首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   89548篇
  免费   1179篇
  国内免费   416篇
电工技术   863篇
综合类   2324篇
化学工业   12159篇
金属工艺   4872篇
机械仪表   3192篇
建筑科学   2577篇
矿业工程   576篇
能源动力   1287篇
轻工业   4056篇
水利工程   1320篇
石油天然气   365篇
无线电   9803篇
一般工业技术   17290篇
冶金工业   3789篇
原子能技术   294篇
自动化技术   26376篇
  2021年   68篇
  2020年   61篇
  2019年   89篇
  2018年   14540篇
  2017年   13486篇
  2016年   10069篇
  2015年   712篇
  2014年   356篇
  2013年   543篇
  2012年   3381篇
  2011年   9708篇
  2010年   8507篇
  2009年   5770篇
  2008年   7060篇
  2007年   8036篇
  2006年   377篇
  2005年   1428篇
  2004年   1275篇
  2003年   1329篇
  2002年   720篇
  2001年   218篇
  2000年   307篇
  1999年   191篇
  1998年   360篇
  1997年   236篇
  1996年   204篇
  1995年   124篇
  1994年   121篇
  1993年   112篇
  1992年   72篇
  1991年   78篇
  1990年   47篇
  1989年   57篇
  1988年   65篇
  1987年   64篇
  1986年   55篇
  1985年   49篇
  1984年   57篇
  1982年   39篇
  1981年   40篇
  1980年   44篇
  1979年   47篇
  1977年   49篇
  1976年   65篇
  1968年   57篇
  1967年   42篇
  1966年   56篇
  1965年   51篇
  1955年   63篇
  1954年   70篇
排序方式: 共有10000条查询结果,搜索用时 311 毫秒
51.
52.
53.
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   
54.
The physical gestures that operate music instruments are responsible for the qualities of the sound being produced in a performance. Gestural information is thereby crucial for a model of music performance, paired with a model of sound synthesis where this information is applied. The highly constrained nature of performers gestures makes this task suitable to be modeled via a constraint-based approach, coupled with a strategy aimed at maximizing the gestural comfort of performers. We illustrate the problem representation, the search strategy and a validation of the model against human performance.  相似文献   
55.
Approximately 80% of the international transport of goods is carried on by means of ships. A large portion of the transport capacity is represented by Roll-on-Roll-off (RoRo) ships. Especially in Europe this is a relevant potential for the RoRo segment. Consequently, the design and construction of RoRo ships plays an increasing role for German shipyards and their suppliers. In order to make the loading and unloading procedure of trailer economically more competitive, ship owners would like to improve the lashing of trailers on the ship. On the basis of a multibody system formalism, a software tool has been developed which allows for an optimization of the loading of trailers on RoRo ships. Commemorative Contribution.  相似文献   
56.
Structural engineers use design codes formulated to consider uncertainty for both reinforced concrete and structural steel design. For a simple one-bay structural steel frame, we survey typical uncertainties and compute an interval solution for displacements and forces. The naive solutions have large over-estimations, so we explore the Mullen-Muhanna assembly strategy, scaling, and constraint propagation to achieve tight enclosures of the true ranges for displacements and forces in a fraction of the CPU time typically used for simulations. That we compute tight enclosures, even for large parameter uncertainties used in practice, suggests the promise of interval methods for much larger structures.  相似文献   
57.
Casting simulations of self-compacting concrete are carried out in order to obtain a value of the minimum fluidity needed to cast a VHPC precambered composite beam. The mix proportioning of the concrete takes into account this minimum value. The numerical predictions are finally compared with the experimental observations during two casting tests and the real casting of the two 13 m beams. Although the simplifying assumptions needed to carry out the simulations are numerous, there is an agreement between the predictions and the real casting.  相似文献   
58.
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   
59.
A series of Al-Cu-Ni alloys of various compositions were made and annealed at 800 °C. The equilibrium phases were studied by metallography, X-ray diffraction (XRD) analysis, and electron probe microanalysis. The isothermal section of the ternary Al-Cu-Ni system at 800 °C was then determined based on these experimental results and the available phase relationship knowledge of the three constituent binary systems. No ternary compound was found. All three phases, AlNi3, AlNi, and Al3Ni2, have very high ternary solubility, especially the AlNi phase, which almost reaches the binary Al-Cu side. However, no continuous solid solution was formed between the AlNi phase and any of the binary Al-Cu phases. Interfacial reactions of Al/Ni, Al/Cu, Al-Cu/Ni, and Al-Ni/Cu at 800 °C were investigated by using reaction couple techniques. The results showed that Al3Ni and Al3Ni2 phases were formed in the Al/Ni couples; β-AlCu4, γ 1-Al4Cu9, and ɛ 2-Al2Cu3 phases were formed in the Al/Cu couples. As for the results in the Al-2 at. pct Ni/Cu, Al-5 at. pct Ni/Cu, and Al-2 at. pct Cu/Ni, Al-4.5 at. pct Cu/Ni, and Al-6 at. pct Cu/Ni were similar to those in the binary Al/Cu and Al/Ni couples, respectively. A different reaction path was found in the Al-7.5 at. pct Cu/Ni couples, and an AlNi solid solution layer was formed instead of the Al3Ni and Al3Ni2 phases.  相似文献   
60.
44 male and 74 female patients (aged 22–78 yrs) in a multidisciplinary pain clinic rated their preferences for 9 pain treatment modalities: ice, transcutaneous electronic nerve stimulation (TENS), relaxation, group therapy, social work, physical therapy, massage, heat, and lectures. Relaxation, physical therapy, and ice were most liked; TENS, heat, and social work were least liked. Multiple regression analyses indicated that preference for relaxation was the best predictor of decreased pain ratings, while preference for heat was correlated with increased pain ratings. Liking for physical therapy predicted self-ratings at discharge of positive well-being and minor life disruption. Liking for heat predicted self-ratings of major life disruption and nurses' ratings of pain behavior at discharge. Results suggest that treatment regimens should take into account patients' moods and personality styles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号