全文获取类型
收费全文 | 2044篇 |
免费 | 115篇 |
国内免费 | 14篇 |
专业分类
化学 | 1448篇 |
晶体学 | 14篇 |
力学 | 42篇 |
综合类 | 1篇 |
数学 | 277篇 |
物理学 | 391篇 |
出版年
2023年 | 20篇 |
2022年 | 24篇 |
2021年 | 48篇 |
2020年 | 66篇 |
2019年 | 68篇 |
2018年 | 37篇 |
2017年 | 41篇 |
2016年 | 89篇 |
2015年 | 76篇 |
2014年 | 56篇 |
2013年 | 116篇 |
2012年 | 104篇 |
2011年 | 140篇 |
2010年 | 62篇 |
2009年 | 62篇 |
2008年 | 125篇 |
2007年 | 102篇 |
2006年 | 113篇 |
2005年 | 83篇 |
2004年 | 77篇 |
2003年 | 56篇 |
2002年 | 59篇 |
2001年 | 39篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 20篇 |
1997年 | 23篇 |
1996年 | 22篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 32篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 20篇 |
1988年 | 19篇 |
1987年 | 12篇 |
1986年 | 17篇 |
1985年 | 25篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1975年 | 10篇 |
1974年 | 12篇 |
1973年 | 9篇 |
排序方式: 共有2173条查询结果,搜索用时 484 毫秒
1.
When an organization solves a portfolio problem with public projects evaluated by multiple criteria, in which the economic dimension is not essential or not well characterized, the classical methods are not useful. We propose a non-linear preference model developed from normative Value Theory and using fuzzy sets to model some sources of imprecision. This model can be considered as a generalization of the classical approaches. However, the optimization problem is very complex in order to be solved with non-linear programming techniques. Therefore, the model is exploited by an evolutionary algorithm, able to achieve a strong improvement of the quality of solution. 相似文献
2.
The problem of finding the Euclidean distance between two convex polyhedra can be reduced to the combinatorial optimization problem of finding the minimum distance between their faces. This paper presents a global optimality criterion for this problem. An algorithm (QLDPA) for the fast computation of the distance between convex and bounded polyhedra is proposed as an application of it. Computer experiments show its fast performance, especially when the total number of vertices is large. 相似文献
3.
4.
Sherif Yehia C. Mitros Sanjeev Kumar S. Jha Glenn M. Julian R. A. Dunlap 《Hyperfine Interactions》1987,34(1-4):415-418
The systematics of hyperfine magnetic fields at sp impurities on the Z-sites in Co based Heusler alloys are investigated. New TDPAC measurements of Cd hyperfine fields are reported. 相似文献
5.
In this paper, three new direct Mutually Orthogonal Latin Squares (MOLS) constructions are presented for 7 MOLS(24), 7 MOLS(75) and 8 MOLS(36); then using recursive methods, several new constructions for 7 and 8 MOLS are obtained. These reduce the largest value for which 7 MOLS are unknown from 780 to 570, and the largest odd value for which 8 MOLS are unknown from 1935 to 419. © 2003 Wiley Periodicals, Inc. 相似文献
6.
E. Casarejos P. Armbruster L. Audouin J. Benlliure M. Bernas A. Boudard R. Legrain S. Leray B. Mustapha S. Czajkowski T. Enqvist B. Fernandez J. Pereira M. Pravikoff F. Rejmund K. -H. Schmidt C. Stephan J. Taieb L. Tassan-Got C. Villagrasa C. Volant W. Wlazlo 《Physics of Atomic Nuclei》2003,66(8):1413-1420
The isotopic production cross sections of heavy residues in relativistic heavy-ion collisions have been investigated in inverse kinematics. The primary reaction products were fully identified in mass and atomic number prior to beta decay using the fragment separator FRS. The huge collection of data obtained helps in the understanding of the two main reaction mechanisms involved: fragmentation and fission. These data provide basic information for future radioactive ion beam facilities and for technical applications like intense neutron sources by means of spallation targets. 相似文献
7.
8.
Ultrasonic analysis of edible fats and oils 总被引:7,自引:0,他引:7
Low intensity ultrasound is a powerful analytical technique for investigating the physico-chemical properties of many biological and non-biological materials. In this article its application for the characterization of edible fats and oils is assessed. Ultrasound can be used to determine the dynamic rheology and composition of oils, the oil content and droplet size of emulsions and the solid fat content of partially crystalline emulsions. It is capable of rapid and precise measurements, is non-destructive and non-invasive, can be used on-line or off-line and is relatively inexpensive. Ultrasonic techniques will therefore prove a useful addition to the existing analytical techniques used to characterize fats and oils. 相似文献
9.
Novel oscillatory flow results of phenoxy/organoclay nanocomposites are analysed considering the blocking effect of nanostructure on polymer chain mobility. The modification provoked by this hindering effect on loss tangent spectrum is investigated. The study of three different systems, involving a pristine montmorillonite and two montmorillonites modified with one alkyl tail and two alkyl tails, respectively, leads to conclude that polymer-alkyl repulsive interactions play the most important role in the chain mobility obstruction process. Our results suggest that polymer-alkyl interactions increase with temperature. 相似文献
10.