全文获取类型
收费全文 | 25126篇 |
免费 | 457篇 |
国内免费 | 100篇 |
专业分类
化学 | 13993篇 |
晶体学 | 154篇 |
力学 | 762篇 |
综合类 | 9篇 |
数学 | 3472篇 |
物理学 | 7293篇 |
出版年
2022年 | 316篇 |
2021年 | 391篇 |
2020年 | 357篇 |
2019年 | 312篇 |
2018年 | 404篇 |
2017年 | 363篇 |
2016年 | 625篇 |
2015年 | 516篇 |
2014年 | 602篇 |
2013年 | 972篇 |
2012年 | 1249篇 |
2011年 | 1425篇 |
2010年 | 795篇 |
2009年 | 754篇 |
2008年 | 1196篇 |
2007年 | 1179篇 |
2006年 | 1065篇 |
2005年 | 1496篇 |
2004年 | 1533篇 |
2003年 | 1084篇 |
2002年 | 726篇 |
2001年 | 607篇 |
2000年 | 558篇 |
1999年 | 350篇 |
1998年 | 292篇 |
1997年 | 291篇 |
1996年 | 360篇 |
1995年 | 320篇 |
1994年 | 310篇 |
1993年 | 328篇 |
1992年 | 321篇 |
1991年 | 263篇 |
1990年 | 219篇 |
1989年 | 204篇 |
1988年 | 184篇 |
1987年 | 178篇 |
1986年 | 178篇 |
1985年 | 224篇 |
1984年 | 213篇 |
1983年 | 184篇 |
1982年 | 190篇 |
1981年 | 185篇 |
1980年 | 170篇 |
1979年 | 155篇 |
1978年 | 178篇 |
1977年 | 139篇 |
1976年 | 136篇 |
1975年 | 114篇 |
1974年 | 132篇 |
1973年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
Summary The application of GLC, HPLC and TLC to the analysis of pharmaceutical creams is discussed with special attention to sample clean-up. The results of the determination of hydrocortisone acetate, salicylic acid, benzoic acid, diethyl stilbestrol, chloramphenicol, diphenhydramine HCl, tretinoin and some cream base components by reversed phase HPLC are given.Presented at the 14th International Symposium on Chromatography London, September, 1982 相似文献
133.
D. S. Gouveia R. Rosenhaim M. A. M. A. de Maurera S. J. G. Lima C. A. Paskocimas E. Longo A. G. Souza I. M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2004,75(2):453-460
With the aim of obtaining materials with applications in pigments, CoxZn7-xSb2O12 spinels were synthesized using the Pechini method. This method consists in the formation of a polymeric net, where the metallic
cations are homogeneously distributed. In this work, two types of alcohol (ethyl glycol and ethylene glycol) were used for
the synthesis of a zinc antimoniate spinel, CoxZn7-xSb2O12 (x=0-7). The materials were characterized by termogravimetry (TG) and differential thermal analysis (DTA). TG results indicated
a decrease in total mass loss when cobalt was added to the solution substituting zinc, for samples prepared using the two
different alcohols. Decomposition temperatures, obtained by TG and DTA, presented a decreasing behavior as cobalt was added
to the material. In relation to the alcohols, all results indicated a better polymerization of the resin when ethylene glycol
was used, being the most indicated one for cation immobilization. X-ray diffraction did not show differences between the two
alcohols - both presented the spinel phase (Co, Zn)2.33Sb0.67O4. Samples with higher quantity of cobalt also presented ilmenite phase (Co, Zn)Sb2O6.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
134.
F. F. C. Bazito S. I. Córdoba de Torresi R. M. Torresi 《Journal of Solid State Electrochemistry》2007,11(11):1471-1479
Poly(phenylene sulfide phenyleneamine), PPSA, is a copolymer of poly(aniline) and poly(phenylene sulfide), soluble in conventional
organic solvents as tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and cyclohexanone. In this research, its electrochemical
behavior has been studied in acetonitrile in the presence of different electrolytes, where the loss of electroactivity was
observed after few cycles. In this paper, the charge compensation dynamics of PPSA is analyzed through electrochemical quartz
crystal microbalance experiments and electroacoustic impedance measurements. Raman spectroscopy data have shown that once
the oxidation of the sulfur atom occurs, a loss of electroactivity is observed, being not possible to recover the pristine
state of the polymer. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data obtained for the fully oxidized polymer
are consistent with the formation of a networked polymer due to the electrophilic attack of the positive sulfur atom on the
activated aromatic rings. Electrochemical quartz crystal microbalance results clearly show that the degree of irreversibility
fully depends on the chemical nature of the anions with a negligible participation of the cations of the electrolytic solution.
This work is in memoriam of Prof. Dr. Francisco C. Nart, dearest friend and colleague, whose scientific skills and enthusiasm
will always be remembered. 相似文献
135.
Treatment of methyl 3,5-dideoxy-β---pentofuranoside with the Ph3P-CCl4 reagent gave none of the expected 2-chloro derivative but a mixture of l→2 linked oligosaccharides, , with some higher homologues, terminated by αa 2-chloro-2,3,5-trideoxy-α---pentofuranosyl unit at the non reducing end. 相似文献
136.
Pilar Alonso Isabel de Frutos Teresa Gutiérrez Antonio Doadrio López 《Transition Metal Chemistry》1987,12(2):133-136
Summary The synthesis and the dinuclear or mononuclear nature of several molybdenum(VI) and molybdenum(V) oxocomplexes derived from 1,3-diphenyl-1,3-propanedione (HLL) are described. These complexes were identified by i.r. and electronic spectra, magnetic susceptibility and analytical data, and are assigned the following formulae: [MoO2(LL)2], [Mo2O5(LL)2], [Mo2O4(LL)2], [MoOCl(LL)2], [MoCl2(LL)] and [MoO(OH)(LL)2)]. The low magnetic moments of the dinuclear complexes are due, in part, to intramolecular interactions. The i.r. data show that the dionate is bound by two oxygen atoms forming a chelate six-membered ring. 相似文献
137.
138.
I. V. Katal'nikov V. A. Kuz'min P. P. Levin K. de Jonge G. R. Myul'man 《Russian Chemical Bulletin》1989,38(8):1758-1760
The spectrokinetic indices of the triplet states of nitroaromatic amides were established. The quenching of triplet states by tertiary aromatic amines in apolar solvents leads to the formation of triplet exciplexes. A charge transfer state makes the major contribution to the structure of these exciplexes. Hydrogen atom transfer proceeds efficiently in the case of secondary aromatic amines, leading to the formation of the corresponding neutral radicals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1912–1915, August, 1989. 相似文献
139.
为了研究白血病骨髓移植病人全血微量元素铜的变化及其意义 ,用原子吸收光谱法检测了正常对照组与白血病骨髓移植患者预处理前及移植后骨髓空虚期全血微量元素铜的含量。结果表明 ,正常对照组全血铜浓度与白血病骨髓移植患者预处理前全血铜浓度差异无显著性 (P >0 0 5 ) ,而与骨髓空虚期全血铜浓度有显著性差异 (P <0 0 5 ) ,说明白血病缓解后血铜接近正常对照组水平 ,而白血病骨髓移植患者预处理后骨髓空虚期全血铜含量高于正常对照组 ,说明预处理影响微量元素铜的代谢 ,本文就其影响机理进行了研究 相似文献
140.