全文获取类型
收费全文 | 1607篇 |
免费 | 314篇 |
国内免费 | 469篇 |
专业分类
化学 | 1191篇 |
晶体学 | 25篇 |
力学 | 136篇 |
综合类 | 38篇 |
数学 | 304篇 |
物理学 | 696篇 |
出版年
2024年 | 7篇 |
2023年 | 37篇 |
2022年 | 41篇 |
2021年 | 35篇 |
2020年 | 20篇 |
2019年 | 43篇 |
2018年 | 30篇 |
2017年 | 29篇 |
2016年 | 26篇 |
2015年 | 37篇 |
2014年 | 99篇 |
2013年 | 98篇 |
2012年 | 114篇 |
2011年 | 90篇 |
2010年 | 65篇 |
2009年 | 89篇 |
2008年 | 94篇 |
2007年 | 94篇 |
2006年 | 79篇 |
2005年 | 82篇 |
2004年 | 79篇 |
2003年 | 90篇 |
2002年 | 152篇 |
2001年 | 228篇 |
2000年 | 76篇 |
1999年 | 57篇 |
1998年 | 43篇 |
1997年 | 42篇 |
1996年 | 26篇 |
1995年 | 33篇 |
1994年 | 28篇 |
1993年 | 33篇 |
1992年 | 36篇 |
1991年 | 34篇 |
1990年 | 27篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1958年 | 5篇 |
1957年 | 6篇 |
1954年 | 6篇 |
1953年 | 6篇 |
排序方式: 共有2390条查询结果,搜索用时 0 毫秒
91.
Qing Yan CHENG Wei LI Ying ZHOU Ming Hui ZHANG Nai Jia GUAN Ke Yi TAO* Department of Material Chemistry Nankai University Tianjin 《中国化学快报》2001,(12)
The various distillation of petroleum contains arenes. For environmental protection, the hydrogenation of arenes becomes important. The amorphous alloy is a new class of material with special catalytic properties for reduction arenes1-4. In this paper, we prepared the Ni-B/TiO2 and Ni-B/Al2O3 amorphous catalysts by impregnation and reduction by KBH4 solution. Their catalytic activities for hydrogenation arenes were tested by the hydrogenation of 1,3,5-trimethylbenzene (TMB) in the co… 相似文献
92.
New diterpenoid glucosides from Siegesbeckia pubescens 总被引:5,自引:0,他引:5
Jiang XIONG Qi Duan JIN Yun Long XU* Kunming Institute of Botany The Chinese Academy of Sciences Kunming 《中国化学快报》2001,(1)
Plants of the genus Siegesbeckia are annual herbs widely distributed in tropical and temperate zones and they are used as a traditional medicine to treat rheumatic arthritis, hypertension, malaria, neurasthenia and snake-bite in China. In previous papers, we reported on five new ent-kaurane and ent-pimarane diterpenoids, siegesbeckioside, siegesbeckiol and siegesbeckic acid1, orientalin A and B, and eight know compounds2,3. The present paper describes the isolation and structural elucidation … 相似文献
93.
Guang Xing WANG Jing Xin ZHANG Shu Feng CHEN Xiao Tian LIANG* Institute of Materia Medica Chinese Academy of Medical Sciences Peking Union Medical College Beijing 《中国化学快报》2001,(3)
Chrysotricine 1 was isolated from the Chinese herb medicine Hedyotis Chrysotricha and was shown to possess antitumor activity1. Its structure has been elucidated as a novel zwitterionic (-carboline alkaloid containing a 2,2,5-trisubstituted tetrahydrofuranyl group. The (-carboline compounds have attracted considerable attraction in recent years because of their promising and intriguing biological activities2. Recently, we have established the absolute configuration of chrysotricine by the fir… 相似文献
94.
Li Jun HE Qing Song CAI Shi Jun SHAO Sheng Xiang JIANG* Lanzhou Institute of Chemical Physics Chinese Academy of sciences Lanzhou 《中国化学快报》2001,(6)
Calixpyrroles, as new macrocyclic receptors, have gain increasing interest in host-guest chemistry. Pioneering work in this area by Sessler and co-workers have evidenced that calix[4]pyrroles are effective anion binding agents and have used for anion binding, sensing and new anion separation technologies1, 2. In this letter, we report that calix[4]pyrroles A, B and C3,4 (Scheme 1) can serve as additives in CZE for the separa- tion of halide ions. Scheme 1 A B C When analyzing anions with… 相似文献
95.
Cheng Quan Wang Hui Wang Yan Ming Liu* College of Chemistry Chemical Engineering Xinyang Normal University Xinyang China 《中国化学快报》2007,18(4):452-454
A rapid and sensitive method for the analysis of three catecholamines by capillary electrophoresis(CE)with directchemiluminescence(CL)detection is described.The detection limits(S/N=3)were 1.3*10-8g/mL for isoprenaline,1.0*10-8g/mL for epinephrine and 2.8*10-8g/mL for dopamine.The proposed method was successfully applied to theanalysis of catecholamines in urine samples of cigarette smokers and nonsmokers.The results showed that there is a close relationbetween the release of dopamine in human body fluids and cigarette smoking/nonsmoking. 相似文献
96.
97.
Jun JIA Xing Wang WANG Yi Li ZHAO Yu ZHU Jing Chao TAO* Department of Chemistry Zhengzhou University Zhengzhou Chemical Engineering Institute of Henan Province Zhengzhou 《中国化学快报》2004,15(3):292-295
Proteins containing dinuclear Cu (II), Zn (II) centers play paramount roles in biology1. As mimetic of metal-dependent esterase, dinuclear Cu (II) and Zn (II) complexes have received a great deal of attentions2~6. They are of interest in the field of biomimetic chemistry to provide an improved understanding of the function of the biological sites and as potential catalysts for substrate oxidations. Schiff base type polydentate ligands which contain centeral hydroxyl group have been wid… 相似文献
98.
Xiao Long WANG Jian Peng FENG Xin Gang XIE Xiao Ping CAO* Xin Fu PAN* Department of Chemistry & State Key Laboratory of Applied Organic Chemistry Lanzhou University Lanzhou 《中国化学快报》2004,(9)
Aiphanol was isolated from the seeds of Aiphanes aculeate Willd. (Arecaceae) collected in Peru and was reported to exhibit significant inhibitory activities against cyclooxyge- nases-1 and -2. The structure of aiphanol was elucidated by spectroscopic methods as an unprecedented stilbenolignan skeleton in which a stilbene moiety is linked to a phenylpropane unit through a dioxane bridge1. In our previous works the synthetic approach to 1,4-benzodioxane lignans were achieved2. Since aiphanol… 相似文献
99.
ZOUYi* HE Deping* & JIANG Jiaqiao Department of Material Science Engineering Southeast University Nanjing China 《中国科学B辑(英文版)》2004,47(5):407-413
The Ultra Light Metal Structure with variouskinds of pores (open, close) realizes the lightness andmultifunction of structural material. The functionsinclude lightness (ρ < 1), high specific strength, highenergy absorption, sound insulation, heat insulationand electromagnetism shield. It is one of the hotspotsin material research nowadays[1— . The requirements 6]of high speed movement and high technology make Alalloy foam, which has higher specific st… 相似文献
100.
Thermal decomposition kinetics of titanium hydride and Al alloy melt foaming process 总被引:3,自引:0,他引:3
YANG Donghui* HE Deping*& YANG Shangrun* . Department of Materials Science Engineering Southeast University Nanjing China . Department of Chemistry Nanjing University Nanjing China 《中国科学B辑(英文版)》2004,47(6):512-520
Metal foams, now one of research foci, are a newclass of materials with low densities and novel physi-cal, mechanical, thermal, electrical and acoustic prop-erties[1—8]. Demands from high-tech make Al alloyfoam, which has much higher specific strength than ofpure Al foam, the new development focus[9—11]. Melt foaming process is one of the approaches tofabricate Al foam and Al alloy foam and their porestructure (pore diameter and porosity) has close rela-tionship with the thermal decompo… 相似文献