全文获取类型
收费全文 | 412919篇 |
免费 | 4955篇 |
国内免费 | 2063篇 |
专业分类
化学 | 218352篇 |
晶体学 | 6584篇 |
力学 | 18254篇 |
综合类 | 61篇 |
数学 | 47589篇 |
物理学 | 129097篇 |
出版年
2020年 | 3279篇 |
2019年 | 3613篇 |
2018年 | 4772篇 |
2017年 | 4733篇 |
2016年 | 6946篇 |
2015年 | 4471篇 |
2014年 | 6884篇 |
2013年 | 17539篇 |
2012年 | 13870篇 |
2011年 | 17095篇 |
2010年 | 12085篇 |
2009年 | 11942篇 |
2008年 | 15832篇 |
2007年 | 15972篇 |
2006年 | 15082篇 |
2005年 | 13705篇 |
2004年 | 12459篇 |
2003年 | 10989篇 |
2002年 | 10913篇 |
2001年 | 12272篇 |
2000年 | 9373篇 |
1999年 | 7114篇 |
1998年 | 6029篇 |
1997年 | 5919篇 |
1996年 | 5773篇 |
1995年 | 5151篇 |
1994年 | 5168篇 |
1993年 | 5122篇 |
1992年 | 5458篇 |
1991年 | 5630篇 |
1990年 | 5272篇 |
1989年 | 5150篇 |
1988年 | 5109篇 |
1987年 | 4969篇 |
1986年 | 4814篇 |
1985年 | 6493篇 |
1984年 | 6695篇 |
1983年 | 5575篇 |
1982年 | 5884篇 |
1981年 | 5676篇 |
1980年 | 5305篇 |
1979年 | 5639篇 |
1978年 | 5886篇 |
1977年 | 5838篇 |
1976年 | 5903篇 |
1975年 | 5398篇 |
1974年 | 5558篇 |
1973年 | 5624篇 |
1972年 | 4160篇 |
1971年 | 3394篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A. V. Ivanchenko S. A. Gromilov S. M. Zemskova I. A. Baidina L. A. Glinskaya 《Foundations of Physics Letters》2002,15(1):554-558
A new mixed-ligand complex, Cd(S2CN(C4H9)2)2Phen, is synthesized and investigated by thermal, element, and IR analyses and by diffractometry of polycrystals (DRON-3M, CuKα radiation, Ni filter). The crystal structure was determined on a CAD-4 Enraf-Nonius automatic diffractometer (MoKα radiation, θ from 1.5 to 25?, 2325 nonzero independent reflections, 190 refined parameters, R = 0.036 for I > 2Σ(I)). Crystal data for C30H44CdN4S4 : a = 15.592(3), b = 22.724(5), c = 9.922(2) å, space group Pbcn, V = 3515.5(12) å3, Z = 4, M = 701.33, dcalc = 1.325 g/cm3. The structure involves monomeric molecules in which the cadmium atom has a distorted octahedral environment. 相似文献
992.
This report focuses on a theoretical study of the cobalt-cabon bond activation mechanism in Vitamin B12, its co enzyme complexes, and model compounds such as cobalamins (Cbl), cobaloximes and cobalt porphyrins. In particular, emphasis is placed on the nucleotide loop and its role in the base on and base off mechanism. 相似文献
993.
Laser driven shocks can lead to a dynamic failure, called film spallation. Here, we use a modified laser spallation set-up
to measure the dynamic adhesion of thin films and we propose a novel diagnostic technology. Based on correlation theory, new
spallation criteria for characterizing the progressive damage at the interface between the film and the substrate are established,
such as interface delamination, film spallation and film expulsion. With the help of the theory, the degree of damage and
the dimension of damage (i.e. fracture), such as the minimum width of delamination radius, the thickness of the film etc.,
are estimated. Experiments are carried out on epoxy/stainless steel and epoxy/Al, and the experimental results show that their
dynamic bonding strengths are about 25 MPa and 20 MPa, respectively. The detailed results, analyses and discussions are presented
in this paper.
Received: 6 February 2001 / Accepted: 3 December 2001 / Published online: 11 February 2002 相似文献
994.
C.-S. Huang T. Li L. Wei Q.-S. Yan 《The European Physical Journal C - Particles and Fields》2002,23(1):195-199
It is shown that new sources of CP violation can be generated in models with more than one extra dimension. In the supersymmetric models on the space-time , where the radius moduli have auxiliary vacuum expectation values and the supersymmetry breaking is mediated by the Kaluza–Klein
states of the gauge supermultiplets, we analyze the gaugino masses and trilinear couplings for two scenarios and obtain the
result that there exist relative CP violating phases among the gaugino masses and trilinear couplings.
Received: 10 October 2001 / Published online: 20 December 2001 相似文献
995.
L. I. Kurkina 《Physics of the Solid State》2002,44(1):176-180
This paper reports on a study of the excitation and ionization of small sodium clusters by femtosecond light pulses with a maximum intensity of 5×1012–1×1014 W/cm2 and photon energy from 1 to 3 eV made in terms of the density functional theory and jellium model through direct numerical solution of the Kohn-Sham time-dependent equation. The dependence of the degree of ionization on the intensity, duration, and frequency of the light pulses, as well as on the cluster size, is studied. The efficiency of the processes is shown to be determined primarily by the field intensity rather than by the total pulse energy. 相似文献
996.
The Fokker–Planck-type kinetic equation is constructed with the help of the evolution equation for the transverse energy of channelized particles, which in its turn is derived beyond the framework of perturbation theory proceeding from the condition of nonconcervation of the adiabatic invariant. 相似文献
997.
We study the propagation of the light mesons σ,ω,ρ, and a0(980) in dense hadronic matter in an extended derivative scalar coupling model. Within the scheme proposed it is possible
to unambiguously define effective density-dependent couplings at the Lagrangian level. We first apply the model to study asymmetric
nuclear matter with fixed isospin asymmetry, and then we pay particular attention to hypermatter in β-equilibrium. The equation
of state and the potential contribution to the symmetry coefficient arising from the mean-field approximation are investigated.
Received: 16 October 2001 / Accepted: 10 January 2002 相似文献
998.
The maximum likely and optimal (Bayesian) algorithms for detecting an arbitrary-shaped signal observed against the background of Gaussian white noise and for measuring the duration are synthesized. Exact expressions for the characteristics of the maximum likely algorithms are found. The characteristics of the Bayesian algorithms are obtained using computer simulations. 相似文献
999.
1000.
Eremenko L. T. Oreshko G. V. Nesterenko D. A. Lagodzinskaya G. V. Eremenko I. L. 《Russian Chemical Bulletin》2002,51(1):157-159
The reactions of ethylene glycol mononitrate and glycerol 1,3-dinitrate with methylphosphonic dichloride afforded new nitroxyalkyl methylphosphonates. 相似文献