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   1374篇
  免费   96篇
  国内免费   53篇
化学   150篇
晶体学   4篇
力学   69篇
综合类   7篇
数学   213篇
物理学   278篇
综合类   802篇
  2024年   1篇
  2023年   15篇
  2022年   25篇
  2021年   23篇
  2020年   27篇
  2019年   21篇
  2018年   26篇
  2017年   27篇
  2016年   38篇
  2015年   33篇
  2014年   82篇
  2013年   77篇
  2012年   84篇
  2011年   129篇
  2010年   87篇
  2009年   87篇
  2008年   65篇
  2007年   75篇
  2006年   78篇
  2005年   58篇
  2004年   46篇
  2003年   60篇
  2002年   60篇
  2001年   38篇
  2000年   46篇
  1999年   35篇
  1998年   18篇
  1997年   23篇
  1996年   20篇
  1995年   13篇
  1994年   17篇
  1993年   12篇
  1992年   14篇
  1991年   10篇
  1990年   14篇
  1989年   9篇
  1988年   10篇
  1987年   6篇
  1986年   4篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   5篇
  1978年   1篇
排序方式: 共有1523条查询结果,搜索用时 78 毫秒
71.
Summary The influence of the distance between the solvent entry and the starting zone positions, Z0, on the average plate height was studied. This factor was found to be of major importance and could be optimized. The Guiochon and Siouffi model greatly underestimates the plate height for low values of Z0.  相似文献   
72.
傅铁峰 《应用光学》1995,16(5):43-46
本文介绍了使用简易弧高计测量球面弧高时的误差公式,并用实例说明了此类弧高计在一般光学元件件加工测量中的可靠性。  相似文献   
73.
We present in this paper a new 3D half-moment model for radiative transfer in a gray medium, called the model, which uses maximum entropy closure. This model is a generalization to 3D of the 1D version recently proposed in (J. Comp. Phys. 180 (2002) 584). The direction space Ω is divided into two pieces, Ω+ and Ω-, in a dynamical way by the plane perpendicular to the total radiative flux, and the half moments are defined from these subspaces. The model closure and the integrations of the radiative transfer equation performed on the moving Ω± spaces are detailed. 1D planar results, which have motivated the extension of the model of (J. Comp. Phys. 180 (2002) 584) to multi-dimensions, are shown. These results are very good. The model is thereafter derived for 3D spherically symmetric geometry, where the correctness of the non-trivial border terms can be checked. Two 3D spherically symmetric problems are numerically solved in order to show the accuracy of the closure and the role of the border terms. Once again, compared to the solution obtained with a ray tracing solver, results are very good. From the 3D half-moment model, a new moment model, called , is derived for the particular case of a 3D hot and opaque source radiating into a cold medium, for applications such as simulations of stellar atmospheres and fires. Two-dimensional numerical results are presented and compared to those obtained solving the RTE and with other moment models. They demonstrate the very good accuracy of the model, its good convergence properties, and better prediction compared to all other existing moment models in its domain of applicability.  相似文献   
74.
The continuous-wave laser properties of an efficient diode-pumped Nd:GdVO4 crystal operating at formed with a simple plane-concave cavity have been studied. With the incident pump power of 21 W, an output power of 6.9 W was obtained, giving an optical conversion efficiency of 32.8% and a slope efficiency of 35.3%. The laser characterization of two different Nd3+-doped concentration of Nd:GdVO4 crystals were studied.  相似文献   
75.
The paper presents a formula for the γ-interior of a set under special conditions for , more general than those in the previous paper [Acta Math. Hungar. 80 (1998) 89-93]. There are also some applications.  相似文献   
76.
We introduce the notion of horospherical ridges for submanifolds of codimension 2 in hyperbolic n-space, and study some of their properties.*Work partially supported by DGCYT grant no. BFM2003-02037.  相似文献   
77.
We develop a notion of an n-fold monoidal category and show that it corresponds in a precise way to the notion of an n-fold loop space. Specifically, the group completion of the nerve of such a category is an n-fold loop space, and free n-fold monoidal categories give rise to a finite simplicial operad of the same homotopy type as the classical little cubes operad used to parametrize the higher H-space structure of an n-fold loop space. We also show directly that this operad has the same homotopy type as the n-th Smith filtration of the Barratt-Eccles operad and the n-th filtration of Berger's complete graph operad. Moreover, this operad contains an equivalent preoperad which gives rise to Milgram's small model for when n=2 and is very closely related to Milgram's model of for n>2.  相似文献   
78.
boundedness is considered for the commutator of higher-dimensional Marcinkiewicz integral. Some conditions implying the and the boundedness for the commutator of the Marcinkiewicz integral are obtained.  相似文献   
79.
At zero temperature, the 3-state antiferromagnetic Potts model on a square lattice maps exactly onto a point of the 6-vertex model whose long-distance behavior is equivalent to that of a free scalar boson. We point out that at nonzero temperature there are two distinct types of excitation: vortices, which are relevant with renormalization-group eigenvalue 1/2 and non-vortex unsatisfied bonds, which are strictly marginal and serve only to renormalize the stiffness coefficient of the underlying free boson. Together these excitations lead to an unusual form for the corrections to scaling: for example, the correlation length diverges as J/kT according to Ae 2 (1+be +···), where b is a nonuniversal constant that may nevertheless be determined independently. A similar result holds for the staggered susceptibility. These results are shown to be consistent with the anomalous behavior found in the Monte Carlo simulations of Ferreira and Sokal.  相似文献   
80.

We give optimal bounds of the height, curvature, area and volume of -surfaces in bounding a planar curve. The spherical caps are characterized as the unique -surfaces achieving these bounds.

  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