全文获取类型
收费全文 | 453篇 |
免费 | 0篇 |
国内免费 | 4篇 |
专业分类
化学 | 286篇 |
力学 | 18篇 |
数学 | 92篇 |
物理学 | 61篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 23篇 |
2011年 | 26篇 |
2010年 | 19篇 |
2009年 | 16篇 |
2008年 | 35篇 |
2007年 | 31篇 |
2006年 | 25篇 |
2005年 | 14篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 26篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有457条查询结果,搜索用时 15 毫秒
31.
Functionalization at C-2 and C-5 of N-benzenesulfonyl-4-azaindole 1 was performed by lithiation reactions and original palladium-catalyzed chemistry. It led to very useful new substituted 4-azaindole derivatives in fair to high yields. 相似文献
32.
Stepan Oryshchyn Volodymyr Babizhetskyy Olga Zhak Jean-Yves Pivan Arndt Simon 《Journal of solid state chemistry》2010,183(11):2534-2543
The new ternary pnictides Er12Ni30P21 and Er13Ni25As19 have been synthesized from the elements. They crystallize with hexagonal structures determined from single-crystal X-ray data for Er12Ni30P21 (space group P63/m, a=1.63900(3) nm, c=0.37573(1) nm, Z=1, RF=0.062 for 1574 F-values and 74 variable parameters), and for Er13Ni25As19 (Tm13Ni25As19-type structure, space group P6?, a=1.6208(1) nm, c=0.38847(2) nm, Z=1, RF=0.026 for 1549 F-values and 116 variable parameters). These compounds belong to a large family of hexagonal structures with a metal-metalloid ratio of 2:1. HRTEM investigations were conducted to probe for local ordering of the disordered structure at the nanoscale. The magnetic properties of the phosphide Er12Ni30P21 have been studied in the temperature of range 2<T<300 K and with applied fields up to 5 T. The magnetic susceptibility follows the Curie-Weiss law from 4 to 300 K. The measured value of μeff=9.59 μB corresponds to the theoretical value of Er3+. 相似文献
33.
Jean-Yves Raty Céline Otjacques Jean-Pierre Gaspard Christophe Bichara 《Solid State Sciences》2010,12(2):193-198
Ge1Sb2Te4 is one of the most commonly used phase change materials, due to the large optical and electrical contrast between a metastable crystalline phase and the amorphous phase. We use ab initio molecular dynamics to generate an amorphous Ge1Sb2Te4 structure. By analysing the distance distributions, we show that the structure can be analysed in terms of 21% of tetrahedrally coordinated Ge atoms and 79% of 3-fold Ge atoms. These are involved in distorted octahedral shells with bond length correlations that are similar to the a-GeTe structure as a consequence of a Peierls-distortion. The electronic properties are shown to be in reasonable agreement with the experiment with an electronic gap of 0.45 eV with. The optical conductivity curve is also in agreement with the experiment, with a maximal conductivity at an energy of ~3 eV. 相似文献
34.
Badr Benmansour Ludovic Stephan Jean-Yves Cabon Laure Deschamps Philippe Giamarchi 《Journal of fluorescence》2011,21(3):843-850
This work presents spectroscopic properties of some Endocrine Disrupting Compounds (EDCs), frequently found in food and in
natural water. Studied molecules belong to the groups of phenolic and phthalate EDCs. In a first part, we have examined their
absorption and fluorescence properties. Fluorescence emission wavelengths are about 300 nm for phenolic compounds and 360 nm
for phtalate compounds; main excitation wavelengths being comprised between 210 nm and 230 nm. Fluorescence lifetimes measured
are short (about 4 ns) and the fluorescence quantum yield has been determined. In a second part, to avoid the time consuming
solvent extraction step, an analytical application to evaluate the performance of a direct analysis by laser induced fluorescence
spectroscopy of ECDs traces in tap water and in raw water is presented. Good detection limits have been obtained, i.e.: 0.35 μg.L−1 of chlorophenol in tap water, which are always lower than the reported Predictive Non Efficient Concentration (PNEC). 相似文献
35.
It was recently shown that fluctuations in the initial geometry of a heavy-ion collision generally result in a dipole asymmetry of the distribution of outgoing particles. This asymmetry, unlike the usual directed flow, is expected to be present at a wide range of rapidity--including midrapidity. The first evidence of this phenomenon can be seen in recent two-particle correlation data by the STAR Collaboration, providing the last element necessary to quantitatively describe long-range dihadron correlations. We extract differential directed flow from these data and propose a new direct measurement. 相似文献
36.
Yu Shen Jean-Yves Potvin Jean-Marc Rousseau Serge Roy 《Annals of Operations Research》1995,61(1):189-211
In this paper, we describe an expert consulting system for a dispatcher working in a courier service company. The system integrates interactive-graphic features and a learning module to support the dispatcher in his(her) task, and to suggest appropriate decisions when new requests come in. An experiment with a professional dispatcher is also reported. 相似文献
37.
Jean-Yves Welschinger 《Comptes Rendus Mathematique》2003,336(4):341-344
Following the approach of Gromov and Witten, we construct invariants under deformation of real rational symplectic 4-manifolds. These invariants provide lower bounds for the number of real rational J-holomorphic curves in a given homology class passing through a given real configuration of points. To cite this article: J.-Y. Welschinger, C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献
38.
39.
Atkinson AP Planchat A Graton J Renault E Grégoire G Le Questel JY 《Physical chemistry chemical physics : PCCP》2011,13(6):2272-2277
The gas phase structures of epibatidine, one of the most potent agonists of nicotinic acetylcholine receptors (nAChRs), are determined by means of infrared multiphoton dissociation (IRMPD) spectroscopy and quantum chemistry calculations. Comparison of the experimental and theoretical spectra provides evidence that about 15% of epibatidine is protonated on the Nsp(2) nitrogen in the gas phase. In contrast, the computational study of deschloroepibatidine shows that in the gas phase, the molecule is present only protonated on the Nsp(2) nitrogen. The main minima of the Nsp(2) protonated forms of the two molecules are strongly stabilized by intramolecular CH···Nsp(3) hydrogen bonds. The fundamental insights obtained in the present study on these two important nAChRs agonists show how subtle chemical modifications can have a deep impact on important physicochemical properties. 相似文献
40.
J.‐Y. Chemin 《纯数学与应用数学通讯》2011,64(12):1587-1598
This article studies the problem of L2 stability and weak‐strong uniqueness of solutions of the incompressible Navier‐Stokes on the whole space \input amssym ${\Bbb S}^3$ constructed by Kato's approach in spaces coming from Littlewood‐Paley theory and using the L1 smoothing effect for the heat flow. © 2011 Wiley Periodicals, Inc. 相似文献