全文获取类型
收费全文 | 5824篇 |
免费 | 894篇 |
国内免费 | 435篇 |
专业分类
化学 | 1067篇 |
晶体学 | 39篇 |
力学 | 1376篇 |
综合类 | 77篇 |
数学 | 1383篇 |
物理学 | 3211篇 |
出版年
2024年 | 12篇 |
2023年 | 67篇 |
2022年 | 104篇 |
2021年 | 123篇 |
2020年 | 168篇 |
2019年 | 178篇 |
2018年 | 165篇 |
2017年 | 202篇 |
2016年 | 195篇 |
2015年 | 186篇 |
2014年 | 286篇 |
2013年 | 451篇 |
2012年 | 322篇 |
2011年 | 338篇 |
2010年 | 246篇 |
2009年 | 333篇 |
2008年 | 278篇 |
2007年 | 288篇 |
2006年 | 324篇 |
2005年 | 293篇 |
2004年 | 268篇 |
2003年 | 252篇 |
2002年 | 236篇 |
2001年 | 206篇 |
2000年 | 188篇 |
1999年 | 190篇 |
1998年 | 141篇 |
1997年 | 118篇 |
1996年 | 106篇 |
1995年 | 113篇 |
1994年 | 87篇 |
1993年 | 88篇 |
1992年 | 61篇 |
1991年 | 57篇 |
1990年 | 61篇 |
1989年 | 55篇 |
1988年 | 66篇 |
1987年 | 56篇 |
1986年 | 41篇 |
1985年 | 32篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 29篇 |
1981年 | 21篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 22篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1973年 | 8篇 |
排序方式: 共有7153条查询结果,搜索用时 31 毫秒
61.
Unconventional antiferromagnetic correlations of the doped Haldane gapsystem Y 2 BaNi 1 - x Zn x O 5
V. Villar R. Mélin C. Paulsen J. Souletie E. Janod C. Payen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(1):39-51
We make a new proposal to describe the very low temperature susceptibility of the doped Haldane gap compound Y2BaNi1-xZnxO5. We propose a new mean field model relevant for this compound. The ground state of this mean field model is unconventional
because antiferromagnetism coexists with random dimers. We present new susceptibility experiments at very low temperature.
We obtain a Curie-Weiss susceptibility χ(
T
) ∼
C
/(Θ +
T
) as expected for antiferromagnetic correlations but we do not obtain a direct signature of antiferromagnetic long range order.
We explain how to obtain the “impurity” susceptibility
(
T
) by subtracting the Haldane gap contribution to the total susceptibility. In the temperature range [1 K, 300 K] the experimental
data are well fitted by T
(
T
) =
C
imp
1 +
T
imp
/
T
. In the temperature range [100 mK, 1 K] the experimental data are well fitted by T
(
T
) =
A
ln(
T
/
T
c
), where T
c
increases with x. This fit suggests the existence of a finite Néel temperature which is however too small to be probed directly in our experiments.
We also obtain a maximum in the temperature dependence of the ac-susceptibility
(
T
) which suggests the existence of antiferromagnetic correlations at very low temperature.
Received 17 July 2001 相似文献
62.
本文对垂直低温两相流管底部液氮汽泡的上升速度运用高速摄像机进行了可视化实验研究,对所采集的实时图像进行处理.在Cole和Mendelson汽泡上升速度经验公式的基础上,通过对液氮汽泡的上升速度的分析,提出了圆管管路底部液氮汽泡的上升速度的拟合公式,分析研究其变化规律,为进一步探求圆管内液氮弹状汽泡的生成机理提供依据. 相似文献
63.
P. Kh. Atanasova T. L. Bojadjiev S. N. Dimova 《Computational Mathematics and Mathematical Physics》2006,46(4):666-679
Partial critical dependences of the form current-magnetic field in a two-layered symmetric Josephson junction are modeled. A numerical experiment shows that, for the zero interaction coefficient between the layers of the junction, jumps of the critical currents corresponding to different distributions of the magnetic fluxes in the layers may appear on the critical curves. This fact allows a mathematical interpretation of the results of some recent experimental results for two-layered junctions as a consequence of discontinuities of partial critical curves. 相似文献
64.
We investigate the statistical and dimensional properties of uniform star polymers attached by the branching vertex of degreef in a wedge geometry in three dimensions and described by the wedge angles and. We show that the growth constant is equal to
f
, where is the self-avoiding walk limit. Thef and (, ) dependences of the corresponding critical exponent
f
(, ) are studied using Monte Carlo techniques. In the casef=1, our results are compared with existing predictions obtained from series expansion and renormalization group methods. We have also estimated the amplitudes for the mean square radius of gyration and the mean square end-to-end branch length. Our results for the ratio of the mean square radius of gyration of anf-star to that of a linear polymer of the same degree of polymerization attached in a similar wedge, and the analogous ratio for the mean square end-to-end branch length, are consistent with these ratios being lattice-independent quantities. 相似文献
65.
Domingos H. U. Marchetti 《Journal of statistical physics》1990,61(3-4):909-911
A simple argument is presented by which one can show that the critical inverse temperature
c
of a two-dimensional Coulomb gas (standard or hard-core) with activityz satisfies
, where
in the low-activity limit. Previous results yield
. 相似文献
66.
A model is considered in which the bonds of a lattice are covered by rodlike molecules. Neighboring molecular ends interact with orientation-dependent interactions. The model exhibits closed -loop phase diagrams and double critical points. Exact coexistence surfaces are calculated for the model on the Bethe, honeycomb, and square lattices. The nature of the doubling of the critical exponent near a double critical point is calculated. The behavior of the critical line in the neighborhood of a double critical point is calculated exactly. 相似文献
67.
For an exactly soluble classical spin model with long-range inhomogeneous coupling it is proved that in the absence of external magnetic field the free energy is aC
function of the temperature at the critical point. 相似文献
68.
This paper describes a numerical realization of an extended continuous Newton method defined by Diener. It traces a connected set of locally one-dimensional trajectories which contains all critical points of a smooth functionf:
n
. The results show that the method is effectively applicable.The authors would like to thank L. C. W. Dixon for pointing out some errors in the original version of this paper and for several suggestions of improvements. 相似文献
69.
We derive scaling forms for the thermodynamic and correlation quantities for the turn-weighted fully and partially directed self-avoiding walks on the hypercubic lattices ind2. In the grand canonical (fixed fugacity per step) ensemble, the conformational rod-to-coil transition sets up in the regimew¯N=O(1), wherew is the weight of each 90° turn and¯N is the (fugacity-dependent) average number of steps. Contrary to the conventional critical phenomena wisdom, the scaling functions for the two different walk models, directed and partially directed, become universal only in the limitd. 相似文献
70.
Bruce J. West Raoul Kopelman Katja Lindenberg 《Journal of statistical physics》1989,54(5-6):1429-1439
The conditions for macroscopic segregation ofA andB in a steady-stateA+B 0 reaction are studied in infinite systems. Segregation occurs in one and two dimensions and is marginal ford=3. We note the dependence of these results on the precise experimental conditions assumed in the theory. We also note the difference between these results and our earlier ones for finite systems where the critical dimension isd=2. 相似文献