全文获取类型
收费全文 | 7279篇 |
免费 | 566篇 |
国内免费 | 363篇 |
专业分类
化学 | 4602篇 |
晶体学 | 59篇 |
力学 | 317篇 |
综合类 | 40篇 |
数学 | 994篇 |
物理学 | 2196篇 |
出版年
2023年 | 77篇 |
2022年 | 120篇 |
2021年 | 215篇 |
2020年 | 261篇 |
2019年 | 221篇 |
2018年 | 189篇 |
2017年 | 176篇 |
2016年 | 275篇 |
2015年 | 290篇 |
2014年 | 280篇 |
2013年 | 483篇 |
2012年 | 502篇 |
2011年 | 562篇 |
2010年 | 368篇 |
2009年 | 360篇 |
2008年 | 449篇 |
2007年 | 422篇 |
2006年 | 382篇 |
2005年 | 357篇 |
2004年 | 290篇 |
2003年 | 235篇 |
2002年 | 207篇 |
2001年 | 154篇 |
2000年 | 101篇 |
1999年 | 105篇 |
1998年 | 69篇 |
1997年 | 59篇 |
1996年 | 72篇 |
1995年 | 66篇 |
1994年 | 76篇 |
1993年 | 57篇 |
1992年 | 57篇 |
1991年 | 41篇 |
1990年 | 46篇 |
1989年 | 33篇 |
1988年 | 27篇 |
1987年 | 26篇 |
1986年 | 20篇 |
1985年 | 36篇 |
1984年 | 53篇 |
1983年 | 24篇 |
1982年 | 41篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 42篇 |
1978年 | 29篇 |
1977年 | 20篇 |
1976年 | 26篇 |
1975年 | 17篇 |
1974年 | 23篇 |
排序方式: 共有8208条查询结果,搜索用时 156 毫秒
991.
992.
993.
通过分子动力学方法模拟了Cu-Al合金液相,然后模拟降温过程得到Cu-Al非晶合金.通过计算机编程建立了Cu-Al-M非晶基体、Cu-Al-M非晶表面及吸附O原子Cu-Al-M非晶表面原子结构模型.利用实空间连分数方法,研究了添加微量合金元素Zr,Nb,Ta,V,Y,Sc对Cu基大块非晶合金的腐蚀行为的影响机理.研究发现合金元素Zr,Nb,Ta,V,Sc不向清洁Cu基非晶表面偏聚,但除Y外向有氧吸附的表面偏聚,说明有氧吸附后Cu基非晶表面偏聚发生逆转.键级积分计算表明Zr,Nb,Ta,V,Y,Sc元素均增大与氧之间的结合力,易形成氧化膜,提高Cu基大块非晶的耐蚀性.稀土Y提高Cu基大块非晶的耐蚀性可能是由于它向合金与氧化膜界面偏聚并提高了合金与氧化膜的结合力. 相似文献
994.
995.
996.
997.
A. Celletti S. Di Ruzza C. Lhotka L. Stefanelli 《The European physical journal. Special topics》2010,186(1):33-66
The influence of dissipative effects on classical dynamical models of Celestial Mechanics is of basic importance. We introduce
the reader to the subject, giving classical examples found in the literature, like the standard map, the Hénon map, the logistic
mapping. In the framework of the dissipative standard map, we investigate the existence of periodic orbits as a function of
the parameters. We also provide some techniques to compute the breakdown threshold of quasi-periodic attractors. Next, we
review a simple model of Celestial Mechanics, known as the spin-orbit problem which is closely linked to the dissipative standard
map. In this context we present the conservative and dissipative KAM theorems to prove the existence of quasi-periodic tori
and invariant attractors. We conclude by reviewing some dissipative models of Celestial Mechanics. Among the rotational dynamics
we consider the Yarkovsky and YORP effects; within the three-body problem we introduce the so-called Stokes and Poynting–Robertson
effects. 相似文献
998.
Veronica Zaconte Marco Casolino Luca Di Fino Chiara La Tessa Marianna Larosa Livio Narici Piergiorgio Picozza 《Radiation measurements》2010,45(2):168-172
The ALTEA (Anomalous Long Term Effects on Astronauts) detector was used to characterize the radiation environment inside the USLab of the International Space Station (ISS), where it measured the abundances of ions from Be to Fe. We compare the ALTEA results with Alteino results obtained in the PIRS module of the Russian segment of the ISS, and normalize to the high energy Si abundances given by Simpson. These are the first particle spectral measurements, which include ions up to Fe, performed in the USLab. The small differences observed between those made inside the USLab and the Simpson abundances can be attributed to the transport through the spacecraft hull. However, the low abundance of Fe cannot be attributed to only this process. 相似文献
999.
A. M. Castro Luna A. Bonesi W. E. Triaca A. Di Blasi A. Stassi V. Baglio V. Antonucci A. S. Aricò 《Journal of nanoparticle research》2010,12(1):357-365
Three cathode catalysts (60% Pt/C, 30% Pt/C and 60% Pt–Fe/C), with a particle size of about 2–3 nm, were prepared to investigate
the effect of ethanol cross-over on cathode surfaces. All samples were studied in terms of structure and morphology by using
X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Their electrocatalytic behavior in terms of oxygen
reduction reaction (ORR) was investigated and compared using a rotating disk electrode (RDE). The tolerance of cathode catalysts
in the presence of ethanol was evaluated. The Pt–Fe/C catalyst showed both higher ORR activity and tolerance to ethanol cross-over
than Pt/C catalysts. Moreover, the more promising catalysts were tested in 5 cm2 DEFC single cells at 60 and 80 °C. An improvement in single cell performance was observed in the presence of the Pt–Fe catalyst,
due to an enhancement in the oxygen reduction kinetics. The maximum power density was 53 mW cm−2 at 2 bar rel. cathode pressure and 80 °C. 相似文献
1000.
E. Vardaci A. Di Nitto A. Brondi G. La Rana R. Moro P. N. Nadotchy M. Trotta A. Ordine A. Boiano M. Cinausero E. Fioretto G. Prete V. Rizzi D. Shetty M. Barbui D. Fabris M. Lunardon G. Montagnoli S. Moretto G. Viesti N. Gelli F. Lucarelli G. N. Knyazheva E. M. Kozulin 《The European Physical Journal A - Hadrons and Nuclei》2010,43(2):127-130