全文获取类型
收费全文 | 119477篇 |
免费 | 2776篇 |
国内免费 | 462篇 |
专业分类
电工技术 | 1017篇 |
综合类 | 2355篇 |
化学工业 | 19571篇 |
金属工艺 | 5463篇 |
机械仪表 | 3694篇 |
建筑科学 | 3259篇 |
矿业工程 | 631篇 |
能源动力 | 2321篇 |
轻工业 | 9966篇 |
水利工程 | 1579篇 |
石油天然气 | 511篇 |
武器工业 | 2篇 |
无线电 | 10762篇 |
一般工业技术 | 21488篇 |
冶金工业 | 9841篇 |
原子能技术 | 501篇 |
自动化技术 | 29754篇 |
出版年
2024年 | 73篇 |
2023年 | 296篇 |
2022年 | 765篇 |
2021年 | 1068篇 |
2020年 | 750篇 |
2019年 | 913篇 |
2018年 | 15401篇 |
2017年 | 14268篇 |
2016年 | 11034篇 |
2015年 | 1621篇 |
2014年 | 1591篇 |
2013年 | 2783篇 |
2012年 | 5139篇 |
2011年 | 11526篇 |
2010年 | 9944篇 |
2009年 | 7214篇 |
2008年 | 8251篇 |
2007年 | 9085篇 |
2006年 | 1243篇 |
2005年 | 2141篇 |
2004年 | 2043篇 |
2003年 | 1961篇 |
2002年 | 1252篇 |
2001年 | 617篇 |
2000年 | 690篇 |
1999年 | 643篇 |
1998年 | 2459篇 |
1997年 | 1607篇 |
1996年 | 1146篇 |
1995年 | 622篇 |
1994年 | 529篇 |
1993年 | 558篇 |
1992年 | 218篇 |
1991年 | 217篇 |
1990年 | 166篇 |
1989年 | 184篇 |
1988年 | 171篇 |
1987年 | 147篇 |
1986年 | 121篇 |
1985年 | 172篇 |
1984年 | 113篇 |
1983年 | 101篇 |
1982年 | 109篇 |
1981年 | 121篇 |
1980年 | 113篇 |
1978年 | 59篇 |
1977年 | 185篇 |
1976年 | 342篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Kunkel Mark A.; Hector Mark A.; Góngora Coronado Elías; Castillo Vales Victor 《Canadian Metallurgical Quarterly》1989,36(3):322
Conducted a study of client expectations of psychological services in Yucatán, Mexico, under the sponsorship of a grant from the Organization of American States. The Expectations about Counseling–Brief form (EAC-B) questionnaire was translated and administered to 488 subjects across age, sex, and experience with psychological services. Subsequent analyses supported the reliability and robustness of the Spanish EAC-B, with factor structure similar to the EAC-B in English. Some relation was found among age, sex, prior counseling experience, and expectations about counseling. Implications of these data for future research and comparison with U.S. subjects are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
72.
ABSTRACT: Trimethylamine N-oxide demethylase (TMAOase) activity of several internal organs of hake were studied for 2 consecutive y. The correlation between enzymatic activity and season of year, sex, weight, and length were analyzed. While kidney and spleen showed the highest activities, liver, heart, bile, and gall bladder activities were much lower, and in some cases they were below the detection limit. A correlation between TMAOase activity of kidney and season was found. During winter and spring (February to May), the months matching the spawning peak, high activities were detected, while in summer months the activity level was lower. TMAOase activity in the rest of the organs did not seem to have a seasonal influence. Keywords: TMAOase, season, biological condition, hake, soluble protein 相似文献
73.
Less may not be more,but it still counts: The state of social capital in Yeoville,Johannesburg 总被引:2,自引:2,他引:0
Kirsten Harrison 《Urban Forum》2002,13(1):67-84
74.
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
75.
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
76.
Various influence diagnostics in Multiple Discriminant Analysis can be found in the literature. Almost all of them are based
on the overall probability of misclassification. Two case-deletion diagnostics which evaluate the effect of the omission on
the linear functions which determine Fisher’s Linear Discriminant Rule are proposed in this paper. Both measures are based
on the L
2-norm: The first diagnostic is calculated from the data set and the second diagnostic is calculated in the minimum hypercube
which covers it. 相似文献
77.
78.
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
79.
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
80.
The comfort diagrams and the so-called PMV-PPD values are already used today directly and indirectly in a wide field in technical practice, even at a standard level. This theory is known also in Hungary, and the PMV-PPD values have been used by us for the solution of a design problem. The task was to elaborate a calculation method, an index number suitable for the determination of the thermal confort effect in the case of occasional underheating of residential and communal buildings in winter.The results of this work are presented in this paper. 相似文献