全文获取类型
收费全文 | 786篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
化学 | 643篇 |
晶体学 | 2篇 |
力学 | 11篇 |
数学 | 77篇 |
物理学 | 81篇 |
出版年
2023年 | 10篇 |
2022年 | 31篇 |
2021年 | 45篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 14篇 |
2017年 | 14篇 |
2016年 | 30篇 |
2015年 | 24篇 |
2014年 | 24篇 |
2013年 | 56篇 |
2012年 | 72篇 |
2011年 | 86篇 |
2010年 | 49篇 |
2009年 | 32篇 |
2008年 | 60篇 |
2007年 | 39篇 |
2006年 | 30篇 |
2005年 | 32篇 |
2004年 | 31篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有814条查询结果,搜索用时 15 毫秒
91.
92.
Clifton LA Sanders MR Castelletto V Rogers SE Heenan RK Neylon C Frazier RA Green RJ 《Physical chemistry chemical physics : PCCP》2011,13(19):8881-8888
The self-assembly in solution of puroindoline-a (Pin-a), an amphiphilic lipid binding protein from common wheat, was investigated by small angle neutron scattering, dynamic light scattering and size exclusion chromatography. Pin-a was found to form monodisperse prolate ellipsoidal micelles with a major axial radius of 112 ± 4.5 ? and minor axial radius of 40.4 ± 0.18 ?. These protein micelles were formed by the spontaneous self-assembly of 38 Pin-a molecules in solution and were stable over a wide pH range (3.5-11) and at elevated temperatures (20-65 °C). Pin-a micelles could be disrupted upon addition of the non-ionic surfactant dodecyl-β-maltoside, suggesting that the protein self-assembly is driven by hydrophobic forces, consisting of intermolecular interactions between Trp residues located within a well-defined Trp-rich domain of Pin-a. 相似文献
93.
We study in this work the global existence of solutions to a system of reaction cross diffusion equations appearing in the modeling of multiple sclerosis, in the one-dimensional case. Weak solutions are obtained for general initial data, and existence, uniqueness, stability and smoothness are proven when initial data are smooth.
相似文献94.
Valeria N. Movchun Alexander A. Kolomeitsev Yurii L. Yagupolskii 《Journal of fluorine chemistry》1995,70(2):255-257
Aryltrifluoromethyl-sulfides, -sulfoxides and -sulfones can be prepared by trifluoromethylation of the corresponding arylsulfenyl, -sulfinyl and -sulfonyl halides using (trifluoromethyl)trimethylsilane in the presence of fluoride sources, such as TASF [tris(dimethylamino)sulfonium difluorotrimethylsilicate]. 相似文献
95.
In the solution of large linear systems, a condition guaranteeing that a minimal residual Krylov subspace method makes some
progress, i.e., that it does not stagnate, is that the symmetric part of the coefficient matrix be positive definite. This
condition results in a well-established worst-case bound for the convergence rate of the iterative method, due to Elman. This
bound has been extensively used, e.g., when the linear system comes from discretized partial differential equations, to show
that the convergence of GMRES is independent of the underlying mesh size. In this paper we introduce more general non-stagnation
conditions, which do not require the symmetric part of the coefficient matrix to be positive definite, and that guarantee,
for example, the non-stagnation of restarted GMRES for certain values of the restarting parameter.
Work on this paper was supported in part by the U.S. Department of Energy under grant DE-FG02-05ER25672. 相似文献
96.
Alberto Mariani Valeria Alzari Orietta Monticelli John A. Pojman Giuseppe Caria 《Journal of polymer science. Part A, Polymer chemistry》2007,45(19):4514-4521
Frontal polymerization (FP) has been successfully applied, for the first time, to obtain polymeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) in an amine‐cured epoxy matrix. Variations of maximum temperature (Tmax) and front velocity (Vf) have been studied. A comparison of these products with the corresponding materials, obtained by the classical batch polymerization technique, demonstrated that FP allows a higher degree of conversion than batch polymerization. The products have been characterized in terms of their thermal behavior with DSC analysis. SEM and X‐ray analyses revealed the morphology and the structures of the nanocomposites. The nanocomposites obtained by FP have the same characteristics of those synthesized, in much longer times, by batch polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4514–4521, 2007 相似文献
97.
98.
A quantitative high-performance thin-layer chromatographic method for determination of beta-asarone in Calamus rhizome was developed and validated. The method is suitable for proper identification of Acorus calamus. Through the use of caffeine-modified silica gel as the stationary phase and toluene-ethyl acetate (93 + 7, v/v) as the mobile phase, beta-asarone is baseline separated from its isomer alpha-asarone. Scanning densitometry with absorption measurement at 313 nm allows specific, accurate, and precise quantification of beta-asarone. The working range of 40 to 200 ng absolute of the target substance is sufficient to establish whether a given sample passes the limit test of 0.5% maximum as required by the Swiss Pharmacopoeia. 相似文献
99.
Relating Categorical Semantics for Intuitionistic Linear Logic 总被引:1,自引:0,他引:1
Maria?Emilia?MaiettiEmail author Paola?Maneggia Valeria?de?Paiva Eike?Ritter 《Applied Categorical Structures》2005,13(1):1-36
There are several kinds of linear typed calculus in the literature, some with their associated notion of categorical model. Our aim in this paper is to systematise the relationship between three of these linear typed calculi and their models. We point out that mere soundness and completeness of a linear typed calculus with respect to a class of categorical models are not sufficient to identify the most appropriate class uniquely. We recommend instead to use the notion of internal language when relating a typed calculus to a class of models. After clarifying the internal languages of the categories of models in the literature we relate these models via reflections and coreflections.
Mathematics Subject Classifications (2000) 03G30, 03B15, 18C50, 03B20. 相似文献
100.
A simple synthesis of ethyl 3,7-dimethyl-2,4,6-nonatriene-8-ynoates and their corresponding alcohols is presented; codensation with various cyclic ketones can lead to retinoids having modified ring structures. 相似文献