全文获取类型
收费全文 | 2177篇 |
免费 | 71篇 |
国内免费 | 5篇 |
专业分类
化学 | 1349篇 |
晶体学 | 5篇 |
力学 | 63篇 |
数学 | 459篇 |
物理学 | 377篇 |
出版年
2024年 | 3篇 |
2023年 | 29篇 |
2022年 | 53篇 |
2021年 | 60篇 |
2020年 | 55篇 |
2019年 | 62篇 |
2018年 | 35篇 |
2017年 | 30篇 |
2016年 | 97篇 |
2015年 | 72篇 |
2014年 | 80篇 |
2013年 | 118篇 |
2012年 | 180篇 |
2011年 | 155篇 |
2010年 | 90篇 |
2009年 | 100篇 |
2008年 | 131篇 |
2007年 | 131篇 |
2006年 | 117篇 |
2005年 | 96篇 |
2004年 | 104篇 |
2003年 | 77篇 |
2002年 | 87篇 |
2001年 | 29篇 |
2000年 | 19篇 |
1999年 | 17篇 |
1998年 | 21篇 |
1997年 | 13篇 |
1996年 | 22篇 |
1995年 | 14篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1966年 | 2篇 |
1948年 | 1篇 |
1939年 | 1篇 |
1910年 | 1篇 |
排序方式: 共有2253条查询结果,搜索用时 0 毫秒
31.
We completely characterize the boundedness on Wiener amalgam spaces of the short-time Fourier transform (STFT), and on both L
p
and Wiener amalgam spaces of a special class of pseudodifferential operators, called localization operators. Precisely, sufficient conditions for the STFT to be bounded on the Wiener amalgam spaces W(L
p
, L
q
) are given and their sharpness is shown. Localization operators are treated similarly: using different techniques from those
employed in the literature, we relax the known sufficient boundedness conditions for these operators to be bounded on L
p
spaces and prove the optimality of our results. Next, we exhibit sufficient and necessary conditions for such operators to
be bounded on Wiener amalgam spaces. 相似文献
32.
Rebeca P. Medina Angela R. Araujo Raymond J. Andersen Marcos A. Soares Fabio de A. Silva 《Natural product research》2019,33(3):443-446
Endophytic fungi were isolated from red alga Asparagopsis taxiformis - Falkenbergia stage, collected from the Brazilian coast, and were identified as Annulohypoxylon stygium (AT-03) and A. yungensis (AT-06) based on their macro/micromorphological and molecular features. Bioassay-guided fractionation of the EtOAc extract from laboratory cultures of both strains yielded known compounds pyrogallol from A. stygium, (3R)-scytalone and (3R,4R)-4-hydroxy-scytalone from A. yungensis. Pyrogallol was active against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli strains. An inactive fraction from A. stygium afforded two additional compounds, (3R,4R)-3,4,5-trihydroxy-1-tetralone and tyrosol. Optically active compounds had their stereochemistry determined by circular dichroism (CD) spectroscopy. 相似文献
33.
Nonlinear Dynamics - Many physical processes in nature exhibit complex dynamics that result from a combination of multiscale, nonlinear, non-local, and memory effects. Recent experimental... 相似文献
34.
Nonlinear Dynamics - We first present a brief review of nonlinear asset-pricing models and contributions in which such models have been used as benchmarks to evaluate the effectiveness of a number... 相似文献
35.
Dr. Sebastian C. Cosgrove Dr. Matthew P. Thompson Dr. Syed T. Ahmed Dr. Fabio Parmeggiani Prof. Nicholas J. Turner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18313-18317
The combination of biocatalysis and chemo-catalysis increasingly offers chemists access to more diverse chemical architectures. Here, we describe the combination of a toolbox of chiral-amine-producing biocatalysts with a Buchwald–Hartwig cross-coupling reaction, affording a variety of α-chiral aniline derivatives. The use of a surfactant allowed reactions to be performed sequentially in the same flask, preventing the palladium catalyst from being inhibited by the high concentrations of ammonia, salts, or buffers present in the aqueous media in most cases. The methodology was further extended by combining with a dual-enzyme biocatalytic hydrogen-borrowing cascade in one pot to allow for the conversion of a racemic alcohol to a chiral aniline. 相似文献
36.
Pioger P Couderc V Lefort L Barthelemy A Baronio F De Angelis C Min Y Quiring V Sohler W 《Optics letters》2002,27(24):2182-2184
We show numerically and experimentally that spatial trapping can be induced in quadratic media even if the pump pulse's duration is shorter than the group-delay mismatch between fundamental wave and second-harmonic components. The influence of phase mismatch and pulse power on the trapping effect is discussed. Spatial, temporal, and spectral behaviors that accompany self-trapped propagation are highlighted. 相似文献
37.
Fabio Nicola 《Journal d'Analyse Mathématique》2005,96(1):297-311
We give necessary and sufficient conditions for a lower bound with a gain of 3/2 derivatives (the so-called Weak-Hörmander inequality) for a class of systems with double characteristics. 相似文献
38.
We study a class of random variational inequalities on random sets and give measurability, existence, and uniqueness results in a Hilbert space setting. In the special case where the random and the deterministic variables are separated, we present a discretization technique based on averaging and truncation, prove a Mosco convergence result for the feasible random set, and establish norm convergence of the approximation procedure. 相似文献
39.
Victor B. Tinti Debora Marani Andre S. Ferlauto Fabio C. Fonseca Vincenzo Esposito Daniel Z. de Florio 《Particle & Particle Systems Characterization》2020,37(2):1900472
A fast and accurate experimental method is demonstrated to assess the fraction of exsolved metallic nanoparticles using magnetic measurements. As a benchmark, nanometric metallic nickel exsolved from (La1−xSrx)(Cr1−yNiy)O3−δ is used for its high relevance as a solid oxide fuel cell component. The method is based on the difference in the magnetic response of the exsolved metallic nickel (ferromagnetic) and Sr-doped lanthanum chromite ceramic matrix (paramagnetic). The exsolved nickel results in coherent nanoparticles pinned on the surface of the Sr-doped lanthanum chromite ceramic matrix, as evidenced by electron microscopy analyses. The results obtained indicate the procedure as a fast and sensitive method to study the exsolution of ferromagnetic nanoparticles. 相似文献
40.