全文获取类型
收费全文 | 640篇 |
免费 | 38篇 |
国内免费 | 2篇 |
专业分类
化学 | 405篇 |
晶体学 | 5篇 |
力学 | 7篇 |
数学 | 120篇 |
物理学 | 143篇 |
出版年
2023年 | 9篇 |
2022年 | 7篇 |
2021年 | 23篇 |
2020年 | 22篇 |
2019年 | 22篇 |
2018年 | 13篇 |
2017年 | 4篇 |
2016年 | 27篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 40篇 |
2012年 | 43篇 |
2011年 | 40篇 |
2010年 | 21篇 |
2009年 | 27篇 |
2008年 | 31篇 |
2007年 | 41篇 |
2006年 | 38篇 |
2005年 | 36篇 |
2004年 | 26篇 |
2003年 | 18篇 |
2002年 | 20篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有680条查询结果,搜索用时 15 毫秒
71.
Gonzalo Contreras 《Journal of Geometric Analysis》1998,8(4):533-569
We study the regularity of the Hausdorff dimension of the harmonic class of a surface M of negative curvature as a function
of the riemannian metric. We prove that it is a Cr− 3 function of the metric in the Banach manifold of Cr riemannian metrics on M. We also prove regularity results for some asymptotic quantities associated to the Brownian motion
on M. 相似文献
72.
J.Hernández Mendez R.Carabias Martínez E.Rodriguez Gonzalo J.Perez Trancon 《Analytica chimica acta》1990
The amperometric determination of parathion in the presence of its metabolites paraoxon and p-nitrophenol in a flow-injection system is reported. The method is based on the measurement of the oxidation signal yielded by p-nitrophenol on hydrolysis of parathion in the presence of Pd(II) or Hg(II). The oxidation of the metabolite was preferred to its reduction as it avoids the removal of oxygen, which poses major problems in flow-through configurations. 相似文献
73.
Gonzalo Martínez‐García Verónica Serafín Lourdes Agüí Paloma Yáñez‐Sedeño José M. Pingarrón 《Electroanalysis》2015,27(5):1119-1126
An electrochemical immunosensor for ghrelin (GHRL) determination in saliva is reported. Anti‐GHRL was immobilized onto Protein G‐magnetic beads and a competitive immunoassay involving biotinylated GHRL and alkaline phosphatase‐streptavidin was implemented. Once conjugate was magnetically captured on a screen‐printed carbon electrode, GHRL quantization was accomplished by DPV of 1‐naphtol formed upon addition of 1‐naphtyl phosphate. A linear range between 10?3 and 103 ng/mL GHRL, and a LOD of 7 pg/mL, much smaller than those from commercial ELISA kits, were found. The usefulness of the immunosensor was demonstrated by analyzing human saliva spiked with GHRL at 0.01, 0.1, 1 and 10 ng/mL. 相似文献
74.
García JI Jiménez-Osés G Mayoral JA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(2):529-539
An extensive computational study has been carried out on different catalytic systems for cyclopropanation reactions based on copper. Most DFT schemes used present drawbacks that preclude the calculation of accurate absolute kinetic properties (energy barriers) of such systems, excepting the M05 and M06 suites of density functionals. On the other hand, there is a wide range of DFT methods capable of reproducing relative energy values, which can be easily translated into selectivities. Most of the theoretical levels used tend to overestimate activation barriers, allowing the location of the transition state (TS) on the potential-energy surface (PES) of the most reactive systems, which are probably artifacts of the method. However, after a thorough analysis of the calculated PES, and the origin of the energy differences obtained for the different alkene approaches in chiral systems, it is found that energy differences are almost constant over a wide range of geometries covering the reaction channel zone in which the true TS on the Gibbs free-energy surface (GFES) lies. Therefore, many computational schemes can still be used confidently to explain and predict enantioselectivities in these systems. 相似文献
75.
We give necessary and sufficient conditions on a row-finite graph E so that the Leavitt path algebra L(E) is purely infinite simple. This result provides the algebraic analog to the corresponding result for the Cuntz-Krieger C∗-algebra C∗(E) given in [T. Bates, D. Pask, I. Raeburn, W. Szymański, The C∗-algebras of row-finite graphs, New York J. Math. 6 (2000) 307-324]. 相似文献
76.
We present a piecewise- linear map of the unit interval in which the resolvent of the Frobenius- Perron operator, considered
in a polynomial basis, has an essen-tial singularity at the origin. Associated with the essential singularity are polynomial
shift states, which are obtained from creation and annihilation operators in non- self- dual function spaces. Correlation
functions of general polynomial observables have decay components that vanish in a finite time. 相似文献
77.
The pyrolyses of four alkyl allyl sulfides with substituents on the α? C atom of the alkyl moiety have been studied in a stirred-flow system over the temperature range 340-400°C and pressures between 2 and 12 torr. The only products formed are propene and thioaldehydes. The reactions showed first-order kinetics with the rate coefficients following the Arrhenius equations: Chloromethyl allyl sulfide: Cyanomethyl allyl sulfide: 1-cyanoethyl allyl sulfide: Neopentyl allyl sulfide: The effects of these and other substituents on the reactivity is discussed in relation with the stabilization of a polar six-centered transition state. The results support a non-concerted mechanism where the 1–5 α? H atom shift is assisted by its acidic character. 相似文献
78.
79.
Gonzalo Garcia de Polavieja 《Foundations of Physics Letters》1996,9(5):411-424
We study the properties of a causal quantum theory in phase space for which phase space classical mechanics is obtained as a limit. The causal quantum theory is obtained from a generalized coherent state representation. The behavior for the one particle case and the manyparticle case are illustrated for the harmonic oscillator. We also answer to the arguments against the possibility of constructing causal theories in phase space. 相似文献
80.
Formation enthalpy of self-association of indoles in non-polar solvents is obtained from the behaviour of their fluorescence spectra areas with temperature. Formation enthalpy of skatole self-association thus obtained is in agreement with that found by another method. This supports the hypothesis that the spectral anomalies observed are due to self-association. The method can be extended to other molecules and it is independent of the spectral structure. 相似文献