全文获取类型
收费全文 | 7333篇 |
免费 | 169篇 |
国内免费 | 28篇 |
专业分类
化学 | 4618篇 |
晶体学 | 127篇 |
力学 | 190篇 |
数学 | 1012篇 |
物理学 | 1583篇 |
出版年
2021年 | 52篇 |
2020年 | 95篇 |
2019年 | 91篇 |
2018年 | 66篇 |
2017年 | 57篇 |
2016年 | 143篇 |
2015年 | 126篇 |
2014年 | 168篇 |
2013年 | 312篇 |
2012年 | 285篇 |
2011年 | 364篇 |
2010年 | 231篇 |
2009年 | 221篇 |
2008年 | 304篇 |
2007年 | 280篇 |
2006年 | 291篇 |
2005年 | 261篇 |
2004年 | 236篇 |
2003年 | 214篇 |
2002年 | 201篇 |
2001年 | 134篇 |
2000年 | 161篇 |
1999年 | 99篇 |
1998年 | 104篇 |
1997年 | 100篇 |
1996年 | 122篇 |
1995年 | 109篇 |
1994年 | 95篇 |
1993年 | 110篇 |
1992年 | 100篇 |
1991年 | 110篇 |
1990年 | 85篇 |
1989年 | 101篇 |
1988年 | 111篇 |
1987年 | 98篇 |
1986年 | 104篇 |
1985年 | 96篇 |
1984年 | 88篇 |
1983年 | 87篇 |
1982年 | 69篇 |
1981年 | 103篇 |
1980年 | 96篇 |
1979年 | 94篇 |
1978年 | 96篇 |
1977年 | 79篇 |
1976年 | 75篇 |
1975年 | 57篇 |
1974年 | 56篇 |
1973年 | 59篇 |
1970年 | 42篇 |
排序方式: 共有7530条查询结果,搜索用时 15 毫秒
71.
K. Wagner W. Görner M. Hedrich P. Jost C. Segebade 《Analytical and bioanalytical chemistry》1998,362(4):382-386
The analysis of halogens in various matrices is described. Activation analysis with mainly high energy bremsstrahlung (PAA)
and pile neutrons (NAA) was applied. In the case of chlorine, fast procedures were worked out requiring not more than 100
min for one determination. The particular problems of fluorine analysis are discussed. The described techniques were applied
for the following cases: Determination of total chlorine resp. bromine in oil samples; determination of chlorine in wood,
glasses and TiN powders; determination of iodine in ZnSe single crystals using instrumental photoactivation.The limits of
detection are: (interference-free in μg/g) F: 0.03/–; Cl: 0.1/0.05; Br: 0.04/0.003 and I: 0.1/0.01 using PAA/NAA. Activation
analysis, being independent upon the chemical status of the analyte and usually less affected by blank problems has been found
to be a useful complement to conventional chemical analysis.
Received: 28 February 199 / Revised: 14 April 1998 / Accepted: 18 April 1998 相似文献
72.
Christian R. Noe M. Knollmüller G. Steinbauer E. Wagner H. Kürner P. Ettmayer H. Völlenkle 《Monatshefte für Chemie / Chemical Monthly》1991,122(4):299-317
Summary Enantiomerically pure 1,2-diols bearing optionallysyn oranti configurated secondary hydroxylic groups are synthesized from acetal-protected cyanohydrins. After resolution of the diastereomers the cyanohydrins are converted into -alkoxy-ketones by Grignard-reaction followed by reduction using common chelating or non-chelating agents. Among others syntheses of enantiomerically pure pheromones,endo-Brevicomin,exo-Brevicomin and Dispalure are given as examples.
Prof. Dr. Hans Berbalk zum 70. Geburtstag gewidmet 相似文献
73.
I. Wichterle J. Linek Z. Wagner J.-C. Fontaine K. Sosnkowska-Kehiaian et al. 《Transition Metal Chemistry》1991,16(5):546-547
Inorganic Chemistry Nomenclature
IUPAC Commission on Inorganic Chemistry Nomenclature; Newsletter 1990 相似文献74.
Summary We describe an algorithm for (bivariate) cardinal interpolation which can be applied to translates of basis functions which include box splines or radial basis functions. The algorithm is based on a representation of the Fourier transform of the fundamental interpolant, hence Fast Fourier Transform methods are available. In numerical tests the 4-directional box spline (transformed to the characteristical submodule of 2), the thin plate spline, and the multiquadric case give comparably equal and good results. 相似文献
75.
76.
77.
Ditzler WR Hill D Hoftiezer J Johnson KF Lopiano D Shima T Shimizu H Spinka H Stanek R Underwood D Wagner RG Yokosawa A Burleson GR Faucett JA Fontenla CA Garnett RW Luchini C Rawool-Sullivan MW Bhatia TS Glass G Hiebert JC Kenefick RA Nath S Northcliffe LC Damjanovich R Jarmer JJ Vaninetti J Jeppesen RH Tripard GE 《Physical review D: Particles and fields》1992,46(7):2792-2830
78.
A. Malki J. P. Coffin G. Guillaume F. Jundt K. Krishan F. Rami P. Wagner P. Fintz M. Zahar M. Gonin B. Heusch M. Ohta B. Rastegar D. Rebreyend F. Merchez J. Mistretta S. Kox 《Zeitschrift für Physik A Hadrons and Nuclei》1991,339(2):283-292
In an attempt to separate preequilibrium and thermalised emissions of light particles in low impact parameter heavy-ion collisions, the40Ar+24Mg reaction has been studied at 27.5 MeV/nucleon. Exclusive measurements have permitted us to examine, in some detail, heavy fragments and charged particles (p, d, t,-particle). The fragments recognized as evaporation residues have been selected and, due to inverse kinematic conditions, the related preequilibrium and statistical emissions of light particles resulting from incomplete fusion reaction appear to be distinguishable to a fair extent. This separation is fully supported by Monte Carlo calculations. Some experimental characteristics of the light particles have been examined and compared to the predictions of dynamical calculations. These calculations, associating a preequilibrium (interpreted as prompt emitted particles) model with a statistical-decay model, follow the evolution of the collision from the point of contact between the projectile and the target to the final evaporation-residue formation on an event by event basis. The predictions of these calculations have been compared to experimental data and satisfactory agreement is achieved for fragment-mass distribution, proton-energy spectra, and proton-angular distribution. 相似文献
79.
80.
Joachim G. Liehr Gareth A. Brenton John H. Beynon James A. McCloskey Wolfgang Blum Wilhelm J. Richter 《Helvetica chimica acta》1981,64(3):835-843
In isobutane chemical ionization mass spectrometry benzyl alcohol exhibits ions at m/z 147 (‘M + 39’) that arise by a loss of H2O from [M + C4H9]+, i.e. ‘M + 57’ complex ions. Electrophilic aromatic substitution of a proton at an ortho-position of neutral C6H5CH2OH with [t-C4H9]+ and, alternatively, nucleophilic substitution of H2O at the benzylic carbon in \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C_6 H_5 CH_2}\mathop {\rm O}\limits^+ {\rm H}_2 $\end{document} with CH2?C (CH3)2 are discussed as possible pathways. Evidence in favor of the latter is derived from the analysis of C6D5CH2OH and C6H5CD2OH for the origin of the H-atoms lost in H2O. The inferred ion structure of m/z 147 is verified by mass-analyzed ion kinetic energy (MIKE.) measurements of its collision-activated (CA.) decomposition. MIKE./CA. spectra of mass-selected m/z 147 ions, once generated by (CI(i-C4H10) from benzyl alcohol and, once, from 2-methyl-4-phenyl-2-butanol match closely and, thus, reflect identical ion structures. With reference to the simple genesis of this ion from the latter precursor, the structure in question can be concluded to be \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C_6 H_5 CH_2 CH_2}\mathop {\rm C}\limits^+ ({\rm CH}_3)_2 $\end{document} . 相似文献