全文获取类型
收费全文 | 3356篇 |
免费 | 188篇 |
国内免费 | 7篇 |
专业分类
化学 | 2374篇 |
晶体学 | 5篇 |
力学 | 84篇 |
数学 | 623篇 |
物理学 | 465篇 |
出版年
2023年 | 53篇 |
2022年 | 44篇 |
2021年 | 82篇 |
2020年 | 98篇 |
2019年 | 116篇 |
2018年 | 62篇 |
2017年 | 42篇 |
2016年 | 155篇 |
2015年 | 127篇 |
2014年 | 146篇 |
2013年 | 181篇 |
2012年 | 225篇 |
2011年 | 239篇 |
2010年 | 136篇 |
2009年 | 99篇 |
2008年 | 151篇 |
2007年 | 139篇 |
2006年 | 146篇 |
2005年 | 127篇 |
2004年 | 99篇 |
2003年 | 74篇 |
2002年 | 76篇 |
2001年 | 28篇 |
2000年 | 27篇 |
1999年 | 23篇 |
1998年 | 33篇 |
1997年 | 30篇 |
1996年 | 35篇 |
1995年 | 25篇 |
1994年 | 26篇 |
1993年 | 45篇 |
1992年 | 27篇 |
1991年 | 20篇 |
1990年 | 22篇 |
1989年 | 20篇 |
1988年 | 30篇 |
1987年 | 36篇 |
1986年 | 25篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 28篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1980年 | 25篇 |
1979年 | 13篇 |
1978年 | 16篇 |
1976年 | 15篇 |
1974年 | 21篇 |
1966年 | 12篇 |
1909年 | 11篇 |
排序方式: 共有3551条查询结果,搜索用时 15 毫秒
951.
The standard approach to calculating electrostatic forces and capacitances involves solving a surface integral equation of
the first kind. However, discretizations of this problem lead to ill-conditioned linear systems and second-kind integral equations
usually solve for the dipole density, which can not be directly related to electrostatic forces. This paper describes a second-kind
equation for the monopole or charge density and investigates different discretization schemes for this integral formulation.
Numerical experiments, using multipole accelerated matrix–vector multiplications, demonstrate the efficiency and accuracy
of the new approach.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
952.
953.
954.
Andrea Kroner Fernando Rinaldi Johannes Michael Ostermann Rainer Michalzik 《Optics Communications》2007,270(2):332-335
We present inverted surface relief vertical-cavity surface-emitting lasers (VCSELs) showing a side-mode suppression ratio above 30 dB up to maximum optical output powers of 6.3 mW and differential quantum efficiencies exceeding 90%. An evaluation of 160 relief devices on a sample incorporating graded layers yields 157 lasers with single-mode output powers of at least 2.9 mW, proving the high effectiveness of the technique despite the comparatively simple manufacture. 相似文献
955.
In an earlier paper (Anal. Chim. Acta 514 (2004) 137) we claimed that the maximal extractability of a metal from soil or sediment for a user-defined extractant, i.e. the chemical availability in that particular extractant, may be biased as a result of inadequate volume to mass (V/m) ratios. Correcting for that artifact using an implementation of the simple linear isotherm model gave good results although we cautioned the general applicability. In this paper we will theoretically derive the limitations of that approach based on the more general assumption that sorption processes are described by a Langmuir isotherm.NIST reference material 8704 was extracted with 1 mol l−1 NaOAc (adjusted to pH 5) to experimentally verify the applicability of the Langmuir isotherm approach and illustrate the deviations obtained for some metals using the linear isotherm approach. Of the seven metals measured (Cr, Co, Ni, Cu, Zn, Cd, and Ba) only for Cr and Cu severe discrepancies between both approaches were found, which could be traced back to non-linear isotherm behaviour. Moreover, the Langmuir isotherm approach showed that the above mentioned extractability artifact is even more serious than earlier assumed applying the linear isotherm approach. 相似文献
956.
Lin N Stepanow S Vidal F Barth JV Kern K 《Chemical communications (Cambridge, England)》2005,(13):1681-1683
High-resolution scanning tunneling microscopy has revealed how ligand control can be successfully employed to eliminate isomeric phases and defects in 2D coordination networks that are self-assembled at a surface support by replacing symmetric dicarboxylato linker ligands to dissymmetric carboxylpyridyl linker ligands. 相似文献
957.
Lodola A Mor M Hermann JC Tarzia G Piomelli D Mulholland AJ 《Chemical communications (Cambridge, England)》2005,(35):4399-4401
Fatty acid amide hydrolase (FAAH), a promising target for the treatment of several central and peripheral nervous system disorders, such as anxiety, pain and hypertension, has an unusual catalytic site, and its mechanism has been uncertain; hybrid quantum mechanics/molecular mechanics (QM/MM) calculations reveal a new mechanism of nucleophile activation (involving a Lys-Ser-Ser catalytic triad), with potentially crucial insights for the design of potent and selective inhibitors. 相似文献
958.
Interferometric methods to measure orbital and spin, or the total angular momentum of a single photon 总被引:1,自引:0,他引:1
Leach J Courtial J Skeldon K Barnett SM Franke-Arnold S Padgett MJ 《Physical review letters》2004,92(1):013601
We propose interferometric methods capable of measuring either the total angular momentum, or simultaneously measuring the spin and orbital angular momentum of single photons. This development enables the measurement of any angular momentum eigenstate of a single photon. The work allows the investigation of single-photon two-qubit entangled states and has implications for high density information transfer. 相似文献
959.
We comment on the recent Letter by Jiao et al. [Opt. Lett. 28, 1206 (2003)] in which a polarization-sensitive optical coherence tomography system was presented. Interrogating a sample with two orthogonal incident polarization states cannot always recover birefringence correctly. A previously presented fiber-based polarization-sensitive system was inaccurately characterized, and its method of eliminating the polarization distortion caused by single-mode optical fiber was presented earlier by Saxer et al. [Opt. Lett. 25, 1355 (2000)]. 相似文献
960.
Inclined ZnO thin films produced by pulsed-laser deposition 总被引:1,自引:0,他引:1
M.?Peruzzi J.D.?PedarnigEmail author D.?B?uerle W.?Schwinger F.?Sch?ffler 《Applied Physics A: Materials Science & Processing》2004,79(8):1873-1877
ZnO thin films with a uniformly inclined structure are grown by pulsed-laser deposition on SrTiO3. The c-axis of ZnO films is inclined by an angle =20±0.5° and =42±0.5° against the surface normal of 25° miscut (100) SrTiO3 and (110) SrTiO3 single crystal substrates, respectively. The inclined structure is due to epitaxial growth of hexagonal ZnO on cubic SrTiO3 as evidenced by X-ray diffraction and high-resolution transmission electron microscopy investigations. The range of deposition parameters (substrate temperature, oxygen background pressure) to achieve epitaxial growth is determined. The inclined films are smooth with an rms surface roughness of 1.5 nm for layer thicknesses up to 700 nm. PACS 61.10.-i; 68.37.-d; 81.15.Fg 相似文献