全文获取类型
收费全文 | 370605篇 |
免费 | 3226篇 |
国内免费 | 1040篇 |
专业分类
化学 | 199682篇 |
晶体学 | 5810篇 |
力学 | 16196篇 |
综合类 | 13篇 |
数学 | 40620篇 |
物理学 | 112550篇 |
出版年
2018年 | 3657篇 |
2017年 | 3591篇 |
2016年 | 5572篇 |
2015年 | 3528篇 |
2014年 | 5410篇 |
2013年 | 14775篇 |
2012年 | 10980篇 |
2011年 | 13529篇 |
2010年 | 9370篇 |
2009年 | 9000篇 |
2008年 | 12505篇 |
2007年 | 12756篇 |
2006年 | 12197篇 |
2005年 | 11258篇 |
2004年 | 10256篇 |
2003年 | 9301篇 |
2002年 | 9149篇 |
2001年 | 10095篇 |
2000年 | 7782篇 |
1999年 | 6106篇 |
1998年 | 5409篇 |
1997年 | 5374篇 |
1996年 | 5060篇 |
1995年 | 4756篇 |
1994年 | 4734篇 |
1993年 | 4449篇 |
1992年 | 5082篇 |
1991年 | 5078篇 |
1990年 | 4946篇 |
1989年 | 4817篇 |
1988年 | 4908篇 |
1987年 | 4821篇 |
1986年 | 4567篇 |
1985年 | 6098篇 |
1984年 | 6479篇 |
1983年 | 5407篇 |
1982年 | 5789篇 |
1981年 | 5560篇 |
1980年 | 5581篇 |
1979年 | 5567篇 |
1978年 | 5970篇 |
1977年 | 5814篇 |
1976年 | 5930篇 |
1975年 | 5531篇 |
1974年 | 5444篇 |
1973年 | 5824篇 |
1972年 | 3961篇 |
1971年 | 3222篇 |
1968年 | 3013篇 |
1967年 | 3111篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
A simple method is proposed for increasing the accuracy of computation of the eigenvalues of elliptic operators, which does not require high-order accurate schemes.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 63, pp. 63–68, 1987. 相似文献
12.
F. G. Vagizov 《Hyperfine Interactions》1995,95(1):85-95
We present the results of an experimental investigation of a RF splitting of57Fe hyperfine lines in the regime of NMR and Mössbauer double resonance. The experiments have been performed as a function of RF field intensity and static magnetic field magnitude. The intensity of the RF components and the separation between them are extremely sensitive to the frequency and amplitude of the RF magnetic field. The RF splitting of hyperfine lines is inversely proportional to the strength of the static magnetic field. 相似文献
13.
To investigate local ordering and segregation phenomenon in a Ni91Pt9-alloy after sputtering and annealing a 3D optical atom probe (OAP) has been used. The specimen tips have been prepared from polycrystalline samples. To sputter the samples a separate preparation chamber with a scannable Ar-sputter-gun is connected to the OAP vessel. When necessary, the sample can be electrically heated to induce segregation and cure the altered layer. After a heat treatment of a Ni91 at. %Pt 9 at.% specimen at 1100 K the surface of a (111)-oriented specimen is enriched in platinum by a factor of two in relation to the bulk. The phenomenon of short-range ordering has been investigated on the surface and in the subsurface volume. A 3D reconstruction of this annealed NiPt specimen shows regions with high concentration of platinum that gives an indication at short-range ordering. Uniform sputtering of the tip without a heat treatment induces a decisive depletion of Pt on the surface and the following subatomic layers. The atom-probe results of specimens in thermal equilibrium are in close agreement to further surface sensitive results obtained from Ion Scattering Spectroscopy (ISS) and Auger Electron Spectroscopy (AES). 相似文献
14.
The radiation emitted by charged, scalar particles in a Schwarzschild field with maximal acceleration corrections is calculated classically and in the tree approximation of quantum field theory. In both instances the particles emit radiation that has characteristics similar to those of gamma-ray bursters. 相似文献
15.
D. V. Vyalykh A. M. Shikin G. V. Prudnikova A. Yu. Grigor’ev A. G. Starodubov V. K. Adamchuk 《Physics of the Solid State》2002,44(1):164-170
This paper reports on the first experimental observation of quantum-well states and sp-type resonances in thin single-crystal gold, silver, and copper layers formed on single-crystal W(110) surfaces, which result from spatial localization of Bloch-type electronic wave functions in a quantum well with potential barriers at the vacuum/metal and metal/W(110) interfaces. The quantization of the valence-band electronic structure in Au/W(110), Ag/W(110), and Cu/W(110) systems was studied experimentally using angle-resolved photoelectron spectroscopy. 相似文献
16.
17.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems. 相似文献
18.
G. L. Booth 《Acta Mathematica Hungarica》1989,54(3-4):201-208
19.
Rajiv Manohar G. Tripathi A.K. Srivastava A.K. Prajapati 《Journal of Physics and Chemistry of Solids》2006,67(11):2300-2304
Dielectric properties of polymer-liquid crystal mixture, having constituent polymer, poly-butyl methacrylate (PBMA) and liquid crystal, cholesteryl nonanoate, are reported as a function of frequency and temperature. The measurement has been done in a temperature range of 300-375 K and frequency range of 100 Hz-10 MHz. The dielectric permittivity and dielectric loss shows significant changes with the addition of polymer molecules in liquid crystal. The significant feature of composite formation is that the pure liquid crystal and polymer do not show dielectric relaxation in the frequency range covered, while the composite shows relaxation peak at a particular frequency. The optical transmittance of pure liquid crystal and composite has also been measured and compared. 相似文献
20.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献