全文获取类型
收费全文 | 114654篇 |
免费 | 2359篇 |
国内免费 | 440篇 |
专业分类
电工技术 | 1086篇 |
综合类 | 2369篇 |
化学工业 | 18214篇 |
金属工艺 | 5286篇 |
机械仪表 | 3577篇 |
建筑科学 | 4006篇 |
矿业工程 | 638篇 |
能源动力 | 1970篇 |
轻工业 | 6255篇 |
水利工程 | 1556篇 |
石油天然气 | 506篇 |
武器工业 | 3篇 |
无线电 | 11418篇 |
一般工业技术 | 21956篇 |
冶金工业 | 7964篇 |
原子能技术 | 458篇 |
自动化技术 | 30191篇 |
出版年
2023年 | 277篇 |
2022年 | 452篇 |
2021年 | 703篇 |
2020年 | 509篇 |
2019年 | 596篇 |
2018年 | 14990篇 |
2017年 | 13899篇 |
2016年 | 10724篇 |
2015年 | 1403篇 |
2014年 | 1249篇 |
2013年 | 2107篇 |
2012年 | 4755篇 |
2011年 | 11369篇 |
2010年 | 9656篇 |
2009年 | 6907篇 |
2008年 | 8403篇 |
2007年 | 9253篇 |
2006年 | 1561篇 |
2005年 | 2429篇 |
2004年 | 2207篇 |
2003年 | 2100篇 |
2002年 | 1439篇 |
2001年 | 645篇 |
2000年 | 710篇 |
1999年 | 601篇 |
1998年 | 577篇 |
1997年 | 494篇 |
1996年 | 523篇 |
1995年 | 456篇 |
1994年 | 444篇 |
1993年 | 449篇 |
1992年 | 399篇 |
1991年 | 255篇 |
1990年 | 324篇 |
1989年 | 326篇 |
1988年 | 287篇 |
1987年 | 300篇 |
1986年 | 290篇 |
1985年 | 309篇 |
1984年 | 270篇 |
1983年 | 264篇 |
1982年 | 242篇 |
1981年 | 216篇 |
1980年 | 179篇 |
1979年 | 187篇 |
1978年 | 168篇 |
1977年 | 144篇 |
1976年 | 139篇 |
1975年 | 138篇 |
1974年 | 112篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Yanqiu Shao Jiqing Han Ting Liu Yongzhen Zhao 《International Journal of Speech Technology》2007,10(1):45-55
In real speech, not like lexical words (LWs), prosodic words (PWs) are basic rhythmic units. The naturalness of a Text-to-Speech
(TTS) system is directly influenced by the segmentation of the PWs. Most of the PWs are the combination of several LWs. In
this paper, three Lexical Combination Models are proposed to combine LWs into PWs, including a Directed Acyclic Graph Model,
a Segmentation Model and a Markov Model (MM). To cope with the situation where some long LWs should be segmented into two
or more PWs, a Lexical Split Model (LSM) is applied to the long LWs. Experimental results prove that relatively constant results
with various training data can be obtained from a MM. The Transformation-Based Error Driven Learning (TBED) algorithm, for
its high performance of individual property, is applied in combination with the MM to improve the precision of PW segmentation.
Experiments show that among the three proposed models, the MM combined with TBED and LSM, leads to the best performance, in
which a precision of 93.00% and a recall of 93.23% are achieved. The perception test indicates that by using PWs as the lowest
prosodic units a speech sounds more natural and acceptable than by using LWs.
This paper is supported by NSFC Project (60503071); 973 Natural Basic Research Program of China (2004CB318102); Postdoctor
Science Foundation of P. R. China (20070420275). 相似文献
22.
In this paper we describe, from a theoretical point of view, critical configurations for the projective reconstruction of
a set of points, for a single view, i.e. for calibration of a camera, in the case of projections from ℙk to ℙ2 for k ≥ 4. We give first a general result describing these critical loci in ℙk, which, if irreducible, are algebraic varieties of dimension k−2 and degree 3. If k=4 they can be either a smooth ruled surface or a cone and if k = 5 they can be a smooth three dimensional variety, ruled in planes, or a cone. If k≥ 6, the variety is always a cone, the
vertex of which has dimension at least k − 6. The reducible cases are studied in Appendix A.
These results are then applied to determine explicitly the critical loci for the projections from ℙk which arise from the dynamic scenes in ℙ3 considered in [13].
Marina Bertolini is currently Associate Professor of Geometry at the Department of Mathematics at the Università degli Studi di Milano, Italy.
Her main field of research is Complex Projective Algebraic Geometry, with particular interest for the classification of projective
varieties and for the geometry of Grassmann varieties. On these topics M. Bertolini has published more than twenty reviewed
papers on national and international journals. She has been for some years now interested also in applications of Algebraic
Geometry to Computer Vision problems.
Cristina Turrini is Associate Professor of Geometry at the Department of Mathematics of Università degli Studi di Milano, Italy. Her main
research interest is Complex Projective Algebraic Geometry: subvarieties of Grassmannians, special varieties, automorphisms,
classification. In the last two years she has started to work on applications of Algebraic Geometry to problems of Computer
Vision. She is author or co-author of about thirty reviewed papers. She is also involved in popularization of Mathematics,
and on this subject she is co-editor of some books. 相似文献
23.
Linking Entrepreneurship to Growth: The Case of West Germany 总被引:1,自引:0,他引:1
24.
25.
Jon T. Carter Paul E. Krajewski Ravi Verma 《JOM Journal of the Minerals, Metals and Materials Society》2008,60(11):77-81
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive
applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect
of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General
Motors Corporation is reviewed. 相似文献
26.
Toshihiko Hoshide Junpei Fujita 《Journal of Materials Engineering and Performance》2008,17(5):627-632
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction
for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based
on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual
stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison
of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated
by using the proposed procedure. 相似文献
27.
A model is presented for the thermal shock damage in plates subjected to a sudden rise in temperature. Spalling is assumed to follow localized buckling caused by the thermally induced compressive stresses above subsurface flaws. The minimum size o flaw required to cause spalling is determined as a function of the material properties of the plate, the temperature rise, the position of the paw, and the time after the thermal shock. 相似文献
28.
Previous solid state analyses of sintering in Ti4+ -doped-commercial alumina are shown to be in error because a liquid phase exists in the appropriate region of the Al2 O3 −TiO3 −Na2 Ophase diagram at least by 1350° C, a temperature lower than that at which "solid state" studies were conducted. It is suggested that liquid-phase sintering is a much more common occurrence than was realized formerly. 相似文献
29.
Tested the ability of 4 adult male Sprague-Dawley rats to use odors in discrimination among littermates living as a group. Ss were trained in a Y-maze to discriminate the presence of a littermate from its absence. Results from transfer of training in 3 subsequent testing periods indicated that the animals were capable of distinguishing among individuals when relatedness and familiarity were held constant, that this ability was not due to training, and that performance was based solely on odor cues. Results suggest that laboratory rats exhibit odor sensitivities conmensurate with very complex social processes. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.
Ron Kimmel Doron Shaked Michael Elad Irwin Sobel 《IEEE transactions on image processing》2005,14(6):796-803
Gamut mapping deals with the need to adjust a color image to fit into the constrained color gamut of a given rendering medium. A typical use for this tool is the reproduction of a color image prior to its printing, such that it exploits best the given printer/medium color gamut, namely the colors the printer can produce on the given medium. Most of the classical gamut mapping methods involve a pixel-by-pixel mapping and ignore the spatial color configuration. Recently proposed spatial-dependent approaches for gamut mapping are either based on heuristic assumptions or involve a high computational cost. In this paper, we present a new variational approach for space-dependent gamut mapping. Our treatment starts with the presentation of a new measure for the problem, closely related to a recent measure proposed for Retinex. We also link our method to recent measures that attempt to couple spectral and spatial perceptual measures. It is shown that the gamut mapping problem leads to a quadratic programming formulation, guaranteed to have a unique solution if the gamut of the target device is convex. An efficient numerical solution is proposed with promising results. 相似文献