首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   18084篇
  免费   1323篇
  国内免费   1006篇
化学   541篇
晶体学   37篇
力学   3000篇
综合类   193篇
数学   14099篇
物理学   2543篇
  2024年   12篇
  2023年   172篇
  2022年   205篇
  2021年   250篇
  2020年   414篇
  2019年   389篇
  2018年   436篇
  2017年   469篇
  2016年   456篇
  2015年   320篇
  2014年   748篇
  2013年   1445篇
  2012年   820篇
  2011年   952篇
  2010年   828篇
  2009年   1144篇
  2008年   1223篇
  2007年   1285篇
  2006年   1149篇
  2005年   948篇
  2004年   784篇
  2003年   849篇
  2002年   715篇
  2001年   566篇
  2000年   550篇
  1999年   522篇
  1998年   445篇
  1997年   426篇
  1996年   315篇
  1995年   261篇
  1994年   192篇
  1993年   160篇
  1992年   162篇
  1991年   151篇
  1990年   97篇
  1989年   58篇
  1988年   63篇
  1987年   58篇
  1986年   49篇
  1985年   64篇
  1984年   56篇
  1983年   25篇
  1982年   41篇
  1981年   28篇
  1980年   20篇
  1979年   26篇
  1978年   20篇
  1977年   19篇
  1976年   9篇
  1957年   4篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
Hengcan Zhao 《中国物理 B》2022,31(11):117103-117103
CePdAl has been recently recognized as a frustrated antiferromagnetic heavy-fermion compound with a pressure- or field-tuned, extended quantum critical phase at zero temperature. Identifying characteristic signatures of the emerging quantum critical phase, which are expected to be distinct from those near a quantum critical point, remains challenging. In this work, by performing ultrasonic and thermoelectric measurements down to very low temperatures in a 3He-4He dilution refrigerator in the presence of magnetic field, we are able to obtain some crucial thermodynamic and thermal transport features of the quantum critical phase, including a frustration-related elastic softening detected by ultrasound and a Fermi-surface change probed by thermoelectric effect.  相似文献   
2.
To control the temporal profile of a relativistic electron beam to meet requirements of various advanced scientific applications like free-electron-laser and plasma wakefield acceleration, a widely-used technique is to manipulate the dispersion terms which turns out to be one-to-many problems. Due to their intrinsic one-to-many property, current popular stochastic optimization approaches on temporal shaping may face the problems of long computing time or sometimes suggesting only one solution. Here we propose a real-time solver for one-to-many problems of temporal shaping, with the aid of a semi-supervised machine learning method, the conditional generative adversarial network (CGAN). We demonstrate that the CGAN solver can learn the one-to-many dynamics and is able to accurately and quickly predict the required dispersion terms for different custom temporal profiles. This machine learning-based solver is expected to have the potential for wide applications to one-to-many problems in other scientific fields.  相似文献   
3.
The AB system is the basic integrable model to describe unstable baroclinic wave packets in geophysical fluids and the propagation of mesoscale gravity flows in nonlinear optics. On the basis of the spectral analysis of a Lax pair and the inverse scattering method, we establish the Riemann–Hilbert problem of the AB system. Then, the inverse problems are formulated and solved with the aid of the Riemann–Hilbert problem, from which the potentials can be reconstructed according to the asymptotic expansion of the sectional analytic function and the related symmetry relations. As an application, we obtain the multi-bright-dark soliton solutions to the AB system in the reflectionless case and discuss the dynamic behavior of elastic soliton collisions by choosing appropriate free parameters.  相似文献   
4.
We consider percolation on the Voronoi tessellation generated by a homogeneous Poisson point process on the hyperbolic plane. We show that the critical probability for the existence of an infinite cluster tends to 1/2 as the intensity of the Poisson process tends to infinity. This confirms a conjecture of Benjamini and Schramm [5].  相似文献   
5.
Miao Yu 《中国物理 B》2022,31(6):64303-064303
Nonlinear elastic metamaterial, a topic which has attracted extensive attention in recent years, can enable broadband vibration reduction under relatively large amplitude. The combination of damping and strong nonlinearity in metamaterials may entail extraordinary effects and offer the capability for low-frequency and broadband vibration reduction. However, there exists a clear lack of proper design methods as well as the deficiency in understanding properties arising from this concept. To tackle this problem, this paper numerically demonstrates that the nonlinear elastic metamaterials, consisting of sandwich damping layers and collision resonators, can generate very robust hyper-damping effect, conducive to efficient and broadband vibration suppression. The collision-enhanced hyper damping is persistently presented in a large parameter space, ranging from small to large amplitudes, and for small and large damping coefficients. The achieved robust effects greatly enlarge the application scope of nonlinear metamaterials. We report the design concept, properties and mechanisms of the hyper-damping and its effect on vibration transmission. This paper reveals new properties offered by nonlinear elastic metamaterials, and offers a robust method for achieving efficient low-frequency and broadband vibration suppression.  相似文献   
6.
《Discrete Mathematics》2022,345(4):112748
It is known that all planar graphs and all projective planar graphs have an edge partition into three forests. Gonçalves proved that every planar graph has an edge partition into three forests, one having maximum degree at most four [5]. In this paper, we prove that every projective planar graph has an edge partition into three forests, one having maximum degree at most four.  相似文献   
7.
The max-cut problem is a fundamental combinatorial optimisation problem, with many applications. Poljak and Turzik found some facet-defining inequalities for the associated polytope, which we call 2-circulant inequalities. We present a more general family of facet-defining inequalities, an exact separation algorithm that runs in polynomial time, and some computational results.  相似文献   
8.
This article studies a posteriori error analysis of fully discrete finite element approximations for semilinear parabolic optimal control problems. Based on elliptic reconstruction approach introduced earlier by Makridakis and Nochetto [25], a residual based a posteriori error estimators for the state, co-state and control variables are derived. The space discretization of the state and co-state variables is done by using the piecewise linear and continuous finite elements, whereas the piecewise constant functions are employed for the control variable. The temporal discretization is based on the backward Euler method. We derive a posteriori error estimates for the state, co-state and control variables in the $L^\infty(0,T;L^2(\Omega))$-norm. Finally, a numerical experiment is performed to illustrate the performance of the derived estimators.  相似文献   
9.
双边配给问题描述了现实生活中一类带有二部图结构的稀缺资源配置问题, 例如, 在自然灾害期间救援物资的配给; 电力和天然气等自然资源按需分配; 高校引进人才调配等。本文通过求解线性规划, 并从联盟边际贡献的角度出发定义了双边配给问题的一个Shapley解。之后, 通过合作对策模型和解的公理化方法说明新解的合理性。首先, 建立双边配给问题的合作对策模型, 论证了新解与双边配给合作对策的Shapley值一致; 其次, 证明了Shapley解是唯一满足优先一致性的有效配给方案。最后, 将Shapley解应用于博物馆通票问题的研究, 探讨了博物馆合作制定通票后所得单票和通票收益的分配方式。  相似文献   
10.
Given a graph sequence denote by T3(Gn) the number of monochromatic triangles in a uniformly random coloring of the vertices of Gn with colors. In this paper we prove a central limit theorem (CLT) for T3(Gn) with explicit error rates, using a quantitative version of the martingale CLT. We then relate this error term to the well-known fourth-moment phenomenon, which, interestingly, holds only when the number of colors satisfies . We also show that the convergence of the fourth moment is necessary to obtain a Gaussian limit for any , which, together with the above result, implies that the fourth-moment condition characterizes the limiting normal distribution of T3(Gn), whenever . Finally, to illustrate the promise of our approach, we include an alternative proof of the CLT for the number of monochromatic edges, which provides quantitative rates for the results obtained in [7].  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号