parametric
PDFs and prior probabilities are calculated using an inequality constrained least squares method. The non-parametric PDFs
are then learnt and the segmentation solution is spatially regularised using a level sets framework. The log ratio of the
posterior probabilities is used to drive the level set evolution. As background to our approach, we recall related developments
in level set methods. Results are presented for a set of synthetic and natural images as well as simulated and real medical
images of various anatomical organs. Results on a range of images show the effectiveness of the proposed algorithm. 相似文献
43.
Carl Lederman Anand Joshi Ivo Dinov John Darrell Van Horn Luminita Vese Arthur Toga 《Journal of Mathematical Imaging and Vision》2016,55(2):179-198
We introduce a new volumetric registration technique that effectively combines active surfaces with the finite element method. The method simultaneously aligns multi-label automatic structural segmentation results, which can be obtained by the application of existing segmentation software, to produce an anatomically accurate 3D registration. This registration is obtained by the minimization of a single energy functional. Just like registering raw images, obtaining a 3D registration this way still requires solving a fundamentally ill-posed problem. We explain through academic examples as well as an MRI dataset with manual anatomical labels, which are hidden from the registration method, how the quality of a registration method can be measured and the advantages our approach offers. 相似文献
44.
Many tasks in AI require representation and manipulation of complex functions. First-Order Decision Diagrams (FODD) are a compact knowledge representation expressing functions over relational structures. They represent numerical functions that, when constrained to the Boolean range, use only existential quantification. Previous work has developed a set of operations for composition and for removing redundancies in FODDs, thus keeping them compact, and showed how to successfully employ FODDs for solving large-scale stochastic planning problems through the formalism of relational Markov decision processes (RMDP). In this paper, we introduce several new ideas enhancing the applicability of FODDs. More specifically, we first introduce Generalized FODDs (GFODD) and composition operations for them, generalizing FODDs to arbitrary quantification. Second, we develop a novel approach for reducing (G)FODDs using model checking. This yields – for the first time – a reduction that maximally reduces the diagram for the FODD case and provides a sound reduction procedure for GFODDs. Finally we show how GFODDs can be used in principle to solve RMDPs with arbitrary quantification, and develop a complete solution for the case where the reward function is specified using an arbitrary number of existential quantifiers followed by an arbitrary number of universal quantifiers. 相似文献
45.
Joshi A Qian X Dione DP Bulsara KR Breuer CK Sinusas AJ Papademetris X 《IEEE transactions on visualization and computer graphics》2008,14(6):1603-1610
The effective visualization of vascular structures is critical for diagnosis, surgical planning as well as treatment evaluation. In recent work, we have developed an algorithm for vessel detection that examines the intensity profile around each voxel in an angiographic image and determines the likelihood that any given voxel belongs to a vessel; we term this the "vesselness coefficient" of the voxel. Our results show that our algorithm works particularly well for visualizing branch points in vessels. Compared to standard Hessian based techniques, which are fine-tuned to identify long cylindrical structures, our technique identifies branches and connections with other vessels. Using our computed vesselness coefficient, we explore a set of techniques for visualizing vasculature. Visualizing vessels is particularly challenging because not only is their position in space important for clinicians but it is also important to be able to resolve their spatial relationship. We applied visualization techniques that provide shape cues as well as depth cues to allow the viewer to differentiate between vessels that are closer from those that are farther. We use our computed vesselness coefficient to effectively visualize vasculature in both clinical neurovascular x-ray computed tomography based angiography images, as well as images from three different animal studies. We conducted a formal user evaluation of our visualization techniques with the help of radiologists, surgeons, and other expert users. Results indicate that experts preferred distance color blending and tone shading for conveying depth over standard visualization techniques. 相似文献
46.
Caban J Joshi A Rheingans P 《IEEE transactions on visualization and computer graphics》2007,13(6):1472-1479
Analyzing, visualizing, and illustrating changes within time-varying volumetric data is challenging due to the dynamic changes occurring between timesteps. The changes and variations in computational fluid dynamic volumes and atmospheric 3D datasets do not follow any particular transformation. Features within the data move at different speeds and directions making the tracking and visualization of these features a difficult task. We introduce a texture-based feature tracking technique to overcome some of the current limitations found in the illustration and visualization of dynamic changes within time-varying volumetric data. Our texture-based technique tracks various features individually and then uses the tracked objects to better visualize structural changes. We show the effectiveness of our texture-based tracking technique with both synthetic and real world time-varying data. Furthermore, we highlight the specific visualization, annotation, registration, and feature isolation benefits of our technique. For instance, we show how our texture-based tracking can lead to insightful visualizations of time-varying data. Such visualizations, more than traditional visualization techniques, can assist domain scientists to explore and understand dynamic changes. 相似文献
47.
48.
Stephen M. Pizer P. Thomas Fletcher Sarang Joshi Andrew Thall James Z. Chen Yonatan Fridman Daniel S. Fritsch A. Graham Gash John M. Glotzer Michael R. Jiroutek Conglin Lu Keith E. Muller Gregg Tracton Paul Yushkevich Edward L. Chaney 《International Journal of Computer Vision》2003,55(2-3):85-106
M-reps (formerly called DSLs) are a multiscale medial means for modeling and rendering 3D solid geometry. They are particularly well suited to model anatomic objects and in particular to capture prior geometric information effectively in deformable models segmentation approaches. The representation is based on figural models, which define objects at coarse scale by a hierarchy of figures—each figure generally a slab representing a solid region and its boundary simultaneously. This paper focuses on the use of single figure models to segment objects of relatively simple structure.A single figure is a sheet of medial atoms, which is interpolated from the model formed by a net, i.e., a mesh or chain, of medial atoms (hence the name m-reps), each atom modeling a solid region via not only a position and a width but also a local figural frame giving figural directions and an object angle between opposing, corresponding positions on the boundary implied by the m-rep. The special capability of an m-rep is to provide spatial and orientational correspondence between an object in two different states of deformation. This ability is central to effective measurement of both geometric typicality and geometry to image match, the two terms of the objective function optimized in segmentation by deformable models. The other ability of m-reps central to effective segmentation is their ability to support segmentation at multiple levels of scale, with successively finer precision. Objects modeled by single figures are segmented first by a similarity transform augmented by object elongation, then by adjustment of each medial atom, and finally by displacing a dense sampling of the m-rep implied boundary. While these models and approaches also exist in 2D, we focus on 3D objects.The segmentation of the kidney from CT and the hippocampus from MRI serve as the major examples in this paper. The accuracy of segmentation as compared to manual, slice-by-slice segmentation is reported. 相似文献
49.
On Using a Warehouse to Analyze Web Logs 总被引:1,自引:0,他引:1
Analyzing Web Logs for usage and access trends can not only provide important information to web site developers and administrators, but also help in creating adaptive web sites. While there are many existing tools that generate fixed reports from web logs, they typically do not allow ad-hoc analysis queries. Moreover, such tools cannot discover hidden patterns of access embedded in the access logs. We describe a relational OLAP (ROLAP) approach for creating a web-log warehouse. This is populated both from web logs, as well as the results of mining web logs. We discuss the design criteria that influenced our choice of dimensions, facts and data granularity. A web based ad-hoc tool for analytic queries on the warehouse was developed. We present some of the performance specific experiments that we performed on our warehouse. 相似文献
50.
Scene change detection techniques for video database systems 总被引:1,自引:0,他引:1
Haitao Jiang Abdelsalam Helal Ahmed K. Elmagarmid Anupam Joshi 《Multimedia Systems》1998,6(3):186-195
Scene change detection (SCD) is one of several fundamental problems in the design of a video database management system (VDBMS).
It is the first step towards the automatic segmentation, annotation, and indexing of video data. SCD is also used in other
aspects of VDBMS, e.g., hierarchical representation and efficient browsing of the video data. In this paper, we provide a
taxonomy that classifies existing SCD algorithms into three categories: full-video-image-based, compressed-video-based, and
model-based algorithms. The capabilities and limitations of the SCD algorithms are discussed in detail. The paper also proposes
a set of criteria for measuring and comparing the performance of various SCD algorithms. We conclude by discussing some important
research directions. 相似文献