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   5549篇
  免费   901篇
  国内免费   694篇
化学   2329篇
晶体学   87篇
力学   709篇
综合类   110篇
数学   1274篇
物理学   2635篇
  2024年   13篇
  2023年   43篇
  2022年   131篇
  2021年   128篇
  2020年   155篇
  2019年   121篇
  2018年   137篇
  2017年   201篇
  2016年   223篇
  2015年   174篇
  2014年   247篇
  2013年   499篇
  2012年   312篇
  2011年   367篇
  2010年   297篇
  2009年   369篇
  2008年   317篇
  2007年   331篇
  2006年   325篇
  2005年   253篇
  2004年   281篇
  2003年   282篇
  2002年   247篇
  2001年   197篇
  2000年   196篇
  1999年   184篇
  1998年   158篇
  1997年   97篇
  1996年   103篇
  1995年   98篇
  1994年   108篇
  1993年   72篇
  1992年   72篇
  1991年   48篇
  1990年   53篇
  1989年   42篇
  1988年   35篇
  1987年   35篇
  1986年   24篇
  1985年   25篇
  1984年   25篇
  1983年   13篇
  1982年   17篇
  1981年   8篇
  1980年   12篇
  1979年   16篇
  1978年   7篇
  1977年   9篇
  1976年   13篇
  1973年   6篇
排序方式: 共有7144条查询结果,搜索用时 15 毫秒
21.
钟纪泉  张学谦 《中国物理 C》1996,20(12):1087-1090
壳模型计算表明,1/2+[411]出现于157Tm核的基态可能是由非轴对称形变造成的.但是新近从157Yb衰变纲图给出的157Tm低激发谱中,指认了一个建立在1/2+[411]带头上的基态转动带,并认为该带的性质是轴对称的,提取了该带的惯性参数与脱耦合参数.通过对奇ATm核1/2+[411]转动带的系统分析,强调了在157Tm核中非轴对称γ自由度效应的重要性.  相似文献   
22.
The order parameter S of Fe–Pt nanoparticles is estimated from X-ray diffraction (XRD) patterns. The total intensity of a diffraction peak is obtained by Rietveld analysis as well as simply integrating the intensity. The Rietveld analysis is found to provide a plausible value of S even for a sample showing an XRD pattern with broad and overlapped peaks. Another order parameter Q, which is obtained from Mössbauer spectra, is introduced, and it is confirmed that Q is equivalent to the probability of Fe atoms being in the L10-type atomic arrangement. The coercivity of Fe–Pt nanoparticles is directly proportional to Q, while it vanishes at S=0.4, indicating that the magnetic property of Fe–Pt nanoparticles has a closer relationship to Q than S.  相似文献   
23.
付芬  肖志刚  靳根明  冯兆庆 《中国物理 C》2006,30(11):1083-1087
随着兰州重离子加速器冷却储存环(HIRFL-CSR)外靶实验终端中子墙的建立, 为实验测量高能中子提供了机遇. 为确定CSR外靶实验终端对中子流测量的可行性, 基于BUU理论模型分别对对称系统(Ni+Ni, Pb+Pb)和非对称系统(Pb+Ni)进行了模拟计算, 发现当系统能量达到几百MeV/u时, 中子流信号相当明显, 并与碰撞参数有明显的依赖关系. 模拟结果表明, 在前角20°的覆盖范围内, 可以较好地实现中子流测量所需要的反应平面确定及碰撞参数选择. 对双击事件及其对中子流的影响进行了简单的讨论.  相似文献   
24.
介绍了一种检验定性指标的有效方法,可用于确定产品的合格率和评价检验人员的检验水平。用该方法分析了某厂产品的一项实际指标,合格率为91 4%,还对该厂10名检验员的检验水平作了客观的评价。  相似文献   
25.
The melting behaviour, some phase boundaries and the lattice parameters in the region of the NiAs-type phase in the ternary system cobalt-antimony-tellurium have been determined by differential thermal analysis and X-ray diffraction. A projection of the liquidus surface and the phase relationships in different sections with constant antimony/tellurium ratios are presented. The peculiar variation of the lattice parameters with the composition of the nonstoichiometric NiAs-type phase is discussed in terms of the defect structure.Dedicated to Prof. K. L. Komarek on the occasion of his 65th birthday  相似文献   
26.
电磁继电器触点参数的测试   总被引:1,自引:0,他引:1  
本文介绍了电磁继电器触点电参数的测试方法,包括接触电阻、绝缘电阻参数测试。  相似文献   
27.
HBT参数对π源空间分布的敏感性研究(英文)   总被引:1,自引:1,他引:0  
利用理想高斯源的两粒子关联函数,对单高斯源和双高斯源的两π介子HBT关联效应进行了研究,得出了相应的半径参数和A参数.结果表明,半径参数主要取决于高能重离子碰撞中多数π介子产生的中间区域;对产生π介子的边缘区域的空间分布形状不敏感.在边缘区域内产生的π介子主要影响A参数的变化.π介子源空间分布的非高斯形是导致λ参数减少的一个重要因素.The HBT radius parameters and the HBT λ-parameters of single Gaussian source and double Gaussian source are investigated by using two-pion correlation function in HBT intensity interferometry. It is indicated that the radius parameter is insensitive to the spatial shape of the edge zone of source and is mainly affected by the size of the central zone of pions emitted in high energy heavy-ion collisions. The pions produced at the edge of source influence the λ parameter. The non-Gaus...  相似文献   
28.
This paper presents the mathematical approach for the abnormal multiplication of plankton. An abnormal multiplication can be expressed as an unstable problem and the stability of the system is investigated by introducing eigenvalues of a mathematical equation. The stability of the system can be judged by an eigenvalue based on the Lyapunov's stability theory. In this paper, the Arnoldi‐QR method is used to obtain eigenvalues and eigenvectors of the system. The mode superposition method is employed to create spatial distribution needed to analyse the stability. To obtain the objective eigenvalue, the parameter identification technique is employed. The finite element method is used for the discretization in space. Lake Kasumigaura, which is located in Ibaraki Prefecture in Japan, is selected and actual data in 1975, 1976, 1991 and 2000 are used in order to investigate the stability of the specified lake in Japan. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
29.
The character of critical behavior in physical systems depends on the range of interactions. In the limit of infinite range of the interactions, systems will exhibit mean-field critical behavior, i.e., critical behavior not affected by fluctuations of the order parameter. If the interaction range is finite, the critical behavior asymptotically close to the critical point is determined by fluctuations and the actual critical behavior depends on the particular universality class. A variety of systems, including fluids and anisotropic ferromagnets, belongs to the three-dimensional Ising universality class. Recent numerical studies of Ising models with different interaction ranges have revealed a spectacular crossover between the asymptotic fluctuation-induced critical behavior and mean-field-type critical behavior. In this work, we compare these numerical results with a crossover Landau model based on renormalization-group matching. For this purpose we consider an application of the crossover Landau model to the three-dimensional Ising model without fitting to any adjustable parameters. The crossover behavior of the critical susceptibility and of the order parameter is analyzed over a broad range (ten orders) of the scaled distance to the critical temperature. The dependence of the coupling constant on the interaction range, governing the crossover critical behavior, is discussed.  相似文献   
30.
The purpose in this paper is to compute the eigenvalues of Sturm-Liouville problems with quite general separated boundary conditions nonlinear in the eigenvalue parameter using the regularized sampling method, an improvement on the method based on Shannon sampling theory, which does not involve any multiple integration and provides higher order estimates of the eigenvalues at a very low cost. A few examples shall be presented to illustrate the power of the method and a comparison made with the the exact eigenvalues obtained as squares of the zeros of the exact characteristic functions.

  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