全文获取类型
收费全文 | 77880篇 |
免费 | 557篇 |
国内免费 | 113篇 |
专业分类
化学 | 41366篇 |
晶体学 | 1261篇 |
力学 | 3300篇 |
综合类 | 1篇 |
数学 | 7909篇 |
物理学 | 24713篇 |
出版年
2022年 | 630篇 |
2021年 | 870篇 |
2020年 | 968篇 |
2019年 | 1106篇 |
2018年 | 1597篇 |
2017年 | 1690篇 |
2016年 | 2157篇 |
2015年 | 1030篇 |
2014年 | 1725篇 |
2013年 | 3279篇 |
2012年 | 2908篇 |
2011年 | 3286篇 |
2010年 | 2643篇 |
2009年 | 2641篇 |
2008年 | 3006篇 |
2007年 | 2882篇 |
2006年 | 2776篇 |
2005年 | 2444篇 |
2004年 | 2248篇 |
2003年 | 2077篇 |
2002年 | 2138篇 |
2001年 | 2234篇 |
2000年 | 1630篇 |
1999年 | 1256篇 |
1998年 | 1127篇 |
1997年 | 1037篇 |
1996年 | 896篇 |
1995年 | 833篇 |
1994年 | 813篇 |
1993年 | 814篇 |
1992年 | 865篇 |
1991年 | 935篇 |
1990年 | 880篇 |
1989年 | 905篇 |
1988年 | 816篇 |
1987年 | 768篇 |
1986年 | 740篇 |
1985年 | 867篇 |
1984年 | 966篇 |
1983年 | 819篇 |
1982年 | 836篇 |
1981年 | 749篇 |
1980年 | 704篇 |
1979年 | 773篇 |
1978年 | 895篇 |
1977年 | 914篇 |
1976年 | 812篇 |
1975年 | 779篇 |
1974年 | 792篇 |
1973年 | 763篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
134.
Modification of Paving Asphalts with Sulfur 总被引:2,自引:0,他引:2
Syroezhko A. M. Begak O. Yu. Fedorov V. V. Gusarova E. N. 《Russian Journal of Applied Chemistry》2003,76(3):491-496
Sulfur dissolved in oil components of asphalt is a binder, filler, and chemical co-reagent at once. The structure of sulfur-extended asphalt depends on its formula and heating temperature. Road pavement based on sulfur-extended asphalt demonstrates higher durability as compared to that with the conventional binders. 相似文献
135.
C Guéret N Jussien O Lhomme C Pavageau C Prins 《The Journal of the Operational Research Society》2003,54(5):458-465
In this paper, we describe an aircraft loading problem submitted by the French military agency (DGA) as part of a more general military airlift planning problem. It can be viewed as a kind of bi-dimensional bin-packing problem, with heterogeneous bins and several additional constraints. We introduce two-phase methods for solving this NP-hard problem. The first phase consists in building good initial solutions, thanks to two fast algorithms: a list-based heuristic and a loading pattern generation method. Both algorithms call a constraint-based subroutine, able to determine quickly if the items already loaded can be reshuffled to accommodate a new object. The second phase improves these preliminary solutions using local search techniques. Results obtained on real data sets are presented. 相似文献
136.
Amplitude equations, as well as the effective dispersion and nonlinearity parameters, which define the dynamics of a wave
packet formed by two strongly coupled modes, are derived with allowance for the frequency dependence of the linear mode coupling
coefficient. These equations are used to study the onset of the modulation instability of the two-mode wave packet, soliton-like
pulses, and compression modes. Unlike single-mode systems, the last two effects in optical waveguides may arise for both a
negative and positive disper-sion of the waveguide material. 相似文献
137.
O. V. Sizova E. P. Sokolova V. I. Baranovskii D. A. Rozmanov O. A. Tomashenko 《Journal of Structural Chemistry》2004,45(5):762-770
Ab initio MP2 calculations with several basis sets proved the existence of a stable benzonitrile dimer with a planar structure and a short contact between the H atom of one molecule and the N atom of another. The structure is greatly stabilized by attraction between the neighboring oppositely directed dipoles and donor-acceptor interaction between the orbital of the lone electron pair of the N′ atom and the vacant antibonding orbital localized on the C-H bond.Original Russian Text Copyright © 2004 by O. V. Sizova, E. P. Sokolova, V. I. Baranovskii, D. A. Rozmanov, and O. A. Tomashenko__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 807–815, September–October, 2004. 相似文献
138.
O. A. Mulyar 《Journal of Mathematical Sciences》2005,130(3):4735-4746
In the paper we describe automorphisms and derivations of simple Lie algebras of family R. The Lie algebra of the automorphism group is found. Bibliography: 11 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 305, 2003, pp. 165–186. 相似文献
139.
V. Z. Kasimov O. V. Ushakova Yu. P. Khomenko 《Journal of Applied Mechanics and Technical Physics》2003,44(5):612-619
An improved procedure for modeling the operation of a light-gas gun is proposed. The motion of working bodies in both the firing chamber and the light-gas chamber is studied within the framework of the mechanics of heterogeneous media. The problem of barrel heating taking into account its melting and removal of thermal ablation products into the medium inside the bore is solved in a coupled formulation. Heat and mass transfer and friction on the barrel surface are calculated using empirical dependences. The deformable piston is considered compressible and elastoviscoplastic. Allowance is made for the presence of a clearance between the lateral surface of the piston and the barrel bore walls and the associated gas flow between the firing and the light-gas chamber. Calculation results are given. 相似文献
140.
It is shown that the three-dimensional Navier-Stokes equation for incompressible fluid can be represented as an equation including
only quaternions as co-ordinate operators and variables. Only the quaternion operations such as a quaternion product and a
quaternion conjugation over these variables are used. 相似文献