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   499篇
  免费   10篇
  国内免费   1篇
化学   317篇
晶体学   4篇
力学   12篇
数学   75篇
物理学   102篇
  2021年   6篇
  2019年   7篇
  2018年   4篇
  2016年   10篇
  2015年   14篇
  2014年   14篇
  2013年   13篇
  2012年   30篇
  2011年   27篇
  2010年   20篇
  2009年   21篇
  2008年   23篇
  2007年   15篇
  2006年   18篇
  2005年   17篇
  2004年   10篇
  2003年   7篇
  2002年   8篇
  2001年   7篇
  2000年   17篇
  1999年   4篇
  1996年   5篇
  1995年   5篇
  1994年   4篇
  1992年   9篇
  1990年   10篇
  1989年   7篇
  1988年   9篇
  1987年   10篇
  1986年   7篇
  1985年   6篇
  1984年   7篇
  1983年   9篇
  1982年   7篇
  1981年   5篇
  1980年   8篇
  1979年   9篇
  1978年   9篇
  1977年   10篇
  1976年   11篇
  1975年   8篇
  1973年   6篇
  1972年   3篇
  1968年   3篇
  1942年   2篇
  1941年   3篇
  1937年   5篇
  1935年   3篇
  1926年   2篇
  1910年   2篇
排序方式: 共有510条查询结果,搜索用时 31 毫秒
61.
We describe a method for using extensive air shower data to determine whether a Feynman scaling limit exists in the central region for inclusive cross sections. Preliminary analysis suggests that the shower muon to electron ratio is more consistent with a power law increase of pion multiplicity with energy than with the logarithmic multiplicity increase characteristic of a scaling limit, but an analysis of the intra-nuclear cascade is required to reach a firm conclusion.  相似文献   
62.
63.
As a result of research, the propagation characteristics of optical waveguides are becoming well enough understood for system evaluation. In this paper material and structural properties of the waveguide are related to measurements made on present experimental waveguides. Among the conclusions drawn from this work are that intermodal dispersion provides the dominant pulse broadening contribution but that this has been reduced to the nanosecond region by radial index gradient control. For present source spectral bandwidths, material dispersion is not a major contribution to pulse broadening. Waveguides up to 3 km long can be made with negligible intrinsic mode coupling. This gives rise to the possibility of either internal or external control to increase the information carrying capacity of the waveguide. External control has already been demonstrated. However, additional work is required to make this practical.  相似文献   
64.
A study of a 150000-picture exposure of ¯pd at 5.5 GeV/c yielded 152 events satisfying the hypothesis ¯pdp s π+?π0. For the events with proton spectator in the momentum range 100–280 MeV/c we obtained the cross section of 0.11±0.02 mb. Assuming the validity of the impulse approximation we estimate a cross section of 0.43±0.06 mb for the reaction ¯pn→ π+?π0. The rate for single ? meson production and an upper limit for double ? production are given. A modified multiperipheral Regge model was used in order to describe the general features of the data.  相似文献   
65.
In this paper stability properties of the extremal value function are studied for infinite-dimensional nonlinear optimization problems with differentiable perturbations in the objective function and in the constraints. In particular, upper and lower bounds for the directional derivative of the extremal value function as well as necessary and sufficient conditions for the existence of the directional derivative are given.  相似文献   
66.
Let F be the rational field or a p-adic field, and let K an algebraic number field over F. If ω1,…, ωn is an integral basis for the ring DL of integers in K, then the quadratic form Q whose matrix is (traceKF(ωiωj)) has integral coefficients, and is called an integral trace-form. Q is determined by K up to integral equivalence. The purpose of this paper is to show that the genus of Q determines the ramification of primes in K.  相似文献   
67.
Several graph-theoretic notions applied to matroid basis graphs in the preceding paper are now tied more specifically to aspects of matroids themselves. Factorizations of basis graphs and disconnections of neighborhood subgraphs are related to matroid separations. Matroids are characterized whose basis graphs have only one or two of the three types of common neighbor subgraphs. The notion of leveling is generalized and related to matroid sums, minors, and duals. Also, the problem of characterizing regular and graphic matroids through their basis graphs is discussed. Throughout, many results are obtained quite easily with the aid of certain pseudo-combivalence systems of 0–1 matrices.  相似文献   
68.
    
Ohne Zusammenfassung  相似文献   
69.
A model to describe vapor-liquid equilibrium (VLE) and solid-liquid equilibrium (SLE) in the ammonia-phosphoric acid-water system is developed. The model takes into account chemical reactions as well as physical interactions. Using interaction parameters and solubility contants as determined from experimental data on VLE and SLE, the model is capable of describing the phase behavior in this extremely complex system over a wide range of composition.Dedicated to Prof. Dr.-Ing. G. Ernst on the occasion of his 60th birthday.  相似文献   
70.
The cross sections for elastic electron scattering from 3He and 4He were measured for the momentum transfer range from 0.45–2.0 fm?1. The cross sections were separated into their longitudinal (charge) and transverse (magnetic) contributions using the Rosenbluth formula. The charge and magnetic form factors were obtained model-independently.The rms charge radii were found to be 1.671 (14) fm for 4He and 1.976 (15) fm for 3He, and the magnetic rms radius of 3He is 1.99 (6) fm. The mis charge radius for 4He is in excellent agreement with the latest muonic data.Comparison of the form factors was made with Faddeev three-body calculations using realistic two-body NN interactions. At present the theoretical calculation is not able to reproduce the experimental data.  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