全文获取类型
收费全文 | 1422篇 |
免费 | 56篇 |
国内免费 | 7篇 |
专业分类
化学 | 1072篇 |
晶体学 | 12篇 |
力学 | 19篇 |
数学 | 116篇 |
物理学 | 266篇 |
出版年
2022年 | 5篇 |
2021年 | 18篇 |
2020年 | 22篇 |
2019年 | 24篇 |
2018年 | 21篇 |
2017年 | 13篇 |
2016年 | 30篇 |
2015年 | 32篇 |
2014年 | 31篇 |
2013年 | 70篇 |
2012年 | 77篇 |
2011年 | 104篇 |
2010年 | 52篇 |
2009年 | 49篇 |
2008年 | 108篇 |
2007年 | 96篇 |
2006年 | 86篇 |
2005年 | 78篇 |
2004年 | 83篇 |
2003年 | 84篇 |
2002年 | 64篇 |
2001年 | 34篇 |
2000年 | 29篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 16篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1979年 | 6篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1973年 | 6篇 |
1970年 | 4篇 |
排序方式: 共有1485条查询结果,搜索用时 125 毫秒
71.
Masao Hirano Shigetaka Yakabe James H. Clark Hiroyuki Kudo Takashi Morimoto 《合成通讯》2013,43(10):1875-1886
A wide variety of sulphides can be readily converted to the corresponding sulphoxides in good to excellent yields by treatment with a combination of sodium chlorite, (salen)manganese(III) complex, and chromatographic alumina in dichloromethane under mild and neutral conditions. 相似文献
72.
73.
74.
Supramolecular polymer gels from polystyrene bearing cyclic amidine Group and acrylic acid/n‐butyl acrylate copolymers 下载免费PDF全文
Mina Sakuragi Naoto Aoyagi Yoshio Furusho Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2016,54(6):765-770
We have prepared supramolecular polymer gels by mixing solutions of a polystyrene bearing cyclic amidine pendant groups (Poly‐A) and copolymers of acrylic acid and n‐butyl acrylate (Poly‐C), followed by evaporation. FT‐IR analysis indicated that the gels were formed through three‐dimensional network of the amidinium‐carboxylate salt bridge. DSC study showed that the Poly‐A and the Poly‐C were miscible when the salt bridge content was high. On the other hand, the mixtures with small salt bridge content showed phase separation. Dynamic shear measurements showed that the gel prepared from Poly‐A and Poly‐C with acrylic acid unit content of 15% had G' higher than G″ over a temperature range of ?22 °C to 32 °C, in which the G' value reached almost 1 MPa. The gel had a crossover point of G' and G″ at 32 °C, very close to room temperature, which suggested facile processability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 765–770 相似文献
75.
76.
Jensen P Odaka TE Kraemer WP Hirano T Bunker PR 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(4):763-794
We have developed a computational procedure, based on the variational method, for the calculation of the rovibronic energies of a triatomic molecule in an electronic state that become degenerate at the linear nuclear configuration. In such an electronic state the coupling caused by the electronic orbital angular momentum is very significant and it is called the Renner effect. We include it, and the effect of spin-orbit coupling, in our program. We have developed the procedure to the point where spectral line intensities can be calculated so that absorption and emission spectra can be simulated. In order to gain insight into the nature of the eigenfunctions, we have introduced and calculated the overall bending probability density function f(p) of the states. By projecting the eigenfunctions onto the Born-Oppenheimer basis, we have determined the probability density functions f+(rho) and f-(rho) associated with the individual Born-Oppenheimer states phi(-)elec and phi(+)elec. At a given temperature the Boltzmann averaged value of the f(p) over all the eigenstates gives the bending probability distribution function F(rho), and this can be related to the result of a Coulomb Explosion Imaging (CEI) experiment. We review our work and apply it to the molecules CH2+, MgNC and NH2, all of which are of astrophysical interest. 相似文献
77.
Novel ferromagnetism in Ca(1-x)La(x)B(6) is studied in terms of the Ginzburg-Landau theory for excitonic-order parameters, taking into account symmetry of the wave functions. We found that the minima of the free energy break both inversion and time-reversal symmetries, while the product of these two remains preserved. This explains various novelties of the ferromagnetism and predicts a number of magnetic properties, including the magnetoelectric effect, which can be tested experimentally. 相似文献
78.
79.
Excitation migration between 5D0 states of Eu3+ ions in Ca(PO3)2 glass is studied by using the technique of the selective excitation of the inhomogeneously broadened 5D0 levels. In time-resolved emission spectra for 5D0→7F1 transition after the pulse excitation due to 7F0→5D0 transition by the use of a tunable dye laser at 77°K, a subpeak is observed to appear and to grow in intensity with increasing delay time, besides the main peak excited directly by the excitation light. The observed facts are explained by considering the phonon-assisted energy transfer between 5D0 states involving an acoustic phonon. From the analysis of the results, the probability of the excitation migration due to the phonon-assisted process is estimated to be ≌ 10 A ms-1. From the theoretical consideration, the rate of the linewidth change and the probability of the excitation migration due to the resonant transfer process are obtained. These results indicate that the phonon-assisted process is more dominant than the resonant process for the excitation migration in the system studied. 相似文献
80.
Effect of sonication on the photo-catalytic mineralization of some chlorinated organic compounds 总被引:1,自引:0,他引:1
Effects of the irradiation of ultrasound (US) on the photo-catalytic mineralization of some chlorinated organic compounds such as dichloroethane, tri- and tetrachloroethylenes, chloroacetic acids and chloromethanes were examined in oxygen saturated aqueous solutions suspended titanium dioxide (P25) particles. The yields of the sonochemical mineralization for these compounds were found to be extremely low compared to the photo-catalysis. However, the pre-sonication, US irradiation on the sample solution before the photo-irradiation, enhanced significantly the following photo-catalytic degradation to the complete oxidation. The effect was investigated in detail and it was found that the effect was mainly owing to the increase in the capability of the catalysis of which particles were sparsely dispersed by the sonication. The other contribution of the pre-sonication effect was found to be "pre-sonolysis", the initial formation of some intermediated products sonochemically, which are oxidizable more rapidly further to carbon dioxide than the original compound by the following photo-catalytic reactions. The pre-sonolysis effect was observed remarkably for trichloroacetic acid and tetrachloromethane, both of which are known to be hardly reactive to the photo-catalytic degradation. The photo-catalytic degradation with simultaneous sonication were also carried out for these compounds. The synergetic effect in the mineralization was observed both for carbontetrachloride and for trichloroacetic acid, the higher carbon dioxide yield being obtained in the simultaneous reaction than the sum of the yields in the photo-catalysis and the sonolysis each alone, while no significant synergetic effect was observed in the mineralization of other compounds. 相似文献