全文获取类型
收费全文 | 540908篇 |
免费 | 7160篇 |
国内免费 | 2374篇 |
专业分类
化学 | 292347篇 |
晶体学 | 8048篇 |
力学 | 23717篇 |
综合类 | 63篇 |
数学 | 62192篇 |
物理学 | 164075篇 |
出版年
2021年 | 4721篇 |
2020年 | 5258篇 |
2019年 | 5622篇 |
2018年 | 7144篇 |
2017年 | 7039篇 |
2016年 | 10804篇 |
2015年 | 6998篇 |
2014年 | 10539篇 |
2013年 | 25013篇 |
2012年 | 19548篇 |
2011年 | 23728篇 |
2010年 | 16694篇 |
2009年 | 16614篇 |
2008年 | 21782篇 |
2007年 | 21457篇 |
2006年 | 20151篇 |
2005年 | 18026篇 |
2004年 | 16633篇 |
2003年 | 14786篇 |
2002年 | 14566篇 |
2001年 | 16869篇 |
2000年 | 12641篇 |
1999年 | 9945篇 |
1998年 | 8071篇 |
1997年 | 7875篇 |
1996年 | 7617篇 |
1995年 | 6866篇 |
1994年 | 6762篇 |
1993年 | 6399篇 |
1992年 | 7303篇 |
1991年 | 7468篇 |
1990年 | 7114篇 |
1989年 | 6899篇 |
1988年 | 6910篇 |
1987年 | 6766篇 |
1986年 | 6319篇 |
1985年 | 8172篇 |
1984年 | 8338篇 |
1983年 | 6609篇 |
1982年 | 6725篇 |
1981年 | 6571篇 |
1980年 | 6175篇 |
1979年 | 6782篇 |
1978年 | 6994篇 |
1977年 | 6858篇 |
1976年 | 6755篇 |
1975年 | 6214篇 |
1974年 | 6222篇 |
1973年 | 6287篇 |
1972年 | 4379篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
111.
In this paper, we show that in some cases, no proper covering of a locally compact group topologically generated by left translations
of a topological loop can occur as the group topologically generated by left translations of a topological loop.
__________
Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 22, Algebra
and Geometry, 2004. 相似文献
112.
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
113.
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
114.
115.
In this paper we suggest a unique model for estimating the operating cost of each of three waste-collection systems. Under the traditional system, which is widely used, waste is typically collected in plastic bags and a three-man crew is needed on each vehicle. The other two systems require a one-man crew for vehicle collecting street containers. The side-loader system with fixed body automatically empties street containers into the vehicle body and empties the load at the disposal site. The side-loader system with demountable body allows the separation of the waste collection phase from transport to the disposal site, since the vehicle body can be demounted. We also present two case studies and show how the estimation of operating costs is a critical issue in decisions regarding the type of system to be used for waste collection. 相似文献
116.
In this paper necessary and sufficient conditions of null-controllability and approximate null-controllability are obtained for the wave equation on a half-axis. Controls solving these problems are found explicitly. Moreover, bang-bang controls solving the approximate null-controllability problem are constructed with the aid of solutions of a frequency extinguishing problem in the restricted band (−a,a) for this equation and the Markov power moment problem. 相似文献
117.
Let (\gnm)n,m ? \Zst(\gnm)_{n,m\in\Zst} be a Gabor frame for \LtR\LtR for given window gg. We show that the window \ho = \SQI g\ho=\SQI g that generates the canonically associated tight Gabor frame minimizes ||g-h||\|g-h\| among all windows hh generating a normalized tight Gabor frame. We present and prove versions of this result in the time domain, the frequency domain, the time-frequency domain, and the Zak transform domain, where in each domain the canonical \ho\ho is expressed using functional calculus for Gabor frame operators. Furthermore, we derive a Wiener--Levy type theorem for rationally oversampled Gabor frames. Finally, a Newton-type method for a fast numerical calculation of \ho\ho is presented. We analyze the convergence behavior of this method and demonstrate the efficiency of the proposed algorithm by some numerical examples. 相似文献
118.
Monte Carlo simulation within the grand canonical ensemble, the histogram reweighting technique, and finite size scaling analysis are used to explore the phase behaviour of heteronuclear dimers, composed of A and B type atoms, on a square lattice. We have found that for the models with attractive BB and AB nearest-neighbour energy, uBB=uAB=−1, and for non-repulsive energy between AA nearest-neighbour sites, uAA<0, the system belongs to the universality class of the two-dimensional Ising model. However, when uAA>0, the system exhibits a non-universal critical behaviour. We have evaluated the dependences of the critical point characteristics on the value of uAA. 相似文献
119.
120.
A. M. Zheltikov 《Optics and Spectroscopy》2002,93(2):286-290
A harmonic oscillator model is used to demonstrate the possibility of coherent control of acoustic vibrations of metal nanoparticles and thin films with sequences of femtosecond laser pulses. When the interval between the pulses in such a sequence is chosen equal to the oscillation period of the expansion mode of a nanoscale system, the relevant acoustic vibrations can be excited in a resonant and selective way. Sequences of femtosecond pulses with picosecond time intervals between the pulses are shown to be ideally suited for a resonant excitation and coherent control of acoustic modes of silver nanoparticles. 相似文献