全文获取类型
收费全文 | 955篇 |
免费 | 35篇 |
国内免费 | 2篇 |
专业分类
化学 | 624篇 |
晶体学 | 12篇 |
力学 | 37篇 |
数学 | 92篇 |
物理学 | 227篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 25篇 |
2015年 | 35篇 |
2014年 | 22篇 |
2013年 | 48篇 |
2012年 | 48篇 |
2011年 | 65篇 |
2010年 | 36篇 |
2009年 | 31篇 |
2008年 | 61篇 |
2007年 | 70篇 |
2006年 | 46篇 |
2005年 | 38篇 |
2004年 | 50篇 |
2003年 | 34篇 |
2002年 | 26篇 |
2001年 | 19篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 15篇 |
1997年 | 6篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1889年 | 2篇 |
排序方式: 共有992条查询结果,搜索用时 218 毫秒
901.
Stefania Della Sciucca Gloria Spagnoli Maurizio Penco Salvatore Battiato Filippo Samperi Raniero Mendichi 《Journal of Polymer Science.Polymer Physics》2009,47(6):596-607
The structural relaxation of poly(methyl‐methacrylate) (PMMA)‐based copolymers with different chain flexibility has been studied by DSC with the classical procedure of the isothermal and dynamical approach. Modified PMMA with different chain flexibility have been prepared by free radical polymerization in solution using a mixture of monomers containing 10 mol % of alkyl methacrylate (i.e., ethyl, buthyl, and hexyl methacrylate). The molecular characteristics of all the prepared copolymers have been performed by a multiangle laser light scattering (MALS) photometer on‐line to a size exclusion chromatography (SEC) system (SEC‐MALS) after and before the thermal treatments, NMR (1H and 13C) and MALDI‐TOF mass spectrometry. A comparison of the apparent relaxation rate (RH) was appraised from the enthalpy loss by annealing the different samples at the same level of undercooling (Ta = Tg ? 18 °C). It was found an increase of RH increasing the chain flexibility in the copolymers. Dynamical tests, performed at different cooling rates, have been used to estimate the apparent activation energy of the relaxation process. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 596–607, 2009 相似文献
902.
903.
Claudia Della Rosa 《Tetrahedron letters》2007,48(40):7075-7078
The normal electron-demand Diels-Alder reactions between substituted selenophenes, nitro being one of these groups, and dienes of diverse reactivity give benzoselenophenes derivatives. 相似文献
904.
H. Nunokawa A. Rossi V. Semikoz J. W. F. Valle 《Nuclear Physics B - Proceedings Supplements》1999,70(1-3)
This talk summarizes some results of our recent work focusing on the possibility to test solar matter density fluctuations by the future Borexino experiment. 相似文献
905.
If neutrino conversions within the Sun result in partial polarization of initial solar neutrino fluxes, then a new opportunity arises to observe the
's in future neutrino experiments in the low energy region (such as BOREXINO or HELLAZ) and thus to probe the Majorana nature of the neutrinos. The
conversions may take place for low energy solar neutrinos while being unobservable at the Kamiokande and Super-Kamiokande experiments. 相似文献
906.
Leo W.Y. Yeung Sachi Taniyasu Kurunthachalam Kannan Della Z.Y. Xu Keerthi S. Guruge Paul K.S. Lam Nobuyoshi Yamashita 《Journal of chromatography. A》2009,1216(25):4950-4956
A method for the analysis of perfluorinated compounds (perfluoroalkyl sulfonates: C4, C6, C8, C10; perfluoroalkyl sulfinates: C6, C8, C10; perfluorooctanesulfonamide, N-ethyl perfluorooctanesulfonamide, N-ethyl perfluorooctanesulfonamidoacetate, perfluorocarboxylates: C4–C14; fluorotelomer carboxylate (7:3, 8:2) in whole blood using acetonitrile and OASIS WAX® solid phase extraction (SPE) cartridge was developed. Separation of target compounds in two HPLC columns (ion exchange JJ50-2D and C18 Betasil columns) was examined. Matrix recoveries of the developed methods ranged from 70% to 120%. Separation of possible inferences such as taurodeoxycholic acid (TDC) was accomplished using an ion exchange JJ50-2D column, and this separation was validated using whole blood of different animals. 相似文献
907.
We present algorithmic and computational complexity results for several single machine scheduling problems where some job characteristics are uncertain. This uncertainty is modeled through a finite set of well-defined scenarios. We use here the so-called absolute robustness criterion to select among feasible solutions. 相似文献
908.
I. C. Gonçalves A. G. Ramalho I. F. Gonçalves J. Salgado J. Pertusa A. Irles F. Mascarenhas M. Castro F. Valle J. Toscano Rico V. Alcober 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(2):431-432
The goal of this work is to pursue the research activity in BNC and the installation of a therapy facility in the position
presently occupied by the thermal column. With these objectives the experimental studies in mice and cells are continuing
while improvements in the facilities are created or prepared. For this effect: (1) the installation of lead shield in the
vertical access of the thermal column, which resulted in an enhancement of the Φ
th
toD
γ ratio, was performed, (2) the adaptation of a beam tube to deliver a dominantly thermal or epithermal beam in two possible
beam openings is being done and (3) Monte Carlo calculations aiming at the optimization of the conditions for the therapy
installation are in progress. 相似文献
909.
Alberto DELLA VEDOVA Roberto PAOLETTI 《数学学报(英文版)》2007,23(12):2155-2188
The study of the volume of big line bundles on a complex projective manifold M has been one of the main veins in the recent interest in the asymptotic properties of linear series. In this article, we consider an equivariant version of this problem, in the presence of a linear action of a reductive group on M. 相似文献
910.
Laurent?ChaunierEmail authorView authors OrcID profile Guy?Della Valle Michèle?Dalgalarrondo Denis?Lourdin Didier?Marion Eric?Leroy 《Rheologica Acta》2017,56(11):941-953
Zeins, storage proteins from maize, are suitable for making biobased thermoplastic materials. The rheological behavior of a commercial zein plasticized with 20 w% glycerol was studied in the molten state by steady-state flow experiments in extrusion conditions and oscillatory rheometry. For low residence times, a shear-thinning viscoelastic behavior was observed, with G″ exceeding G′. After 300 s at 130 °C, the complex viscosity |η ?|?=?7?×?103 ω ?0.46 was found to be similar to that of thermoplastic polymer melts used in fused deposition modeling. However, the ratio between the exponents of the power laws describing G′(ω) and G″(ω) did not meet the typical value of 2 for entangled polymer melts. Moreover, for longer residence times, the viscosity increased and a gelation phenomenon was observed with a crossing over of G′(ω) and G″(ω). Gel times ranged from 6000 s at 120 °C to 1700 s at 150 °C. The evolution of the macromolecular structure assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high-performance size exclusion chromatography suggested that this gelation phenomenon involves various types of covalent and non-covalent cross-links. Disulfide bonds played a significant role in gelation kinetics despite a very low cysteine residue content in the protein primary structure (about 1 mol%). These results suggested that plasticized zeins initially behave like a low-viscosity non-entangled polymer melt, before cross-linking progressively led to a continuous network. 相似文献