全文获取类型
收费全文 | 15557篇 |
免费 | 3278篇 |
国内免费 | 1913篇 |
专业分类
化学 | 11513篇 |
晶体学 | 139篇 |
力学 | 910篇 |
综合类 | 89篇 |
数学 | 1582篇 |
物理学 | 6515篇 |
出版年
2024年 | 54篇 |
2023年 | 331篇 |
2022年 | 410篇 |
2021年 | 509篇 |
2020年 | 696篇 |
2019年 | 614篇 |
2018年 | 518篇 |
2017年 | 591篇 |
2016年 | 895篇 |
2015年 | 896篇 |
2014年 | 1043篇 |
2013年 | 1546篇 |
2012年 | 1116篇 |
2011年 | 1198篇 |
2010年 | 989篇 |
2009年 | 1068篇 |
2008年 | 1138篇 |
2007年 | 1133篇 |
2006年 | 949篇 |
2005年 | 844篇 |
2004年 | 696篇 |
2003年 | 596篇 |
2002年 | 410篇 |
2001年 | 339篇 |
2000年 | 321篇 |
1999年 | 262篇 |
1998年 | 240篇 |
1997年 | 199篇 |
1996年 | 119篇 |
1995年 | 141篇 |
1994年 | 114篇 |
1993年 | 93篇 |
1992年 | 85篇 |
1991年 | 71篇 |
1990年 | 57篇 |
1989年 | 51篇 |
1988年 | 60篇 |
1987年 | 47篇 |
1986年 | 42篇 |
1985年 | 52篇 |
1984年 | 38篇 |
1983年 | 12篇 |
1982年 | 30篇 |
1981年 | 30篇 |
1980年 | 20篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1974年 | 8篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
Molar extinction coefficients of aqueous solutions of some organic compounds, viz. formamide (CH3NO),N-methylformamide (C2H5NO),NN-dimethylformamide (C3H7NO),NN-dimethylacetamide (C4H9NO), 1,4-dioxane (C4H8O24), succinimide (C4H5NO2) and solutions of acetamide (C2H5NO) and benzoic acid (C7H6O2) in 1,4-dioxane (C4H8O2) have been determined by narrow beam γ-ray transmission method at 81, 356, 511, 662, 1173 and 1332 keV. The experimental
values of mass attenuation coefficients of these compounds have been used to calculate effective atomic numbers and electron
densities. The additivity rule earlier used for aqueous solution has been extended to non-aqueous (1,4-dioxane) solutions. 相似文献
132.
133.
134.
在Brueckner-Hartree-Fock理论框架内, 研究了同位旋非对称核物质中质子和中子单粒子势的动量相关性及其随同位旋非对称度的变化, 在此基础上计算了同位旋对称势, 并讨论了三体核力的影响. 结果表明同位旋对称势对于同位旋非对称度的依赖性很弱, 但对于动量和密度均有较强的依赖性. 当密度固定时, 同位旋对称势随动量增加而减小. 尽管三体核力对于质子和中子单粒子势的动量相关性有较大影响, 但对同位旋对称势的影响很小. 还与目前重离子碰撞输运理论模型中所使用的各种参数化的唯象对称势进行了比较. 相似文献
135.
V. B. Kobychev N. M. Vitkovskaya I. L. Zaitseva B. A. Trofimov 《Journal of Structural Chemistry》2004,45(6):940-944
The profiles of reactions leading to pyrrole anion N-adducts with CO2 and CS2 have been studied by the ab initio (RHF/6-31+G*, MP2/6-31+G*) and density functional (B3LYP/6-31+G*) methods. Addition of the pyrrole anion to the carbon disulfide molecule is accompanied by the appearance of a minimum corresponding to a pre-reaction complex. The transformation of the complex to the N-pyrrolyldithiocarboxylate anion occurs via a low activation barrier, which is due to repolarization of the C=S bonds. The profile of the reaction leading to the pyrrole anion N-adduct with CO2 does not contain any intermediate stationary points throughout the whole route from reagents to products.Original Russian Text Copyright © 2004 by V. B. Kobychev, N. M. Vitkovskaya, I. L. Zaitseva, and B. A. Trofimov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 990–993, November–December, 2004. 相似文献
136.
137.
138.
Precipitate-forming chemical reactions have been studied in chemically cross-linked poly(vinyl alcohol) gel medium. One of the reactive components was incorporated into the gel, the other was allowed to diffuse into it. Depending on the experimental conditions the reaction-diffusion process often results in patterns of different type. Experiments performed in tubes and in thin layers were carried out in order to investigate the effects of various factors (cross-linking density, swelling degree as well as the concentrations of the outer and inner electrolytes) on the morphologies of the precipitate patterns. It was found that precipitation occurs not only in the Liesegang bands, but also between bands. Beside Liesegang-type structures, tree-like patterns have been observed, showing a characteristic periodicity in the density profile obtained by digitalized image analyses. 相似文献
139.
140.
Ro Jin Pak Ayanendranath Basu 《Annals of the Institute of Statistical Mathematics》1998,50(3):503-521
This paper deals with the minimum disparity estimation in linear regression models. The estimators are defined as statistical quantities which minimize the blended weight Hellinger distance between a weighted kernel density estimator of errors and a smoothed model density of errors. It is shown that the estimators of the regression parameters are asymptotic normally distributed and efficient at the model if the weights of the density estimators are appropriately chosen. 相似文献