全文获取类型
收费全文 | 436833篇 |
免费 | 5599篇 |
国内免费 | 1231篇 |
专业分类
化学 | 235081篇 |
晶体学 | 6496篇 |
力学 | 18772篇 |
综合类 | 13篇 |
数学 | 50021篇 |
物理学 | 133280篇 |
出版年
2021年 | 3832篇 |
2020年 | 4229篇 |
2019年 | 4561篇 |
2018年 | 5885篇 |
2017年 | 5785篇 |
2016年 | 8902篇 |
2015年 | 5620篇 |
2014年 | 8599篇 |
2013年 | 20277篇 |
2012年 | 15727篇 |
2011年 | 19375篇 |
2010年 | 13574篇 |
2009年 | 13417篇 |
2008年 | 17746篇 |
2007年 | 17617篇 |
2006年 | 16299篇 |
2005年 | 14616篇 |
2004年 | 13578篇 |
2003年 | 11929篇 |
2002年 | 11753篇 |
2001年 | 13443篇 |
2000年 | 10100篇 |
1999年 | 7920篇 |
1998年 | 6578篇 |
1997年 | 6327篇 |
1996年 | 6089篇 |
1995年 | 5483篇 |
1994年 | 5400篇 |
1993年 | 5204篇 |
1992年 | 5834篇 |
1991年 | 5929篇 |
1990年 | 5669篇 |
1989年 | 5481篇 |
1988年 | 5503篇 |
1987年 | 5380篇 |
1986年 | 5093篇 |
1985年 | 6564篇 |
1984年 | 6696篇 |
1983年 | 5302篇 |
1982年 | 5389篇 |
1981年 | 5370篇 |
1980年 | 4961篇 |
1979年 | 5359篇 |
1978年 | 5496篇 |
1977年 | 5389篇 |
1976年 | 5330篇 |
1975年 | 4915篇 |
1974年 | 4885篇 |
1973年 | 4883篇 |
1972年 | 3455篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
M.A. Tawhid 《Journal of Optimization Theory and Applications》2002,113(1):149-164
In this paper, we give some sufficient conditions for the local uniqueness of solutions to nonsmooth variational inequalities where the underlying functions are H-differentiable and the underlying set is a closed convex set/polyhedral set/box/polyhedral cone. We show how the solution of a linearized variational inequality is related to the solution of the variational inequality. These results extend/unify various similar results proved for C
1 and locally Lipschitzian variational inequality problems. When specialized to the nonlinear complementarity problem, our results extend/unify those of C
2 and C
1 nonlinear complementarity problems. 相似文献
192.
The semiclassical theory of proximity effects predicts a gap E g~?D/L 2 in the excitation spectrum of a long diffusive superconductor/normal-metal/superconductor (SNS) junction. Mesoscopic fluctuations lead to anomalously localized states in the normal part of the junction.As a result, a nonzero, yet exponentially small, density of states (DOS) appears at energies below E g. In the framework of the supermatrix nonlinear σ model, these prelocalized states are due to the instanton configurations with broken supersymmetry. The exact result for the DOS near the semiclassical threshold is found, provided the dimensionless conductance of the normal part G N is large. The case of poorly transparent interfaces between the normal and superconductive regions is also considered. In this limit, the total number of subgap states may be large. 相似文献
193.
G. Montero L. Gonzlez E. Flrez M. D. García A. Surez 《Numerical Linear Algebra with Applications》2002,9(3):239-247
Parallel preconditioners are presented for the solution of general linear systems of equations. The computation of these preconditioners is achieved by orthogonal projections related to the Frobenius inner product. So, minM∈??∥AM?I∥ F and matrix M0∈?? corresponding to this minimum (?? being any vectorial subspace of ??n(?)) are explicitly computed using accumulative formulae in order to reduce computational cost when subspace ?? is extended to another one containing it. Every step, the computation is carried out taking advantage of the previous one, what considerably reduces the amount of work. These general results are illustrated with the subspace of matrices M such that AM is symmetric. The main application is developed for the subspace of matrices with a given sparsity pattern which may be constructed iteratively by augmenting the set of non‐zero entries in each column. Finally, the effectiveness of the sparse preconditioners is illustrated with some numerical experiments. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
194.
195.
An analysis is made of the conditions of formation and the stability region of static-soliton-type magnetic nonuniformities
in a (001)-crystal plate with combined anisotropy. It is shown that if demagnetizing fields in the plate are taken into account,
static solitons can localize at certain defects for appropriate parameters of the material. The soliton stability region was
found to be bounded by two extreme values of the material parameters, namely, those at which the soliton is unstable against
collapse and at which it expands. It was also found that the soliton stability region differs considerably from that predicted
theoretically in the model disregarding the finite size of the sample and the presence of defects.
Fiz. Tverd. Tela (St. Petersburg) 40, 1498–1502 (August 1998) 相似文献
196.
Experimental data on the effect of thallium and sodium impurities on the lattice heat conductivity of PbTe at room temperature
are reported. Because the lattice of lead chalcogenides is strongly polarized near charged impurities, the effect of impurities
on the lattice heat conductivity depends substantially on their charge state. This property of the material has been used
to determine the charge state of the thallium impurity in PbTe. The results obtained argue for a model of quasi-local thallium-impurity
states which assumes low electron-correlation energy at an impurity center.
Fiz. Tverd. Tela (St. Petersburg) 40, 1206–1208 (July 1998) 相似文献
197.
Jonathan M. Levin Lawrence L. Wald Marc J. Kaufman Marjorie H. Ross Luis C. Maas Perry F. Renshaw 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,130(2):292-295
Residual effects of an initial bolus of gadolinium contrast agent have been previously demonstrated in sequential dynamic susceptibility contrast MR experiments. While these residual effects quickly reach a saturation steady state, their etiology is uncertain, and they can lead to spurious estimates of hemodynamic parameters in activation experiments. The possible influence ofT1effects is now investigated with experiments in whichT1weighting is varied as well as with serial regionalT1measurements. Little evidence for significant residualT1effects is found, suggesting instead that susceptibility effects underlie these observations. An initial saturation dose of contrast agent minimizes this effect. 相似文献
198.
199.
M. Georgelin A. Pocheau 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):169-174
The polycrystalline perovskitelike manganese oxides La1-xAxMnO (A = Na, and K, ) have been fabricated by sol-gel technique. For all the compositions explored in this work, the average manganese oxidation
state is practically constant, at for A = Na, and for A = K, respectively. A close relationship is confirmed to hold between the Curie temperature (Tc) and the bond distance of Mn-O. Results of magnetic measurements show that these materials can be utilized as suitable candidates
for magnetic refrigerants with wide applied temperature span, for their significant entropy change and the easily tuned Curie
temperature.
Received: 12 September 1997 / Revised: 18 December 1997 / Accepted: 21 January 1998 相似文献
200.
P. Seelig A. Dax S. Faber M. Gerlach G. Huber T. Kühl D. Marx P. Merz W. Quint F. Schmitt H. Winter M. Würtz 《Hyperfine Interactions》1998,114(1-4):135-139
The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric
and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in 207Pb81+. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique
using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics
from an ion beam at relativistic velocities.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献