全文获取类型
收费全文 | 3307篇 |
免费 | 152篇 |
国内免费 | 21篇 |
专业分类
化学 | 2476篇 |
晶体学 | 13篇 |
力学 | 87篇 |
数学 | 380篇 |
物理学 | 524篇 |
出版年
2023年 | 47篇 |
2022年 | 34篇 |
2021年 | 74篇 |
2020年 | 119篇 |
2019年 | 99篇 |
2018年 | 69篇 |
2017年 | 44篇 |
2016年 | 110篇 |
2015年 | 83篇 |
2014年 | 101篇 |
2013年 | 152篇 |
2012年 | 265篇 |
2011年 | 361篇 |
2010年 | 134篇 |
2009年 | 118篇 |
2008年 | 214篇 |
2007年 | 184篇 |
2006年 | 202篇 |
2005年 | 144篇 |
2004年 | 137篇 |
2003年 | 107篇 |
2002年 | 80篇 |
2001年 | 37篇 |
2000年 | 60篇 |
1999年 | 29篇 |
1998年 | 25篇 |
1997年 | 12篇 |
1996年 | 26篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 34篇 |
1992年 | 26篇 |
1991年 | 22篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 22篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1973年 | 11篇 |
排序方式: 共有3480条查询结果,搜索用时 31 毫秒
11.
12.
The effect of ITO films thickness on the properties of flexible organic light emitting diode 总被引:1,自引:0,他引:1
Indium tin oxide (ITO) thin films were deposited on cyclic olefin copolymer substrate at room temperature by an inverse target sputtering system. The crystal structure and the surface morphology of the deposited ITO films were examined by X-ray diffraction and atomic force microscopy, separately. The electrical properties of the conductive films were explored by four-point probing. Visible spectrometer was used to measure the optical properties of ITO-coated films. The performance of the flexible organic light emitting diode device with different thickness anode was investigated in this study. 相似文献
13.
C.M.Lin C.T. Chia Y.J. Shu Y.K. Tseng 《光散射学报》2005,17(3):216-218
Weperformedthehigh-pressureRaman measurementofthethreenanosizedZnOcrystals. Wefoundthesmallerthesize,thehigherthe pressuretoinducethephasetransitionfrom w櫣rzitetorock-saltstructure. High-pressureRamanmeasurementsof nona-shapedZnOcrystalswerepreformed.The… 相似文献
14.
A new co‐ordinate invariant streamwise upwind formulation for convection dominated flows is developed. The eddy diffusivity/viscosity is added directly to the equations in order to remove the oscillations in the solution. The equations then can be solved by any high‐order scheme and the solution retains the accuracy of the high‐order scheme. The accuracy and reduced lateral thickness growth rate are demonstrated with several numerical examples, including pure convective flows and lid‐driven cavity flow. The lateral spreading due to the numerical diffusion is controlled by the anisotropic tensor. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
15.
Let G be a d‐regular graph G on n vertices. Suppose that the adjacency matrix of G is such that the eigenvalue λ which is second largest in absolute value satisfies λ = o(d). Let Gp with p = α/d be obtained from G by including each edge of G independently with probability p. We show that if α < 1, then whp the maximum component size of Gp is O(log n) and if α > 1, then Gp contains a unique giant component of size Ω(n), with all other components of size O(log n). © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 2004 相似文献
16.
O. Moze M. Hofmann J. M. Cadogan K. H. J. Buschow D. H. Ryan 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,36(4):511-518
The magnetic structure and ordering temperatures of three intermetallic compounds which crystallize in the tetragonal ThCr2Si2 structure, TbCr2Si2, HoCr2Si2 and ErCr2Si2, have been determined by neutron diffraction, differential scanning calorimetry and magnetization measurements. The Cr-sublattice orders anti-ferromagnetically with Néel temperatures of 758 K for TbCr2Si2, 718 K for HoCr2Si2 and 692 K for ErCr2Si2. Chromium atoms located at 4d crystallographic sites are aligned anti-parallel along the c-axis, with GZCr magnetic modes. In contrast with metallic bcc Cr, the refined room temperature value of the ordered Cr moment is anomalously large for all three compounds. No long range magnetic order of the R sublattice in TbCr2Si2 and HoCr2Si2 is observed, whilst the Er sublattice in ErCr2Si2 orders independently of the Cr sublattice below 2.4 K with moments ferromagnetically aligned in the basal plane.Received: 4 November 2003, Published online: 30 January 2004PACS:
75.25. + z Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.) - 75.30.Cr Saturation moments and magnetic susceptibilities - 75.50.Ee Antiferromagnetics 相似文献
17.
Reported are fiber de-multiplexers based on side-polished fibers with a long interaction length and intra-core fiberBragg gratings. In conjunction with the silicon processing technologies, we demonstrate fiber filters and advantages ofour approaches are addressed. 相似文献
18.
Ross W. Mair David G. Cory Sharon Peled Ching-Hua Tseng Samuel Patz Ronald L. Walsworth 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,135(2):478-486
Pulsed-field-gradient NMR techniques are demonstrated for measurements of time-dependent gas diffusion. The standard PGSE technique and variants, applied to a free gas mixture of thermally polarized xenon and O2, are found to provide a reproducible measure of the xenon diffusion coefficient (5.71 × 10−6m2s−1for 1 atm of pure xenon), in excellent agreement with previous, non-NMR measurements. The utility of pulsed-field-gradient NMR techniques is demonstrated by the first measurement of time-dependent (i.e., restricted) gas diffusion inside a porous medium (a random pack of glass beads), with results that agree well with theory. Two modified NMR pulse sequences derived from the PGSE technique (named the Pulsed Gradient Echo, or PGE, and the Pulsed Gradient Multiple Spin Echo, or PGMSE) are also applied to measurements of time dependent diffusion of laser polarized xenon gas, with results in good agreement with previous measurements on thermally polarized gas. The PGMSE technique is found to be superior to the PGE method, and to standard PGSE techniques and variants, for efficiently measuring laser polarized noble gas diffusion over a wide range of diffusion times. 相似文献
19.
M. Bahra D. Elliott M. Reading R. Ryan 《Journal of Thermal Analysis and Calorimetry》1992,38(4):543-555
A novel instrument is described called the Thin film Analyser (TFA) which quantitatively measures changes in mechanical and rheological properties of drying films in-situ on a test panel. It is based around a simple force-sensing device, capable of carrying various probes, which can be positioned in anX-Y plane over the panel. Temperature control is achieved by means of a heating block under the sample. By imposing a thermal gradient along the block, measurements can be obtained at a series of temperatures in a single experiment. Several applications of the TFA to the drying of curable and latex-based coatings are discussed, as well as some more specialized uses. The TFA concept represents a novel approach to the thermal analysis of thin films.The authors gratefully acknowledge the design, engineering and software development work of the Instrument Group at ICI Paints, in particular John Hayton, Neil Burrows, Tony Evans and Ian Francis, who have now built three versions of the TFA. 相似文献
20.
Model or variable selection is usually achieved through ranking models according to the increasing order of preference. One of methods is applying Kullback–Leibler distance or relative entropy as a selection criterion. Yet that will raise two questions, why use this criterion and are there any other criteria. Besides, conventional approaches require a reference prior, which is usually difficult to get. Following the logic of inductive inference proposed by Caticha [Relative entropy and inductive inference, in: G. Erickson, Y. Zhai (Eds.), Bayesian Inference and Maximum Entropy Methods in Science and Engineering, AIP Conference Proceedings, vol. 707, 2004 (available from arXiv.org/abs/physics/0311093)], we show relative entropy to be a unique criterion, which requires no prior information and can be applied to different fields. We examine this criterion by considering a physical problem, simple fluids, and results are promising. 相似文献