全文获取类型
收费全文 | 4079篇 |
免费 | 796篇 |
国内免费 | 420篇 |
专业分类
化学 | 1253篇 |
晶体学 | 38篇 |
力学 | 344篇 |
综合类 | 55篇 |
数学 | 845篇 |
物理学 | 2760篇 |
出版年
2024年 | 5篇 |
2023年 | 52篇 |
2022年 | 97篇 |
2021年 | 77篇 |
2020年 | 158篇 |
2019年 | 119篇 |
2018年 | 99篇 |
2017年 | 121篇 |
2016年 | 149篇 |
2015年 | 128篇 |
2014年 | 193篇 |
2013年 | 326篇 |
2012年 | 214篇 |
2011年 | 291篇 |
2010年 | 241篇 |
2009年 | 296篇 |
2008年 | 275篇 |
2007年 | 279篇 |
2006年 | 260篇 |
2005年 | 208篇 |
2004年 | 246篇 |
2003年 | 183篇 |
2002年 | 214篇 |
2001年 | 142篇 |
2000年 | 134篇 |
1999年 | 123篇 |
1998年 | 115篇 |
1997年 | 76篇 |
1996年 | 51篇 |
1995年 | 50篇 |
1994年 | 61篇 |
1993年 | 39篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 19篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 26篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有5295条查询结果,搜索用时 15 毫秒
11.
ZHANG Shun-Li 《理论物理通讯》2006,45(6):969-978
The generalized conditional symmetry is developed to study the variable
separation for equations of type uxt=A(u,ux)uxx+B(u,ux). Complete classification of those equations which admit derivative-dependent functional separable solutions is obtained and some of their
exact separable solutions are constructed. 相似文献
12.
The transition from the quantum to the classical world is not yet understood. Here, we take a new approach. Central to this is the understanding that measurement and actualization cannot occur except on some specific basis. However, we have no established theory for the emergence of a specific basis. Our framework entails the following: (i) Sets of N entangled quantum variables can mutually actualize one another. (ii) Such actualization must occur in only one of the 2N possible bases. (iii) Mutual actualization progressively breaks symmetry among the 2N bases. (iv) An emerging “amplitude” for any basis can be amplified by further measurements in that basis, and it can decay between measurements. (v) The emergence of any basis is driven by mutual measurements among the N variables and decoherence with the environment. Quantum Zeno interactions among the N variables mediates the mutual measurements. (vi) As the number of variables, N, increases, the number of Quantum Zeno mediated measurements among the N variables increases. We note that decoherence alone does not yield a specific basis. (vii) Quantum ordered, quantum critical, and quantum chaotic peptides that decohere at nanosecond versus femtosecond time scales can be used as test objects. (viii) By varying the number of amino acids, N, and the use of quantum ordered, critical, or chaotic peptides, the ratio of decoherence to Quantum Zeno effects can be tuned. This enables new means to probe the emergence of one among a set of initially entangled bases via weak measurements after preparing the system in a mixed basis condition. (ix) Use of the three stable isotopes of carbon, oxygen, and nitrogen and the five stable isotopes of sulfur allows any ten atoms in the test protein to be discriminably labeled and the basis of emergence for those labeled atoms can be detected by weak measurements. We present an initial mathematical framework for this theory, and we propose experiments. 相似文献
13.
14.
Irina Legchenkova Mark Frenkel Nir Shvalb Shraga Shoval Oleg V. Gendelman Edward Bormashenko 《Entropy (Basel, Switzerland)》2022,24(6)
Properties of the Voronoi tessellations arising from random 2D distribution points are reported. We applied an iterative procedure to the Voronoi diagrams generated by a set of points randomly placed on the plane. The procedure implied dividing the edges of Voronoi cells into equal or random parts. The dividing points were then used to construct the following Voronoi diagram. Repeating this procedure led to a surprising effect of the positional ordering of Voronoi cells, reminiscent of the formation of lamellae and spherulites in linear semi-crystalline polymers and metallic glasses. Thus, we can conclude that by applying even a simple set of rules to a random set of seeds, we can introduce order into an initially disordered system. At the same time, the Shannon (Voronoi) entropy showed a tendency to attain values that are typical for completely random patterns; thus, the Shannon (Voronoi) entropy does not distinguish the short-range ordering. The Shannon entropy and the continuous measure of symmetry of the patterns demonstrated the distinct asymptotic behavior, while approaching the close saturation values with the increase in the number of iteration steps. The Shannon entropy grew with the number of iterations, whereas the continuous measure of symmetry of the same patterns demonstrated the opposite asymptotic behavior. The Shannon (Voronoi) entropy is not an unambiguous measure of order in the 2D patterns. The more symmetrical patterns may demonstrate the higher values of the Shannon entropy. 相似文献
15.
《Journal of Nonlinear Mathematical Physics》2013,20(3):411-427
The μ-Camassa–Holm (μCH) equation is a nonlinear integrable partial differential equation closely related to the Camassa–Holm and the Hunter–Saxton equations. This equation admits quadratic pseudo-potentials which allow us to compute some first-order nonlocal symmetries. The found symmetries preserve the mean of solutions. Finally, we discuss also the associated μCH equation. 相似文献
16.
We predict the possibility of observing analogue of the Aharonov-Bohm effect due to long range interaction between spins originating
in the framework of spin gauge theory developed earlier. The effect is predicted for both electrons (fermions) and photons.
Appropriate experimental set-ups are suggested. 相似文献
17.
Multiply-connected Calabi–Yau threefolds are of particular interest for both string theorists and mathematicians. Recently it was pointed out that one of the generic degenerations of these spaces (occurring at codimension one in moduli space) is an isolated singularity which is a finite cyclic quotient of the conifold; these were called hyperconifolds. It was also shown that if the order of the quotient group is even, such singular varieties have projective crepant resolutions, which are therefore smooth Calabi–Yau manifolds. The resulting topological transitions were called hyperconifold transitions, and change the fundamental group as well as the Hodge numbers. Here Batyrev?s construction of Calabi–Yau hypersurfaces in toric fourfolds is used to demonstrate that certain compact examples containing the remaining hyperconifolds — the Z3 and Z5 cases — also have Calabi–Yau resolutions. The mirrors of the resulting transitions are studied and it is found, surprisingly, that they are ordinary conifold transitions. These are the first examples of conifold transitions with mirrors which are more exotic extremal transitions. The new hyperconifold transitions are also used to construct a small number of new Calabi–Yau manifolds, with small Hodge numbers and fundamental group Z3 or Z5. Finally, it is demonstrated that a hyperconifold is a physically sensible background in Type IIB string theory. In analogy to the conifold case, non-perturbative dynamics smooth the physical moduli space, such that hyperconifold transitions correspond to non-singular processes in the full theory. 相似文献
18.
For a nonholonomic system, a new type of Lie symmetrical non-Noether conserved quantity is given under general infinitesimal transformations of groups in which time is variable. On the basis of the invariance theory of differential equations of motion under infinitesimal transformations for t and q_s, we construct the Lie symmetrical determining equations, the constrained restriction equations and the additional restriction equations of the system. And a new type of Lie symmetrical non-Noether conserved quantity is directly obtained from the Lie symmetry of the system, which only depends on the variables t, q_s and \dot{q}_s. A series of deductions are inferred for a holonomic nonconservative system, Lagrangian system and other dynamical systems in the case of vanishing of time variation. An example is given to illustrate the application of the results. 相似文献
19.
给出了电磁学中通用的国际单位制及相当流行的实用单位制之间的简单并且便于记忆及使用的转换方式。 相似文献
20.
In this study, Higgs and Z boson associated production with subsequent decay is attempted in the framework of alternative left-right model, which is motivated by superstring-inspired E_6 model at CEPC and future linear colliders. We systematically analyze each decay channel of Higgs with theoretical constraints and latest experimental methods. Due to the mixing of scalars in the Higgs sector, charged Higgs bosons can play an essential role in the phenomenological analysis of this process. Even though the predictions of this model for the signal strengths of this process are close to the standard model expectations, it can be distinct under high luminosity. 相似文献