全文获取类型
收费全文 | 210篇 |
免费 | 4篇 |
国内免费 | 5篇 |
专业分类
化学 | 122篇 |
晶体学 | 3篇 |
力学 | 4篇 |
数学 | 4篇 |
物理学 | 86篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2019年 | 4篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 4篇 |
2012年 | 6篇 |
2011年 | 15篇 |
2010年 | 12篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有219条查询结果,搜索用时 15 毫秒
71.
Lambert TN Boon JM Smith BD Pérez-Payán MN Davis AP 《Journal of the American Chemical Society》2002,124(19):5276-5277
Cholate esters with phenylurea groups at the 7alpha- and 12alpha-positions are highly effective promoters of phosphatidylcholine translocation across vesicle and cell membranes. The urea groups are essential for strong binding of the highly polar phosphate portion of the phosphocholine headgroup and apparently cannot be replaced by simple amide, alcohol, or amine moieties. NMR and UV studies show that these synthetic translocases have very weak affinity for phosphatidylethanolamine and phosphatidylserine. 相似文献
72.
A. Bayón F. Gascón R. Medina F.J. Nieves F. Salazar 《European Journal of Mechanics - A/Solids》2011,30(3):423-431
In this work the flexural vibration of a free cylinder of any aspect ratio is analysed. A general solution by powers series of the coordinates is proposed here to represent the displacements, with restrictions on the powers of the radial coordinates which prevent potential energy and stress singularities at the axis of the cylinder. By means of an analytic method, it is concluded that certain points of the cylinder have no axial motion. As a result of the pure transverse movement and of the fact that the cylinder bends, it is inferred that the axis is extended. Furthermore, in the symmetric modes, the points situated at the centres of the bases are displaced in the same direction and sense, and hence the distance between them does not vary in time. Flexural natural frequencies are numerically calculated by Ritz’s method with the general solution series proposed. Since the series used are more adequate, convergence is better than with classic series. The results are verified by FEM. Some consequences are extended to a rectangular plate, whose points of the middle surface vibrate transversally in the double-symmetric mode. In order to verify the theoretical results, a set of experiments with a laser interferometer is carried out. The experimental frequencies agree with the theoretical values. 相似文献
73.
74.
We present results for exclusive semileptonic decay widths of ground state spin-1/2 and spin-3/2 cb baryons corresponding to a c → s, d transition at the quark level. The relevance of hyperfine mixing in spin-1/2 cb baryons is shown. Our form factors are compatible with heavy quark spin symmetry constraints obtained in the infinite heavy quark mass limit. 相似文献
75.
Heavy quark spin symmetry is discussed in the context of single and doubly heavy baryons. A special attention is paid to the constraints/simplifications that this symmetry imposes on the non-relativistic constituent quark model wave functions and on the b ?? c semileptonic decays of these hadrons. 相似文献
76.
Rosa Montes Sandra Mndez Nieves Carro Julio Cobas Nelson Alves Teresa Neuparth Miguel Machado Santos Jos Benito Quintana Rosario Rodil 《Molecules (Basel, Switzerland)》2022,27(12)
Contaminants of emerging concern (CECs) are compounds of diverse origins that have not been deeply studied in the past which are now accruing growing environmental interest. The NOR-Water project aimed to identify the main CECs and their sources in the water environment of Northern Portugal–Galicia (located in northwest Spain) transnational region. To achieve these goals, a suspect screening analytical methodology based on the use of liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) was applied to 29 sampling sites in two campaigns. These sampling sites included river and sea water, as well as treated wastewater. The screening was driven by a library of over 3500 compounds, which included 604 compounds prioritized from different relevant lists on the basis of the persistency, mobility, and toxicity criteria. Thus, a total of 343 chemicals could be tentatively identified in the analyzed samples. This list of 343 identified chemicals was submitted to the classification workflow used for prioritization and resulted in 153 chemicals tentatively classified as persistent, mobile, and toxic (PMT) and 23 as very persistent and very mobile (vMvP), pinpointing the relevance of these types of chemicals in the aqueous environment. Pharmaceuticals, such as the antidepressant venlafaxine or the antipsychotic sulpiride, and industrial chemicals, especially high production volume chemicals (HPVC) such as ε-caprolactam, were the groups of compounds that were detected at the highest frequencies. 相似文献
77.
Juanjo Cabezas-Giménez Dr. Vanesa Lillo Dr. José Luis Núñez-Rico Dr. M. Nieves Corella-Ochoa Dr. Jesús Jover Prof. Dr. José Ramón Galán-Mascarós Prof. Dr. Anton Vidal-Ferran 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16956-16965
TAMOF-1 , a homochiral metal-organic framework (MOF) constructed from an amino acid derivative and Cu(II), was investigated as a heterogeneous catalyst in kinetic resolutions involving the ring opening of styrene oxide with a set of anilines. The branched products generated from the ring opening of styrene oxide with anilines and the unreacted epoxide were obtained with moderately high enantiomeric excesses. The linear product arising from the attack on the non-benzylic position of styrene oxide underwent a second kinetic resolution by reacting with the epoxide, resulting in an amplification of its final enantiomeric excess and a concomitant formation of an array of isomeric aminodiols. Computational studies confirmed the experimental results, providing a deep understanding of the whole process involving the two successive kinetic resolutions. Furthermore, TAMOF-1 activity was conserved after several catalytic cycles. The ring opening of a meso-epoxide with aniline catalyzed by TAMOF-1 was also studied and moderate enantioselectivities were obtained. 相似文献
78.
79.