全文获取类型
收费全文 | 112997篇 |
免费 | 2113篇 |
国内免费 | 520篇 |
专业分类
电工技术 | 1179篇 |
综合类 | 2545篇 |
化学工业 | 16859篇 |
金属工艺 | 5402篇 |
机械仪表 | 3657篇 |
建筑科学 | 3186篇 |
矿业工程 | 655篇 |
能源动力 | 2090篇 |
轻工业 | 7553篇 |
水利工程 | 1508篇 |
石油天然气 | 505篇 |
武器工业 | 6篇 |
无线电 | 11536篇 |
一般工业技术 | 20396篇 |
冶金工业 | 9076篇 |
原子能技术 | 504篇 |
自动化技术 | 28973篇 |
出版年
2023年 | 173篇 |
2022年 | 551篇 |
2021年 | 861篇 |
2020年 | 587篇 |
2019年 | 669篇 |
2018年 | 15002篇 |
2017年 | 14043篇 |
2016年 | 10618篇 |
2015年 | 1193篇 |
2014年 | 1146篇 |
2013年 | 1761篇 |
2012年 | 4444篇 |
2011年 | 11010篇 |
2010年 | 9434篇 |
2009年 | 6786篇 |
2008年 | 7851篇 |
2007年 | 8716篇 |
2006年 | 981篇 |
2005年 | 2106篇 |
2004年 | 2059篇 |
2003年 | 2015篇 |
2002年 | 1354篇 |
2001年 | 822篇 |
2000年 | 741篇 |
1999年 | 598篇 |
1998年 | 2138篇 |
1997年 | 1395篇 |
1996年 | 999篇 |
1995年 | 630篇 |
1994年 | 504篇 |
1993年 | 565篇 |
1992年 | 245篇 |
1991年 | 311篇 |
1990年 | 239篇 |
1989年 | 202篇 |
1988年 | 223篇 |
1987年 | 166篇 |
1986年 | 166篇 |
1985年 | 181篇 |
1984年 | 129篇 |
1983年 | 93篇 |
1982年 | 118篇 |
1981年 | 121篇 |
1980年 | 116篇 |
1979年 | 91篇 |
1978年 | 75篇 |
1977年 | 141篇 |
1976年 | 237篇 |
1975年 | 82篇 |
1954年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
21.
A. P. J. Voncken A. F. J. Hammen A. T. A. M. de Waele 《Journal of Low Temperature Physics》1996,102(3-4):335-348
In this paper we describe the effect of the vicinity of a liquid3He-vacuum interface on the behavior of a vibrating wire viscometer. It was found that in the fluid near the liquid interface the quality factor is lower than in the bulk liquid. We further report on the observation of a doubling of the resonance peak of the wire in a saturated3He-4He mixture. The frequencies and amplitudes of the two peaks strongly depend on the distance between the phase boundary and the vibrating wire; the temperature and the velocity of the phase boundary have no significant influence on the peak frequencies. The observed peak doubling is attributed to the coupling of the vibrating wire with a standing second-sound wave in the dilute phase where the volume of the dilute phase can be regarded as a resonating cavity for second sound. 相似文献
22.
23.
24.
J-M Choe 《欧洲信息系统杂志》2002,11(2):142-158
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms. 相似文献
25.
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
26.
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
27.
28.
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
29.
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
30.
From visual data exploration to visual data mining: a survey 总被引:8,自引:0,他引:8
Ferreira de Oliveira M.C. Levkowitz H. 《IEEE transactions on visualization and computer graphics》2003,9(3):378-394
We survey work on the different uses of graphical mapping and interaction techniques for visual data mining of large data sets represented as table data. Basic terminology related to data mining, data sets, and visualization is introduced. Previous work on information visualization is reviewed in light of different categorizations of techniques and systems. The role of interaction techniques is discussed, in addition to work addressing the question of selecting and evaluating visualization techniques. We review some representative work on the use of information visualization techniques in the context of mining data. This includes both visual data exploration and visually expressing the outcome of specific mining algorithms. We also review recent innovative approaches that attempt to integrate visualization into the DM/KDD process, using it to enhance user interaction and comprehension. 相似文献