全文获取类型
收费全文 | 532553篇 |
免费 | 5756篇 |
国内免费 | 1533篇 |
专业分类
化学 | 286427篇 |
晶体学 | 7972篇 |
力学 | 23249篇 |
综合类 | 16篇 |
数学 | 61204篇 |
物理学 | 160974篇 |
出版年
2021年 | 4416篇 |
2020年 | 4943篇 |
2019年 | 5312篇 |
2018年 | 6867篇 |
2017年 | 6782篇 |
2016年 | 10433篇 |
2015年 | 6601篇 |
2014年 | 10071篇 |
2013年 | 24374篇 |
2012年 | 18796篇 |
2011年 | 23008篇 |
2010年 | 16166篇 |
2009年 | 16116篇 |
2008年 | 21240篇 |
2007年 | 21009篇 |
2006年 | 19699篇 |
2005年 | 17666篇 |
2004年 | 16312篇 |
2003年 | 14540篇 |
2002年 | 14326篇 |
2001年 | 16683篇 |
2000年 | 12514篇 |
1999年 | 9797篇 |
1998年 | 7933篇 |
1997年 | 7730篇 |
1996年 | 7475篇 |
1995年 | 6759篇 |
1994年 | 6655篇 |
1993年 | 6314篇 |
1992年 | 7251篇 |
1991年 | 7419篇 |
1990年 | 7057篇 |
1989年 | 6862篇 |
1988年 | 6882篇 |
1987年 | 6746篇 |
1986年 | 6289篇 |
1985年 | 8145篇 |
1984年 | 8319篇 |
1983年 | 6591篇 |
1982年 | 6714篇 |
1981年 | 6559篇 |
1980年 | 6159篇 |
1979年 | 6772篇 |
1978年 | 6972篇 |
1977年 | 6848篇 |
1976年 | 6743篇 |
1975年 | 6206篇 |
1974年 | 6210篇 |
1973年 | 6279篇 |
1972年 | 4375篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
T. I. Khabakhpasheva 《Fluid Dynamics》2003,38(4):592-600
The problem of surface wave diffraction on a floating elastic plate is considered. The relation between the parameters of the elastic vibrations of the plate and the transmitted and reflected wave amplitudes is investigated. It is shown that the maximum amplitudes of the plate stresses and deflections depend nonmonotonically on the incident wave frequency and are reached simultaneously with the maxima of both the transmission coefficient and the length of the wave penetrating into the plate. This makes it possible to use the transmission coefficient as a parameter for investigating the maximum and minimum amplitudes of the hydroelastic vibrations of the plate. As an example, this criterion is used to minimize the vibrations of a plate whose leading edge is elastically connected to the bottom. 相似文献
992.
993.
Mary E. Neubert DAVID G. ABDALLAH Jr Sandra S. Keast Julie M. Kim Soonnam Lee Ryan M. Stayshich Margaret E. Walsh Rolfe G. Petschek Shin-Tson Wu 《Liquid crystals》2003,30(6):711-731
New diphenyldiacetylenes of the type with A, B = H and/or F; m = 0, 1; n = 1-4; and X = C n H 2n + 1 , F, CF 3 or CN were synthesized and their mesomorphic properties determined by hot stage polarizing microscopy and DSC. When m = 0, all of these compounds showed only a nematic phase except when X = CF 3 when both nematic and smectic A phases were seen. Both clearing and melting temperatures were higher than those reported for substitution with the corresponding alkyl chains but the much larger increase in clearing temperatures produced considerably wider nematic phases. Eutectic mixtures of a few of these olefins yielded nematic materials also having much wider temperature ranges and higher clearing temperatures than the eutectic mixtures of the alkyl compounds, while retaining their high birefringence and low viscosities. Such materials are of interest for beam-steering devices.
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
994.
995.
996.
997.
V. G. Lakhtin V. L. Ryabkov A. V. Kisin V. M. Nosova M. V. Polyakova E. A. Chernyshev 《Russian Chemical Bulletin》1995,44(11):2163-2167
Liquid-phase chlorination of a number of chloro(chlorovinyl)methylsilanes was investigated. A number of novelC-chlorosilanes were characterized by IR and1H NMR spectra. Some regularities of these reactions were determined; correlations between the structure of chloro(chlorovinyl)methylsilanes and their reactivities were identified.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2256–2260, November, 1995. 相似文献
998.
S. M. Natanzon 《Proceedings of the Steklov Institute of Mathematics》2007,259(1):137-148
We prove that the quaternionic miniversal deformations of an A
n singularity have the structure of a noncommutative Frobenius manifold in the sense of the extended cohomological field theory. 相似文献
999.
S. Azimpour M. Chaichi M. Toomanian 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(5):270-277
A 4-dimensional Walker metric on a semi Riemanian manifold M, for the canonical metric with c = 0, have been investigated by M. Chaichi, E. García—Río and Y. Matsushita. The paper generalizes these notions to the case of constant c ≠ 0. Specially the form of defining functions of this metric in locally conformally flat 4-dimensional Walker manifolds is found. 相似文献
1000.
N. M. Bogoliubov 《Journal of Mathematical Sciences》2007,143(1):2729-2737
We consider random walks of two essentially different classes of random walkers, namely, of vicious and friendly ones, on
one-dimensional lattices with periodic boundary conditions. The walkers are called vicious since, arriving at a lattice site,
they annihilate not only one another but all the remaining walkers as well. On the contrary, an arbitrary number of friendly
walkers can share the same lattice sites. It is shown that a natural model describing the behavior of friendly walkers is
an integrable model of the boson type. A representation of the generating function for the number of the lattice paths performed
by a fixed number of friendly walkers for a certain number of steps is obtained. Bibliography: 22 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 335, 2006, pp. 59–74. 相似文献