全文获取类型
收费全文 | 4204篇 |
免费 | 642篇 |
国内免费 | 418篇 |
专业分类
化学 | 984篇 |
晶体学 | 45篇 |
力学 | 618篇 |
综合类 | 80篇 |
数学 | 1429篇 |
物理学 | 2108篇 |
出版年
2024年 | 8篇 |
2023年 | 36篇 |
2022年 | 75篇 |
2021年 | 100篇 |
2020年 | 92篇 |
2019年 | 104篇 |
2018年 | 92篇 |
2017年 | 132篇 |
2016年 | 152篇 |
2015年 | 119篇 |
2014年 | 196篇 |
2013年 | 296篇 |
2012年 | 241篇 |
2011年 | 266篇 |
2010年 | 222篇 |
2009年 | 296篇 |
2008年 | 323篇 |
2007年 | 285篇 |
2006年 | 268篇 |
2005年 | 224篇 |
2004年 | 190篇 |
2003年 | 190篇 |
2002年 | 176篇 |
2001年 | 160篇 |
2000年 | 125篇 |
1999年 | 122篇 |
1998年 | 116篇 |
1997年 | 103篇 |
1996年 | 97篇 |
1995年 | 66篇 |
1994年 | 66篇 |
1993年 | 40篇 |
1992年 | 47篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 19篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有5264条查询结果,搜索用时 15 毫秒
1.
Prof. Dr. Peter Hess 《Chemphyschem》2022,23(6):e202100880
In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials. 相似文献
2.
We give a sheaf theoretic interpretation of Potts models with external magnetic field, in terms of constructible sheaves and their Euler characteristics. We show that the polynomial countability question for the hypersurfaces defined by the vanishing of the partition function is affected by changes in the magnetic field: elementary examples suffice to see non-polynomially countable cases that become polynomially countable after a perturbation of the magnetic field. The same recursive formula for the Grothendieck classes, under edge-doubling operations, holds as in the case without magnetic field, but the closed formulae for specific examples like banana graphs differ in the presence of magnetic field. We give examples of computation of the Euler characteristic with compact support, for the set of real zeros, and find a similar exponential growth with the size of the graph. This can be viewed as a measure of topological and algorithmic complexity. We also consider the computational complexity question for evaluations of the polynomial, and show both tractable and NP-hard examples, using dynamic programming. 相似文献
3.
The possibility of realizing SASE Free Election Laser in x-ray waveband with EM-wave wiggler is studied in this paper. SASE effect including saturation length, saturation power and nonlinear process is explored through a 3-D simulation code. A utilization of seed light from laser plasma x-ray is also analyzed, which demonstrates the feature of shortening the interaction length for saturation. The results show that sizeable output power of x-ray laser would be generated with a middle energy electron beam. 相似文献
4.
5.
6.
During the course of our investigation of the electron transfer properties of some redox species through highly hydrophobic
long chain alkanethiol molecules on gold in aqueous and non-aqueous solvents, we obtained some intriguing results such as
unusually low interfacial capacitance, very high values of impedance and film resistance, all of which pointed to the possible
existence of a nanometer size interfacial gap between the hydrophobic monolayer and aqueous electrolyte. We explain this phenomenon
by a model for the alkanethiol monolayer—aqueous electrolyte interface, in which the extremely hydrophobic alkanethiol film
repels water molecules adjacent to it and in the process creates a shield between the monolayer film and water. This effectively
increases the overall thickness of the dielectric layer that is manifested as an abnormally low value of interfacial capacitance.
This behaviour is very much akin to the ‘drying transition’ proposed by Lum, Chandler and Weeks in their theory of length
scale dependent hydrophobicity. For small hydrophobic units consisting of apolar solutes, the water molecules can reorganize
around them without sacrificing their hydrogen bonds. Since for an extended hydrophobic unit, the existence of hydrogen bonded
water structure close to it is geometrically unfavourable, there is a net depletion of water molecules in the vicinity leading
to the possible creation of a hydrophobic interfacial gap. 相似文献
7.
We introduce the notion of an invariant of characteristics for a system of first-order partial differential equations. We prove that the existence of invariants is connected with passiveness of some systems. We describe a few methods for construction of new invariants from those already known. We give a scheme for application of the invariants to reduction and integration of systems of partial differential equations. As an application we consider the equation of gas dynamics. 相似文献
8.
9.
M/G/1非空竭服务休假排队系统随机分解的简化算法 总被引:2,自引:0,他引:2
本文根据M/G/1非空竭服务休假排队系统稳态队长随机分解的结构特征提出一种统一算法,该方法简洁高效,避免了再生循环方法繁杂的运算。运用该方法得出的结果与已知的用再生循环方法得出的结论一致。并且修正了Levy(1989)关于Bernoulli闸门服务休假排队系统随机分解的一个错误。 相似文献
10.