全文获取类型
收费全文 | 3478篇 |
免费 | 163篇 |
国内免费 | 10篇 |
专业分类
化学 | 2312篇 |
晶体学 | 7篇 |
力学 | 116篇 |
数学 | 611篇 |
物理学 | 605篇 |
出版年
2024年 | 5篇 |
2023年 | 44篇 |
2022年 | 73篇 |
2021年 | 83篇 |
2020年 | 72篇 |
2019年 | 99篇 |
2018年 | 70篇 |
2017年 | 48篇 |
2016年 | 145篇 |
2015年 | 121篇 |
2014年 | 126篇 |
2013年 | 194篇 |
2012年 | 303篇 |
2011年 | 329篇 |
2010年 | 183篇 |
2009年 | 161篇 |
2008年 | 254篇 |
2007年 | 231篇 |
2006年 | 220篇 |
2005年 | 189篇 |
2004年 | 156篇 |
2003年 | 114篇 |
2002年 | 98篇 |
2001年 | 42篇 |
2000年 | 43篇 |
1999年 | 27篇 |
1998年 | 19篇 |
1997年 | 15篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1979年 | 4篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1929年 | 4篇 |
1903年 | 3篇 |
排序方式: 共有3651条查询结果,搜索用时 15 毫秒
71.
72.
Séan J. Cassady Rishav Choudhary Vivek Boddapati Nicolas H. Pinkowski David F. Davidson Ronald K. Hanson 《国际化学动力学杂志》2020,52(11):725-738
The pyrolysis of propane plays an important role in determining the combustion properties of natural gas mixtures and offers insight into the cracking patterns of larger fuels. This work investigates propane pyrolysis behind reflected shock waves with a multiwavelength laser-absorption speciation technique. Nine laser wavelengths, sensitive to key pyrolysis species, were used to measure absorbance time histories during the decomposition of 2% propane in argon between 1022 and 1467 K, 3.7-4.3 atm. Absorbance models were developed at each diagnostic wavelength to interrogate common initial conditions, and time histories of all major species are reported at 1250, 1290, 1330, 1370, and 1410 K. Nearly complete carbon recovery observed at lower temperatures enabled the inference of hydrogen formation from atomic conservation, while decaying carbon recovery at high temperatures suggests the formation of allene and 1-butene. The results show systematically faster pyrolysis than predicted by kinetic modeling and motivate further study into the kinetics of propane pyrolysis. 相似文献
73.
Bertin Karine Klutchnikoff Nicolas Panloup Fabien Varvenne Maylis 《Statistical Inference for Stochastic Processes》2020,23(2):271-300
Statistical Inference for Stochastic Processes - We build and study a data-driven procedure for the estimation of the stationary density f of an additive fractional SDE. To this end, we also prove... 相似文献
74.
The oxygen isotopic exchange technique is a powerful tool to investigate the oxygen transport kinetics in an oxide solid. In a solid oxide fuel cell, isotopic surface exchange and diffusion coefficients are classically determined by using the Isotopic Exchange Depth Profiling method followed by ex situ SIMS characterizations. Despite its relevance, the utilization of in situ or operando techniques to measure the isotopic exchange under an electrical bias remains marginal. We developed here a set-up which enables operando monitoring of oxygen exchange in SOFC type cells under polarization. The system has been used for studying the oxygen mobility dependency upon polarization on a symmetrical Pt/YSZ/Pt cell (YSZ: yttria-stabilized zirconia). Homomolecular and heterolytic exchange reactions were undertaken to investigate the oxygen activation step and discriminate the limiting step among the sequence of elementary steps which constitute the oxygen transport process in the SOFC system. Oxygen ions incorporation into the dense ionic conductor was identified to be the rate determining step, and its first order rate constant dependency on applied potential was established. 相似文献
75.
Nicolas G. Fournier 《Journal of Heuristics》2007,13(6):587-639
A new analytical tool is presented to provide a better understanding of the search space of k-sat. This tool, termed the local value distribution , describes the probability of finding assignments of any value q′ in the neighbourhood of assignments of value q. The local value distribution is then used to define a Markov model to model the dynamics of a corresponding stochastic local
search algorithm for k-sat. The model is evaluated by comparing the predicted algorithm dynamics to experimental results. In most cases the fit of the
model to the experimental results is very good, but limitations are also recognised. 相似文献
76.
Nicolas Zufferey 《Optimization Letters》2012,6(5):963-973
In most ant algorithms, the role of each ant is to build a solution in a constructive way, basing each decision on the greedy
force and the trails. However, different roles are possible for each individual ant, ranging from a negligible help in the
decision process to a refined local search heuristic. In this paper, the importance of the role assigned to each ant is discussed.
Three general ant methodologies are presented. Comparative results are analyzed for the well-known graph coloring problem. 相似文献
77.
Michel Nicolas 《原子核物理评论》2020,37(3):586-594
利用耦合道Gamow壳模型计算了17O和17F的低激发能谱以及16O(p,p)反应的低能弹性散射截面。结果表明,17O和17F中非束缚共振态能级的核子发射宽度的计算需要合理地考虑连续态耦合效应。计算得到的17O和17F的低激发能谱以及16O(p,p)反应的低能弹性散射激发函数都与实验数据吻合较好。这说明基于现实核力的计算可更好地描述16O(p,p)反应的低能弹性散射截面。 相似文献
78.
Stephen?J.?HardimanEmail author Nicolas?Bercot Jean-Philippe?Bouchaud 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(10):442
We model the arrival of mid-price changes in the E-mini S&P futures contract as a self-exciting Hawkes process. Using several estimation methods, we find that the Hawkes kernel is power-law with a decay exponent close to ?1.15 at short times, less than ≈ 103 s, and crosses over to a second power-law regime with a larger decay exponent ≈–1.45 for longer times scales in the range [103 ,106 ] seconds. More importantly, we find that the Hawkes kernel integrates to unity independently of the analysed period, from 1998 to 2011. This suggests that markets are and have always been close to criticality, challenging a recent study which indicates that reflexivity (endogeneity) has increased in recent years as a result of increased automation of trading. However, we note that the scale over which market events are correlated has decreased steadily over time with the emergence of higher frequency trading. 相似文献
79.
Jérémie Boulanger Nicolas Le Bihan Stefan Catheline Vincent Rossetto 《Annals of Physics》2012,327(3):952-958
We report the experimental observation of a geometric phase for elastic waves in a waveguide with helical shape. The setup reproduces the experiment by Tomita and Chiao [A. Tomita, R.Y. Chiao, Phys. Rev. Lett. 57 (1986) 937–940, 2471] that showed first evidence of a Berry phase, a geometric phase for adiabatic time evolution, in optics. Experimental evidence of a non-adiabatic geometric phase has been reported in quantum mechanics. We have performed an experiment to observe the polarization transport of classical elastic waves. In a waveguide, these waves are polarized and dispersive. Whereas the wavelength is of the same order of magnitude as the helix’s radius, no frequency dependent correction is necessary to account for the theoretical prediction. This shows that in this regime, the geometric phase results directly from geometry and not from a correction to an adiabatic phase. 相似文献
80.
In the framework of a nonparametric functional estimation for the drift of a Brownian motion we construct Stein type estimators of the form which are superefficient when is a superharmonic functional on the Wiener space for the Malliavin derivative D. To cite this article: N. Privault, A. Réveillac, C. R. Acad. Sci. Paris, Ser. I 343 (2006). 相似文献