全文获取类型
收费全文 | 52263篇 |
免费 | 3745篇 |
国内免费 | 2179篇 |
专业分类
化学 | 37048篇 |
晶体学 | 460篇 |
力学 | 1873篇 |
综合类 | 136篇 |
数学 | 7974篇 |
物理学 | 10696篇 |
出版年
2023年 | 495篇 |
2022年 | 859篇 |
2021年 | 1018篇 |
2020年 | 1231篇 |
2019年 | 1252篇 |
2018年 | 943篇 |
2017年 | 924篇 |
2016年 | 1695篇 |
2015年 | 1585篇 |
2014年 | 1952篇 |
2013年 | 2865篇 |
2012年 | 3688篇 |
2011年 | 3987篇 |
2010年 | 2372篇 |
2009年 | 2109篇 |
2008年 | 3339篇 |
2007年 | 3056篇 |
2006年 | 3081篇 |
2005年 | 2751篇 |
2004年 | 2285篇 |
2003年 | 1920篇 |
2002年 | 1876篇 |
2001年 | 943篇 |
2000年 | 811篇 |
1999年 | 765篇 |
1998年 | 681篇 |
1997年 | 683篇 |
1996年 | 745篇 |
1995年 | 548篇 |
1994年 | 568篇 |
1993年 | 494篇 |
1992年 | 472篇 |
1991年 | 451篇 |
1990年 | 372篇 |
1989年 | 333篇 |
1988年 | 291篇 |
1987年 | 291篇 |
1986年 | 260篇 |
1985年 | 435篇 |
1984年 | 385篇 |
1983年 | 324篇 |
1982年 | 374篇 |
1981年 | 308篇 |
1980年 | 317篇 |
1979年 | 259篇 |
1978年 | 251篇 |
1977年 | 242篇 |
1976年 | 231篇 |
1975年 | 204篇 |
1974年 | 180篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The kinetic behaviour of aluminum naphthenate/benzene system in the process of gelation and degradation was systematically studied. The results obtained from the kinetic experiments indicated that the gelation stage was in accordance with a kinetic model of an auto-catalytic first-order reaction, and the degradation stage was a simple first-order reaction. The rate constants in these two stages at various temperaturs were measured. And the determined apparent activation energies for the gelation stage and for the degradation stage are 27.5±2.0 and 37.7±2.3 kJ/mol, respectively. 相似文献
102.
103.
This article describes the technique of fast atom bombardment mass spectrometry (FAB MS) and its applications to the analysis of organometallic and coordination complexes. Sections on ion generation and matrices are followed by a Periodic Group-based review of FAB MS results obtained from Transition Metal and Main Group compounds, organometallic cluster carbonyls and their derivatives, and salts of poly-oxo-anions. The literature has been surveyed from 1981 to approximately mid-1986. 相似文献
104.
105.
Due to the Meissner effect, a permanent magnet is levitated, when released above a high temperature superconductor. When there is an inhomogeneous temperature field around the magnet, the magnet might start to oscillate with increasing amplitude until it remains in a continuous rotation. A mathematical model for the described effect is presented which couples heat transfer and electromagnetic forces with the equation of motion, yielding to a multiphysics task. In a detailed analysis it is found, that the torque which drives the rotation of the magnet, is explicitly given in terms of Bessel functions and the Fourier coefficients of order zero and one of the temperature field of the surrounding air. 相似文献
106.
The synthesis of chiral oxazolidinedione derived bicalutamide analogs has been discussed. 相似文献
107.
Michael I. Mishchenko 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,101(3):411-415
The volume integral equation formalism is used to prove the scale invariance rule for an arbitrarily sized scatterer with an arbitrary shape, morphology, and orientation. The only assumptions are that the scatterer is made of optically isotropic linear materials and is embedded in a homogeneous, linear, isotropic, and nonabsorbing infinite medium. 相似文献
108.
Z.X. Cheng S.J. ZhangF. Song H.C. GuoJ.R. Han H.C. Chen 《Journal of Physics and Chemistry of Solids》2002,63(11):2011-2017
Erbium and ytterbium codoped double tungstates NaY(WO4)2 crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290-2000 nm have been recorded at room temperature. The Judd-Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er3+ ions in NaY(WO4)2 crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb3+ to Er3+ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels. 相似文献
109.
110.
Adel A. George Michael 《Arkiv f?r Matematik》2006,44(1):92-96
In this paper, we generalize a theorem of Kallman [2, Theorem 1.1] and we resolve the unsettled case there. 相似文献