全文获取类型
收费全文 | 61589篇 |
免费 | 14801篇 |
国内免费 | 5428篇 |
专业分类
化学 | 59687篇 |
晶体学 | 773篇 |
力学 | 2248篇 |
综合类 | 288篇 |
数学 | 5009篇 |
物理学 | 13813篇 |
出版年
2024年 | 89篇 |
2023年 | 713篇 |
2022年 | 1105篇 |
2021年 | 1448篇 |
2020年 | 2651篇 |
2019年 | 3853篇 |
2018年 | 2182篇 |
2017年 | 1855篇 |
2016年 | 4749篇 |
2015年 | 5057篇 |
2014年 | 5151篇 |
2013年 | 6216篇 |
2012年 | 5619篇 |
2011年 | 4798篇 |
2010年 | 4587篇 |
2009年 | 4652篇 |
2008年 | 4304篇 |
2007年 | 3356篇 |
2006年 | 2940篇 |
2005年 | 2840篇 |
2004年 | 2313篇 |
2003年 | 1940篇 |
2002年 | 2596篇 |
2001年 | 1851篇 |
2000年 | 1700篇 |
1999年 | 790篇 |
1998年 | 352篇 |
1997年 | 326篇 |
1996年 | 260篇 |
1995年 | 232篇 |
1994年 | 165篇 |
1993年 | 191篇 |
1992年 | 152篇 |
1991年 | 118篇 |
1990年 | 95篇 |
1989年 | 71篇 |
1988年 | 76篇 |
1987年 | 55篇 |
1986年 | 64篇 |
1985年 | 61篇 |
1984年 | 40篇 |
1983年 | 29篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 21篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A composite film of ethylenediamine tetraacetic acid (EDTA)‐ZrO2 organic‐inorganic hybrid was prepared based on the chelation between Zr(IV) and EDTA. The direct electrochemical behavior of cytochrome c (cyt. c) at the hybrid film modified glassy carbon electrodes was investigated. The immobilized EDTA can promote the redox of heme in horse heart cyt. c which gives rise to a pair of reversible redox peaks with a formal potential of 40 mV (vs. SCE). The peak current increased linearly with the increase of cyt. c concentration in the range of 1.6 × 10?6—8.0 × 10?5 mol·L?1 with the correlation coefficient of 0.996. Further investigation shows that metal ions can impede the electron transfer of cyt. c. The impediment capability of metal ions depends on their coordination capability with EDTA and their valence number. 相似文献
992.
Six‐membered cyclic α‐aminonitrile has been prepared from anodic cyanation of N‐benzylpiperidine. Good yields of α‐aminonitriles could be obtained through potentiostatic electrolysis under different conditions. The results also explain why high yield α‐aminonitriles could not be obtained under constant current electrolysis. 相似文献
993.
Balkis Al‐Saleh Morsy Ahmed El‐Apasery Rasha Safwat Abdel‐Aziz Mohamed Hilmy Elnagdi 《Journal of heterocyclic chemistry》2005,42(4):563-566
The 3‐anilinoenones 3a,b were prepared from the corresponding 3‐dimemyl‐aminopropenones. The reactivity of 3a,b towards a variety of carbon and nitrogen nucleophiles as well as naphthoquinones is reported. 相似文献
994.
Peng CY Nam WJ Fonash SJ Gu B Sen A Strawhecker K Natarajan S Foley HC Kim SH 《Journal of the American Chemical Society》2003,125(31):9298-9299
We describe the use of hard etching methods to create nanodimensional channels and their use as templates for the formation of polymer filament arrays with precise dimensional and orientational control in a single integrated step. The procedure is general as illustrated by the radical, coordination, and photochemical polymerizations that were performed in these nanochannels. The nanochannel templates (20 nm high, 20-200 nm wide, and 100 mum long) were fabricated by the combined use of electron-beam lithography and a sacrificial metal line etching technique. Radical polymerization of acrylates, metal-catalyzed polymerization of norbornene, and photochemical polymerization of 1,4-diiodothiophene were carried out in these nanochannels. The polymers grown follow the dimensions and orientation of the channels, and the polymer filaments can be released without breaking. The approach opens up the possibility of just-in-place manufacturing and processing of patterns and devices from nanostructured polymers using well-established polymer chemistry. 相似文献
995.
996.
997.
Polymer-supported phosphine ligand 3b derived from ferrocene was prepared,and applied in palladium-catalyzed Suzuki- Miyaura reactions.A range of aryl bromides can couple with phenylboronic acid to obtain corresponding biaryls in excellent yields. The recycling of the polymer-bound catalyst was tested without adding palladium. 相似文献
998.
the interaction of hemin with chloroquine,quinine and quinidine was investigated in 50% water-propylene glycol mixture at pH=9,8.1,7.4 and 6.8using a spectrophotometric method.The data could be well fitted into a model consistent with the formation of a 1:1 complex between the reacting partners.In addition,the results indicated that hemin complexed more strongly with quinidine than with chloroquine and quinine,and the binding constants were pH-dependent.Moreover,it was proved that the water-propylene glycol mixture is well suitable to the study of the systems containing hemin and quinolinebased drugs. 相似文献
999.
1000.
The title reduction of nitroaromatics ArNO(2) by vinyl halide radical cations CH(2)[double bond]CH-X(+*)(X = Cl or Br) to form arylnitrenium ions ArNH(+) involves a change in oxidation number of nitrogen from +3 to -1. This novel reaction provides a new route for the generation of arylnitrenium ions, a highly selective method for the detection of explosives in mixtures, and offers clues to the carcinogenic activity of nitroaromatics in vivo. 相似文献