全文获取类型
收费全文 | 922篇 |
免费 | 65篇 |
国内免费 | 5篇 |
专业分类
化学 | 686篇 |
晶体学 | 7篇 |
力学 | 25篇 |
数学 | 151篇 |
物理学 | 123篇 |
出版年
2023年 | 8篇 |
2022年 | 3篇 |
2021年 | 17篇 |
2020年 | 34篇 |
2019年 | 22篇 |
2018年 | 20篇 |
2017年 | 4篇 |
2016年 | 29篇 |
2015年 | 27篇 |
2014年 | 41篇 |
2013年 | 62篇 |
2012年 | 59篇 |
2011年 | 64篇 |
2010年 | 39篇 |
2009年 | 30篇 |
2008年 | 62篇 |
2007年 | 54篇 |
2006年 | 48篇 |
2005年 | 53篇 |
2004年 | 35篇 |
2003年 | 33篇 |
2002年 | 23篇 |
2001年 | 16篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 19篇 |
1995年 | 8篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1970年 | 4篇 |
1885年 | 2篇 |
1876年 | 2篇 |
排序方式: 共有992条查询结果,搜索用时 15 毫秒
891.
de Groot FM Glatzel P Bergmann U van Aken PA Barrea RA Klemme S Hävecker M Knop-Gericke A Heijboer WM Weckhuysen BM 《The journal of physical chemistry. B》2005,109(44):20751-20762
1s2p resonant inelastic X-ray scattering (RIXS) spectroscopy has been measured for a series of iron oxides, including octahedral and tetrahedral Fe(II) and Fe(III) systems. Their spectral shapes have been analyzed and explained using crystal-field multiplet simulations. The RIXS planes and the K-edge and L-edge X-ray absorption spectra related to these RIXS planes will be discussed with respect to their analytical opportunities. It is concluded that the full power and possibilities of 1s2p RIXS needs an overall resolution of 0.3 eV. This will yield a technique with more detailed information than K-edge and L-edge X-ray absorption combined, obtained in a single experiment. Another major advantage is that 1s2p RIXS involves only hard X-rays, and experiments under essentially any condition and on any system are feasible. 相似文献
892.
Katrien Monsieurs Kristof T.J. Loones J.A. Dirk De Ridder Kees Goubitz Roger A. Dommisse Bert U.W. Maes 《Tetrahedron》2007,63(18):3870-3881
In search for the structural elucidation of samoquasine A, a natural product isolated from the seeds of Annona squamosa L., two benzo[f]phthalazinone isomers have been synthesized. The synthetic pathway followed to build up these skeletons is based on the combination of two Suzuki reactions on a pyridazinone precursor and a ring closure reaction via a condensation reaction. 1H NMR data of the synthesized compound allowed to establish that the structure of the natural product samoquasine A is not benzo[f]phthalazin-4(3H)-one, as previously suggested. 相似文献
893.
Vytautas Gapsys Laura Prez-Benito Matteo Aldeghi Daniel Seeliger Herman van Vlijmen Gary Tresadern Bert L. de Groot 《Chemical science》2020,11(4):1140
Ligand binding affinity calculations based on molecular dynamics (MD) simulations and non-physical (alchemical) thermodynamic cycles have shown great promise for structure-based drug design. However, their broad uptake and impact is held back by the notoriously complex setup of the calculations. Only a few tools other than the free energy perturbation approach by Schrödinger Inc. (referred to as FEP+) currently enable end-to-end application. Here, we present for the first time an approach based on the open-source software pmx that allows to easily set up and run alchemical calculations for diverse sets of small molecules using the GROMACS MD engine. The method relies on theoretically rigorous non-equilibrium thermodynamic integration (TI) foundations, and its flexibility allows calculations with multiple force fields. In this study, results from the Amber and Charmm force fields were combined to yield a consensus outcome performing on par with the commercial FEP+ approach. A large dataset of 482 perturbations from 13 different protein–ligand datasets led to an average unsigned error (AUE) of 3.64 ± 0.14 kJ mol−1, equivalent to Schrödinger''s FEP+ AUE of 3.66 ± 0.14 kJ mol−1. For the first time, a setup is presented for overall high precision and high accuracy relative protein–ligand alchemical free energy calculations based on open-source software.Relative ligand binding affinity calculations based on molecular dynamics (MD) simulations and non-physical (alchemical) thermodynamic cycles have shown great promise for structure-based drug design. 相似文献
894.
Bert den Boer 《Integral Equations and Operator Theory》1978,1(1):19-27
In this paper it is shown that after a suitable extension an operator function A, which is holomorphic on an open set in , is equivalent on to a linear pencil S-V. If is bounded, then V turns out to be right invertible, and in that case a further extension is equivalent on to a linear pencil T-I. 相似文献
895.
Bert Vanhaecht Bart Rimez Rudolph Willem Monique Biesemans Cor E. Koning 《Journal of polymer science. Part A, Polymer chemistry》2002,40(12):1962-1971
The effects of the partial substitution of 1,4‐disubstituted cyclohexane monomers for linear aliphatic monomers in polyamides are discussed. More specifically, the relation between the stereochemistry of the cycloaliphatic residues and the thermal properties [melting temperature (Tm) and crystallization temperature (Tcr)] was investigated. For this purpose, two different types of copolyamides were synthesized: in polyamides 12.6, the adipic acid residues were partially replaced by cis/trans‐1,4‐cyclohexanedicarboxylic acid (1,4‐CHDA), whereas in polyamides 4.14, the 1,4‐diaminobutane residues were partially substituted with cis/trans‐1,4‐diaminocyclohexane (1,4‐DACH). For both systems, increasing the degree of substitution of cycloaliphatic residues for linear aliphatic residues resulted in a rise of both Tm and Tcr. This points to the isomorphous crystallization of the linear and cycloaliphatic residues. In contrast to the use of 1,4‐DACH as a comonomer, 1,4‐CHDA residues showed isomerization upon thermal treatment of the polyamides. This isomerization of the cyclohexane residues influenced the thermal properties of the copolyamides. The use of a nonisomerizing cis–trans mixture of 1,4‐DACH exhibited the large influence of the stereochemistry of the cycloaliphatic residues on the Tm of the copolyamides. For both the 1,4‐CHDA‐ and 1,4‐DACH‐based copolyamides, differential scanning calorimetry analysis revealed that recrystallization occurs during melting. This exothermal effect becomes less pronounced with an increasing content of rigid cycloaliphatic residues. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1962–1971, 2002 相似文献
896.
The 2′-deoxyisoguanosine ( 1 ) was synthesized by a two-step procedure from 2′-deoxyguanosine ( 5 ). Amination of silylated 2′-deoxyguanosine yielded 2-amino-2′-deoxyadenosine ( 6 ) which was subjected to selective deamination of the 2-NH2 group resulting in compound 1 . Also 2′,3′-dideoxyisoguanosine ( 2 ) was prepared employing the photo-substitution of the 2-substituent of 2-chloro-2′,3′-dideoxyadenosine ( 4 ). The latter was synthesized by Barton deoxygenation from 2-chloro-2′-deoxyadenosine ( 3 ) or via glycosylation of 2,6-dichloropurine ( 12 ) with the lactol 13 . Compound 1 was less stable at the N-glycosylic bond than 2′-deoxyguanosine ( 5 ). The dideoxynucleoside 2 was deaminated by adenosine deaminase affording 2′,3′-dideoxyxanthosine ( 17 ). 相似文献
897.
898.
899.
900.
We study the maps induced on cohomology by a Nikulin (i.e. a symplectic) involution on a K3 surface. We parametrize the 11-dimensional irreducible components of the moduli space of algebraic K3 surfaces with a Nikulin involution and we give examples of the general K3 surface in various components. We conclude with some remarks on Morrison–Nikulin involutions, these are Nikulin involutions
which interchange two copies of E
8(−1) in the Néron Severi group.
The second author is supported by DFG Research Grant SA 1380/1-1. 相似文献