全文获取类型
收费全文 | 221615篇 |
免费 | 3740篇 |
国内免费 | 1847篇 |
专业分类
化学 | 123364篇 |
晶体学 | 2657篇 |
力学 | 9139篇 |
综合类 | 85篇 |
数学 | 24827篇 |
物理学 | 67130篇 |
出版年
2020年 | 1946篇 |
2019年 | 2079篇 |
2018年 | 2646篇 |
2017年 | 2661篇 |
2016年 | 3911篇 |
2015年 | 2633篇 |
2014年 | 3779篇 |
2013年 | 9219篇 |
2012年 | 8120篇 |
2011年 | 9823篇 |
2010年 | 6942篇 |
2009年 | 6725篇 |
2008年 | 9080篇 |
2007年 | 9128篇 |
2006年 | 8602篇 |
2005年 | 7902篇 |
2004年 | 7029篇 |
2003年 | 6125篇 |
2002年 | 5662篇 |
2001年 | 6590篇 |
2000年 | 4862篇 |
1999年 | 3477篇 |
1998年 | 2861篇 |
1997年 | 2878篇 |
1996年 | 2857篇 |
1995年 | 2623篇 |
1994年 | 2706篇 |
1993年 | 2567篇 |
1992年 | 2792篇 |
1991年 | 2877篇 |
1990年 | 2669篇 |
1989年 | 2572篇 |
1988年 | 2527篇 |
1987年 | 2462篇 |
1986年 | 2479篇 |
1985年 | 3274篇 |
1984年 | 3319篇 |
1983年 | 2774篇 |
1982年 | 3012篇 |
1981年 | 2769篇 |
1980年 | 2576篇 |
1979年 | 2751篇 |
1978年 | 2972篇 |
1977年 | 3009篇 |
1976年 | 3029篇 |
1975年 | 2777篇 |
1974年 | 2888篇 |
1973年 | 2939篇 |
1972年 | 2301篇 |
1971年 | 1826篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
71.
Annals of Operations Research - The vehicle routing problem is a traditional combinatorial problem with practical relevance for a wide range of industries. In the literature, several specificities... 相似文献
72.
73.
Gazizov M. B. Ismagilov R. K. Ivanova S. Yu. Karimova R. F. Pistsova A. L. Khairullin R. A. Gazizova N. N. Shaikhutdinova L. R. Gubaidullin A. T. Gnezdilov O. I. 《Russian Chemical Bulletin》2022,71(3):457-463
Russian Chemical Bulletin - Diethylphosphinylmethanehydrazide, the first representative of the phosphorylated formic acid hydrazides with three P—C bonds was obtained, which can exhibit... 相似文献
74.
Application of TiO2-nanotubes/PbO2 as an anode for the electrochemical elimination of Acid Red 1 dye
Santos José Eudes L. de Moura Dayanne Chianca da Silva Djalma Ribeiro Panizza Marco Martínez-Huitle Carlos A. 《Journal of Solid State Electrochemistry》2019,23(2):351-360
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an... 相似文献
75.
Skotnikova D. S. Mochalova A. E. Smirnova L. A. 《Russian Journal of Applied Chemistry》2019,92(5):634-638
Russian Journal of Applied Chemistry - Chitosan copolymers with vinyl monomers: 4-N-vinylpyridine, acrylamide, and acrylic acid, were synthesized and these sorption properties were investigated.... 相似文献
76.
Ganina O. G. Bondarenko G. N. Isaeva V. I. Kustov L. M. Beletskaya I. P. 《Russian Journal of Organic Chemistry》2019,55(12):1813-1820
The catalytic activity of copper-containing heterogeneous catalysts, in particular metal-organic frameworks, zeolites, and alumina-supported nanoparticles, in the carboxylation of terminal alkynes and oxiranes has been evaluated. Temperature dependences of these reactions have been studied.
相似文献77.
Study of Sorption Properties of Bog Ores for Extraction of Manganese and Iron Ions from Ground Water
Russian Journal of Applied Chemistry - Results are presented of a study of the sorption properties of iron-manganese bog ores, aimed to assess the possibility of using these ores to purify natural... 相似文献
78.
Russian Journal of Organic Chemistry - Three-component reaction of methyl 4-aryl-2,4-dioxobutanoates with aromatic aldehyde and 2-aminoacetonitrile sulfate in glacial acetic acid in the presence of... 相似文献
79.
Russian Journal of Organic Chemistry - A rapid and efficient catalytic approach has been proposed for the synthesis of dimethyl 2-[2-(aryl-amino)but-3-en-1-yl]- and... 相似文献
80.
Gary W. Breton Lauren A. Hahn Kenneth L. Martin 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(9):1208-1212
Tetrahydrotetrazoles are five‐membered‐ring heterocycles containing four contiguous saturated nitrogen atoms. Very few examples of such compounds have been reported in the literature. Our previous attempt at the synthesis of a member of this class of compound suggested that the N—N bonds may be more labile than expected. This finding raised the question as to whether the structures of any of the previously reported tetrahydrotetrazoles had been properly assigned. We have reproduced the synthesis of a reported tetrahydrotetrazole, namely 1,2‐di‐tert‐butyl 3‐phenyl‐1H,2H,3H,10bH‐[1,2,3,4]tetrazolo[5,1‐a]isoquinoline‐1,2‐dicarboxylate, C25H30N4O4, and have now confidently confirmed its structure via X‐ray crystallography. However, while sufficiently stable in the crystal phase, we discovered that it remains very labile in solution (having a half‐life of only 15 min at 20 °C in CDCl3). A tentative reaction pathway for its dissociation based on 1H NMR spectral evidence is provided. 相似文献