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   77753篇
  免费   523篇
  国内免费   117篇
化学   41313篇
晶体学   1260篇
力学   3278篇
综合类   1篇
数学   7837篇
物理学   24704篇
  2022年   629篇
  2021年   872篇
  2020年   967篇
  2019年   1106篇
  2018年   1597篇
  2017年   1686篇
  2016年   2149篇
  2015年   1025篇
  2014年   1721篇
  2013年   3272篇
  2012年   2903篇
  2011年   3282篇
  2010年   2638篇
  2009年   2636篇
  2008年   3003篇
  2007年   2881篇
  2006年   2771篇
  2005年   2435篇
  2004年   2239篇
  2003年   2073篇
  2002年   2134篇
  2001年   2235篇
  2000年   1625篇
  1999年   1252篇
  1998年   1125篇
  1997年   1036篇
  1996年   892篇
  1995年   832篇
  1994年   811篇
  1993年   812篇
  1992年   868篇
  1991年   934篇
  1990年   877篇
  1989年   905篇
  1988年   817篇
  1987年   768篇
  1986年   740篇
  1985年   865篇
  1984年   961篇
  1983年   818篇
  1982年   834篇
  1981年   746篇
  1980年   701篇
  1979年   768篇
  1978年   890篇
  1977年   913篇
  1976年   808篇
  1975年   774篇
  1974年   790篇
  1973年   760篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Solutions of the dispersion equations for polariton states in finite one-dimensional crystals of arbitrary length are obtained. The appearance and evolution of the radiative and nonradiative polariton branches are traced as the length varies from two monomers to limiting values, above which the spectrum no longer undergoes significant changes. The dependences of the frequencies and radiative widths on the polariton wave vector are found for various orientations of the dipole moment of the quantum transition. The evolution of superradiance as the length of the crystal increases is traced. Some previously unknown significant features of the polariton spectrum are noted particularly the damping of the branch traditionally termed nonradiative as a consequence of emission from the end faces. Fiz. Tverd. Tela (St. Petersburg) 40, 2136–2140 (November 1998)  相似文献   
22.
The long-range sound propagation from a deep ocean to a receiving system located on the shelf is modeled. The waveguide model is constructed on the basis of the data of an acoustic-oceanographic experiment carried out in the northwestern Pacific. The sensitivity and the frequency dependence of the difference in the sound field levels at the crossing of the frontal zone on the geoacoustic characteristics of the bottom of the shelf and the continental slope are investigated. It is shown that the level difference decreases by 8.2 dB as the velocity of longitudinal waves increases by 100 m/s in the range within 1490–1820 m/s.  相似文献   
23.
We consider the arithmetic properties of the factor-rank and term-rank functions for matrices over semirings. In particular, we investigate the sets of matrices that satisfy the extremes of inequalities for these rank functions of matrix union. The classification of the linear transformations that keep these sets invariant is obtained. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 9, No. 3, pp. 175–197, 2003.  相似文献   
24.
In the article, it is proved that any nonnegative solution of an elliptic quasilinear inequality that vanishes on a subset of positive measure is trivial. __________ Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 25, pp. 112–118, 2005.  相似文献   
25.
Experimental data demonstrate that a study of accelerated aging can enable prognostication of the working capacity and storage life of polymeric formulations used in aircraft components on the basis of changes in thermogravimetric constants of these polymeric formulations.  相似文献   
26.
27.
Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied.  相似文献   
28.
Optics and Spectroscopy - The fluorescence of the nematic liquid crystal n-butyl-n′-methoxyazoxybenzene (BMAOB) in the form of a layer and in porous glasses with pores of different diameter...  相似文献   
29.
Pre—Separation Axioms in Fuzzifying Topology   总被引:1,自引:0,他引:1  
1  IntroductionYing[5,6 ] introduced and elementally developed so called fuzzifying topology with the semanticmethod of continuous valued L ogic.Shen[7] introduced and studied T0 -,T1-,T2 (Hausdorff) -,T3(regularity) -,T4 (normality) -separation axioms in fuzzifying topology.In [3 ]the concepts of thefamily of fuzzifying pre-open sets,fuzzifying pre-neighbourhood structure of a point and fuzzifyingpre-closure are introduced and studied.It is worth to mention that pre-separation axioms are …  相似文献   
30.
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