全文获取类型
收费全文 | 399626篇 |
免费 | 3744篇 |
国内免费 | 1366篇 |
专业分类
化学 | 211863篇 |
晶体学 | 6794篇 |
力学 | 17638篇 |
综合类 | 5篇 |
数学 | 42203篇 |
物理学 | 126233篇 |
出版年
2018年 | 3845篇 |
2017年 | 3719篇 |
2016年 | 5899篇 |
2015年 | 3881篇 |
2014年 | 6088篇 |
2013年 | 16934篇 |
2012年 | 11964篇 |
2011年 | 14885篇 |
2010年 | 10399篇 |
2009年 | 10308篇 |
2008年 | 13655篇 |
2007年 | 13781篇 |
2006年 | 13100篇 |
2005年 | 11866篇 |
2004年 | 10984篇 |
2003年 | 9809篇 |
2002年 | 9588篇 |
2001年 | 11774篇 |
2000年 | 9033篇 |
1999年 | 7108篇 |
1998年 | 5844篇 |
1997年 | 5799篇 |
1996年 | 5588篇 |
1995年 | 5128篇 |
1994年 | 5002篇 |
1993年 | 4964篇 |
1992年 | 5526篇 |
1991年 | 5544篇 |
1990年 | 5311篇 |
1989年 | 5296篇 |
1988年 | 5251篇 |
1987年 | 5167篇 |
1986年 | 4869篇 |
1985年 | 6561篇 |
1984年 | 6780篇 |
1983年 | 5540篇 |
1982年 | 5819篇 |
1981年 | 5727篇 |
1980年 | 5557篇 |
1979年 | 5793篇 |
1978年 | 6134篇 |
1977年 | 5883篇 |
1976年 | 5908篇 |
1975年 | 5500篇 |
1974年 | 5502篇 |
1973年 | 5520篇 |
1972年 | 3774篇 |
1971年 | 3148篇 |
1968年 | 3333篇 |
1967年 | 3347篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A. Bartnik H. Fiedorowicz R. Jarocki L. Juha J. Kostecki R. Rakowski M. Szczurek 《Applied physics. B, Lasers and optics》2006,82(4):529-532
The first results of experiments on direct photo-etching of heated PTFE using a 10 Hz X-ray source based on a laser-irradiated gas puff target are presented. X-ray radiation in the wavelength range from 6 to 20 nm was produced as a result of irradiation of a double-stream gas puff target with Nd:YAG laser pulses of energy 0.8 J and time duration 3 ns. The resulting X-ray pulses with energy of about 100–200 mJ were used to irradiate samples of PTFE to create microstructures by direct photo-etching. Strong enhancement of the photo-etching process was observed for samples heated up to 300 °C. PACS 52.38.Ph; 81.65.Cf; 61.82.Pv 相似文献
992.
Methods for calculating the total and differential cross sections for the production of Ωscb baryons in photon-photon collisions and the results of respective calculations are described. 相似文献
993.
A. I. Burkhanov P. V. Bondarenko S. I. Raevskaya A. V. Shil’nikov I. P. Raevskiĭ 《Physics of the Solid State》2006,48(6):1114-1116
The dielectric properties of a ceramic and a single crystal of the same composition 0.9NaNbO3-0.1Gd1/3NbO3 (NNG10) with different prehistories of the material are investigated in the low-and infralow-frequency ranges. It is revealed that the dielectric aging of the material based on the NaNbO3 antiferroelectric with a smeared phase transition differs in character from similar phenomena observed in relaxor ferroelectrics. 相似文献
994.
995.
996.
Ph. Laurent M. Abgrall Ch. Jentsch P. Lemonde G. Santarelli A. Clairon I. Maksimovic S. Bize Ch. Salomon D. Blonde J.F. Vega O. Grosjean F. Picard M. Saccoccio M. Chaubet N. Ladiette L. Guillet I. Zenone Ch. Delaroche Ch. Sirmain 《Applied physics. B, Lasers and optics》2006,84(4):683-690
In this paper we describe the cold atom clock PHARAO, designed for microgravity operation. All elements of the PHARAO engineering model have been manufactured and delivered to CNES, the French space agency. We present the clock design, its main characteristics, and initial science operation. PHARAO is one of the main components of the Atomic Clock Ensemble in Space payload that is scheduled to fly on board the International Space Station in 2010. PACS 07.87.+v; 06.30.Ft; 95.55.Sh; 32.80.Pj 相似文献
997.
T. Rietmann S. Sohn M. Schröder D. Lipinsky H.F. Arlinghaus 《Applied Surface Science》2006,252(19):6640-6643
In order to improve quantification of high mass ions, the influence of cluster composition on detection efficiencies has been studied using a TOF-SIMS IV with the extended capability of postaccelerating ions up to 20 keV. In this experimental study, we focus on the comparison of detection efficiencies for three types of negatively charged secondary cluster ions: gold-alkanethiolate-clusters (AuxMy), gold-sulfur-clusters (AuxSy) and gold-clusters (Aux). The clusters were sputtered from self-assembled monolayers of hexadecanethiols on gold substrates using 10 keV Ar+ primary ions. The detection efficiencies were derived on the basis of a function for the secondary electron yield and a fourth-order approximated Poisson probability distribution for electron propagation and amplification within the microchannel plate.In addition to the well-known dependence of detection efficiencies on ion mass and energy, which has already been studied for positively charged ions, we were able to show a similar behaviour for the investigated negatively charged secondary ions. We have observed major variations among the three types of clusters at similar mass and energy as predicted in a theoretical approach. The observed differences are due to the different composition of the investigated clusters which has a major influence on the kinetic ion induced electron emission within the microchannel plate. For the first time it was possible to experimentally verify these predictions for detection efficiencies. 相似文献
998.
This paper considers the general synchronization dynamics of coupled Van der Pol–Duffing oscillators. The linear and nonlinear stability analysis on the synchronization process is derived through the Whittaker method and the Floquet theory in addition to the multiple time scales method. A stability map displaying different dynamical states of the system is performed. Numerical simulation is carried out to support and to complement the accuracy of the analytical treatment. 相似文献
999.
Summary A non-destructive method is described for the determination of major and minor constituents in archeological specimens by energy-dispersive X-ray fluorescence. Homogeneity tests are made by measuring at various sites of the specimen. In the same way, mean values are obtained for inhomogeneous specimen without taking samples. For calibration, powder standards are used. In case of the determination of elements with numbers up to 14 (Si) a vacuum chamber is used and the dimensions of the specimens are limited by the dimensions of that vacuum chamber, whereas for the determination of elements from K up to U specimens of any size, form or weight are suitable.
Zerstörungsfreie Analyse von archäologischen Proben mit Hilfe der Energie-dispersiven Röntgenfluorescenzanalyse
Zusammenfassung Eine zerstörungsfreie Methode für die Bestimmung von Haupt- und Nebenbestandteilen in archäologischen Proben mit Hilfe der Energie-dispersiven Röntgenfluorescenzanalyse wird beschrieben. Für Homogenitätstests wird an mehreren Stellen der Probe gemessen. In der gleichen Weise werden für inhomogene Proben Mittelwerte erhalten ohne Probenahme. Für die Eichung werden Pulverstandards verwendet. Im Falle der Bestimmung von Elementen mit Ordnungszahlen bis 14 (Si) wird eine Vakuumkammer eingesetzt, und die Dimensionen der Proben sind durch die Dimensionen dieser Vakuumkammer begrenzt, während für die Bestimmung der Elemente K bis U Proben jeder Größe, jeder Form oder jeden Gewichts verwendbar sind.相似文献
1000.