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   1371篇
  免费   25篇
  国内免费   31篇
化学   351篇
晶体学   1篇
力学   103篇
综合类   1篇
数学   403篇
物理学   568篇
  2024年   6篇
  2023年   40篇
  2022年   8篇
  2021年   17篇
  2020年   15篇
  2019年   18篇
  2018年   18篇
  2017年   12篇
  2016年   32篇
  2015年   21篇
  2014年   49篇
  2013年   115篇
  2012年   75篇
  2011年   65篇
  2010年   56篇
  2009年   83篇
  2008年   75篇
  2007年   89篇
  2006年   54篇
  2005年   56篇
  2004年   42篇
  2003年   42篇
  2002年   29篇
  2001年   26篇
  2000年   33篇
  1999年   27篇
  1998年   53篇
  1997年   15篇
  1996年   23篇
  1995年   16篇
  1994年   19篇
  1993年   12篇
  1992年   7篇
  1991年   8篇
  1990年   6篇
  1989年   8篇
  1988年   7篇
  1987年   17篇
  1986年   9篇
  1985年   17篇
  1984年   15篇
  1983年   16篇
  1982年   13篇
  1981年   9篇
  1980年   11篇
  1979年   12篇
  1978年   9篇
  1977年   7篇
  1976年   3篇
  1973年   4篇
排序方式: 共有1427条查询结果,搜索用时 15 毫秒
1.
The definition of the fundamental quantity, the chemical potential, is badly confused in the literature: there are at least three distinct definitions in various books and papers. While they all give the same result in the thermodynamic limit, major differences between them can occur for finite systems, in anomalous cases even for finite systems as large as a cm3. We resolve the situation by arguing that the chemical potential defined as the symbol μ conventionally appearing in the grand canonical density operator is the uniquely correct definition valid for all finite systems, the grand canonical ensemble being the only one of the various ensembles usually discussed (microcanonical, canonical, Gibbs, grand canonical) that is appropriate for statistical thermodynamics, whenever the chemical potential is physically relevant. The zero–temperature limit of this μ was derived by Perdew et al. for finite systems involving electrons, generally allowing for electron–electron interactions; we extend this derivation and, for semiconductors, we also consider the zero–T limit taken after the thermodynamic limit. The enormous finite size corrections (in macroscopic samples, e.g. 1 cm3) for one rather common definition of the c.p., found recently by Shegelski within the standard effective mass model of an ideal intrinsic semiconductor, are discussed. Also, two very–small–system examples are given, including a quantum dot.  相似文献   
2.
We start with a stochastic flow of diffeomorphisms of the space. Particles enter the space at random times and places. Each particle is carried by the flow for some random amount of time. We examine the point process formed by the particles at a fixed time, on the evolution of that point process as time varies, and on the equilibrium law of the point process.  相似文献   
3.
4.
In a previous paper we considered an extension of the hard hexagon model to a solvable two-dimensional lattice gas with at most two particles per pair of adjacent sites. Here we use various mathematical identities (in particular Gordon's generalization of the Rogers-Ramanujan relations) to express the local densities in terms of elliptic functions. The critical behavior is then readily obtained.Supported in part by the National Science Foundation Grant MCS 8201733.  相似文献   
5.
We present a statistical mechanics treatment of the stability of globular proteins which takes explicitly into account the coupling between the protein and water degrees of freedom. This allows us to describe both the cold and the warm unfolding, thus qualitatively reproducing the known thermodynamics of proteins. Received: 19 March 1998 / Revised and Accepted: 25 May 1998  相似文献   
6.
The nanogranular nature of C-S-H   总被引:6,自引:0,他引:6  
Despite its ubiquitous presence as binding phase in all cementitious materials, the mechanical behavior of calcium-silicate-hydrates (C-S-H) is still an enigma that has deceived many decoding attempts from experimental and theoretical sides. In this paper, we propose and validate a new technique and experimental protocol to rationally assess the nanomechanical behavior of C-S-H based on a statistical analysis of hundreds of nanoindentation tests. By means of this grid indentation technique we identify in situ two structurally distinct but compositionally similar C-S-H phases heretofore hypothesized to exist as low density (LD) C-S-H and high density (HD) C-S-H, or outer and inner products. The main finding of this paper is that both phases exhibit a unique nanogranular behavior which is driven by particle-to-particle contact forces rather than by mineral properties. We argue that this nanomechanical blueprint of material invariant behavior of C-S-H is a consequence of the hydration reactions during which precipitating C-S-H nanoparticles percolate generating contact surfaces. As hydration proceeds, these nanoparticles pack closer to center on-average around two characteristic limit packing densities, the random packing limit (η=64%) and the ordered face-centered cubic (fcc) or hexagonal close-packed (hcp) packing limit (η=74%), forming a characteristic LD C-S-H and HD C-S-H phase.  相似文献   
7.
A method of using algebraic curves to obtain estimates of critical points accurate enough to identify them as simple algebraic numbers (if that is what they are) is discussed and illustrated with an application to the (q-state Potts model on the triangular lattice for cases of pure two-site interactions and pure three-site interactions. In the latter case the critical point is conjectured to be . In a similar conjecture for the critical percolation probability on thedirected square lattice,q c 1/2 (q c +3)=2(q c +p c =1).  相似文献   
8.
A two-dimensional quantum Hamiltonian N,M commuting with the layer-to-layer transfer matrix of the three-dimensional Zamolodchikov model is derived. This Hamiltonian is defined on a lattice ofN×M sites. The special casesN×2, 2×M, and 3×M are studied.This paper is dedicated to Cyril Domb.  相似文献   
9.
Very recently, it has been shown that there are chiralN-state Potts models in statistical mechanics that satisfy the star-triangle relation. Here it is shown that the relation implies that the free energy (and its derivatives) satisfies certain functional relations. These can be used to obtain the free energy: in particular, we expand about the critical case and find that the exponent is 1–2/N.  相似文献   
10.
用统计模拟分光光度法测定复方消咳新片4个组分含量。按均匀设计表制备合成样品,绘制溶液的UV-VIS吸收曲线,获得有限但足够的实验数据,用逐步回归法构造反映该复方制剂组分在灵敏波长的吸光度-组分含量经验关系的“最优”数学模型,用改进单纯形法寻优,求出未知样品的各组分含量。磺胺甲基异恶唑、甲氧苄胺嘧啶、盐酸溴已新、枸橼酸维静宁的回收率分别为1003%、1004%、999%、990%,标准差分别为091%、14%、12%、39%。  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