全文获取类型
收费全文 | 304799篇 |
免费 | 1794篇 |
国内免费 | 648篇 |
专业分类
化学 | 146406篇 |
晶体学 | 4470篇 |
力学 | 15078篇 |
综合类 | 6篇 |
数学 | 46490篇 |
物理学 | 94791篇 |
出版年
2020年 | 1971篇 |
2019年 | 2267篇 |
2018年 | 10955篇 |
2017年 | 11674篇 |
2016年 | 8001篇 |
2015年 | 3110篇 |
2014年 | 3933篇 |
2013年 | 9373篇 |
2012年 | 10881篇 |
2011年 | 19880篇 |
2010年 | 12517篇 |
2009年 | 12563篇 |
2008年 | 17834篇 |
2007年 | 21221篇 |
2006年 | 7821篇 |
2005年 | 12978篇 |
2004年 | 9274篇 |
2003年 | 8886篇 |
2002年 | 6852篇 |
2001年 | 6097篇 |
2000年 | 4994篇 |
1999年 | 3510篇 |
1998年 | 3054篇 |
1997年 | 3055篇 |
1996年 | 2993篇 |
1995年 | 2427篇 |
1994年 | 2504篇 |
1993年 | 2530篇 |
1992年 | 2666篇 |
1991年 | 2730篇 |
1990年 | 2634篇 |
1989年 | 2617篇 |
1988年 | 2556篇 |
1987年 | 2524篇 |
1986年 | 2436篇 |
1985年 | 3121篇 |
1984年 | 3300篇 |
1983年 | 2653篇 |
1982年 | 2919篇 |
1981年 | 2797篇 |
1980年 | 2592篇 |
1979年 | 2825篇 |
1978年 | 2954篇 |
1977年 | 2889篇 |
1976年 | 2897篇 |
1975年 | 2741篇 |
1974年 | 2714篇 |
1973年 | 2900篇 |
1972年 | 1912篇 |
1967年 | 1868篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
961.
The cation distribution in spinel-related titanium-substituted lithium ferrite, Li0.5+0.5xFe2.5−1.5xTixO4 has been explored using interatomic potential and ab initio calculations. The results suggest that the cation distribution with Ti4+ substituting for Fe3+ on octahedral B sites and excess Li+ substituting for Fe3+ on tetrahedral A sites is stabilised by the formation of clusters of two octahedrally coordinated Ti4+ ions and one tetrahedrally coordinated Li+ ion linked through a common oxygen. 相似文献
962.
963.
Active noise control usually aims at reducing the total acoustic pressure due to a noise source; it may also be used in principle to reduce the scattered acoustic radiation from a reflecting body in order to render it invisible to incident acoustic waves. In this paper, a real-time control strategy is introduced to achieve, with ordinary noise sources and sensors, the effective suppression of the noise scattered by a 3-D surface. Numerical simulations of 2-D and 3-D control are used to illustrate the potential of this control strategy. Preliminary experimental results are also given for the 1-D case of a rigid body inserted into a duct. 相似文献
964.
It is suggested that the question of existence of a jamming phase transition in a broad class of single-lane cellular-automaton traffic models may be studied using a correspondence to the asymmetric chipping model. In models where such correspondence is applicable, jamming phase transition does not take place. Rather, the system exhibits a smooth crossover between free-flow and jammed states, as the car density is increased. 相似文献
965.
J. L. Hernández–Pastora O. V. Manko V. S. Manko J. Martín E. Ruiz 《General Relativity and Gravitation》2004,36(4):781-797
The extended quadruple–Kerr metric is used to consider equilibrium states of four collinear Kerr particles. We explain our previous failure to solve numerically the full set of the balance equations, and we derive a self–consistent system of the axis conditions leading to the equilibrium of all four constituents which can be black holes or hyperextreme objects. The equilibrium configurations obtained in this paper exhibit similar features with those occurring in the systems of two Kerr particles, for instance, the balance of four Kerr black holes with positive masses does not seem possible. Equilibrium states of two identical compound Kerr objects are also discussed. 相似文献
966.
E.V. Jansson 《Applied Acoustics》2004,65(12):1197-1205
Good violins have a broad hill in the 2-3 kHz range of their frequency response. This hill has previously been attributed to the first in-plane resonance of the violin bridge. Experiments prove, however, that the hill is the result of two forces acting in opposite directions at the bridge feet. The experiments reported here show that the hill can be “tuned” by altering the distance between the bridge feet. It can be tuned both in terms of frequency and level but the properties of the violin cannot be neglected. 相似文献
967.
968.
The construction of non-Abelian affine Toda models is discussed in terms of its underlying Lie algebraic structure. It is shown that a subclass of such non-conformal two-dimensional integrable models naturally leads to the construction of a pair of actions, which share the same spectra and are related by canonical transformations. 相似文献
969.
A semiclassical theory of electromagnetically induced transparency in a Bose-Einstein condensate is considered. A nonlinear Schrödinger equation that describes the interaction of the Bose-Einstein condensate with an electromagnetic field is derived. An analysis of the obtained solutions to this equation demonstrates a decrease in the group velocity of the light pulse. 相似文献
970.