全文获取类型
收费全文 | 3266篇 |
免费 | 68篇 |
国内免费 | 13篇 |
专业分类
化学 | 1884篇 |
晶体学 | 21篇 |
力学 | 90篇 |
数学 | 521篇 |
物理学 | 831篇 |
出版年
2021年 | 25篇 |
2020年 | 31篇 |
2019年 | 32篇 |
2017年 | 25篇 |
2016年 | 61篇 |
2015年 | 46篇 |
2014年 | 42篇 |
2013年 | 145篇 |
2012年 | 133篇 |
2011年 | 156篇 |
2010年 | 76篇 |
2009年 | 72篇 |
2008年 | 137篇 |
2007年 | 150篇 |
2006年 | 141篇 |
2005年 | 140篇 |
2004年 | 148篇 |
2003年 | 97篇 |
2002年 | 97篇 |
2001年 | 76篇 |
2000年 | 70篇 |
1999年 | 55篇 |
1998年 | 49篇 |
1997年 | 37篇 |
1996年 | 68篇 |
1995年 | 51篇 |
1994年 | 57篇 |
1993年 | 57篇 |
1992年 | 59篇 |
1991年 | 47篇 |
1990年 | 50篇 |
1989年 | 35篇 |
1988年 | 60篇 |
1987年 | 39篇 |
1986年 | 38篇 |
1985年 | 57篇 |
1984年 | 44篇 |
1983年 | 42篇 |
1982年 | 55篇 |
1981年 | 52篇 |
1980年 | 37篇 |
1979年 | 44篇 |
1978年 | 36篇 |
1977年 | 30篇 |
1976年 | 46篇 |
1975年 | 34篇 |
1974年 | 38篇 |
1973年 | 30篇 |
1972年 | 18篇 |
1970年 | 20篇 |
排序方式: 共有3347条查询结果,搜索用时 323 毫秒
1.
D. I. Naiduss W. W. Kiesewetter S. L. Dikanskaja J. Schapiro R. Meurice J. Cartiaux E. F. Posorski G. N. Murthy S. Mihaéloff A. D. Rich J. J. Vollertsen Gh. Ghimicescu G. Kotsis C. T. Townsend J. A. Esty F. C. Baselt R. Dubrisay J. Gascon E. R. Scheggia K. M. Renner E. S. Miller C. A. Mitchell A. G. Sossin und S. E. Spektor 《Fresenius' Journal of Analytical Chemistry》1939,118(1-2):48-51
Ohne Zusammenfassung 相似文献
2.
M. Missous C. Mitchell J. Sly K. T. Lai R. Gupta S. K. Haywood 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):496
Highly strained quantum cascade laser (QCL) and quantum well infrared photodetector (QWIPs) structures based on InxGa(1−x)As−InyAl(1−y)As (x>0.8,y<0.3) layers have been grown by molecular beam epitaxy. Conditions of exact stoichiometric growth were used at a temperature of 420°C to produce structures that are suitable for both emission and detection in the 2–5 μm mid-infrared regime. High structural integrity, as assessed by double crystal X-ray diffraction, room temperature photoluminescence and electrical characteristics were observed. Strong room temperature intersubband absorption in highly tensile strained and strain-compensated In0.84Ga0.16As/AlAs/In0.52Al0.48As double barrier quantum wells grown on InP substrates is demonstrated. Γ–Γ intersubband transitions have been observed across a wide range of the mid-infrared spectrum (2–7 μm) in three structures of differing In0.84Ga0.16As well width (30, 45, and 80 Å). We demonstrate short-wavelength IR, intersubband operation in both detection and emission for application in QC and QWIP structures. By pushing the InGaAs–InAlAs system to its ultimate limit, we have obtained the highest band offsets that are theoretically possible in this system both for the Γ–Γ bands and the Γ–X bands, thereby opening up the way for both high power and high efficiency coupled with short-wavelength operation at room temperature. The versatility of this material system and technique in covering a wide range of the infrared spectrum is thus demonstrated. 相似文献
3.
Chaotic dynamics in open systems produces fractals. This can be seen, for example, in the ionization of an electron from a
hydrogen atom in applied parallel electric and magnetic fields. We summarize some of our recent work on the order that can
be found in these fractals. 相似文献
4.
We obtain Dirac’s classic monopole charge quantization from the point of view of geometric quantization and demonstrate how this leads to the conclusion that the electromagnetic field is a U(1)-gauge field. 相似文献
5.
6.
C. Baumgarten B. Braun G. Court G. Ciullo P. Ferretti G. Graw W. Haeberli M. Henoch R. Hertenberger N. Koch H. Kolster P. Lenisa A. Nass S.P. Pod'yachev D. Reggiani K. Rith M.C. Simani E. Steffens J. Stewart T. Wise 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):37-49
The use of storage cells has become a standard technique for internal gas targets in conjunction with high energy storage
rings. In case of spin-polarized hydrogen and deuterium gas targets the interaction of the injected atoms with the walls of
the storage cell can lead to depolarization and recombination. Thus the number of wall collisions of the atoms in the target
gas is important for modeling the processes of spin relaxation and recombination. It is shown in this article that the diffusion
process of rarefied gases in long tubes or storage cells can be described with the help of the one-dimensional diffusion equation.
Mathematical methods are presented that allow one to calculate collision age distributions (CAD) and their moments analytically.
These methods provide a better understanding of the different aspects of diffusion than Monte Carlo calculations. Additionally
it is shown that measurements of the atomic density or polarization of a gas sample taken from the center of the tube allow
one to determine the possible range of the corresponding density weighted average values along the tube. The calculations
are applied to the storage cell geometry of the HERMES internal polarized hydrogen and deuterium gas target.
Received 9 July 2001 and Received in final form 18 September 2001 相似文献
7.
8.
9.
本文讨论圆形区域内芽虫分布模型,特别研究了芽虫与天敌接触时产生与避免outbreak状态的可能性。 相似文献
10.
A current interpretation of XPS spectra of Ni metal assumes that the main 6 eV satellite is due to a two hole c3d94s2 (c is a core hole) final state effect. We report REELS observation in AES at low voltages of losses (plasmons and inter-band transitions) corresponding to the satellite structures in Ni metal 2p spectra. The satellite near 6 eV is attributed to a predominant surface plasmon loss. A current interpretation of Ni 2p spectra of oxides and other compounds is based on charge transfer assignments of the main peak at 854.6 eV and the broad satellite centred at around 861 eV to the cd9L and the unscreened cd8 final-state configurations, respectively (L is a ligand hole). Multiplet splittings have been shown to be necessary for assignment of Fe 2p and Cr 2p spectral profiles and chemical states. The assignments of Ni 2p states are re-examined with intra-atomic multiplet envelopes applied to Ni(OH)2, NiOOH and NiO spectra. It is shown that the free ion multiplet envelopes for Ni2+ and Ni3+ simulate the main line and satellite structures for Ni(OH)2 and NiOOH. Fitting the NiO Ni 2p spectral profile is not as straightforward as the hydroxide and oxyhydroxide. It may involve contributions from inter-atomic, non-local electronic coupling and screening effects with multiplet structures significantly different from the free ions as found for MnO. A scheme for fitting these spectra using multiplet envelopes is proposed. 相似文献