全文获取类型
收费全文 | 756篇 |
免费 | 46篇 |
专业分类
化学 | 448篇 |
晶体学 | 3篇 |
力学 | 24篇 |
数学 | 130篇 |
物理学 | 197篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 14篇 |
2018年 | 21篇 |
2017年 | 8篇 |
2016年 | 55篇 |
2015年 | 37篇 |
2014年 | 45篇 |
2013年 | 92篇 |
2012年 | 38篇 |
2011年 | 40篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 34篇 |
2007年 | 20篇 |
2006年 | 35篇 |
2005年 | 18篇 |
2004年 | 17篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有802条查询结果,搜索用时 31 毫秒
71.
Łukasz Dębowski 《Journal of Theoretical Probability》2014,27(2):539-551
We investigate stationary hidden Markov processes for which mutual information between the past and the future is infinite. It is assumed that the number of observable states is finite and the number of hidden states is countably infinite. Under this assumption, we show that the block mutual information of a hidden Markov process is upper bounded by a power law determined by the tail index of the hidden state distribution. Moreover, we exhibit three examples of processes. The first example, considered previously, is nonergodic and the mutual information between the blocks is bounded by the logarithm of the block length. The second example is also nonergodic but the mutual information between the blocks obeys a power law. The third example obeys the power law and is ergodic. 相似文献
72.
Łukasz Janczewski Małgorzata Walczak Justyna Frączyk Zbigniew J. Kamiński 《合成通讯》2013,43(23):3290-3300
The microwave-assisted Cannizzaro reaction was studied in order to develop fully reproducible synthetic protocols for transformation of aldehydes to carboxylic acid and alcohols. Optimised were the following process parameters: power, temperature, and time. Aromatic, heteroaromatic and aliphatic aldehydes were used in the studies. It was found that furfural, thiophene-2-carbaldehyde, pyridinecarboxaldehyde and aromatic aldehydes react under mild conditions, while 1-methyl-pyrrole-2-carboxaldehyde derivatives and aliphatic aldehydes require more drastic reaction conditions and a longer exposure time to microwave radiation. 相似文献
73.
Sajewicz Mieczysław Wojtal Łukasz Hajnos Michał Waksmundzka-Hajnos Monika Kowalska Teresa 《平面色谱法杂志一现代薄层色谱法》2010,23(4):270-276
JPC – Journal of Planar Chromatography – Modern TLC - In a previous paper we discussed the possibility of fractionating the essential oils of different sage species by low-temperature... 相似文献
74.
In this paper, the numerical modelling of the flow through the low‐pressure steam turbine last stage was presented. On the basis of predicted wet steam flow‐field, the aerodynamic as well as thermodynamic losses were estimated. For calculations of the wet steam steady flow‐field three numerical methods were employed. The first method was a streamline curvature method (SCM). The commercial CFD code (CFX‐TACflow) and an in‐house code, both solving the 3‐D RANS equations, were the next two methods. In the wet steam region, by means of all three methods, the equilibrium flow was modelled. Additionally, the in‐house CFD code was used for modelling of the non‐equilibrium steam condensing flow. In this work, the comparison of the cascade loss coefficient for stator and rotor and selected flow parameters for the stage were presented, compared and discussed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
75.
L. Łukaszuk 《Zeitschrift fur Physik C Particles and Fields》1991,50(1):133-138
We perform summation of ladder diagrams in the high energy, large momentum limit. This leads to new results for both perturbative and non-perturbative approaches. In particular, an explicit expression for any diagram's contribution is given, the non-perturbative form of asymptotically non-analytic terms is found and representation of amplitude as a series of Regge poles is presented.Supported in part by Polish Ministery of National Education, grant no. CPBP 01.03 相似文献
76.
Summary Diffusion of a fractal cluster of dimensiond
f
in a three-dimensional space is investigated. The diffusion process is assumed to be modelled by a standard parabolic diffusion
equation, although a more general case represented by the Fokker-Planck-Kolmogoroff equation is also introduced. The mean-square
displacement of the cluster mass centre is analysed and its anomalous behaviour is presented and critically discussed. The
results obtained can be applied to describe some effects which may occur during the diffusion-limited cluster-cluster aggregation
process, especially when the viscosity of the solvent is changed in time and/or a directed transport of clusters is present
in the system.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
77.
Nuclear resonance studies of the two different types impurity doped potassium hexachloro-stannates, the isomorphic system
such as (K–Rb)2SnCl6 and K2(Sn–Re)Cl6 and the nonisomorphic system K2SnCl6:Al3+ in the high temperature cubic phase revealed contrasting features with one the other characterized by static in the former
and dynamic feature in the latter case respectively. The resonance spectra of the nonisomorphic system indicate additionally
a sign of the local structural transition above the conventional structural phase transition temperature. This seems to be
triggered by the ligand-deficient octahedral defects and can be explained in terms of the enhanced activity of the octahedral
defects for the hindered rotation. 相似文献
78.
79.
80.
Kalska B. Szymański K. Dobrzyński L. SatuŁa D. Wäppling R. Broddefalk A. Nordblad P. 《Hyperfine Interactions》2002,141(1-4):169-173
Properties of amorphous alloy Fe0.66Er0.19B0.15 are reported. A reorientation of the Fe and Er magnetic moments during sample cooling through the compensation point in a
large magnetic field is found by means of monochromatic circularly polarised radiation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献