全文获取类型
收费全文 | 437306篇 |
免费 | 3415篇 |
国内免费 | 1199篇 |
专业分类
化学 | 234855篇 |
晶体学 | 6803篇 |
力学 | 18994篇 |
综合类 | 15篇 |
数学 | 50507篇 |
物理学 | 130746篇 |
出版年
2019年 | 4019篇 |
2018年 | 5555篇 |
2017年 | 5467篇 |
2016年 | 7806篇 |
2015年 | 4569篇 |
2014年 | 7310篇 |
2013年 | 18200篇 |
2012年 | 13571篇 |
2011年 | 16559篇 |
2010年 | 11795篇 |
2009年 | 11509篇 |
2008年 | 15674篇 |
2007年 | 15924篇 |
2006年 | 14866篇 |
2005年 | 13452篇 |
2004年 | 12123篇 |
2003年 | 11053篇 |
2002年 | 10939篇 |
2001年 | 11814篇 |
2000年 | 9290篇 |
1999年 | 7099篇 |
1998年 | 6232篇 |
1997年 | 6250篇 |
1996年 | 5856篇 |
1995年 | 5165篇 |
1994年 | 5359篇 |
1993年 | 5116篇 |
1992年 | 5682篇 |
1991年 | 5706篇 |
1990年 | 5593篇 |
1989年 | 5427篇 |
1988年 | 5464篇 |
1987年 | 5355篇 |
1986年 | 5117篇 |
1985年 | 6770篇 |
1984年 | 7127篇 |
1983年 | 5857篇 |
1982年 | 6253篇 |
1981年 | 6070篇 |
1980年 | 5842篇 |
1979年 | 6024篇 |
1978年 | 6390篇 |
1977年 | 6315篇 |
1976年 | 6377篇 |
1975年 | 5954篇 |
1974年 | 5994篇 |
1973年 | 6282篇 |
1972年 | 4392篇 |
1971年 | 3722篇 |
1967年 | 3712篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
91.
Fix integers m, n such that 1 ≤ m ≤ n ? 3. Let X ? Pn be an integral non-degenerate m-dimensional variety. Assume either char(K) = 0 or char(K) > deg(X). Here we prove that all general 0-dimensional sections of X containing a tangent vector to a smooth point of X are protectively equivalent if and only if n ? m + 1 ≤ deg(X) ≤ n ? m + 2. 相似文献
92.
A semiclassical theory of electromagnetically induced transparency in a Bose-Einstein condensate is considered. A nonlinear Schrödinger equation that describes the interaction of the Bose-Einstein condensate with an electromagnetic field is derived. An analysis of the obtained solutions to this equation demonstrates a decrease in the group velocity of the light pulse. 相似文献
93.
94.
Russian Journal of General Chemistry - 相似文献
95.
Glezer A.M. Blinova E.N. Pozdnyakov V.A. Shelyakov A.V. 《Journal of nanoparticle research》2003,5(5-6):551-560
Journal of Nanoparticle Research - It was shown that the thermoelastic martensite transformation B2 ? B19 inside nanoparticles surrounded by amorphous matrix in Ni–Ti–Cu alloys as... 相似文献
96.
E. A. Sopkina 《Journal of Mathematical Sciences》2004,124(1):4832-4836
An invariant of a closed set that is equal to the sum of roots is introduced. For a closed subset in a root system, we describe symmetric and special parts and its stabilizer in the Weyl group by means of the sum of roots. We determine associated bases with respect to which the closed set has the simplest form. All possible values of the root sum are found. Bibliography: 9 titles. 相似文献
97.
Aji P. Mathew Gabriel Groeninckx G. H. Michler H. J. Radusch Sabu Thomas 《Journal of Polymer Science.Polymer Physics》2003,41(14):1680-1696
The effects of the blend ratio and initiating system on the viscoelastic properties of nanostructured natural rubber/polystyrene‐based interpenetrating polymer networks (IPNs) were investigated in the temperature range of ?80 to 150 °C. The studies were carried out at different frequencies (100, 50, 10, 1, and 0.1 Hz), and their effects on the damping and storage and loss moduli were analyzed. In all cases, tan δ and the storage and loss moduli showed two distinct transitions corresponding to natural rubber and polystyrene phases, which indicated that the system was not miscible on the molecular level. However, a slight inward shift was observed in the IPNs, with respect to the glass‐transition temperatures (Tg's) of the virgin polymers, showing a certain degree of miscibility or intermixing between the two phases. When the frequency increased from 0.1 to 100 Hz, the Tg values showed a positive shift in all cases. In a comparison of the three initiating systems (dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile), the dicumyl peroxide system showed the highest modulus. The morphology of the IPNs was analyzed with transmission electron microscopy. The micrographs indicated that the system was nanostructured. An attempt was made to relate the viscoelastic behavior to the morphology of the IPNs. Various models, such as the series, parallel, Halpin–Tsai, Kerner, Coran, Takayanagi, and Davies models, were used to model the viscoelastic data. The area under the linear loss modulus curve was larger than that obtained by group contribution analysis; this showed that the damping was influenced by the phase morphology, dual‐phase continuity, and crosslinking of the phases. Finally, the homogeneity of the system was further evaluated with Cole–Cole analysis. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1680–1696, 2003 相似文献
98.
E. Sh. Gutshabash 《JETP Letters》2003,78(11):740-744
The integration procedure based on the generalized Darboux transform is suggested for the Ishimori magnet model. Exact solutions are constructed for the model on the background of spiral structures. The possibility of phase transition in the system is hypothesized. 相似文献
99.
In the present paper, the notion of norm series with respect to the norm residue symbol is generalized to high-dimensional local fields. Necessary and sufficient conditions for the existence of norm series are obtained. Bibliography: 12 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 305, 2003, pp. 60–83. 相似文献
100.
The results of optical study and quantum-chemical simulation of a conjugated organic system, 2-cyclooctylamino-5-nitropyridine (COANP)-fullerene, performed to determine its potential for application as a limiter of visible and near-IR laser radiation and as a material for diffraction elements in systems for reversible recording of optical information, are presented. Complexation between a COANP molecule and fullerene is considered as one of the main mechanisms responsible for the corresponding properties of this system. For the first time, nonlinear optical characteristics of COANP-C60 and COANP-C70 systems are comparatively studied and the intermolecular interaction between a COANP molecule and fullerene is analyzed on the quantum-chemical level. 相似文献