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   1466篇
  免费   225篇
  国内免费   163篇
化学   565篇
晶体学   33篇
力学   67篇
综合类   12篇
数学   493篇
物理学   684篇
  2024年   2篇
  2023年   25篇
  2022年   57篇
  2021年   72篇
  2020年   67篇
  2019年   56篇
  2018年   58篇
  2017年   72篇
  2016年   73篇
  2015年   60篇
  2014年   75篇
  2013年   131篇
  2012年   77篇
  2011年   72篇
  2010年   65篇
  2009年   78篇
  2008年   100篇
  2007年   75篇
  2006年   85篇
  2005年   41篇
  2004年   37篇
  2003年   36篇
  2002年   52篇
  2001年   45篇
  2000年   45篇
  1999年   39篇
  1998年   44篇
  1997年   26篇
  1996年   28篇
  1995年   14篇
  1994年   19篇
  1993年   9篇
  1992年   15篇
  1991年   13篇
  1990年   11篇
  1989年   9篇
  1988年   8篇
  1987年   9篇
  1986年   14篇
  1985年   11篇
  1984年   8篇
  1983年   1篇
  1982年   10篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1975年   1篇
  1973年   1篇
排序方式: 共有1854条查询结果,搜索用时 15 毫秒
111.
Polyrakis  Ioannis A. 《Positivity》2000,4(2):197-201
We establish that an ordered Banach space is order-isomorphic to c0 if and only if it is a -Dedekind complete vector lattice and its norm dual is order-isomorphic to 1.  相似文献   
112.
We considered the Heisenberg model on the recursive lattices with multi-spin interaction in a strong magnetic field as an approximation of the two-dimensional kagome lattice, as well as hexagonal recursive lattices as an approximation of triangular lattice, for solid 3He. In a strong magnetic field it is possible to approximate the Heisenberg model with the Izing one. Using dynamic approach, we obtain exact recursion relations for partition functions. Diagrams of the magnetization versus external magnetic field with different spin-exchange parameters and temperatures are presented. Magnetization plateaux, bifurcation points, and doublings are obtained.  相似文献   
113.
At sufficiently low temperatures, the configurational phase space of a large spin-glass system breaks into many separated domains, each of which is referred to as a macroscopic state. The system is able to visit all spin configurations of the same macroscopic state, while it can not spontaneously jump between two different macroscopic states. Ergodicity of the whole configurational phase space of the system, however, can be recovered if a temperature-annealing process is repeated an infinite number of times. In a heating-annealing cycle, the environmental temperature is first elevated to a high level and then decreased extremely slowly until a final low temperature T is reached. Different macroscopic states may be reached in different rounds of the annealing experiment; while the probability of finding the system in macroscopic state α decreases exponentially with the free energy F α (T) of this state. For finite-connectivity spin glass systems, we use this free energy Boltzmann distribution to formulate the cavity approach of Mézard and Parisi [Eur. Phys. J. B, 2001, 20: 217] in a slightly different form. For the ±J spin-glass model on a random regular graph of degree K = 6, the predictions of the present work agree with earlier simulational and theoretical results.   相似文献   
114.
Thermoporosimetry (TPM), a differential scanning calorimetry technique that relies on the shift of transition temperatures caused by the confinement of liquids, was applied to elucidate the complex morphology of drug‐loaded polymeric microcapsules prepared by the emulsion solvent evaporation method. For the very first time, TPM has been applied simultaneously with two liquids as structural probes. It was found that Miglyol, which dissolves the selected drug (Ibuprofen), is confined inside vesicles having a mean radius of 26.3 nm, whereas water, which is the continuous phase, is trapped inside a swollen polymeric network of Eudragit with an average mesh radius of 1.7 nm. A proposed hierarchical structure is given, which predicts that Eudragit microcapsules are formed from a collection of inert oil vesicles partitioned by polymeric Eudragit membranes swollen by water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1939–1945, 2010  相似文献   
115.
116.
An efficient and easy to implement method to generate Cartesian grids is presented. The presented method generates various kinds of Cartesian grids such as uniform, octree and embedded boundary grids. It supports the variation of grid size along each spatial direction as well as anisotropic and non‐graded refinements. The efficiency and ease of implementation are the main benefits of the presented method in contrast to the alternative methods. Regarding octree grid generation, applying a simple and efficient data compression method permits to store all grid levels without considerable memory overhead. The presented method generates octree grids up to a 13‐level refinement (81923 grids on the finest level) from a complicated geometry in a few minutes on the traditional desktop computers. The FORTRAN 90 implementation of the presented method is freely available under the terms of the GNU general public license. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
117.
118.
Summary A detailed experimental analysis of the inelastic crosssection along the [111]-direction in Co−Ni alloys is presented. Using a simple model and studying the cross-section as a function of both composition and temperature, it is shown that interesting information about the h.c.p.-f.c.c. transition can be gained in these alloys.
Riassunto Nel presente lavoro si describe un’analisi sperimentale dettagliata della sezione d’urto anelastica dei neutroni lungo la direzione [111] in leghe Co−Ni. Impiegando un modello relativamente semplice e studiando la sezione d’urto in funzione di temperatura e concentrazione, si mostra che si possono ottenere utili informazioni riguardanti la transizione h.c.p.-f.c.c.
  相似文献   
119.
120.
郝立丽  郝立柱 《东北数学》2008,24(6):534-544
Aiming to provide an appropriate number K of clusters, in this paper, we propose a new criterion function - H criterion function, whose three properties have also been proved. We validate the performance of the H criterion function on one artificial dataset and three real-world datasets, and the results are almostly consistent with a previous method. The nonparametric criterion we proposed is intuitive, simple and the computational cost is acceptable.  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