全文获取类型
收费全文 | 104796篇 |
免费 | 32728篇 |
国内免费 | 25885篇 |
专业分类
化学 | 45208篇 |
晶体学 | 938篇 |
力学 | 4963篇 |
综合类 | 20篇 |
数学 | 9444篇 |
物理学 | 51969篇 |
综合类 | 50867篇 |
出版年
2024年 | 574篇 |
2023年 | 884篇 |
2022年 | 901篇 |
2021年 | 977篇 |
2020年 | 1835篇 |
2019年 | 4899篇 |
2018年 | 4977篇 |
2017年 | 5829篇 |
2016年 | 6094篇 |
2015年 | 6051篇 |
2014年 | 5975篇 |
2013年 | 7028篇 |
2012年 | 6729篇 |
2011年 | 8046篇 |
2010年 | 11671篇 |
2009年 | 11373篇 |
2008年 | 4508篇 |
2007年 | 4083篇 |
2006年 | 3280篇 |
2005年 | 3704篇 |
2004年 | 5144篇 |
2003年 | 4058篇 |
2002年 | 3612篇 |
2001年 | 3487篇 |
2000年 | 2601篇 |
1999年 | 2881篇 |
1998年 | 2445篇 |
1997年 | 2273篇 |
1996年 | 2459篇 |
1995年 | 2896篇 |
1994年 | 3015篇 |
1993年 | 3168篇 |
1992年 | 2733篇 |
1991年 | 2454篇 |
1990年 | 1990篇 |
1989年 | 2051篇 |
1988年 | 2112篇 |
1987年 | 1267篇 |
1986年 | 1311篇 |
1985年 | 929篇 |
1984年 | 997篇 |
1982年 | 898篇 |
1981年 | 731篇 |
1980年 | 768篇 |
1979年 | 525篇 |
1978年 | 530篇 |
1977年 | 633篇 |
1976年 | 1041篇 |
1973年 | 436篇 |
1972年 | 532篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
163.
164.
We present all-atom molecular dynamics simulations ofn-hexane on the basal plane of graphite at monolayer and multilayer coverages. In keeping with experimental data, we find the
presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with excess liquid
adsorbate. Using a simulation method that does not impose any particular periodicity on the adsorbed layer, we quantitatively
compare our results to the results of neutron diffraction experiments and find a structural transition from a uniaxially incommensurate
lattice to a fully commensurate structure on increasing the coverage from a monolayer to a multilayer. The zig-zag backbone
planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules
are observed to attain the perpendicular orientation at monolayer coverage.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
165.
High-density event-related potentials (ERPs) were measured when participants were required to evaluate oneself, significant others (father and mother) and the most familiar public figures (Lei Feng and Jiang Qing) based on trait adjectives. There were three referential conditions and a non-referential control condition including self-evaluation (SE), significant other-evaluation (SOE), general other-evaluation (GOE), and semantic positivity-evaluation (SPE). The behavioral data showed that RTs to GOE condition were longer than the other three conditions. Scalp ERP analysis revealed that (1) SPE condition elicited a more negative N2 than SE condition, which was associated with inhibition of responses; (2) SE condition elicited a more positive P300 than SPE condition, which was an index of attention to self-relevant stimuli; (3) there was no difference on the amplitude and latency of P300 between SE and SOE conditions, which reflected that the concept of “self” included intimate others (e.g., father and mother) in Chinese culture. 相似文献
166.
167.
168.
The Raman shifts of nanocrystalline GaSb excited by an Ar^ ion laser at wavelengths 514.5, 496.5, 488.0, 476.5,and 457.9nm are studied by an SPEX-1403 laser Raman spectrometer respectively, and they are explained by phonon confinement, tensile stress, resonant Raman scattering and quantum size effects. The Stokes and anti-Stokes Raman spectra of GaSb nanocrystals strongly support the Raman feature of GaSb nanocrystals. The calculated optical spectra compare well with experimental data on Raman scattering GaSb nanocrystals. 相似文献
169.
在程序升温条件下 ,用DSC研究了标题化合物的放热分解反应动力学 .用线性最小二乘法、迭代法以及二分法与最小二乘法相结合的方法 ,以积分方程、微分方程和放热速率方程拟合DSC数据 .在逻辑选择建立了微分和积分机理函数的最可几一般表达式后 ,用放热速率方程得到相应的表观活化能 (Ea)、指前因子 (A)和反应级数 (n)的值 .结果表明 :该反应的微分形式的经验动力学模式函数、Ea 和A值分别为 (1-α) 0 .44、2 30 .4kJ/mol和 10 18.16s-1.借助加热速率和所得动力学参数值 ,提出了标题化合物放热分解反应的动力学方程 .该化合物的热爆炸临界温度为 30 2 .6℃ .上述动力学参数对分析、评价标题化合物的稳定性和热变化规律十分有用 . 相似文献
170.
Investigation of the mean free path of projectile fragments produced in 16O-Em collision at 60 A GeV 下载免费PDF全文
Results are presented for an investigation of the mean free path of projectile fragments with charge 3≤Z≤8, produced by 60 A GeV {}^{16}O in nuclear emulsion. No dependence of mean free path on the distance from the point of the fragment emission is observed and our result is consistent with the nonexistence of anomalons. 相似文献