全文获取类型
收费全文 | 3309篇 |
免费 | 77篇 |
国内免费 | 17篇 |
专业分类
化学 | 2016篇 |
晶体学 | 20篇 |
力学 | 113篇 |
数学 | 556篇 |
物理学 | 698篇 |
出版年
2022年 | 24篇 |
2021年 | 29篇 |
2020年 | 44篇 |
2019年 | 39篇 |
2018年 | 35篇 |
2017年 | 35篇 |
2016年 | 65篇 |
2015年 | 75篇 |
2014年 | 75篇 |
2013年 | 138篇 |
2012年 | 158篇 |
2011年 | 172篇 |
2010年 | 115篇 |
2009年 | 86篇 |
2008年 | 177篇 |
2007年 | 196篇 |
2006年 | 195篇 |
2005年 | 152篇 |
2004年 | 122篇 |
2003年 | 106篇 |
2002年 | 119篇 |
2001年 | 68篇 |
2000年 | 71篇 |
1999年 | 52篇 |
1998年 | 38篇 |
1997年 | 37篇 |
1996年 | 53篇 |
1995年 | 33篇 |
1994年 | 45篇 |
1993年 | 52篇 |
1992年 | 46篇 |
1991年 | 37篇 |
1990年 | 32篇 |
1989年 | 32篇 |
1988年 | 25篇 |
1986年 | 23篇 |
1985年 | 32篇 |
1984年 | 39篇 |
1983年 | 27篇 |
1982年 | 40篇 |
1981年 | 35篇 |
1980年 | 38篇 |
1979年 | 37篇 |
1978年 | 32篇 |
1977年 | 31篇 |
1976年 | 24篇 |
1975年 | 26篇 |
1974年 | 35篇 |
1973年 | 38篇 |
1970年 | 18篇 |
排序方式: 共有3403条查询结果,搜索用时 15 毫秒
21.
22.
23.
The Huber criterion for data fitting is a combination of thel
1 and thel
2 criteria which is robust in the sense that the influence of wild data points can be reduced. We present a trust region and a Marquardt algorithm for Huber estimation in the case where the functions used in the fit are non-linear. It is demonstrated that the algorithms converge under the usual conditions. 相似文献
24.
L. Käubler W. Enghardt H. Prade P. Carlé L. O. Norlin K. -G. Rensfelt U. Rosengård 《Zeitschrift für Physik A Hadrons and Nuclei》1988,329(2):143-150
Using the reaction138Ba(α,2n)140Ce the magnetic moment of the 10 1 + isomer atE x =3714.7 keV in theN=82 nucleus140Ce has been determined by means of the TDPAD method toμ=+10.3(4)μ N . Measuredg-factors in140Ce are compared to calculations within the shell model with configuration mixing. For the 10 1 + isomer in140Ce the four proton configuration π(1g 7 2/2 ,2d 5 2/2 ) has been found to be dominant. From theg-factor measurement strong contributions of multiparticle excitations to thegp2d 3/2,π3s 1 2 or π1h 11 2 shells and admixtures of neutron excitations to the wave function of the 10 1 + state could be excluded. The strongE1γ-branch of the deexcitation of the 10 1 + isomer in140Ce can be explained by means of small admixtures of configurations which contain the outer subshell excitationsπ2f 7/2 andπ1h 9/2. On this basisE1 transitions experimentally observed in theN=82 nuclei140Ce,141Pr and145Eu may be understood. 相似文献
25.
Surface composition of spray-dried milk protein-stabilised emulsions in relation to pre-heat treatment of proteins 总被引:2,自引:0,他引:2
Millqvist-Fureby A Elofsson U Bergenståhl B 《Colloids and surfaces. B, Biointerfaces》2001,21(1-3):47-58
Several important technical properties of spray-dried food powders depend on particle-liquid interactions (e.g. wettability, dispersability) and particle-particle interactions (e.g. flowability). It can be assumed that the chemical composition of the surface layer of the particles to a large extent determine these properties. The present study has been aimed to investigate the relation between the surface composition of spray-dried milk protein-stabilised emulsions and pre-heat treatment of the proteins. Solutions of WPC were heat-treated at low (60-90 degrees C) and high (140 degrees C) temperature and the degree of denaturation was determined, prior to the preparation of emulsions with rapeseed oil. The surface composition of the dry powders were established by using ESCA (electron spectroscopy of chemical analysis). The emulsions were characterised by droplet size distribution before spray drying and after dissolution of the powders. Also free fat extractions and estimations of wettability (dissolution rates) were performed. The powder surface coverage of protein decreased with increasing degree of protein denaturation before the emulsification, whereas the emulsion droplet size increased both before spray drying and after reconstitution of powders. The free fat extraction as well as the dissolution rate, whereof the latter decreased with increasing surface fat coverage, correlated well with the fat coverage of the powder surface. 相似文献
26.
27.
28.
A new pyridine synthesis has been found by refluxing certain simple secondary car☐amides in HMPA. Thus 2,6-dimethylpyridine, 2-ethyl-6-methylpyridine, 2,3,6-trimethylpyridine, 2-ethyl-3,6-dimethylpyridine, 2-benzyl-6-methyl-3-phenylpyridine, 2-ethyl-3-methyl-5,6,7,8-tetrahydroquinoline and 2-t-butyl-6-methylpyridine were prepared in 15–40% yield. 相似文献
29.
Andersson I Gorzsás A Pettersson L 《Dalton transactions (Cambridge, England : 2003)》2004,(3):421-428
A detailed study of the quaternary aqueous H+/H2VO4-/H2O2/picolinate (Pi-) system has been performed at 25 degrees C in 0.150 M Na(Cl) medium using quantitative 51 V NMR (500 MHz) and potentiometric data (glass electrode). In the ternary H+/H2VO4-/Pi- system, six complexes have been found in the pH region 1-10. In the quaternary H+/H2VO4-/H2O2/Pi- system, eight additional complexes have been found. Generally, equilibria are fast in both systems. The rate of peroxide decomposition depends on the species in solution. Chemical shifts, compositions and formation constants for the species are given. Equilibrium conditions and the fit of the model to the experimental data are illustrated in distribution diagrams. Possible formation of mixed ligand species with imidazole, lactic acid and citric acid have been investigated and ruled out under the same experimental conditions. Structural proposals are given, based on 1)C NMR data and available crystal structures. 相似文献
30.
Gert E. V. Zubets O. V. Shishonok M. V. Torgashov V. I. Kaputskii F. N. 《Russian Journal of Applied Chemistry》2003,76(4):595-599
The capability of cotton and wood cellulose in the common and microcrystalline forms to transform into cellulose-II under the action of 68-69% HNO3 was studied. The influence of temperature on the course of the phase transition in cellulose samples differing in origin and morphological structure and the dynamics of concomitant hydrolytic degradation and esterification of these materials were studied. 相似文献