全文获取类型
收费全文 | 86500篇 |
免费 | 15662篇 |
国内免费 | 19351篇 |
专业分类
化学 | 35549篇 |
晶体学 | 2084篇 |
力学 | 3725篇 |
综合类 | 1820篇 |
数学 | 7740篇 |
物理学 | 23986篇 |
无线电 | 46609篇 |
出版年
2024年 | 499篇 |
2023年 | 1421篇 |
2022年 | 3299篇 |
2021年 | 3232篇 |
2020年 | 2818篇 |
2019年 | 2619篇 |
2018年 | 2619篇 |
2017年 | 3789篇 |
2016年 | 2903篇 |
2015年 | 4295篇 |
2014年 | 5360篇 |
2013年 | 6469篇 |
2012年 | 6871篇 |
2011年 | 7144篇 |
2010年 | 7277篇 |
2009年 | 7613篇 |
2008年 | 7910篇 |
2007年 | 7687篇 |
2006年 | 7208篇 |
2005年 | 6105篇 |
2004年 | 4787篇 |
2003年 | 3284篇 |
2002年 | 2946篇 |
2001年 | 3008篇 |
2000年 | 3114篇 |
1999年 | 1491篇 |
1998年 | 726篇 |
1997年 | 516篇 |
1996年 | 481篇 |
1995年 | 474篇 |
1994年 | 429篇 |
1993年 | 468篇 |
1992年 | 396篇 |
1991年 | 282篇 |
1990年 | 296篇 |
1989年 | 295篇 |
1988年 | 198篇 |
1987年 | 192篇 |
1986年 | 144篇 |
1985年 | 121篇 |
1984年 | 138篇 |
1983年 | 91篇 |
1982年 | 83篇 |
1981年 | 93篇 |
1980年 | 64篇 |
1979年 | 81篇 |
1978年 | 26篇 |
1977年 | 21篇 |
1965年 | 19篇 |
1959年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
Ferrocene-terminated trans-Ru(dppm)2 (dppm=Ph2PCH2pph2)-containing molecular wires with alligator clips were prepared.They are suitable for self-assembly on gold electrode to investigate the influence of metal incorporation on the electron transportation property of the molecular wires. 相似文献
992.
Zhi Huai SI Guo Chang WANG* He Xian LI Jia Long YUAN Bing Lin HE State Key Laboratory of Functional Polymer Materials for Adsorption Separation Institute of Polymer Chemistry Nankai University Tianjin 《中国化学快报》2003,14(1)
The aggregation of amphiphilic block copolymers is a crucial phenomenon that controls various applications, and has been extensively treated in the literature1-3. Pyrene is a widely used fluorescence probe for the relative intensities of the vibrational fine structure (five bands) of its fluorescence spectra have been found to be sensitive to the polarity of its environment, the so-called Ham effect4. We report the studies of the aggregation properties of a PS-b-PAA copolymer using pyrene … 相似文献
993.
XingZhouLI KeMeiWU LiangHUANG 《中国化学快报》2003,14(4):338-340
Synthesis of the optically active metabolite of clausenamide cm2(3,5-dihydroxy-5-(α-hydroxylbenzyl)-1-methyl-4-benzylpyrrolidin-2-one)from 3-O-acetyl-clausenamide was described. 相似文献
994.
FuYouLI XiaoRongZOU ChunHuiHUANG 《中国化学快报》2003,14(6):641-644
A novel dye dimer,bis-{[1-(N-hexadecyl-4-pyridinium)-2-(4-N,N-dimethylaminopheyl)] ethenyl} methane diiodide (C16BP) was synthesized,and the photoelectrochemistry of the dye Langmuir-Blodgett monolayer modified ITO electrode was investigated.For comparison,the photoelectrochemistry of the monomer (E)-N-hexadexyl-4-[2-(4-N,N-dimethylaminophenyl) ethenyl] pyridinium iodide (C16P) was also measured.The results show that the photocurrent generation property of the dimer is enhanced.The photocurrent generation quantum yield is 0.38% for C16BP,while that for C16P is 0.23%. 相似文献
995.
ZhuanNiYU XiRong HUANG ShaoFangSONG DanWANG XueMeiLU YueZhongLI YinBoQU PeiJiGAO 《中国化学快报》2003,14(8):836-839
The inhibition of lingninase by hydrogen peroxide in the presence of cationic surfactant CTAB was studied by kinetic speetrophotometdc technique. Results showed that addition of CTAB enhanced the inhibition by H202, but it did not alter the inhibition pattern and the inhibition constant changed little with theco-ncentration of CTAB. Modification of the enzymic protein by the surfactant monomer may be responsible for the above mentioned results. 相似文献
996.
Charge-discharge Behavior of Surface-coated LiMn2O3.95F0.05 Cathode Materials at High Temperature 总被引:1,自引:0,他引:1
ZhaoYongCHEN YanRongLI ZuoLongYU 《中国化学快报》2003,14(12):1296-1298
With inorganic salts such as LiNO3, Li2CO3, surface-coated LiMn2O3.95F0.05 were prepared by melt-impregnation method. When these surface-coated LiMn2O3.95F0.05 were used as cathode materials, their charge-discharge characters were carefully compared. As a result, they exhibited good charge-discharge properties at 50℃ high temperature. Especially, LiNO3 surface-coated LiMn2O3.9F50.05 retained nearly 80% initial reversible capacity after 130 cycles at 50℃. 相似文献
997.
Reactions of fluoroarene-Cr(CO)_3 complexes with SmI_2 andcarbonyl compounds in THF/HMPA at-40— -60℃ affordedthe corresponding radical aromatic substitution products in highyield. Compared to the corresponding chloroarene-Cr.(CO)_3complexes, fluoroarene-Cr(CO)_3 complexes showed a higher ef-ficiency and slightly lower regioselectivity. 相似文献
998.
An enhancive synthesis of (±)-1β, 11-diol-4-en-eudesmol,starting from 2-chloroacrylonitrile, is described. The effect oftemperature on the Diels-Alder reaction of 2-chloroacrylonitrilewith 2-methylfuran and the condition of cationic cyclization ofdiene were discussed in detail. 相似文献
999.
IntroductionConstructionoffunctionalmolecularunitsintostruc turallywell definedsupramolecularassemblieshasattract edgreatattentionduetotheirpotentialapplicationsincomplexelectronicstructuresandmoleculardevices .1 5Amongthevariousfunctionalorganicmolecules ,azoben zenederivativeshavebeenwidelystudiedbecauseoftheirinterestingphotoresponsivebehavior .6 11Extensivestudieshaveshownthatsuitablydesignedazobenzenederivativescanformlongrangeorderedarrangementoftwo orthree dimensionalmolecularlatticeat… 相似文献
1000.
As a special substance between isolated molecules and condensed phase, clusters have drawn more and more attention by theoreticians and experimentalists. The protonated rare gas cluster is one kind of simplest clusters, which can be looked on as the simplest solution composed of the simplest solute, proton, and the simplest solvent, rare gas. The study on such a system can help us to know more about the complex condensed matter. However, the information for the molecular properties of protonat… 相似文献