全文获取类型
收费全文 | 2671篇 |
免费 | 71篇 |
国内免费 | 9篇 |
专业分类
化学 | 1734篇 |
晶体学 | 5篇 |
力学 | 41篇 |
数学 | 417篇 |
物理学 | 554篇 |
出版年
2023年 | 19篇 |
2022年 | 39篇 |
2021年 | 70篇 |
2020年 | 62篇 |
2019年 | 73篇 |
2018年 | 71篇 |
2017年 | 41篇 |
2016年 | 90篇 |
2015年 | 58篇 |
2014年 | 92篇 |
2013年 | 122篇 |
2012年 | 152篇 |
2011年 | 165篇 |
2010年 | 98篇 |
2009年 | 106篇 |
2008年 | 112篇 |
2007年 | 106篇 |
2006年 | 98篇 |
2005年 | 98篇 |
2004年 | 71篇 |
2003年 | 63篇 |
2002年 | 65篇 |
2001年 | 24篇 |
2000年 | 26篇 |
1999年 | 37篇 |
1998年 | 20篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 28篇 |
1994年 | 16篇 |
1993年 | 24篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1989年 | 18篇 |
1984年 | 16篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1976年 | 21篇 |
1975年 | 20篇 |
1974年 | 12篇 |
1967年 | 12篇 |
1957年 | 13篇 |
1956年 | 18篇 |
1955年 | 11篇 |
1954年 | 14篇 |
1927年 | 11篇 |
1907年 | 11篇 |
排序方式: 共有2751条查询结果,搜索用时 0 毫秒
51.
Diffusion-limited reactions are studied in detail on the classical coalescing process. We demonstrate how, with the aid of a recent renormalization group approach, fluctuations can be integrated systematically. We thereby obtain an exact relation between the microscopic physics (lattice structure and particle shape and size) and the macroscopic decay rate in the law of mass action. Moreover, we find a strong violation of the law of mass action. The corresponding term in the kinetic equations originates in long-wavelength fluctuations and is a universal function of the macroscopic decay rate. 相似文献
52.
The oxidation of the adsorbed π-allyl (η3-C3H5), prepared on atomic oxygen- and hydroxyl-covered Ag(110) by dissociation of allyl chloride (C3H5Cl), is investigated with temperature-programmed desorption and high-resolution electron energy loss spectroscopy. Allyl chloride adsorbs molecularly on oxygen-covered Ag(110) at 110 K. Upon heating to 180 K, some allyl chloride dissociates to form π-allyl and atomic chlorine, and the remainder desorbs molecularly. The π-allyl undergoes combustion to form hydroxyl or carbonate until all of the free oxygen is consumed by 200 K. Migratory insertion of hydroxyl into excess π-allyl commences near 220 and finishes by 250 K, forming adsorbed allyl alcohol (C3H5OH), which reacts either with excess hydroxyl near 240 K to form allyl alkoxy (η1(O)-C3H5O) and water, or with π-allyl at 250 K to form allyl alkoxy and propylene (C3H6). Th allyl alkoxy evolves acrolein (C3H4O) by β-hydrogen elimination near 285 K, and propylene is evolved concurrently as the hydrogen released by this reaction rapidly scavenges π-allyl. Finally, the remaining π-allyl dimerizes to form 1,5-hexadiene (C6H10), which desorbs at 315 K. The gross observations of reaction pathways and temperatures are used to evaluate important aspects of the thermochemistry of these reactions. 相似文献
53.
Shyjumon Ibrahimkutty Daniel Issenmann Stefan Schleef Anke‐Susanne Müller Yves‐Laurent Mathis Biliana Gasharova Erhart Huttel Ralph Steininger Jörg Göttlicher Tilo Baumbach Albrecht Bartels Christof Janke Anton Plech 《Journal of synchrotron radiation》2011,18(4):539-545
A high‐repetition‐rate pump–probe experiment is presented, based on the asynchronous sampling approach. The low‐α mode at the synchrotron ANKA can be used for a time resolution down to the picosecond limit for the time‐domain sampling of the coherent THz emission as well as for hard X‐ray pump–probe experiments, which probe structural dynamics in the condensed phase. It is shown that a synchronization of better than 1 ps is achieved, and examples of phonon dynamics of semiconductors are presented. 相似文献
54.
K. Büchler K. H. Althoff G. Anton J. Arends W. Beulertz M. Breuer P. Detemple H. Dutz E. Kohlgarth D. Krmer W. Meyer G. Nldeke W. Schneider W. Thiel B. Zucht 《Nuclear Physics A》1994,570(3-4):580-598
The differential cross section of the reaction γp→π+n has been measured with the PHOENICS detector at ELSA in Bonn. For the first time this cross section has been determined simultaneously over a large range of photon energies (Eγ = 220−900 MeV) and pion angles (Θc.m.pi = 35°−135°) with a tagged photon facility. The experimental set-up allowed a considerable kinematic overdetermination of the investigated reaction. Accordingly, the background contributions have been suppressed to below 1%. The measured differential cross section is in good agreement with existing data. The comparison with different model calculations is presented. 相似文献
55.
Elimination of vinyl alcohol from 5‐vinyloxypyrrolines in the presence of superbases (final step of domino 3H‐pyrroles synthesis from ketoximes and acetylene) is studied computationally at different levels of theory in DMSO solution (PCM). The sequences of transformations starting from nucleophilic addition of hydroxide ion to carbon‐carbon or carbon‐nitrogen double bonds are proposed as possible mechanisms. Unusual reactivity of 2,5‐dimethylphenyl substituted 5‐vinyloxypyrroline is explained within these mechanisms. 相似文献
56.
This paper reports on recent progress on angle-resolved desorption leading to structure-sensitive desorption dynamics. The sensitivity is exemplified in NO and N2O reduction on Pd and Rh surfaces. The energy partitioning in the repulsive desorption of hyper-thermal products into their rotational and translational modes is an indispensable concept to examine the structure of a reaction site from desorbing molecules because it connects the structure of a transition state with each energy of desorbed products. The extent of the energy partitioning will be derived from the desorption-angle dependences of both the rotational and translational energies at each vibrational state. Such energy analysis has never been completed for any thermal reactive desorption. A new type of measurement is thus proposed. Additionally, we discuss the inadequate use of the detailed balance principle in desorption dynamics, which has prevented desorption dynamics from being sensitive to surface structures. 相似文献
57.
We consider stimulated pair production employing strong-field QED in a high-intensity laser background. In an infinite plane wave, we show that light-cone quasi-momentum can only be transferred to the created pair as a multiple of the laser frequency, i.e. by a higher harmonic. This translates into discrete resonance conditions providing the support of the pair creation probability which becomes a delta-comb. These findings corroborate the usual interpretation of multi-photon production of pairs with an effective mass. In a pulse, the momentum transfer is continuous, leading to broadening of the resonances and sub-threshold behaviour. The peaks remain visible as long as the number of cycles per pulse exceeds unity. The resonance patterns in pulses are analogous to those of a diffraction process based on interference of the produced pairs. We finally comment on the dependence of the peak positions, and in turn the effective mass, on the pulse shape. 相似文献
58.
59.
60.