全文获取类型
收费全文 | 243021篇 |
免费 | 12305篇 |
国内免费 | 2111篇 |
专业分类
化学 | 155168篇 |
晶体学 | 2749篇 |
力学 | 9344篇 |
综合类 | 7篇 |
数学 | 26343篇 |
物理学 | 63826篇 |
出版年
2021年 | 1571篇 |
2020年 | 2871篇 |
2019年 | 4199篇 |
2018年 | 2940篇 |
2017年 | 2446篇 |
2016年 | 6582篇 |
2015年 | 6186篇 |
2014年 | 6703篇 |
2013年 | 13713篇 |
2012年 | 11734篇 |
2011年 | 12794篇 |
2010年 | 9123篇 |
2009年 | 8855篇 |
2008年 | 11971篇 |
2007年 | 11433篇 |
2006年 | 10588篇 |
2005年 | 10187篇 |
2004年 | 9044篇 |
2003年 | 7795篇 |
2002年 | 8143篇 |
2001年 | 7956篇 |
2000年 | 6339篇 |
1999年 | 4200篇 |
1998年 | 2983篇 |
1997年 | 2933篇 |
1996年 | 2979篇 |
1995年 | 2540篇 |
1994年 | 2476篇 |
1993年 | 2349篇 |
1992年 | 2684篇 |
1991年 | 2580篇 |
1990年 | 2311篇 |
1989年 | 2219篇 |
1988年 | 2217篇 |
1987年 | 2143篇 |
1986年 | 2020篇 |
1985年 | 3059篇 |
1984年 | 3024篇 |
1983年 | 2381篇 |
1982年 | 2636篇 |
1981年 | 2511篇 |
1980年 | 2447篇 |
1979年 | 2390篇 |
1978年 | 2463篇 |
1977年 | 2369篇 |
1976年 | 2362篇 |
1975年 | 2332篇 |
1974年 | 2229篇 |
1973年 | 2304篇 |
1972年 | 1283篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
M. H. Gehlen M. Van der Auweraer F. C. De Schrwer 《Photochemistry and photobiology》1991,54(4):613-618
The luminescence decay of excited probes in micelles in the presence of a Poisson distribution of quenchers is considered under conditions where both probe and quencher within the lifetime of the excited probe may exchange between the micelles. Analytical and numerical results show that the luminescence decay can be expressed by a generalized self convolution product of a multiexponential decay function. 相似文献
992.
993.
D. Guyomard C. Pagnoux J. J. Zah Letho A. Verbaere Y. Piffard 《Journal of solid state chemistry》1991,90(2)
The single phase compound Na3SbO(PO4)2 was prepared by a solid state reaction. It crystallizes in the orthorhombic system, space group P212121 with a = 6.964(1) Å, b = 9.284(2) Å, c = 12.425(2) Å, Z = 4. The structure was determined from 968 reflections collected on a Nonius CAD4 automatic diffractometer with MoKα radiation. The final R index and weighted Rw index are 0.031 and 0.039, respectively. The structure is built up from strings of corner-sharing SbO6 octahedra to which phosphate groups are linked by two of their vertices. These chains, running parallel to the a-axis, are separated from each other by sodium atoms. 相似文献
994.
995.
We study the strong-coupling limit of the AdS/CFT correspondence in the framework of a recently proposed fermionic formulation
of the Bethe ansatz equations governing the gauge theory anomalous dimensions. We give examples of states that do not follow
the Gubser-Klebanov-Polyakov law at a large ’t Hooft coupling λ, in contrast to recent results on the quantum string Bethe
equations that are valid in that regime. This result indicates that the fermionic construction cannot be trusted at large
λ, although it remains an efficient tool for computing the weak-coupling expansion of anomalous dimensions.
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 2, pp. 213–224, August, 2007. 相似文献
996.
Darshan C. Kundaliya 《Solid State Communications》2004,131(8):489-491
The intermetallic compound, YRhAl, has been prepared and is found to be isomorphic with RRhAl (R=Pr, Nd, Gd, Ho and Tm) compounds crystallizing in the orthorhombic TiNiSi-type structure (space group Pnma). Heat capacity and electrical resistivity measurements in the He-3 temperature range reveal that this compound is superconducting with a transition temperature, Tc, of 0.9 K. The electronic specific heat coefficient, γ, and the Debye temperature are found to be 6.1 mJ/mol K and 197 K, respectively. The specific heat jump at the superconducting transition is found to be consistent with the BCS weak-coupling limit. This combined with the earlier observation of superconductivity in LaRhAl (Tc=2.4 K) having a different structure than that of YRhAl, suggests that the underlying structure is not very crucial for the occurrence of superconductivity in RRhAl series of compounds. 相似文献
997.
998.
Audrey A S G Lonni Ieda S Scarminio Lucas M C Silva Dalva T Ferreira 《Analytical sciences》2003,19(7):1013-1017
Phytochemical investigation of the aerial parts of three Baccharis species (Asteraceae family) was performed using HPLC and chemometric methods, with the objective of distinguishing between three morphologically very similar species: Baccharis genistelloides Persoon var. trimera (Less.) DC, B. milleflora (Less.) DC and B. articulata (Lam.) Persoon. With the help of Principal Component Analysis (PCA) and variance weights, it was possible to characterize the chromatographic profiles of the alcoholic extracts of the three species. Application of Soft Independent Modeling of Class Analogy (SIMCA) and K-Nearest Neighbor (KNN) methods on a training set of 74 extracts resulted in models that correctly classified all eight samples in an independent test set. 相似文献
999.
C. Bréchignac Ph. Cahuzac F. Carlier C. Colliex M. de Frutos N. Kébaïli J. Le Roux A. Masson B. Yoon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):265-268
We studied shape relaxation of nano-fractal islands,
during annealing, after their growth from antimony cluster
deposition on graphite surface. Annealing at
180°C shows evidence of an increase
of the fractal branch width with time followed by branch
fragmentation, without changing the fractal dimension. The time
evolution of the width of the arm suggests the surface
self-diffusion mechanism as the main relaxation process. With
Monte Carlo simulations, we confirmed the observed behavior.
Comparison is done with our previous results on fragmentation of
nano-fractal silver islands when impurity added to the incident
cluster promotes rapid fragmentation by surface self-diffusion
enhancement [1]. 相似文献
1000.
E. Casarejos P. Armbruster L. Audouin J. Benlliure M. Bernas A. Boudard R. Legrain S. Leray B. Mustapha S. Czajkowski T. Enqvist B. Fernandez J. Pereira M. Pravikoff F. Rejmund K. -H. Schmidt C. Stephan J. Taieb L. Tassan-Got C. Villagrasa C. Volant W. Wlazlo 《Physics of Atomic Nuclei》2003,66(8):1413-1420
The isotopic production cross sections of heavy residues in relativistic heavy-ion collisions have been investigated in inverse kinematics. The primary reaction products were fully identified in mass and atomic number prior to beta decay using the fragment separator FRS. The huge collection of data obtained helps in the understanding of the two main reaction mechanisms involved: fragmentation and fission. These data provide basic information for future radioactive ion beam facilities and for technical applications like intense neutron sources by means of spallation targets. 相似文献