全文获取类型
收费全文 | 23994篇 |
免费 | 55篇 |
国内免费 | 46篇 |
专业分类
化学 | 10053篇 |
晶体学 | 405篇 |
力学 | 942篇 |
综合类 | 11篇 |
数学 | 3489篇 |
物理学 | 9195篇 |
出版年
2023年 | 13篇 |
2022年 | 180篇 |
2021年 | 367篇 |
2020年 | 372篇 |
2019年 | 549篇 |
2018年 | 1005篇 |
2017年 | 1117篇 |
2016年 | 1322篇 |
2015年 | 533篇 |
2014年 | 1098篇 |
2013年 | 1662篇 |
2012年 | 1496篇 |
2011年 | 1555篇 |
2010年 | 1773篇 |
2009年 | 1723篇 |
2008年 | 1688篇 |
2007年 | 1613篇 |
2006年 | 1412篇 |
2005年 | 878篇 |
2004年 | 614篇 |
2003年 | 324篇 |
2002年 | 315篇 |
2001年 | 308篇 |
2000年 | 614篇 |
1999年 | 349篇 |
1998年 | 449篇 |
1997年 | 428篇 |
1996年 | 111篇 |
1995年 | 33篇 |
1994年 | 31篇 |
1993年 | 5篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1971年 | 4篇 |
1968年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
11.
D. A. Kosmodem’yanskii 《Moscow University Mathematics Bulletin》2007,62(2):56-60
Spectral properties of the following three homogenized problems in the mechanics of strongly nonhomogeneous media are considered: the “double porosity” problem, the oscillation problem for a mixture of two viscous compressible liquids, and the oscillation of a medium consisting of an elastic frame and a viscous liquid. For all three cases results on the structure of the spectrum and on the existence of so-called “spectral gaps” are obtained. 相似文献
12.
13.
The efficiency of suppression of the generation of a photon echo response depending on the mutual spatial orientation of gradients of external nonumform electric fields acting on a resonant medium is studied. The possibility of creating an associative memory where the mutual orientation of the gradients of external electric fields is an associative key is discussed. 相似文献
14.
Several illusions of vision are considered on the basis of a neurophysiological holographic model of visual perception at the level of the eye’s and the retina. It is suggested that the eye’s optical system forms a spatial spectrum of the observed object rather than its image on the retina. The spectrum is encoded by active anisotropic quasi-crystalline structures of rod rhodopsins and cone iodopsins, and a complex Fourier hologram of the observed object consisting of two quadrature components is recorded. The holographic hypothesis is confirmed by the results obtained by digital simulation. 相似文献
15.
S. K. Gorbatsevich I. A. Kaputskaya S. A. Maskevich S. Yu. Mikhnevich N. D. Strekal’ 《Optics and Spectroscopy》2004,97(2):238-243
The fluorescence of solid solutions of CdSe/ZnS quantum dots and the organic dye DODCI is investigated. It is shown that nonradiative transfer of electronic excitation energy to dye molecules, which with some probability lose their acceptor properties as a result of photoisomerization or photodegradation, is responsible for a significant increase in the fluorescence intensity of a donor. The degree of polarization of the donor fluorescence attains values exceeding 0.5, which is due to the difference in the fluorescence quantum yields of donors with different orientations of the oscillator with respect to the electric vector of an excitation light wave. A numerical simulation of the experimentally observed dependences is performed. 相似文献
16.
V. V. Pakal’nis I. V. Zerova S. I. Yakimovich 《Russian Journal of General Chemistry》2007,77(10):1732-1741
Acylhydrazines react with 1,3-diketones of the general formula CF3COCH2COR (where R is an aryl or hetaryl group) at both carbonyl groups. The reaction at the trifluoroacetyl group is favored by donor substituents in the aromatic ring of the 1,3-diketone or by the 2-furyl and, especially, 2-thienyl group as a hetaryl substituent, as well as by elevated temperature. The condensation products at the carbonyl group contiguous to the aryl or hetaryl ring have the structure of 5-hydroxy-4,5-dihydropyrazoles and do not undergo tautomeric transformations in solution. The condensation products at the trifluoroacetyl group have either 5-hydroxy-4,5-dihydropyrazole or hydrazone structure and give rise to ring-chain tautomeric equilibrium in solution. Electron-withdrawing substituents in the aromatic ring of the 1,3-dicarbonyl fragment and CDCl3 as solvent favor formation of the cyclic tautomer. The state of the tautomeric equilibrium is weakly sensitive to structural variations in the hydrazine component. 相似文献
17.
V. I. Burkov E. P. Peredereĭ E. V. Fedotov B. V. Mill’ Yu. V. Pisarevskiĭ 《Crystallography Reports》2008,53(5):843-846
The absorption and circular dichroism spectra of langasite family crystals are studied. Wide bands in the range of 285–500 nm that are related to the structure lattice defects are found. For all the crystals, these bands are in approximately the same spectral region, have identical structures, and can be attributed to one type of defects formed by cation vacancies and excess oxygen atoms in the optically active positions. 相似文献
18.
19.
Electric and spatial characteristics of a pulse-periodic microsecond barrier discharge are investigated in different geometries—triangular
prism, plate, and corrugated electrode—that are in contact with a dielectric plate and form a dihedral angle with it. It is
established that, in the space of the dihedral angle, the regions of discharge represent alternating cylindrical layers with
the axes lying on the contact line. The first conducting layer is formed at some distance from the contact edge of the electrode.
The number of layers and their localization are determined by the angle formed between an electrode and the dielectric plate.
A physical model explaining the main features of the structure formation is proposed. 相似文献
20.