全文获取类型
收费全文 | 257020篇 |
免费 | 5930篇 |
国内免费 | 4757篇 |
专业分类
化学 | 120730篇 |
晶体学 | 3637篇 |
力学 | 15373篇 |
综合类 | 323篇 |
数学 | 42479篇 |
物理学 | 85165篇 |
出版年
2022年 | 2238篇 |
2021年 | 2822篇 |
2020年 | 3122篇 |
2019年 | 3399篇 |
2018年 | 11979篇 |
2017年 | 12504篇 |
2016年 | 8887篇 |
2015年 | 3966篇 |
2014年 | 5032篇 |
2013年 | 7953篇 |
2012年 | 11571篇 |
2011年 | 19638篇 |
2010年 | 12917篇 |
2009年 | 13088篇 |
2008年 | 16868篇 |
2007年 | 19878篇 |
2006年 | 6457篇 |
2005年 | 11313篇 |
2004年 | 7954篇 |
2003年 | 7758篇 |
2002年 | 6072篇 |
2001年 | 4712篇 |
2000年 | 3777篇 |
1999年 | 2766篇 |
1998年 | 2598篇 |
1997年 | 2274篇 |
1996年 | 2282篇 |
1995年 | 1922篇 |
1994年 | 1971篇 |
1993年 | 1905篇 |
1992年 | 1918篇 |
1991年 | 2030篇 |
1990年 | 1969篇 |
1989年 | 1917篇 |
1988年 | 1751篇 |
1987年 | 1693篇 |
1986年 | 1644篇 |
1985年 | 1796篇 |
1984年 | 1913篇 |
1983年 | 1663篇 |
1982年 | 1678篇 |
1981年 | 1484篇 |
1980年 | 1403篇 |
1979年 | 1609篇 |
1978年 | 1757篇 |
1977年 | 1678篇 |
1976年 | 1740篇 |
1975年 | 1583篇 |
1974年 | 1625篇 |
1973年 | 1640篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Wen Zhang Hui Huang Yu Ding Margherita Gavagnin Ernesto Mollo Guido Cimino Yue‐Wei Guo 《Helvetica chimica acta》2006,89(4):813-820
Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds. 相似文献
92.
93.
94.
In a two-dimensional array of magnetic moments with planar magnetization and relatively weak anisotropy in the basal plane, a stepwise phase transition is induced by an external magnetic field parallel to the easy axis of the system. This transition is similar to the spin flop phase transition in weakly anisotropic Heisenberg antiferromagnets with the significant difference that it is accompanied by the rearrangement of the sublattice structure of the magnet; i.e., it can be interpreted as a topological transition. The transition should manifest itself for arrays of submicron magnetic particles (magnetic dots) on nonmagnetic substrates, which have recently become the object of intensive research. 相似文献
95.
Yu. M. Smirnov 《Journal of Applied Spectroscopy》2006,73(6):785-791
Dissociative excitation of the lead atom in e-PbI2 collisions has been studied experimentally. 27 excitation cross sections were measured for an energy of the exciting electrons
equal to 100 eV. Nine optical excitation functions were recorded with variation of the electron energy in the range 0–100
eV. The most probable reaction channels for low electron energies are discussed, as well as the ratio of the dissociative
excitation cross sections for the lead atom in e-PbI2 and e-PbCl2 collisions.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 701–706, November–December, 2006. 相似文献
96.
O. Ya. Savchenko 《Optics and Spectroscopy》2006,101(2):179-182
The efficiency with which a magnetic field acts on sublevels of the first and second doublets of a hydrogen-like atom is shown to vary because of relativistic effects by a factor of 1 ? 2γ(l + 1)/(2l + 3) and 1 ? 2γl/(2l ? 1), respectively, where γ is the ratio of the electron binding energy to the rest energy and l is the quantum number of the orbital angular momentum. 相似文献
97.
S. K. Godunov V. T. Zhukov O. B. Feodoritova 《Computational Mathematics and Mathematical Physics》2006,46(6):971-982
An algorithm is constructed for calculating invariant subspaces of symmetric hyperbolic systems arising in electromagnetic, acoustic, and elasticity problems. Discrete approximations are calculated for subspaces that correspond to minimal eigenvalues and smooth eigenfunctions. Difficulties related to the presence of an infinite-dimensional kernel in the differential operator are successfully handled. The efficiency of the algorithm is demonstrated using acoustics equations. 相似文献
98.
Kurenkov V. F. Zaitseva O. A. Kirdyashova G. N. 《Russian Journal of Applied Chemistry》2002,75(4):641-644
The kinetics of radical copolymerization of acrylamide with lithium, sodium, and potassium 2-acrylamido-2-methylpropanesulfonates in concentrated aqueous solutions in the presence of potassium persulfate as initiating agent at pH 9 and 50°C was studied by dilatometry. 相似文献
99.
A nonlinear, compressible, non-isothermal gravity wave model that involves photochemistry is used to study the effects of gravity wave on atmospheric chemical species distributions in this paper. The changes in the distributions of oxygen compound and hydrogen compound density induced by gravity wave propagation are simulated. The results indicate that when a gravity wave propagates through a mesopause region, even if it does not break, it can influence the background distributions of chemical species. The effect of gravity wave on chemical species at night is larger than in daytime. 相似文献
100.