全文获取类型
收费全文 | 330845篇 |
免费 | 3482篇 |
国内免费 | 942篇 |
专业分类
化学 | 165808篇 |
晶体学 | 5381篇 |
力学 | 15549篇 |
综合类 | 7篇 |
数学 | 38620篇 |
物理学 | 109904篇 |
出版年
2021年 | 3167篇 |
2020年 | 3372篇 |
2019年 | 3805篇 |
2018年 | 5226篇 |
2017年 | 5462篇 |
2016年 | 7427篇 |
2015年 | 4183篇 |
2014年 | 7072篇 |
2013年 | 15966篇 |
2012年 | 12489篇 |
2011年 | 14972篇 |
2010年 | 11080篇 |
2009年 | 10968篇 |
2008年 | 13328篇 |
2007年 | 13266篇 |
2006年 | 12237篇 |
2005年 | 10595篇 |
2004年 | 9878篇 |
2003年 | 8721篇 |
2002年 | 8706篇 |
2001年 | 10403篇 |
2000年 | 7666篇 |
1999年 | 5977篇 |
1998年 | 4979篇 |
1997年 | 4816篇 |
1996年 | 4485篇 |
1995年 | 3870篇 |
1994年 | 3823篇 |
1993年 | 3706篇 |
1992年 | 4098篇 |
1991年 | 4312篇 |
1990年 | 4099篇 |
1989年 | 4009篇 |
1988年 | 3780篇 |
1987年 | 3917篇 |
1986年 | 3684篇 |
1985年 | 4632篇 |
1984年 | 4684篇 |
1983年 | 3889篇 |
1982年 | 3979篇 |
1981年 | 3699篇 |
1980年 | 3649篇 |
1979年 | 3914篇 |
1978年 | 3904篇 |
1977年 | 3909篇 |
1976年 | 3879篇 |
1975年 | 3677篇 |
1974年 | 3616篇 |
1973年 | 3650篇 |
1972年 | 2603篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
983.
The energy levels and oscillator strengths for dipole transitions between the levels of low-lying configurations are calculated for ions of the KI isoelectronic sequence. The calculations are based on the energy approach to the effective potential method with the most important polarization effects taken into account, including core polarization by the outer electron. The results, some of which are obtained here for the first time for potassium-like ions, can be useful in a number of related fields, such as laser physics, plasmas, and so on.Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 3–9, November, 1992. 相似文献
984.
985.
Michael S. Roddy 《Order》1994,11(1):1-9
Theretracts (idempotent, isotone self-maps) of an ordered set are naturally ordered as functions. In this note we characterize the possible ways that one retract can cover another one. This gives some insight into the structure of the ordered set of retracts and leads to a natural generalization of the core of an ordered set.Supported by NSERC Operating Grant 41702. 相似文献
986.
S. E. Kholodovskii 《Journal of Applied Mechanics and Technical Physics》1991,32(6):931-933
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 6, pp. 119–122, November–December, 1991. 相似文献
987.
988.
989.
Let M be a symplectic manifold with a Hamiltonian circle action with isolated fixed points. We prove that σ (M) = b0(M) − b2(M) + b4(M) − b6(M) + … where σ (M) is the signature of M and bi(M) is the ith Betti number of M. 相似文献
990.
P. I. H. Bastiaens S. G. Mayhew E. M. O'Naulláin A. van Hoek A. J. W. G. Visser 《Journal of fluorescence》1991,1(2):95-103
Both a mode-locked argon-ion laser and synchrotron radiation were used as excitation sources to obtain time-resolved polarized fluorescence of the two FAD cofactors in electron transferring flavoprotein fromMegasphaera elsdenii. Red-edge excited and blue-edge detected fluorescence anisotropy decay curves did not contain a fast relaxation process which was observed upon mainband excitation and detection. This relaxation was assigned to homo-energy transfer between the two FAD cofactors. Failure of energy transfer as observed with edge spectroscopy on this protein excludes restricted reorientational motion of the flavins as a possible mechanism of depolarization. From the global analysis of the fluorescence anisotropy decay surface obtained at multiple excitation and detection wavelengths, the distance between and the relative orientation of the flavins could be estimated. The methodology described has general applicability in other multichromophoric biopolymers and has the potential to acquire accurate geometrical parameters in these systems. 相似文献