全文获取类型
收费全文 | 336212篇 |
免费 | 3675篇 |
国内免费 | 934篇 |
专业分类
化学 | 168845篇 |
晶体学 | 5528篇 |
力学 | 15678篇 |
综合类 | 7篇 |
数学 | 39773篇 |
物理学 | 110990篇 |
出版年
2021年 | 3195篇 |
2020年 | 3439篇 |
2019年 | 3918篇 |
2018年 | 5368篇 |
2017年 | 5635篇 |
2016年 | 7742篇 |
2015年 | 4414篇 |
2014年 | 7373篇 |
2013年 | 16514篇 |
2012年 | 12739篇 |
2011年 | 15212篇 |
2010年 | 11312篇 |
2009年 | 11160篇 |
2008年 | 13644篇 |
2007年 | 13528篇 |
2006年 | 12436篇 |
2005年 | 10742篇 |
2004年 | 10025篇 |
2003年 | 8830篇 |
2002年 | 8799篇 |
2001年 | 10482篇 |
2000年 | 7740篇 |
1999年 | 6022篇 |
1998年 | 5039篇 |
1997年 | 4854篇 |
1996年 | 4530篇 |
1995年 | 3916篇 |
1994年 | 3855篇 |
1993年 | 3724篇 |
1992年 | 4129篇 |
1991年 | 4353篇 |
1990年 | 4131篇 |
1989年 | 4054篇 |
1988年 | 3827篇 |
1987年 | 3957篇 |
1986年 | 3726篇 |
1985年 | 4725篇 |
1984年 | 4770篇 |
1983年 | 3940篇 |
1982年 | 4024篇 |
1981年 | 3753篇 |
1980年 | 3704篇 |
1979年 | 3960篇 |
1978年 | 3932篇 |
1977年 | 3935篇 |
1976年 | 3915篇 |
1975年 | 3705篇 |
1974年 | 3638篇 |
1973年 | 3675篇 |
1972年 | 2615篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
D. Fong J. H. Hamilton A. V. Ramayya J. K. Hwang C. Goodin K. Li J. Kormicki J. O. Rasmussen Y. X. Luo S. C. Wu I. Y. Lee A. V. Daniel G. M. Ter-Akopian G. S. Popeko A. S. Fomichev A. M. Rodin Yu. Ts. Oganessian M. Jandel J. Kliman L. Krupa J. D. Cole M. A. Stoyer R. Donangelo W. C. Ma 《Physics of Atomic Nuclei》2006,69(7):1161-1167
The hot bimodal fission of 252Cf is reexamined with new high-statistics data. We constructed a γ-γ-γ coincidence cube for binary fission and LCP-gated γ-γ matrix for ternary fission. By identifying the secondary fission fragments from their γ-ray transitions, we measured the yields for various fission splits. The normal neutron yield distribution is found to be
Gaussian for Xe-Ru. However, the binary fission split of Ba-Mo is found to exhibit a bimodal neutron distribution with the
“hot mode” corresponding to ≈3.1% of the total yield. In α ternary fission, the first measurements of yields for specific fission splits are presented. The Te-α-Ru and Xe-α-Mo neutron yields fit well with a single mode, but the Ba-α-Zr split shows evidence for an enhanced hot mode with an intensity of ≈13.8% of the normal mode.
The text was submitted by the authors in English. 相似文献
992.
993.
A. Yu. Shvykin V. V. Platonov V. A. Proskuryakov K. B. Chilachava S. I. Podshibyakin 《Russian Journal of Applied Chemistry》2006,79(10):1576-1580
A method of synthesis of acetylacetonated humin-like compounds was developed. The effect of modification on the sorption capacity of humin-like compounds with respect to heavy metals was studied. 相似文献
994.
995.
G. Hanna T. Glatzel S. Sadewasser N. Ott H.P. Strunk U. Rau J.H. Werner 《Applied Physics A: Materials Science & Processing》2006,82(1):1-7
The influence of different film textures on the electronic properties of polycrystalline Cu(In,Ga)Se2 absorbers is studied by measuring the laterally resolved optoelectronic properties of differently textured Cu(In,Ga)Se2 films with Kelvin probe force microscopy and cathodoluminescence. The grain boundaries in (112)- and (220/204)-textured films behave differently. The work-function profile measured with the Kelvin probe across a grain boundary in (112)-textured films shows a dip indicating positive charges at the grain boundaries. In panchromatic cathodoluminescence mappings in a transmission electron microscope, such grain boundaries appear dark, i.e. the strongly reduced luminescence indicates that the grain boundaries represent strong non-radiative recombination centers. In contrast, grain boundaries in (220/204)-textured films give rise to a dip or a step in the work function indicating slightly negative charge or neutrality. Cathodoluminescence is reduced at such grain boundaries, but less dramatically than in the (112)-textured case. However, when Na is present in the (220/204)-textured films, the grain boundaries are almost invisible in cathodoluminescence mappings. This strong passivating action of Na occurs only in the (220/204)-textured films, due to a particular grain-boundary population. In (112)-textured films and films without pronounced texture, this passivation effect is much less noticeable. PACS 73.50.Gr; 73.61.Ga; 78.60.Hk; 87.64.Dt 相似文献
996.
997.
Yu. D. Perfiliev V. S. Rusakov L. A. Kulikov A. A. Kamnev K. Alkhatib 《Hyperfine Interactions》2006,167(1-3):881-885
To explain line broadening in emission Mössbauer spectra as compared to the corresponding absorber measurements, the model of trapped electrons has been proposed. Auger electrons (emitted, e.g. after electron capture by 57Co or after the converted isomeric transition of 119mSn), as well as secondary electrons, may be trapped in the proximity to the nucleogenic ion. Electrons captured by lattice traps at different distances from the daughter ion induce an asymmetric distribution of quadrupole splitting in the resulting emission spectra, as shown in a few examples. This model is supported by estimates of quadrupole splitting values which may be caused by such trapped electrons located at specified distances from the nucleogenic atom. 相似文献
998.
The major goal of this paper is to examine the hypothesis that stock returns and return volatility are asymmetric, threshold nonlinear, functions of change in trading volume. A minor goal is to examine whether return spillover effects also display such asymmetry. Employing a double-threshold GARCH model with trading volume as a threshold variable, we find strong evidence supporting this hypothesis in five international market return series. Asymmetric causality tests lend further support to our trading volume threshold model and conclusions. Specifically, an increase in volume is positively associated, while decreasing volume is negatively associated, with the major price index in four of the five markets. The volatility of each series also displays an asymmetric reaction, four of the markets display higher volatility following increases in trading volume. Using posterior odds ratio, the proposed threshold model is strongly favored in three of the five markets, compared to a US news double threshold GARCH model and a symmetric GARCH model. We also find significant nonlinear asymmetric return spillover effects from the US market. 相似文献
999.
A Monte Carlo simulation method is used to study thermal desorption of gas molecules from mixed adlayers containing two species. The effects of lateral interactions among adatoms and initial surface coverage on the desorption spectra are examined. It is shown that attractive lateral interactions lead to sharper peaks and that desorption occurs at high temperatures, whereas repulsive interactions lead to multiple peak spectra. It is found that interactions between unlike molecules affect the spectra for species with lower desorption energy only, and that the two species desorb together only in certain cases. Lateral interactions also affect the desorption kinetics significantly and very different behavior for the two species may be obtained. 相似文献
1000.
S. F. Karpenko 《Ukrainian Mathematical Journal》1989,41(4):487-492
Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 41, No. 4, pp. 559–565, April, 1989. 相似文献