全文获取类型
收费全文 | 541452篇 |
免费 | 4444篇 |
国内免费 | 1403篇 |
专业分类
化学 | 277413篇 |
晶体学 | 7732篇 |
力学 | 26444篇 |
综合类 | 17篇 |
数学 | 70029篇 |
物理学 | 165664篇 |
出版年
2021年 | 5137篇 |
2020年 | 5638篇 |
2019年 | 6372篇 |
2018年 | 8557篇 |
2017年 | 8680篇 |
2016年 | 11872篇 |
2015年 | 6378篇 |
2014年 | 10684篇 |
2013年 | 24109篇 |
2012年 | 18864篇 |
2011年 | 22553篇 |
2010年 | 16785篇 |
2009年 | 16628篇 |
2008年 | 21284篇 |
2007年 | 21169篇 |
2006年 | 19297篇 |
2005年 | 17241篇 |
2004年 | 16048篇 |
2003年 | 14487篇 |
2002年 | 14361篇 |
2001年 | 14905篇 |
2000年 | 11503篇 |
1999年 | 8877篇 |
1998年 | 7746篇 |
1997年 | 7623篇 |
1996年 | 7104篇 |
1995年 | 6416篇 |
1994年 | 6410篇 |
1993年 | 6125篇 |
1992年 | 6499篇 |
1991年 | 7002篇 |
1990年 | 6693篇 |
1989年 | 6586篇 |
1988年 | 6445篇 |
1987年 | 6256篇 |
1986年 | 5965篇 |
1985年 | 7586篇 |
1984年 | 7978篇 |
1983年 | 6678篇 |
1982年 | 7014篇 |
1981年 | 6509篇 |
1980年 | 6201篇 |
1979年 | 6677篇 |
1978年 | 6920篇 |
1977年 | 6774篇 |
1976年 | 6743篇 |
1975年 | 6433篇 |
1974年 | 6267篇 |
1973年 | 6558篇 |
1972年 | 4777篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
A. Drees 《Acta Physica Hungarica A》2006,25(2-4):475-486
Luminosity mainly depends on the beam intensity of the circulating beams and the beam profiles at the interaction points. By either increasing the total beam current or decreasing its size the instantaneous luminosity can be increased. In addition any method to slow down beam growth and debunching processes will further improve the luminosity which can be integrated over a store. Optimizing beam cleaning procedures such as collimation or abort gap cleaning will further increase the amount of usable luminosity for experiments. This paper will give a brief introduction to some accelerator basics of interest and the luminosity as a function of beam parameters. Limitations to the achievable integrated luminosity as well as future upgrades to overcome these limitations are presented. 相似文献
942.
943.
T. V. Esipova A. A. Borisenko P. B. Terent’ev G. V. Grishina R. Herzshuh 《Russian Journal of Organic Chemistry》2006,42(5):742-747
A new class of endocyclic enamines, 1,6-disubstituted 1,2,3,4,5,6,7,8-octahydro-1,6-naphthiridines, was synthesized from 4-piperidone imines by successive subjecting the latter to lithiation with lithium diethylamide, to alkylation with 1-bromo-3-chloropropane, and to intramolecular cyclization. All stages were carried out as a unique process without isolation of the intermediate compounds. A thorough optimization of the process conditions, workup, and product storage was carried out. The conformational study of 1,6-disubstituted 1,2,3,4,5,6,7,8-octahydro-1,6-naphthiridines was performed. 相似文献
944.
945.
946.
A. V. Shchepetilov 《Theoretical and Mathematical Physics》1996,109(3):1556-1564
Quantum mechanical problems are considered for potentials satisfying Bertrand's problem in Lobachevsky space. The self-adjointness of the corresponding Schrödinger operators is proved. The energy levels are calculated both from the Schrödinger equation and by means of the Bohr-Sommerfeld method. The effect of the quantum binding of classically infinite motion was discovered and is presented for the first time. It is shown that the quasi-classical limit is equivalent, in a sense, to the Euclidean limit.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 109, No. 3, pp. 395–405, December, 1996. 相似文献
947.
An upper estimate for the topological entropy of a dynamical system defined by a system of ODE is obtained. The estimate involves
the Lyapunov functions and Losinskii’s logarithmic norm. The proof uses the known fact that the topological entropy of a mapping
acting in a compact space K can be estimated via the fractal dimension of K. Bibliography: 28 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 231, 1995, pp. 62–75.
Translated by V. A. Boichenko and G. A. Leonov. 相似文献
948.
949.
Novosibirsk. Translated fromSibirskiî Matematicheskiî Zhurnal, Vol. 34, No. 3, pp. 3–18, May–June, 1993. 相似文献
950.