全文获取类型
收费全文 | 677054篇 |
免费 | 5803篇 |
国内免费 | 1649篇 |
专业分类
化学 | 332236篇 |
晶体学 | 9731篇 |
力学 | 36246篇 |
综合类 | 27篇 |
数学 | 98453篇 |
物理学 | 207813篇 |
出版年
2021年 | 5825篇 |
2020年 | 6290篇 |
2019年 | 7176篇 |
2018年 | 13617篇 |
2017年 | 13885篇 |
2016年 | 15558篇 |
2015年 | 7599篇 |
2014年 | 12391篇 |
2013年 | 27997篇 |
2012年 | 23812篇 |
2011年 | 31981篇 |
2010年 | 22896篇 |
2009年 | 23019篇 |
2008年 | 29557篇 |
2007年 | 31317篇 |
2006年 | 22003篇 |
2005年 | 22266篇 |
2004年 | 19686篇 |
2003年 | 18319篇 |
2002年 | 17181篇 |
2001年 | 17608篇 |
2000年 | 13701篇 |
1999年 | 10471篇 |
1998年 | 8998篇 |
1997年 | 8911篇 |
1996年 | 8472篇 |
1995年 | 7552篇 |
1994年 | 7618篇 |
1993年 | 7336篇 |
1992年 | 7889篇 |
1991年 | 8285篇 |
1990年 | 8000篇 |
1989年 | 7921篇 |
1988年 | 7726篇 |
1987年 | 7456篇 |
1986年 | 7183篇 |
1985年 | 9188篇 |
1984年 | 9617篇 |
1983年 | 8035篇 |
1982年 | 8270篇 |
1981年 | 7826篇 |
1980年 | 7403篇 |
1979年 | 8054篇 |
1978年 | 8280篇 |
1977年 | 8187篇 |
1976年 | 8189篇 |
1975年 | 7824篇 |
1974年 | 7612篇 |
1973年 | 8015篇 |
1972年 | 5867篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
G. L. Silver C. M. Anderson-Cook 《Journal of Radioanalytical and Nuclear Chemistry》2005,266(3):373-376
Summary Literature data on the radiolytic generation of hydrogen in nitric acid solutions of plutonium are used to construct a model
that predicts G(H2) as a function of the nitric acid and plutonium concentrations. The model indicates that G(H2) decreases with increasing concentration of nitric acid, in agreement with most experimental observations. The effect of
the plutonium concentration on G(H2) is secondary to the effect of the acid concentration. An equation for interpolating Gvalues for total gas is included. 相似文献
992.
993.
J. Fujimoto T. Ishikawa M. Jimbo T. Kaneko T. Kon Y. Kurihara M. Kuroda Y. Shimizu Y. Yasui 《Pramana》2007,69(5):943-946
We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer
code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We
present new results of various two-body decay widths and chargino pair production at ILC (international linear collider) at
one-loop level.
相似文献
994.
The occurrence of two noninteracting forms of Pd-porphin in the ground electronic state in a wide number of Shpolskii matrices maintained at liquid helium temperature was observed with the help of the finestructure phosphorescence spectra of these systems. The ratio between these forms can be varied in wide limits by choosing a particular matrix, which indicates that the matrix plays a significant role in the conformation formation of the tetrapyrrole macrocycle. Based on comparison both with the resonance Raman spectra and with the results of investigations of metal complexes of porphin by the selective spectroscopy methods, the shortwavelength spectral form has been shown to correspond to the planar molecular structure, whereas the longwavelength form has been attributed to a nonplanar molecular structure with the distortion of the porphin macrocycle of the saddle type. The results obtained indicate that the methods of fine structure spectroscopy make it possible to efficiently study distorted molecular structures stabilized in solid matrices at low temperatures. 相似文献
995.
C. Czeranowsky V. M. Baev G. Huber P. A. Khandokhin Ya. I. Khanin I. V. Koryukin E. Yu. Shirokov 《Radiophysics and Quantum Electronics》2004,47(10-11):723-728
Experimental study of low-frequency dynamics of an intracavity frequency-doubled Nd:YAG laser demonstrates the influence of the interaction of orthogonally polarized modes, participating in frequency doubling (type II phase matching), on the stability of the laser output. At a sufficiently low pump rate and low conversion efficiency, the laser shows stable operation with a low noise level at the frequencies of relaxation oscillations. At a high pump power and/or a high conversion efficiency, the laser emission becomes unstable as a result of Hopf bifurcation at the frequencies of relaxation oscillations that are responsible for the anti-phase polarization dynamics of the laser. 相似文献
996.
A brief account of applications of polarized inelastic neutron scattering in condensed matter research is given. We show that
full polarization analysis is the only tool allowing to discriminate unambiguously between different magnetic modes in various
magnetic materials. We show by means of recent results in the Heisenberg ferromagnet EuS that the effects of dipolar interactions
can be studied on a microscopic scale. Moreover, we have found for the first time indications for the divergence of the longitudinal
fluctuations belowT
c. In the itinerant antiferromagnet chromium we demonstrate that the dynamics of the longitudinal and transverse excitations
are very different, resolving a long standing puzzle concerning the slope of their dispersion. Finally, we show that a measurement
of the polarization-dependent part of the cross section of non-centrosymmetric MnSi proves directly that the chirality of
the magnetic fluctuations is left-handed. 相似文献
997.
Dedushenko S. K. Makhina I. B. Mar'in A. A. Mukhanov V. A. Perfiliev Yu. D. 《Hyperfine Interactions》2004,158(1-4):417-421
A colourless quartz crystal doped with 57Fe3+ was obtained by hydrothermal synthesis in an NH4F solution. The crystal was transformed into violet amethyst by gamma-irradiation. The change in colour was accompanied by changes in the Mössbauer spectrum that can be interpreted as the conversion of trivalent iron into the tetravalent state: Fe3+→Fe4+.
相似文献998.
R. Hefelmann P. Mann A. Aignan F. Filsinger und H. Amsel 《Fresenius' Journal of Analytical Chemistry》1902,41(1):66-68
Ohne Zusammenfassung 相似文献
999.
1000.
C. Mavroyannis 《Applied physics. B, Lasers and optics》2003,76(8):839-850
We have calculated the spectral functions for a number of induced excitations near the sum-frequency generation of a bichromatic field interacting with a three-level atom in the cascade configuration. Although the two-photon spontaneous emission is electric dipole forbidden, there are induced peaks whose subnatural line widths and spectral heights depend on the intensities of the bichromatic field. At low intensities of both laser fields, the maximum heights of the induced peaks take positive, zero, and negative values, indicating that the physical processes of absorption (attenuation), dark resonance (nonabsorbing state), and stimulated emission (amplification) are likely to occur at the sum-frequency generation of the two laser fields, respectively. The derived results are graphically presented and discussed. PACS 32.80.-t; 42.50.Hz 相似文献