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   10864篇
  免费   1117篇
  国内免费   1318篇
化学   7757篇
晶体学   38篇
力学   1028篇
综合类   119篇
数学   851篇
物理学   3506篇
  2024年   33篇
  2023年   129篇
  2022年   313篇
  2021年   330篇
  2020年   416篇
  2019年   320篇
  2018年   293篇
  2017年   368篇
  2016年   423篇
  2015年   329篇
  2014年   493篇
  2013年   880篇
  2012年   519篇
  2011年   553篇
  2010年   554篇
  2009年   666篇
  2008年   603篇
  2007年   600篇
  2006年   646篇
  2005年   560篇
  2004年   575篇
  2003年   480篇
  2002年   386篇
  2001年   324篇
  2000年   318篇
  1999年   286篇
  1998年   280篇
  1997年   220篇
  1996年   206篇
  1995年   194篇
  1994年   154篇
  1993年   124篇
  1992年   120篇
  1991年   111篇
  1990年   97篇
  1989年   70篇
  1988年   66篇
  1987年   42篇
  1986年   31篇
  1985年   31篇
  1984年   28篇
  1983年   9篇
  1982年   26篇
  1981年   24篇
  1980年   19篇
  1979年   19篇
  1978年   16篇
  1974年   2篇
  1973年   5篇
  1959年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The concept of blind source separation is described and examples of its use in 1D and 2D NMR spectroscopy are presented. The goal of this data processing method is to extract the spectra of components molecules when only mixtures are available.  相似文献   
92.
The importance of Hund's rule coupling for the stabilization of itinerant ferromagnetism is investigated within a two-band Hubbard model. The magnetic phase diagram is calculated by finite-temperature quantum Monte-Carlo simulations within the dynamical mean-field theory. Ferromagnetism is found in a broad range of electron fillings whereas antiferromagnetism exists only near half filling. The possibility of orbital ordering at quarter filling is also analyzed. Received: 26 February 1998 / Accepted: 17 April 1998  相似文献   
93.
The aim of this paper is to present several features of the couplings occurring between radiative transfer and the kinetics of a moving dielectric. After determining how the velocity field affects the apparent thermo-optical properties of matter, the energy transport problem is investigated in instationary regime and the general form of transient radiative transfer equation inside a moving medium is built. Then, the model is applied to the particular case of turbulent flows: a system of two equations for mean and fluctuating radiative energies is presented, and the resolution of this system is finally carried out.  相似文献   
94.
分离变量法与等腰直角三角形波导的边值问题   总被引:4,自引:0,他引:4  
王学军  黄骝 《应用光学》2002,23(1):13-16
根据叠加原理,讨论等腰直角三角形波导边值问题的IE波解和TM波解,纠正有关文献中的错误解法,指出分离变量法的适用条件。  相似文献   
95.
The constants of binding dye molecules with the micelles of sodium dodecyl sulfate are determined using quenching of delayed fluorescence of acridine dyes by sodium iodide in aqueous–micellar solutions. Kinetic equations have been composed that describe the processes of deactivation of the excited states of dyes. By solving these equations at the concentration of the quencher sodium iodide corresponding to the minimum lifetime of triplet states and at the concentration of micelles corresponding to the least value of the delayed fluorescence quenching rate constants, we obtained the constants of binding dyes with micelles equal to 1.3·107, 2.9·107, and 3.1·107 M–1 for trypaflavine, acridine orange, and acridine yellow, respectively. We calculated the rate constants of quenching of the triplet states of the molecules of dyes by iodide ions (I ) that decreased in transition from trypaflavine to acridine orange and acridine yellow.  相似文献   
96.
97.
In this study, the viscoelastic phase separation process was studied further by time‐resolved light scattering, differential scanning calorimetry, and scanning electron microscopy in the system of poly(ether imide)‐modified bisphenol‐A dicyanate. It was observed that the evolution time of phase structure and relaxation time of diffusion flow of the bisphenol‐A dicyanate were similar with the phase diagram of curing conversion versus content of PEI. The results suggested that the viscoelastic phase separation was affected by the curing conversion of the system at the onset point of phase separation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 517–523, 2006  相似文献   
98.
Mathematical Diagnostics (MD) deals with identification problems arising in different practical areas. Some of these problems can be described by mathematical models where it is required to identify points belonging to two or more sets of points. Most of the existing tools provide some identification rule (a classifier) by means of which a given point is assigned (attributed) to one of the given sets. Each classifier can be viewed as a virtual expert. If there exist several classifiers (experts), the problem of evaluation of experts’ conclusions arises. In the paper for the case of supervised classification the method of virtual experts (the VE-method) is described. Based on this method, a generalized VE method is proposed where each of the classifiers can be chosen from a given family of classifiers. As a result, a new optimization problem with a discontinuous functional is stated. Examples illustrating the proposed approach are provided. The work of the second author was supported by the Russian Foundation for Fundamental Studies (RFFI) under Grant No 03-01-00668.  相似文献   
99.
加拿大TRIUMF实验室利用11C成功验证了一种产生高强度(~108ions/s)放射性束流的方法. 该方法不同于普通在线同位素分离方法, 它利用了13MeV的低能强流质子束, 可以产生一系列核天体物理实验感兴趣的高强度放射性束流.  相似文献   
100.
刘金明  刘三秋 《光子学报》1998,27(7):583-587
本文研究了存在Kerr介质的高Q腔中压缩相干态与级联三能级原子相互作用的光子统计演化规律,讨论了光场参数、Kerr介质及相干振幅对平均光子数的影响.  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