全文获取类型
收费全文 | 5320篇 |
免费 | 241篇 |
国内免费 | 1011篇 |
专业分类
化学 | 6101篇 |
晶体学 | 56篇 |
力学 | 19篇 |
综合类 | 44篇 |
数学 | 1篇 |
物理学 | 351篇 |
出版年
2024年 | 3篇 |
2023年 | 30篇 |
2022年 | 114篇 |
2021年 | 82篇 |
2020年 | 96篇 |
2019年 | 114篇 |
2018年 | 120篇 |
2017年 | 148篇 |
2016年 | 169篇 |
2015年 | 167篇 |
2014年 | 208篇 |
2013年 | 593篇 |
2012年 | 319篇 |
2011年 | 285篇 |
2010年 | 267篇 |
2009年 | 296篇 |
2008年 | 311篇 |
2007年 | 358篇 |
2006年 | 326篇 |
2005年 | 324篇 |
2004年 | 301篇 |
2003年 | 277篇 |
2002年 | 204篇 |
2001年 | 195篇 |
2000年 | 180篇 |
1999年 | 184篇 |
1998年 | 128篇 |
1997年 | 122篇 |
1996年 | 124篇 |
1995年 | 85篇 |
1994年 | 88篇 |
1993年 | 86篇 |
1992年 | 65篇 |
1991年 | 41篇 |
1990年 | 27篇 |
1989年 | 18篇 |
1988年 | 20篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有6572条查询结果,搜索用时 62 毫秒
41.
Titanium dioxide (TiO2) thin films have been prepared on indium doped tin oxide (ITO) glass by sol-gel dip-coating method. Properties of the films
were determined as a function of heat-treatment by X-ray diffraction, scanning electron microscopy and photoelectrochemical
tests. The films heat-treated at higher temperatures show better crystallinity and photoresponse. The microscopic structure
on the film after heat-treatment is attributed to the incorporation of organic polymer into the precursor solution. The performance
of the electrodes treated at different temperature on photoelectrocatalytic degradation of methyl orange was investigated.
The effect of applied potential and the ability of the electrode to be repeatedly used in photoelectrocatalytic degradation
were also evaluated. 相似文献
42.
合成了SiW10Fe2的季胺盐(Fe2POM),并对其结构进行了表征.以Fe2POM为催化剂,研究了甲基橙的起始浓度、催化剂添加量、不同pH值等因素对光脱色速率的影响.利用异丙醇作为·OH捕获剂,探讨了甲基橙在Fe2POM-H2O2体系中的光化学脱色规律和机制.结果表明:体系在较宽的pH范围内具有高的光脱色活性,40—160mg/L初始质量浓度范围内,甲基橙的脱色速率随初始浓度降低而升高,脱色过程符合表观一级反应动力学规律.各体系的光脱色活性依次为:Fe2POM-H2O2单纯的Fe2POM>单纯的光照. 相似文献
43.
A copper(Ⅱ) complex 1 of a novel macrocyclic polyamine ligand with hydroxylethyl pendant groups, 4,11-bis(hydroxylethyl)-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L) has been synthesized and characterized. Rate enhancement for hydrolysis of p-nitrophenyl picolinate (PNPP) catalyzed by 1 was studied kinetically under Brij35 micellar condition. For comparision, the catalytic activity of corresponding copper(Ⅱ) complex 2 of non-substituted macrocyclic polyamine ligand, 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraaza-cyclotetradecane (L') toward the hydrolysis of PNPP was also investigated. The results indicate that the macrocyclic polyamine copper(Ⅱ) complex 1 effectively catalyzed the hydrolysis of PNPP, and the pendant ligand hydroxyl group or deprotonated pendant ligand hydroxyl group can act as catalytically active species in the reaction. A ternary Complex kinetic model involving metal ion, ligand and substrate has been proposed, and the results confirmed the reasonability of such kinetic model. 相似文献
44.
A. G. Tozhibaev K. K. Turgunov B. Tashkhodzhaev Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2006,42(3):340-344
The structures of deoxypeganine (DOP) hydrochloride and oxalate were solved by x-ray structure analysis. An infinite chain
along the crystallographic c axis was formed in the crystal structure of DOP oxalate. A molecular framework consisting of
Cl anions and DOP cation protonated at N1 was found in the structure of unhydrated DOP hydrochloride. The molecular packing
of the “host” (DOP cation) was pseudoisostructural in the studied ion-molecular crystals but differed from other known DOP
salts. The “guest” molecules (acid anions) in the studied and known DOP salts formed different intermolecular contacts.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 280–283, May–June, 2006. 相似文献
45.
(R)-4-Menthenone in the synthesis of optically pure sex pheromone of the peach leafminer moth (Lyonetia clerkella) 总被引:1,自引:0,他引:1
Kharisov R. Ya. Latypova E. R. Talipov R. F. Muslukhov R. R. Ishmuratov G. Yu. Tolstikov G. A. 《Russian Chemical Bulletin》2003,52(10):2267-2269
The synthesis of (14S)-methyloctadec-1-ene, sex pheromone of the peach leafminer moth (Lyonetia clerkella), is described to demonstrate a new potential of the synthetic use of (R)-4-menthenone. 相似文献
46.
47.
盐酸氨溴索在碳糊电极上阳极伏安法的研究 总被引:4,自引:0,他引:4
在0.5 mol/L H2SO4底液中,用碳糊电极阳极伏安法测定盐酸氨溴索,被测的阳极峰电位为1.10V(vs.SCE),另外,在0.46V处还产生一对可逆的氧化还原峰。1.10 V处的峰电流与盐酸氨溴索的浓度在3.98×10~(-7)~6.34 × 10~(-5)mol/L范围内呈良好的线性关系,该方法的检出下限为3.0 × 10~(-8)mol/L。用标准加入法测得回收率范围为92.8%~102%,RSD为2.9%(n=10)。对电极响应机理进行了初步探讨,氨溴索在1.10 V处的氧化为不可逆过程,其氧化产物在0.460V处产生一对2电子2质子受扩散控制的可逆波,用该波也可进行定量测定并且干扰较少,但灵敏度略低。 相似文献
48.
Maria Cazacu Grigore Munteanu Angelica Vlad 《Journal of organometallic chemistry》2006,691(17):3700-3707
Two new polymeric structures containing ferrocene units along the chains, namely poly(silyl ester)s, have been synthesized and characterized: a geminal poly(silyl ester) (g-PSE) and one having a disiloxane spacer between the silyl ester groups (s-PSE). The condensation polymerization of AA/BB monomer systems in solution was used in both cases as preparation method involving a silicon-containing diol, (diphenylsilane diol or 1,3-bis(hydroxy)-tetramethyldisiloxane), and 1,1′-di(chlorocarbonyl)ferrocene. The polymers were investigated by differential pulse voltammetry in order to evaluate the redox behavior. Due to the presence of the silyl ester groups in the chain, these polymers are hydrolytically degradable. 相似文献
49.
50.
Summary A new porous polyaromatic ester packing was synthetized for high performance liquid chromatography. The relationship between retention and chain length of the members of homologous series of alkylbenzenes, N-alkylanilines, alkylarylethers, alkylbenzoates and alkylarylketones on this new stationary phase using different eluents was investigated. Using the alkylarylketone scale the retention indices of the homologues and test compounds were calculated. The results were compared with those obtained for poly (styrene-divinylbenzene) polymers. For both types of packing the first members of each homologous series gave non-linear behaviour. The methylene group index increments are different for the studied homologous series; thus there is no simple additivity of the retention indices. The efficiency of the porous polymeric columns is a function of the capacity factor of the solute and the organic component of the eluent. 相似文献