全文获取类型
收费全文 | 1680篇 |
免费 | 48篇 |
国内免费 | 7篇 |
专业分类
化学 | 1357篇 |
晶体学 | 13篇 |
力学 | 25篇 |
数学 | 210篇 |
物理学 | 130篇 |
出版年
2023年 | 11篇 |
2022年 | 24篇 |
2021年 | 41篇 |
2020年 | 44篇 |
2019年 | 33篇 |
2018年 | 28篇 |
2017年 | 19篇 |
2016年 | 58篇 |
2015年 | 44篇 |
2014年 | 48篇 |
2013年 | 92篇 |
2012年 | 135篇 |
2011年 | 111篇 |
2010年 | 64篇 |
2009年 | 44篇 |
2008年 | 122篇 |
2007年 | 137篇 |
2006年 | 106篇 |
2005年 | 107篇 |
2004年 | 84篇 |
2003年 | 75篇 |
2002年 | 70篇 |
2001年 | 20篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 22篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有1735条查询结果,搜索用时 687 毫秒
131.
Daniel Castaño Díez Max Gunzburger Angela Kunoth 《Numerical Methods for Partial Differential Equations》2008,24(6):1388-1404
We extend the multiscale finite element viscosity method for hyperbolic conservation laws developed in terms of hierarchical finite element bases to a (pre‐orthogonal spline‐)wavelet basis. Depending on an appropriate error criterion, the multiscale framework allows for a controlled adaptive resolution of discontinuities of the solution. The nonlinearity in the weak form is treated by solving a least‐squares data fitting problem. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2008 相似文献
132.
133.
Bartolo Gabriele Raffaella Mancuso Giuseppe Ruffolo Angela Dibenedetto 《Tetrahedron letters》2009,50(52):7330-1772
In the presence of a PdI2-based catalytic system, 1,2-diols undergo an oxidative carbonylation process to afford 5-membered cyclic carbonates in good to excellent yields (84-94%) and with unprecedented catalytic efficiencies for this kind of reaction (up to ca. 190 mol of product per mol of PdI2). Under similar conditions, 6-membered cyclic carbonates are obtained for the first time through a direct catalytic oxidative carbonylation of 1,3-diols (66-74% yields). 相似文献
134.
We construct positive and sign changing multipeak solutions to the pure critical exponent problem in a bounded domain with a shrinking hole, having a peak which concentrates at some point inside the shrinking hole (i.e. outside the domain) and one or more peaks which concentrate at interior points of the domain. These are, to our knowledge, the first multipeak solutions in a domain with a single small hole. 相似文献
135.
Garth A. Jones Angela Acocella Francesco Zerbetto 《Theoretical chemistry accounts》2007,118(1):99-106
An explicit electron dynamics approach has been used to calculate the nonlinear optical properties of C60 and its radical anion. An external perturbation, in the form of an oscillating electric field, induces the time-evolution
of the molecular wavefunction. The time-averaged instantaneous dipole moment of the systems gives the molecular response to
perturbations of varying field intensities and frequency of oscillation. The polarizabilities and the second-order hyperpolarizabilties
have been calculated and are in good qualitative agreement with experimentally available data. In line with previous theoretical
and experimental studies, the nonlinear effect is enhanced for the radical species.
Contribution to the Fernando Bernardi Memorial Issue. 相似文献
136.
The 1,3-dipolar cycloaddition reaction of unsymmetrically N-substituted and N-unsubstituted 1,3-oxazolium-5-olates with selected 3-substituted coumarins has been examined. Various types of pyrrole derivatives are isolated and their formation seems to be a function of the regio- and diastereochemistry of the initial cycloaddition step. 相似文献
137.
Diastereomers of 3-amino-2-hydroxy-6-methylheptanoic acid (AHMHA), a new amino acid unit in perthamides C and D, have been synthesized from commercially available 4-methylpentanol in a concise manner and 50% average overall yield. Comparison of the 1H and 13C NMR data, optical rotation data and Marfey’s analysis of the resulting isomers with the natural fragment unambiguously allowed the configurational assignment of the natural residue as (2R,3R). A structural revision of perthamides C and D is also reported. 相似文献
138.
Maria Laura Mercuri Paola Deplano Luca Pilia Angela Serpe Flavia Artizzu 《Coordination chemistry reviews》2010,254(13-14):1419-1433
Molecule-based materials are extremely versatile materials as they can be built from specifically designed building blocks with the desired size, shape, charge and electronic properties which determine their intermolecular interactions and, thus, their organization in the solid. The intermolecular interactions, therefore, in particular van der Waals interactions, π–π and π–d interactions, H-bonding, etc., play a crucial role in self-assembling these pre-designed molecular units and may provide a powerful way to afford layered mono- and multifunctional molecular materials with new or unknown physical properties. In this review the relationship between interaction modes and physical properties of organic/inorganic hybrids based on transition metal complexes with chalcogenolene ligands will be examined and an outlook will be proposed. With this goal, magnetic materials, highly conducting and metallic single-component materials containing dithiolene complex building blocks, multifunctional materials where the dithiolene complex is the magnetic or conducting component in addition to more complex systems involving other types of building block such as the metal oxalate complexes, will be discussed. 相似文献
139.
Giovanni Pellegrino Angelo Carotti Orazio Nicolotti Leonardo Pisani Angela Stefanachi Marco Catto 《Tetrahedron letters》2010,51(13):1702-7034
A small molecular library of 40 pyrimidine, pyrazole, and isoxazole derivatives, bearing structural features for a promising binding of therapeutically interesting enzymes, was designed and prepared. An efficient and straightforward solid phase synthesis was envisaged and carried out on a Rink amide resin. The assistance of microwave heating in any step reduced the reaction time, increased the reaction yields, and allowed an easy work-up and purification of the targeted compounds. 相似文献
140.
Carlo Bertucci Marco Pistolozzi Angela De Simone 《Analytical and bioanalytical chemistry》2010,398(1):155-166
Chirality plays a fundamental role in determining the pharmacodynamic and pharmacokinetic properties of drugs, and contributes significantly to our understanding of the mechanisms that lie behind biorecognition phenomena. Circular dichroism spectroscopy is the technique of choice for determining the stereochemistry of chiral drugs and proteins, and for monitoring and characterizing molecular recognition phenomena in solution. The role of chirality in our understanding of recognition phenomena at the molecular level is discussed here via several selected systems of interest in the drug discovery and development area. The examples were selected in order to underline the utility of circular dichroism in emerging studies of protein–protein interactions in biological context. In particular, the following aspects are discussed here: the relationship between stereochemistry and pharmacological activity—stereochemical characterization of new leads and drugs; stereoselective binding of leads and drugs to target proteins—the binding of drugs to serum albumins; conformational transitions of peptides and proteins of physiological relevance, and the stereochemical characterization of therapeutic peptides. 相似文献