全文获取类型
收费全文 | 1702篇 |
免费 | 106篇 |
国内免费 | 4篇 |
专业分类
化学 | 1093篇 |
晶体学 | 11篇 |
力学 | 70篇 |
数学 | 242篇 |
物理学 | 396篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 31篇 |
2021年 | 43篇 |
2020年 | 57篇 |
2019年 | 33篇 |
2018年 | 36篇 |
2017年 | 40篇 |
2016年 | 76篇 |
2015年 | 84篇 |
2014年 | 83篇 |
2013年 | 101篇 |
2012年 | 158篇 |
2011年 | 191篇 |
2010年 | 109篇 |
2009年 | 63篇 |
2008年 | 146篇 |
2007年 | 120篇 |
2006年 | 106篇 |
2005年 | 78篇 |
2004年 | 55篇 |
2003年 | 36篇 |
2002年 | 24篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 12篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1812条查询结果,搜索用时 0 毫秒
1.
Advances in Computational Mathematics - Persistence diagrams are one of the main tools in the field of Topological Data Analysis (TDA). They contain fruitful information about the shape of data.... 相似文献
2.
3.
4.
In this paper we derive a priori and a posteriori error estimates for cell centered finite volume approximations of nonlinear conservation laws on polygonal bounded domains. Numerical experiments show the applicability of the a posteriori result for the derivation of local adaptive solution strategies.
5.
Marie‐France Llauro Julien Loiseau Fernande Boisson Frdric Delolme Catherine Ladavire J. Claverie 《Journal of polymer science. Part A, Polymer chemistry》2004,42(21):5439-5462
Low‐molecular‐weight poly(acrylic acid) (PAA) was synthesized by reversible addition fragmentation chain transfer polymerization with a trithiocarbonate as chain‐transfer agent (CTA). With a combination of NMR spectroscopy and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, the PAA end‐groups of the polymer were analyzed before and after neutralization by sodium hydroxide. The polymer prior to neutralization is made up of the expected trithiocarbonate chain‐ends and of the H‐terminated chains issued from a reaction of transfer to solvent. After neutralization, the trithiocarbonates are transformed into thiols, disulfides, thiolactones, and additional H‐terminated chains. By quantifying the different end‐groups, it was possible to demonstrate that fragmentation is the rate limiting step in the transfer reaction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5439–5462, 2004 相似文献
6.
Daniel E. Vogler Ana Lorencak Julien M. Rey Markus W. Sigrist 《Optics and Lasers in Engineering》2005,43(3-5):527
A novel sensitive technique for the determination of losses in fiber cavities is presented. The method is based on the cavity ringdown scheme implemented in silica-based single-mode fibers. Bending losses of fiber cavities of different lengths have been measured showing all an oscillating behavior with respect to the curvature radius of the fiber as predicted by a theoretical model. The best minimum detectable absorbance per cavity pass achieved by this new method is 1.72×10−3 dB within a 10 m-long cavity. This limit suffices well for an accurate determination of optical bending losses even in bend-insensitive fibers. Furthermore, the comparison of the measured bending losses with a theoretical model allows the extraction of different fiber parameters. Good agreement has been found between the experimentally derived parameters and literature data. 相似文献
7.
Claude Didierjean Julien Marin Emmanuel Wenger Jean‐Paul Briand Andr Aubry Gilles Guichard 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(3):o200-o203
X‐ray studies reveal that tert‐butyl (6S)‐6‐isobutyl‐2,4‐dioxopiperidine‐1‐carboxylate occurs in the 4‐enol form, viz. tert‐butyl (6S)‐4‐hydroxy‐6‐isobutyl‐2‐oxo‐1,2,5,6‐tetrahydropyridine‐1‐carboxylate, C14H23NO4, when crystals are grown from a mixture of dichloromethane and pentane, and has an axial orientation of the isobutyl side chain at the 6‐position of the piperidine ring. Reduction of the keto functionality leads predominantly to the corresponding β‐hydroxylated δ‐lactam, tert‐butyl (4R,6S)‐4‐hydroxy‐6‐isobutyl‐2‐oxopiperidine‐1‐carboxylate, C14H25NO4, with a cis configuration of the 4‐hydroxy and 6‐isobutyl groups. The two compounds show similar molecular packing driven by strong O—H⋯O=C hydrogen bonds, leading to infinite chains in the crystal structure. 相似文献
8.
Keith Warren Julien C. Sprott Raymond C. Hawkins 《Nonlinear dynamics, psychology, and life sciences》2002,6(1):55-70
In recent years there has been considerable interest in the construction of nonlinear models of the dynamics of human behavior. In this exploratory article we argue that attempts at controlling problematic thoughts, emotions, or behaviors can lead to nonlinearity in mental/behavioral dynamics. We illustrate our model by fitting threshold autoregression models to self-recorded time series of the daily highs in intensity of anxiety and obsessive ruminations, kept by an individual in therapy for this problem. In our discussion, we raise the possibility that bifurcations that occur in this nonlinear model may offer insight into mental control paradoxes. 相似文献
9.
By using an extended linear-chain model which includes the interlayer forces, we have calculated the new vibrational modes, of Li intercalated InSe. The dispersion curves along thek
z wavevector perpendicular to the layers for the -polytype are determined in the first Brillouin zone. Assuming that the interlayer interaction is not modified upon intercalation and the interaction between lithium atom and adjacent layers in the van der Waals plane has the same value than the interlayer one, the new modes are determined with the force constant given by the rigid layer mode of the, -polytype at 18 cm–1. This model gives the variation of the acoustic branches and the appearance of two optical intercalation modes at higher frequencies. The Brillouin zone boundary modes of the acoustic branches at 18 and 41 cm–1 in the pure material are calculated to be 22 and 50 cm–1 respectively forx=1/2. The dispersion of the new optical branches is flat along thez-direction and frequencies are obtained at 96 cm–1 for the Li mode perpendicular tok
z and at 218 cm–1 for the Li mode parallel tok
z. We compare also our results with the Li mode frequencies obtained in a total energy calculation. Raman scattering experiments have been performed in intercalated sample in order to verify the proposed model. 相似文献
10.
Poschalko A Lancelot N Marin J Larras V Limal D Elbayed K Raya J Piotto M Briand JP Guichard G Bianco A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(18):4532-4537
A novel resin called DEUSS (perdeuterated poly(oxyethylene)-based solid support) has been prepared by anionic polymerization of deuterated [D4]ethylene oxide, followed by cross-linking with deuterated epichlorohydrin. DEUSS can be suspended in a wide range of solvents including organic and aqueous solutions, in which it displays a high swelling capacity. As measured by proton HRMAS of the swollen polymer, the signal intensity of the oxyethylene protons is reduced by a factor of 110 relative to the corresponding nondeuterated poly(oxyethylene)poly(oxypropylene) (POEPOP) resin, thus facilitating detailed HRMAS NMR studies of covalently linked molecules. This 1H NMR invisible matrix was used for the solid-phase synthesis of peptides, oligoureas, and a series of amides as well as their characterization by HRMAS NMR spectroscopy. On-bead NMR spectra of high quality and with resolution comparable to that of liquid samples were obtained and readily interpreted. The complete absence of the parasite resin signals will be of great advantage, for example, for the optimization of multistep solid-phase stereoselective reactions, and for the conformational study of resin-bound molecules in a large variety of solvents. 相似文献