全文获取类型
收费全文 | 183181篇 |
免费 | 2436篇 |
国内免费 | 530篇 |
专业分类
化学 | 99475篇 |
晶体学 | 2572篇 |
力学 | 7067篇 |
综合类 | 8篇 |
数学 | 19921篇 |
物理学 | 57104篇 |
出版年
2021年 | 1336篇 |
2020年 | 1639篇 |
2019年 | 1602篇 |
2018年 | 2112篇 |
2017年 | 2159篇 |
2016年 | 3538篇 |
2015年 | 2323篇 |
2014年 | 3215篇 |
2013年 | 7785篇 |
2012年 | 6447篇 |
2011年 | 7660篇 |
2010年 | 5357篇 |
2009年 | 5190篇 |
2008年 | 7349篇 |
2007年 | 7042篇 |
2006年 | 6850篇 |
2005年 | 6240篇 |
2004年 | 5566篇 |
2003年 | 5050篇 |
2002年 | 4823篇 |
2001年 | 6259篇 |
2000年 | 4549篇 |
1999年 | 3477篇 |
1998年 | 2479篇 |
1997年 | 2574篇 |
1996年 | 2526篇 |
1995年 | 2338篇 |
1994年 | 2371篇 |
1993年 | 2203篇 |
1992年 | 2710篇 |
1991年 | 2638篇 |
1990年 | 2495篇 |
1989年 | 2425篇 |
1988年 | 2369篇 |
1987年 | 2402篇 |
1986年 | 2197篇 |
1985年 | 2835篇 |
1984年 | 2830篇 |
1983年 | 2278篇 |
1982年 | 2301篇 |
1981年 | 2150篇 |
1980年 | 2137篇 |
1979年 | 2412篇 |
1978年 | 2472篇 |
1977年 | 2421篇 |
1976年 | 2318篇 |
1975年 | 2191篇 |
1974年 | 2177篇 |
1973年 | 2156篇 |
1972年 | 1388篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
T. Noiri 《Acta Mathematica Hungarica》1998,80(1-2):105-113
In this paper the notion of pre gs-closed functions is introduced and investigated. Presemiclosed functions are pre gs-closed but not conversely. It is shown that s-normality is preserved under continuous pre gs-closed surjections. 相似文献
2.
3.
4.
We discuss an error estimation procedure for the global error of collocation schemes applied to solve singular boundary value problems with a singularity of the first kind. This a posteriori estimate of the global error was proposed by Stetter in 1978 and is based on the idea of Defect Correction, originally due to Zadunaisky. Here, we present a new, carefully designed modification of this error estimate which not only results in less computational work but also appears to perform satisfactorily for singular problems. We give a full analytical justification for the asymptotical correctness of the error estimate when it is applied to a general nonlinear regular problem. For the singular case, we are presently only able to provide computational evidence for the full convergence order, the related analysis is still work in progress. This global estimate is the basis for a grid selection routine in which the grid is modified with the aim to equidistribute the global error. This procedure yields meshes suitable for an efficient numerical solution. Most importantly, we observe that the grid is refined in a way reflecting only the behavior of the solution and remains unaffected by the unsmooth direction field close to the singular point. 相似文献
5.
6.
S. A. Gurevich T. A. Zaraiskaya S. G. Konnikov V. M. Mikushkin S. Yu. Nikonov A. A. Sitnikova S. E. Sysoev V. V. Khorenko V. V. Shnitov Yu. S. Gordeev 《Physics of the Solid State》1997,39(10):1691-1695
The concentration and chemical state of copper in the subsurface region of Cu/SiO2 composite films obtained by simultaneous magnetron sputtering from two sources (Cu and SiO2) are determined by x-ray photoelectron spectroscopy (XPS). It is established that copper in the as-grown film is primarily in the form of unoxidized atoms dispersed in a SiO2 matrix. Annealing of the film results in practically no oxidation, but about 70% of the copper atoms condense into metallic clusters with sizes below 10 Å in the subsurface region and about 50 Å in the bulk of the film. The changes in the binding energy of core electrons, and especially in the energies of Auger electrons, are so large in this situation that photoelectron and Auger spectroscopy are efficient methods for monitoring the chemical state of this composite material. 相似文献
7.
Ya. V. Fattakhov M. F. Galyautdinov T. N. L’vova I. B. Khaibullin 《Technical Physics》1997,42(12):1457-1459
The first results regarding the formation of a two-dimensional periodic structure of local melting regions on a silicon surface
upon pulsed light irradiation are presented. The conditions are established, and the mechanism of the formation of such structures
is discussed.
Zh. Tekh. Fiz. 67, 97–99 (December 1997) 相似文献
8.
9.
M. A. Mikhaleva B. M. Bolotin T. A. Kizner E. S. Serebrykova 《Chemistry of Heterocyclic Compounds》1994,30(1):79-81
We have synthesized 5-alkyl(alkoxy)-2-(o-lzydroxy-p-alkoxyphenyl)pyrimidines and considered the effect of the OH group on the inesomorphism. We have found that in binuclear o-hydroxyarylpyrimidines, an ortho OH group forming an intramolecular hydrogen bond increases Tmp, inhibits the appearance of nematic properties, and promotes the appearance of a smectic A.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 30, No. 1, pp. 90–92, January, 1994. 相似文献
10.
N. I. Khamidov B. T. Kadyrov N. T. Ul'chenko A. Sh. Isamukhamedov A. I. Glushenkova 《Chemistry of Natural Compounds》1994,30(4):430-433
The phsicochemical indices and the fatty-acid and triacylglycerol compositions of cottonseed and palm oils, of cottonseed
oil hydrogenate, and of compositions based on them have been determined with the aid of IR and UV spectroscopies, GLC analysis,
and chemical transformations. The compositions and amounts of the main classes of lipids in the initial oils and the hydrogenate
have been studied. It has been found that in the process of hydrogenation the amount of oxygenated components falls.
The work was conducted with the financial support of the Uzbek Fund for Fundamental Investigations. 相似文献