全文获取类型
收费全文 | 29888篇 |
免费 | 112篇 |
国内免费 | 278篇 |
专业分类
化学 | 11142篇 |
晶体学 | 266篇 |
力学 | 1414篇 |
综合类 | 12篇 |
数学 | 9141篇 |
物理学 | 8303篇 |
出版年
2021年 | 55篇 |
2020年 | 37篇 |
2019年 | 34篇 |
2018年 | 1204篇 |
2017年 | 1456篇 |
2016年 | 738篇 |
2015年 | 584篇 |
2014年 | 492篇 |
2013年 | 696篇 |
2012年 | 3169篇 |
2011年 | 2377篇 |
2010年 | 1852篇 |
2009年 | 1574篇 |
2008年 | 632篇 |
2007年 | 670篇 |
2006年 | 678篇 |
2005年 | 4500篇 |
2004年 | 3968篇 |
2003年 | 2344篇 |
2002年 | 523篇 |
2001年 | 301篇 |
2000年 | 104篇 |
1999年 | 180篇 |
1998年 | 122篇 |
1997年 | 77篇 |
1996年 | 61篇 |
1995年 | 52篇 |
1994年 | 50篇 |
1992年 | 175篇 |
1991年 | 160篇 |
1990年 | 138篇 |
1989年 | 113篇 |
1988年 | 106篇 |
1987年 | 61篇 |
1986年 | 50篇 |
1985年 | 45篇 |
1984年 | 36篇 |
1982年 | 33篇 |
1979年 | 32篇 |
1978年 | 34篇 |
1976年 | 84篇 |
1975年 | 44篇 |
1974年 | 42篇 |
1973年 | 50篇 |
1972年 | 41篇 |
1970年 | 40篇 |
1969年 | 40篇 |
1968年 | 35篇 |
1967年 | 32篇 |
1966年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
The significance of the electron–phonon interaction for optically stimulated luminescence (OSL) process in quartz is demonstrated. OSL variation with temperature has been investigated for four samples of natural quartz. Changes of the OSL decay rate have been observed for all components of the OSL signal. The scale and tendency of these changes are comparable with outcomes of computer simulations carried out for the model composed of two deep electron traps, one shallow trap and one recombination centre, taking into account the electron–phonon interactions. 相似文献
972.
The beta dose response and Optically Stimulated Luminescence (OSL) signal stability characteristics of human tooth enamel deproteinated by hydrazine reagent under blue photon stimulation are reported. Removal of the protein organic component of tooth enamel resulted in a higher OSL sensitivity and slower fading of OSL signals. The effect of chemical sample preparation on the enamel sample sensitivity is discussed and further steps to make this deproteinization treatment suitable for in vitro dose reconstruction studies are suggested. 相似文献
973.
S. Greilich L. Grzanka N. Bassler C.E. Andersen O. J?kel 《Radiation measurements》2010,45(10):1406-1409
We present an open-source code library for amorphous track modelling which is suppose to faciliate the application and numerical comparability as well as serve as a frame-work for the implementation of new models. We show an example of using the library indicating the choice of submodels has a significant impact on the modelling outcome. 相似文献
974.
Kamel Abbas Izabela Cydzik Riccardo Del Torchio Massimo Farina Efrat Forti Neil Gibson Uwe Holzwarth Federica Simonelli Wolfgang Kreyling 《Journal of nanoparticle research》2010,12(7):2435-2443
Industrially manufactured titanium dioxide nanoparticles have been successfully radiolabelled with 48V by irradiation with a cyclotron-generated proton beam. Centrifugation tests showed that the 48V radiolabels were stably bound within the nanoparticle structure in an aqueous medium, while X-ray diffraction indicated
that no major structural modifications to the nanoparticles resulted from the proton irradiation. In vitro tests of the uptake
of cold and radiolabelled nanoparticles using the human cell line Calu-3 showed no significant difference in the uptake between
both batches of nanoparticles. The uptake was quantified by Inductively Coupled Plasma Mass Spectrometry and high resolution
γ-ray spectrometry for cold and radiolabelled nanoparticles, respectively. These preliminary results indicate that alterations
to the nanoparticles’ properties introduced by proton bombardment can be controlled to a sufficient extent that their further
use as radiotracers for biological investigations can be envisaged and elaborated. 相似文献
975.
J.?Piekarewicz M.?Centelles X.?Roca-Maza X.?Vi?as 《The European Physical Journal A - Hadrons and Nuclei》2010,46(3):379-386
The Garvey-Kelson relations (GKRs) are algebraic expressions originally developed to predict nuclear masses. In this paper
we show that the GKRs provide a fruitful framework for the prediction of other physical observables that also display a slowly varying dynamics. Based on this concept, we extend the GKRs to the study of nuclear charge radii. The GKRs are tested on 455 out of the approximately 800 nuclei whose charge radius is experimentally known. We find a rms
deviation of 0.01fm between the GK predictions and the experimental values. Predictions are provided for 116 nuclei whose
charge radius is presently unknown. 相似文献
976.
977.
Eric Johnsen Johan Larsson Ankit V. Bhagatwala William H. Cabot Parviz Moin Britton J. Olson Pradeep S. Rawat Santhosh K. Shankar Bj?rn Sj?green H.C. Yee Xiaolin Zhong Sanjiva K. Lele 《Journal of computational physics》2010,229(4):1213-1237
Flows in which shock waves and turbulence are present and interact dynamically occur in a wide range of applications, including inertial confinement fusion, supernovae explosion, and scramjet propulsion. Accurate simulations of such problems are challenging because of the contradictory requirements of numerical methods used to simulate turbulence, which must minimize any numerical dissipation that would otherwise overwhelm the small scales, and shock-capturing schemes, which introduce numerical dissipation to stabilize the solution. The objective of the present work is to evaluate the performance of several numerical methods capable of simultaneously handling turbulence and shock waves. A comprehensive range of high-resolution methods (WENO, hybrid WENO/central difference, artificial diffusivity, adaptive characteristic-based filter, and shock fitting) and suite of test cases (Taylor–Green vortex, Shu–Osher problem, shock-vorticity/entropy wave interaction, Noh problem, compressible isotropic turbulence) relevant to problems with shocks and turbulence are considered. The results indicate that the WENO methods provide sharp shock profiles, but overwhelm the physical dissipation. The hybrid method is minimally dissipative and leads to sharp shocks and well-resolved broadband turbulence, but relies on an appropriate shock sensor. Artificial diffusivity methods in which the artificial bulk viscosity is based on the magnitude of the strain-rate tensor resolve vortical structures well but damp dilatational modes in compressible turbulence; dilatation-based artificial bulk viscosity methods significantly improve this behavior. For well-defined shocks, the shock fitting approach yields good results. 相似文献
978.
Marija S. ?iri? Milan Lj. Zlatanovi? Mi?a S. Stankovi? Ljubica S. Velimirovi? 《Applied mathematics and computation》2012,218(12):6648-6655
In this paper geodesic mappings of equidistant generalized Riemannian spaces are discussed. It is proved that each equidistant generalized Riemannian space of basic type admits non-trivial geodesic mapping with preserved equidistant congruence. Especially, there exists non-trivial geodesic mapping of equidistant generalized Riemannian space onto equidistant Riemannian space. An example of geodesic mapping of an equidistant generalized Riemannian spaces is presented. 相似文献
979.
980.
Entropic entanglement measures of a two-dimensional system of two Coulombically interacting particles confined in an anisotropic harmonic potential are discussed in dependence on the anisotropy and the interaction strength. The harmonic approximation appears exact in the strong interaction limit, allowing determination of the asymptotic expression for the linear entropy. Entanglement properties are dramatically influenced by the anisotropy of the confining potential in the strong-correlation regime. 相似文献