全文获取类型
收费全文 | 2352篇 |
免费 | 99篇 |
国内免费 | 30篇 |
专业分类
化学 | 1431篇 |
晶体学 | 14篇 |
力学 | 63篇 |
数学 | 560篇 |
物理学 | 413篇 |
出版年
2023年 | 27篇 |
2022年 | 24篇 |
2021年 | 65篇 |
2020年 | 54篇 |
2019年 | 43篇 |
2018年 | 52篇 |
2017年 | 38篇 |
2016年 | 81篇 |
2015年 | 96篇 |
2014年 | 99篇 |
2013年 | 151篇 |
2012年 | 155篇 |
2011年 | 157篇 |
2010年 | 115篇 |
2009年 | 100篇 |
2008年 | 140篇 |
2007年 | 130篇 |
2006年 | 126篇 |
2005年 | 111篇 |
2004年 | 88篇 |
2003年 | 51篇 |
2002年 | 74篇 |
2001年 | 21篇 |
2000年 | 26篇 |
1999年 | 17篇 |
1998年 | 22篇 |
1997年 | 16篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 9篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1985年 | 11篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 21篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1966年 | 7篇 |
1965年 | 10篇 |
1956年 | 7篇 |
排序方式: 共有2481条查询结果,搜索用时 15 毫秒
991.
992.
993.
Gabriel Ferro 《固体与材料科学评论》2015,40(1):56-76
For a long time now, 3C-SiC has attracted attention of the semiconductor community due to its very interesting properties. The lack of commercial 3C-SiC seeds for epitaxy has forced researchers to prospect for different host materials in order to grow heteroepitaxial thin layers. Because of the obvious economical and technical advantages, silicon is a very attractive substrate so that more than 90% of the thin 3C-SiC heteroepitaxial films are grown on such seed. However, the obstacles to overcome, mainly lattice and thermal mismatch, are challenging. This article reviews the numerous attempts for growing high quality 3C-SiC heteroepitaxial layers on silicon substrate. The various aspects of the heteroepitaxial growth, from substrate carbonization to epitaxy, are discussed as a function of growth parameters. The difficulties encountered and the proposed solutions are described. Perspectives of this heteroepitaxial system are proposed. 相似文献
994.
995.
996.
Jean-Pierre Gabriel Joseph Hersch 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1971,22(1):210-215
Summary For the first eigenvalue 1 of a vibrating membrane, the «method of one-dimensional auxiliary problems» gave the lower bounds (19). We present here two new interpretations of those bounds, by means of cutting the membrane either into infinitesimal strips or else into infinitesimal quadratic cells, and adding positive or negative elastic support on each side of each cut. 相似文献
997.
998.
999.
Ernst Lücker Horst K?nig Wolfgang Gabriel Anton Rosopulo 《Fresenius' Journal of Analytical Chemistry》1992,342(12):941-949
Summary The function of solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) in the laboratory-internal preparation, production and standardization of several animal tissue reference materials is described. SS-GFAAS is successfully applied in the production of a bovine liver reference material with a low content of Pb and Cd. The lab-internal production of 5 bovine teeth and 2 bovine bone reference materials illustrates some of the basic problems entailed in the analysis of Pb in osseus matrices and in the production of the reference material itself. In the production of muscle tissue reference material focal or generalized calcification is a serious source of endogenous Pb contamination. This is shown, by way of example, in the calcification of the larval states of Taenia saginata (Cysticercus bovis) in the bovine muscle. Finally, as further examples of the application of SS-GFAAS, the lab-internal production of reference material from bovine blood and equine renal cortex is described. 相似文献
1000.
O. Andersen R. Bauer G.B. Hagemann M.L. Halbert B. Herskind M. Neiman H. Oeschler H. Ryde 《Nuclear Physics A》1978,295(1):163-188
Reactions between 18O and 16O ions, with energies well above the Coulomb barrier, and 148, 150Nd target nuclei were used to study the cascades of γ-rays in the residual nuclei 161, 162Er. A multi-counter setup was used in which the γ-rays were detected by a Ge(Li) counter coupled in coincidence with up to 9 NaI(Tl) counters. The γ-multiplicity has been studied for γ-rays cascading through states above and along the yrast line. Higher moments of the multiplicity distributions (shape parameters) were deduced from the data. These moments allow the construction of the spin distribution for the entry states. The difference between these spin distributions from reactions induced by 16O and 18O ions was studied. Also the fusion cross section was measured for the two systems as a function of bombarding energy and compared to the multiplicity results at two different excitation energies (Ex = 49.5 and 56.2 MeV). A subtraction technique has been applied in the data analysis with the intention to study the decay of a selected part of the high-spin region, and the results show besides the 4n channel an unexpected large contribution of the 5n channel from this region. The sidefeeding patterns of the multiplicity distributions are extracted and show a significant difference for the 16O and 18O induced reactions, especially at the lowest bombarding energies. The results are compared with statistical model calculations. 相似文献