全文获取类型
收费全文 | 28542篇 |
免费 | 84篇 |
国内免费 | 274篇 |
专业分类
化学 | 10270篇 |
晶体学 | 260篇 |
力学 | 1383篇 |
综合类 | 12篇 |
数学 | 8918篇 |
物理学 | 8057篇 |
出版年
2021年 | 29篇 |
2020年 | 25篇 |
2018年 | 1197篇 |
2017年 | 1452篇 |
2016年 | 712篇 |
2015年 | 551篇 |
2014年 | 462篇 |
2013年 | 646篇 |
2012年 | 3102篇 |
2011年 | 2281篇 |
2010年 | 1785篇 |
2009年 | 1533篇 |
2008年 | 526篇 |
2007年 | 575篇 |
2006年 | 574篇 |
2005年 | 4408篇 |
2004年 | 3889篇 |
2003年 | 2280篇 |
2002年 | 464篇 |
2001年 | 278篇 |
2000年 | 85篇 |
1999年 | 167篇 |
1998年 | 107篇 |
1997年 | 65篇 |
1996年 | 41篇 |
1995年 | 39篇 |
1994年 | 41篇 |
1992年 | 168篇 |
1991年 | 152篇 |
1990年 | 134篇 |
1989年 | 107篇 |
1988年 | 98篇 |
1987年 | 56篇 |
1986年 | 41篇 |
1985年 | 36篇 |
1984年 | 28篇 |
1983年 | 26篇 |
1979年 | 29篇 |
1976年 | 79篇 |
1975年 | 37篇 |
1974年 | 40篇 |
1973年 | 48篇 |
1972年 | 39篇 |
1971年 | 25篇 |
1970年 | 34篇 |
1969年 | 37篇 |
1968年 | 35篇 |
1967年 | 30篇 |
1966年 | 37篇 |
1923年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
No Heading We show that the Dirac-von Neumann formalism for quantum mechanics can be obtained as an approximation of classical statistical
field theory. This approximation is based on the Taylor expansion (up to terms of the second order) of classical physical
variables – maps f : Ω → R, where Ω is the infinite-dimensional Hilbert space. The space of classical statistical states consists of Gaussian measures
ρ on Ω having zero mean value and dispersion σ2(ρ) ≈ h. This viewpoint to the conventional quantum formalism gives the possibility to create generalized quantum formalisms based
on expansions of classical physical variables in the Taylor series up to terms of nth order and considering statistical states ρ having dispersion σ2(ρ) = hn (for n = 2 we obtain the conventional quantum formalism). 相似文献
992.
I.?Weymann J.?Barna?Email author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(2):289-299
Spin-dependent electronic transport through a quantum
dot has been analyzed theoretically in the cotunneling regime by
means of the second-order perturbation theory. The system is
described by the impurity Anderson Hamiltonian with arbitrary
Coulomb correlation parameter U. It is assumed that the dot
level is intrinsically spin-split due to an effective molecular
field exerted by a magnetic substrate. The dot is coupled to two
ferromagnetic leads whose magnetic moments are noncollinear. The
angular dependence of electric current, tunnel magnetoresistance,
and differential conductance are presented and discussed. The
evolution of a cotunneling gap with the angle between magnetic
moments and with the splitting of the dot level is also
demonstrated. 相似文献
993.
We introduce a Selberg type zeta function of two variables which interpolates several higher Selberg zeta functions. The analytic continuation, the functional equation and the determinant expression of this function via the Laplacian on a Riemann surface are obtained.Mathematics Subject Classifications (2000). Primary 11M36, Secondary 33B15 相似文献
994.
Several situations, in which an empty wave causes an observable effect, are reviewed. They include an experiment showing surrealistic trajectories proposed by Englert et al. and protective measurement of the density of the quantum state. Conditions for observable effects due to empty waves are derived. The possibility (in spite of the existence of these examples) of minimalistic interpretation of Bohmian quantum mechanics in which only Bohmian positions supervene on our experience is discussed. 相似文献
995.
Asymptotic properties of electromagnetic waves are studied within the context of Friedmann–Robertson–Walker (FRW) cosmology. Electromagnetic fields are considered as small perturbations on the background spacetime and Maxwells equations are solved for all three cases of flat, closed and open FRW universes. The asymptotic character of these solutions is investigated and their relevance to the problem of cosmological tails of electromagnetic waves is discussed. 相似文献
996.
For a finite dimensional semisimple Lie algebra
and a root q of unity in a field k, we associate to these data a double quiver
. It is shown that a restricted version of the quantized enveloping algebras
is a quotient of the double quiver algebra
.*The author is partially supported by the National Science Foundation of China (Grant. 10271014) and Natural Science Foundation of Beijing City (grant. 1042001) 相似文献
997.
998.
Linfeng?YangEmail author Jiangwei?Chen Huatong?Yang Jinming?Dong 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,43(3):399-403
We have calculated the quantum conductance of single-walled
carbon nanotube (SWNT) waveguide by using a tight binding-based
Greens function approach. Our calculations show that the slow
conductance oscillations as well as the fast conductance
oscillations are manifestations of the intrinsic quantum
interference properties of the conducting SWNTs, being independent
of the defect and disorder of the SWNTs. And zigzag type tubes do
not show the slow oscillations. The SWNT electron waveguide is
also found to have distinctly different transport behavior
depending on whether or not the length of the tube is commensurate
with a (3N+1) rule, with N the number of basic carbon repeat
units along the nanotube length. 相似文献
999.
Bo?Feng Sarada?Bulchand Emre?Yaksi Rainer?W?Friedrich Suresh?JesuthasanEmail author 《BMC neuroscience》2005,6(1):46
Background
Rag1 (Recombination activation gene-1) mediates genomic rearrangement and is essential for adaptive immunity in vertebrates. This gene is also expressed in the olfactory epithelium, but its function there is unknown. 相似文献1000.