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   1573篇
  免费   66篇
  国内免费   123篇
化学   105篇
晶体学   43篇
力学   59篇
综合类   10篇
数学   1269篇
物理学   276篇
  2024年   11篇
  2023年   14篇
  2022年   22篇
  2021年   25篇
  2020年   23篇
  2019年   45篇
  2018年   44篇
  2017年   37篇
  2016年   32篇
  2015年   27篇
  2014年   67篇
  2013年   169篇
  2012年   58篇
  2011年   63篇
  2010年   57篇
  2009年   101篇
  2008年   115篇
  2007年   91篇
  2006年   84篇
  2005年   70篇
  2004年   66篇
  2003年   65篇
  2002年   48篇
  2001年   60篇
  2000年   61篇
  1999年   53篇
  1998年   45篇
  1997年   36篇
  1996年   36篇
  1995年   13篇
  1994年   17篇
  1993年   17篇
  1992年   17篇
  1991年   14篇
  1990年   11篇
  1989年   4篇
  1988年   11篇
  1987年   2篇
  1986年   1篇
  1985年   5篇
  1984年   3篇
  1983年   1篇
  1982年   4篇
  1981年   4篇
  1980年   5篇
  1979年   1篇
  1978年   3篇
  1977年   2篇
  1976年   2篇
排序方式: 共有1762条查询结果,搜索用时 0 毫秒
931.
    
The last step of a crystal structure determination that requires human intervention is the interpretation of Fourier maps, displayed as peaks in a favourable projection. Crystallographers infer bonding by empirically assigning bonds between peaks via purely geometrical criteria. In this paper, a network connecting peaks and passes of the density function is suggested in order to avoid human intervention and bonding inference. A completely automatic algorithm for the full analysis of critical points and recognition of the molecular graph in Fourier maps has been developed and implemented into the package DIRDIF. This procedure has been applied successfully to a wide variety of crystal structures. In most cases, the complete structure is recovered and the connectivity matrix is constructed without any user intervention.  相似文献   
932.
    
In a recent paper [Giacovazzo & Mazzone (2011). Acta Cryst. A 67 , 210–218] a mathematical expression of the variance at any point of the unit cell has been described. The formulas were derived in P1 for any type of Fourier synthesis (observed, difference and hybrid) under the following hypothesis: the current phases are distributed on the trigonometric circle about the correct values according to von Mises distributions. This general hypothesis allows the variance expressions to be valid at any stage of the phasing process. In this paper the method has been extended to any space group, no matter whether centric or acentric. The properties of the variance generated by space‐group symmetry are described; in particular it is shown that the variance is strictly connected with the implication transformations, which are basic for Patterson deconvolution. General formulas simultaneously taking into account phase uncertainty and measurement errors have been obtained, valid no matter what the quality of the model.  相似文献   
933.
    
The construction of reduced order models for flow control via a direct discretization of the input/output behavior of the system is discussed. The spatially discretized equations are linearized such that an explicit formula for the corresponding input/output map can be used to generate a matrix representation of the input/output map. Estimates for the approximation error are derived and the applicability is illustrated via a numerical example for the control of a driven cavity flow.  相似文献   
934.
The topological entropy for some families of one-dimensional unimodal maps is studied. By arranging the windows of constant topological entropy in a binary tree, we have obtained the total measure of these windows. The scaling properties of this measure are studied.  相似文献   
935.
We study the relation between multiplicity-free symplectic manifolds and the multiplicities of group representations obtained by geometric quantization. With the help of a general equivalence theorem we can prove a conjecture of Guillemin and Sternberg in the compact Kähler case.  相似文献   
936.
D. Auroux  S.K. Donaldson 《Topology》2004,43(6):1285-1318
Introducing the notion of stabilized fundamental group for the complement of a branch curve in , we define effectively computable invariants of symplectic 4-manifolds that generalize those previously introduced by Moishezon and Teicher for complex projective surfaces. Moreover, we study the structure of these invariants and formulate conjectures supported by calculations on new examples.  相似文献   
937.
938.
939.
We show by an example that, in a complementarity problem where the given map is continuous and monotone on the nonnegative orthant, the existence of a feasible solution is not sufficient to guarantee existence of a solution to the complementarity problem.The author thanks Professor S. Karamardian and Dr. J. More for helpful discussions regarding this note.  相似文献   
940.
We derive a lower bound for energies of harmonic maps of convex polyhedra in to the unit sphere S2 with tangent boundary conditions on the faces. We also establish that C maps satisfying tangent boundary conditions are dense with respect to the Sobolev norm in the space of continuous tangent maps of finite energy.This revised version was published online in March 2005 with corrections to the cover date.  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