全文获取类型
收费全文 | 6712篇 |
免费 | 301篇 |
国内免费 | 199篇 |
专业分类
化学 | 902篇 |
晶体学 | 14篇 |
力学 | 3757篇 |
综合类 | 32篇 |
数学 | 388篇 |
物理学 | 2119篇 |
出版年
2024年 | 7篇 |
2023年 | 53篇 |
2022年 | 73篇 |
2021年 | 70篇 |
2020年 | 99篇 |
2019年 | 102篇 |
2018年 | 67篇 |
2017年 | 102篇 |
2016年 | 256篇 |
2015年 | 246篇 |
2014年 | 244篇 |
2013年 | 299篇 |
2012年 | 217篇 |
2011年 | 355篇 |
2010年 | 246篇 |
2009年 | 392篇 |
2008年 | 409篇 |
2007年 | 433篇 |
2006年 | 413篇 |
2005年 | 413篇 |
2004年 | 392篇 |
2003年 | 379篇 |
2002年 | 285篇 |
2001年 | 166篇 |
2000年 | 187篇 |
1999年 | 138篇 |
1998年 | 196篇 |
1997年 | 128篇 |
1996年 | 90篇 |
1995年 | 129篇 |
1994年 | 94篇 |
1993年 | 88篇 |
1992年 | 63篇 |
1991年 | 46篇 |
1990年 | 37篇 |
1989年 | 56篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1979年 | 19篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1973年 | 10篇 |
1972年 | 8篇 |
1971年 | 13篇 |
排序方式: 共有7212条查询结果,搜索用时 0 毫秒
141.
Ring-shaped lead zirconate titanate (PZT) piezoelectric vibrators were subjected to non-uniform mechanical stress applied by bolt clamping. The effect of mechanical stress on the effective electromechanical coupling factor (keff) and mechanical quality factor (Qm) of the thickness and wall thickness modes was studied by an equivalent electric circuit analysis. The initiation and propagation of cracks under mechanical stress were also discussed based on the resonance method and the indentation technique. keff for both the thickness and wall thickness modes decreased with increase in mechanical stress due to de-poling of the PZT. Qm of the thickness mode dropped sharply with increase in mechanical stress while Qm of the wall thickness mode remained almost unchange. Existence of microcracks in a PZT vibrator can be detected by the occurrence of spurious vibrations at the wall thickness mode in the electrical impedance vs. frequency spectra. 相似文献
142.
V.S. Gerdjikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):237-241
We compare the Hamiltonian properties of the N-soliton solutions of the NLSE in the adiabatic approximation and show how it matches the Hamiltonian formulation for the
complex Toda chain which describes the adiabatic N-soliton interactions.
Received 21 October 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: gerjikov@inrne.bas.bg 相似文献
143.
144.
The primary resource for quantum computation is Hilbert-space dimension. Whereas Hilbert space itself is an abstract construction, the number of dimensions available to a system is a physical quantity that requires physical resources. Avoiding a demand for an exponential amount of these resources places a fundamental constraint on the systems that are suitable for scalable quantum computation. To be scalable, the effective number of degrees of freedom in the computer must grow nearly linearly with the number of qubits in an equivalent qubit-based quantum computer. 相似文献
145.
The geometrical approach to statistical mechanics is used to discuss changes in entropy upon sequential displacements of the state of the system. An interpretation of the angle between two states in terms of entropy differences is thereby provided. A particular result of note is that any state can be resolved into a state of maximal entropy (both states having the same expectation values for the constraints) and an orthogonal component. A cosine law for the general case is also derived. 相似文献
146.
凑合反推法──流体力学变分原理建立的一条新途径 总被引:6,自引:0,他引:6
凑合反推法是刘商联系统方法[1]的进一步发展,应用这种方法可以方便地构造各种亚广义变分原理及广义变分原理,并可以消除临界变分现象.对于任何二维守恒型流体力学方程,作者推导得到了其广义变分通用公式.几个实例证明这种方法是有效的、简单的,并具有普遍的意义. 相似文献
147.
In a previous paper we considered an extension of the hard hexagon model to a solvable two-dimensional lattice gas with at most two particles per pair of adjacent sites. Here we use various mathematical identities (in particular Gordon's generalization of the Rogers-Ramanujan relations) to express the local densities in terms of elliptic functions. The critical behavior is then readily obtained.Supported in part by the National Science Foundation Grant MCS 8201733. 相似文献
148.
The numerical analysis of variational integrators relies on variational error analysis, which relates the order of accuracy
of a variational integrator with the order of approximation of the exact discrete Lagrangian by a computable discrete Lagrangian.
The exact discrete Lagrangian can either be characterized variationally, or in terms of Jacobi’s solution of the Hamilton-Jacobi
equation. These two characterizations lead to the Galerkin and shooting constructions for discrete Lagrangians, which depend
on a choice of a numerical quadrature formula, together with either a finite-dimensional function space or a one-step method.
We prove that the properties of the quadrature formula, finite-dimensional function space, and underlying one-step method
determine the order of accuracy and momentum-conservation properties of the associated variational integrators. We also illustrate
these systematic methods for constructing variational integrators with numerical examples. 相似文献
149.
A system of N Brownian particles suspended in a nonuniform heat bath is treated as a thermodynamic system with internal degrees of freedom, in this case their velocities and coordinates. Applying the scheme of nonequilibrium thermodynamics, one then easily obtains the Fokker-Planck equation for simultaneous Brownian motion of N particles in a temperature gradient. This equation accounts for couplings in the motion as a result of hydrodynamic interactions between particles. 相似文献
150.
关于相对论等离子体统计力学的一些问题 总被引:1,自引:0,他引:1
陆全康 《核聚变与等离子体物理》1997,17(1):14-17
相对论统计力学的发展已近一个世纪,目前仍处于有争议阶段,本文对相对论等离子体理论的发展、基本概念和一些问题作一简要评述。 相似文献