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   307991篇
  免费   2320篇
  国内免费   1178篇
化学   139735篇
晶体学   4741篇
力学   17314篇
综合类   1篇
数学   56643篇
物理学   93055篇
  2020年   1791篇
  2019年   2049篇
  2018年   12840篇
  2017年   12597篇
  2016年   9805篇
  2015年   3195篇
  2014年   4242篇
  2013年   10348篇
  2012年   11134篇
  2011年   19473篇
  2010年   12122篇
  2009年   12481篇
  2008年   15017篇
  2007年   17142篇
  2006年   8444篇
  2005年   8709篇
  2004年   8360篇
  2003年   8006篇
  2002年   7013篇
  2001年   7307篇
  2000年   5633篇
  1999年   4367篇
  1998年   3735篇
  1997年   3599篇
  1996年   3483篇
  1995年   3125篇
  1994年   3024篇
  1993年   3131篇
  1992年   3205篇
  1991年   3393篇
  1990年   3136篇
  1989年   3083篇
  1988年   3124篇
  1987年   3011篇
  1986年   2857篇
  1985年   3855篇
  1984年   4047篇
  1983年   3233篇
  1982年   3451篇
  1981年   3373篇
  1980年   3275篇
  1979年   3377篇
  1978年   3456篇
  1977年   3368篇
  1976年   3462篇
  1975年   3156篇
  1974年   3162篇
  1973年   3219篇
  1972年   2252篇
  1971年   1857篇
排序方式: 共有10000条查询结果,搜索用时 2 毫秒
81.
The Fokker–Planck-type kinetic equation is constructed with the help of the evolution equation for the transverse energy of channelized particles, which in its turn is derived beyond the framework of perturbation theory proceeding from the condition of nonconcervation of the adiabatic invariant.  相似文献   
82.
We study the asymptotics of some regression functions which occur in the study of high rejections of homogeneous Gaussian random fields.Translated from Statisticheskie Metody Otsenivaniya i Proverki Gipotez, pp. 143–148, 1988.  相似文献   
83.
84.
85.
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   
86.
An equation for the standard enthalpy of solvation of a compound in a binary solvent is derived. The enthalpies of solvation in water-methanol mixtures are estimated for 1,3-propane-and 1,6-hexanediols, 1,2,4-butane-and 1,3,5-pentanetriols, 2-methoxy-and 2-propoxyethanols, and diethylene glycol. The enthalpy of solvation of 1,2-dimethoxyethane in the water-methanol mixed solvent is determined experimentally.  相似文献   
87.
The thermal and dielectric behaviors of poly(vinylidene fluoride-trifluoroethylene) copolymers near the ferroelectric-to-paraelectric phase transition are investigated for samples with 20, 25, 30, and 40 mol% trifluoroethylene (TrFE). The data suggest that the transition becomes continuous for a particular composition near 50 mol% TrFE. Experimental data are sensitive to thermal history (kinetics of crystallization, and kinetics and cycling over the structural transition). It is found that several anomalies are present at the structural change, and in particular the 30 mol% TrFE sample shows the most marked anomalies. These phenomena can be attributed to defects, but another possibility would be the existence of an intemediate supplementary phase. Both hypotheses are discussed.  相似文献   
88.
Summary High-purity indium was analysed by spark source mass spectrometry, using electrical and photoplate detection. For the calibration of the differences in elemental sensitivity, a standard sample was prepared in which 10 impurities were determined by graphite furnace atomic absorption spectrometry. In this way accuracies of less than 40% were obtained for relatively homogeneous elements at ppm and sub-ppm level. About 40 elements could be determined with detection limits of 10 to 30 ppb. Two pattern recognition methods, principal component analysis and clustering analysis, were applied to obtain information on trace element distribution, which indicated that a number of elements were strongly spatially correlated in the analysed sample.
Chemische Analyse und Verteilungsbestimmung von Spurenelementen in Indium-Matrix durch Funkenquellen-Massenspektrometrie

On leave from: Department of Chemistry, Nanjing Normal University, Nanjing, People's Republic of China  相似文献   
89.
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants.  相似文献   
90.
C Dufour  K Dumesnil  P H Mangin 《Pramana》2006,67(1):173-190
Rare earths exhibit complex magnetic phase diagrams resulting from the competition between various contributions to the magnetic energy: exchange, anisotropy and magnetostriction. The epitaxy of a rare-earth film on a substrate induces (i) a clamping to the substrate and (ii) pseudomorphic strains. Both these effects are shown to lead to modifications of the magnetic properties in (0 0 1)Dy, (0 0 1)Tb and (1 1 0)Eu films. In Dy and Tb films, spectacular variations of the Curie temperature have been evidenced. Additionally, Tb films exhibit a new large wavelength magnetic modulation. In Eu films, one of the helical magnetic domains disappears at low temperature whereas the propagation vectors of the other helices are tilted. The link between structural and magnetic properties is underlined via magnetoelastic models. Moreover, molecular beam epitaxy permits the growth of Sm in a metastable dhcp phase. The magnetic structure of dhcp Sm has been elucidated for the first time. In this review, neutron scattering is shown to be a powerful technique to reveal the magnetic structures of rare-earth films.  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