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   27770篇
  免费   1003篇
  国内免费   59篇
化学   16686篇
晶体学   107篇
力学   594篇
数学   4052篇
物理学   7393篇
  2023年   176篇
  2021年   287篇
  2020年   359篇
  2019年   301篇
  2018年   331篇
  2017年   333篇
  2016年   696篇
  2015年   670篇
  2014年   664篇
  2013年   1316篇
  2012年   1326篇
  2011年   1530篇
  2010年   792篇
  2009年   702篇
  2008年   1272篇
  2007年   1267篇
  2006年   1250篇
  2005年   1114篇
  2004年   879篇
  2003年   828篇
  2002年   730篇
  2001年   584篇
  2000年   473篇
  1999年   396篇
  1998年   337篇
  1997年   339篇
  1996年   368篇
  1995年   329篇
  1994年   313篇
  1993年   340篇
  1992年   362篇
  1991年   321篇
  1990年   268篇
  1989年   287篇
  1988年   252篇
  1987年   282篇
  1986年   259篇
  1985年   317篇
  1984年   363篇
  1983年   285篇
  1982年   331篇
  1981年   321篇
  1980年   301篇
  1979年   297篇
  1978年   291篇
  1977年   306篇
  1976年   258篇
  1975年   244篇
  1974年   236篇
  1973年   209篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Times of longitudinal T 1b and transverse T 2b magnetic relaxation of hexane and decane molecules in micropores of ZSM-5 silicalite were measured as functions of the content of these liquid n-alkanes in zeolite and of temperature. The stepwise changes in the T 1b and T 2b times were revealed in the region of 8% content of hydrocarbons. The observed changes in the concentration and temperature dependences of T 1b and T 2b times are explained by the rearrangement of silicalite crystal lattice under the action of adsorbed molecules.  相似文献   
33.
In this paper we present a method to solve numerically elliptic problems with multi-scale data using multiple levels of not necessarily nested grids. The method consists in calculating successive corrections to the solution in patches whose discretizations are not necessarily conforming. It resembles the FAC method (see Math. Comp. 46 (174) (1986) 439–456) and its convergence is obtained by a domain decomposition technique (see Math. Comp. 57 (195) (1991) 1–21). However it is of much more flexible use in comparison to the latter. To cite this article: R. Glowinski et al., C. R. Acad. Sci. Paris, Ser. I 337 (2003).  相似文献   
34.
Book rewiev     
Howard Anton and Robert C. Busby, John Wiley & Sons, Inc., 2002.  相似文献   
35.
Let K be ? or an imaginary quadratic number field, and q ∈ K an integer with ¦q¦ > 1. We give a quantitative version of Σn≥1 an/(qn ? 1) ? K for non-zero periodic sequences (an) in K of period length ≤ 2. As a corollary, we get a quantitative version of the linear independence over K of 1, the q-harmonic series, and a q-analogue of log 2. A similar result on 1, the q-harmonic series, and a q-analogue of ζ(2) is also proved. Mathematics Subject Classification (2000): 11J72, 11J82  相似文献   
36.
The dependence of the strangeness saturation factor on the system size, centrality and energy is studied in relativistic heavy-ion collisions.  相似文献   
37.
Isochronous relaxation of tensile stresses is measured in a bulk Pd40Cu30Ni10P20 metallic glass in the initial state and after certain thermal treatments. The results of measurements are used to find the energy spectrum of irreversible structural relaxation, from which the temperature dependence of shear viscosity is then calculated. This dependence is also found independently from measurements of creep in the same glass. The calculated viscosity is shown to agree well with the experimental data.  相似文献   
38.
39.
The control of piecewise-deterministic processes is studied where only local boundedness of the data is assumed. Moreover the discount rate may be zero. The value function is shown to be solution to the Bellman equation in a weak sense; however the solution concept is strong enough to generate optimal policies. Continuity and compactness conditions are given for the existence of nonrelaxed optimal feedback controls.  相似文献   
40.
We examine certain special features exhibited by various classes of linear operators acting in a hereditarily indecomposable Banach space. For instance, we show that the family of all Riesz operators in a H.I. space forms a closed, 2-sided ideal. We also give further characterizations of the class of scalar-type spectral operators (to those already given in [16]). The final section discusses some properties of the spectral maximal spaces of (necessarily decomposable) linear operators in such spaces. Conferenza tenuta il 16 settembre 1997 The support of the German Academic Exchange Scheme (DAAD) is gratefully acknowledged  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