全文获取类型
收费全文 | 1833篇 |
免费 | 51篇 |
国内免费 | 4篇 |
专业分类
化学 | 1074篇 |
晶体学 | 15篇 |
力学 | 22篇 |
数学 | 251篇 |
物理学 | 526篇 |
出版年
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 11篇 |
2016年 | 37篇 |
2015年 | 40篇 |
2014年 | 35篇 |
2013年 | 73篇 |
2012年 | 56篇 |
2011年 | 75篇 |
2010年 | 69篇 |
2009年 | 38篇 |
2008年 | 81篇 |
2007年 | 92篇 |
2006年 | 83篇 |
2005年 | 75篇 |
2004年 | 78篇 |
2003年 | 50篇 |
2002年 | 44篇 |
2001年 | 42篇 |
2000年 | 38篇 |
1999年 | 20篇 |
1998年 | 24篇 |
1997年 | 29篇 |
1996年 | 42篇 |
1995年 | 32篇 |
1994年 | 30篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 39篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 36篇 |
1983年 | 22篇 |
1982年 | 32篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 29篇 |
1978年 | 23篇 |
1977年 | 15篇 |
1976年 | 21篇 |
1975年 | 14篇 |
1974年 | 41篇 |
1973年 | 22篇 |
1972年 | 12篇 |
排序方式: 共有1888条查询结果,搜索用时 234 毫秒
1.
2.
Hans R. Kricheldorf Lali Vakhtangishvili Gert Schwarz 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5725-5735
Poly(pyridine ether)s were prepared in two ways: the polycondensation of silylated 1,1,1‐tris(4‐hydroxyphenyl)ethane (THPE) with 2,6‐difluoropyridine (method A) and the polycondensation of free THPE with 2,6‐dichloropyridine (method B). With method A, the THPE/difluoropyridine feed ratio was varied from 1.0:1.0 to 1.0:1.6. Cycles, bicycles, and multicycles were the main reaction products, and crosslinking was never observed. When ideal stoichiometry was used exclusively, multicycles free of functional groups were obtained. These multicycles were detectable in matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra up to B38C76 with a mass of approximately 32,000 Da. With method B, the reaction conditions were varied at a fixed feed ratio to achieve an optimum for the preparation of multicyclic polyethers, but because of the lower reactivity of 2,6‐dichloropyridine, a quantitative conversion was not achieved. The reaction products were characterized with MALDI‐TOF mass spectrometry, viscosity measurements, and size exclusion chromatography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5725–5735, 2004 相似文献
3.
We have calculated inclusive two-jet cross sections in next-to-leading order QCD for low Q 2 ep collisions superimposing direct and resolved contributions. Infrared and collinear singularities in the virtual and real contributions are cancelled with the phase space slicing method. Various inclusive two-jet distributions have been computed. The results are compared with recent data from the ZEUS collaboration at HERA. 相似文献
4.
Jürg Kramer 《Elemente der Mathematik》2002,57(3):115-120
5.
6.
We study algebraic geometric codes obtained from rational normal scrolls. We determine the complete weight hierarchy and spectrum
of these codes.
相似文献
7.
Utilizing forward recoil spectrometry (FRES), we have determined the segregation isotherm which describes the interfacial excess zi* of diblock copolymers of poly (d8-styrene-b-2-vinylpyridine) (dPS-PVP) at the interface between the homopolymers PS and PVP as a function of ?∞, the volume fraction of diblock copolymer remaining in the host homopolymer. All the samples were analyzed after annealing at temperatures and times sufficient to achieve equilibrium segregation. The effect of the degree of polymerization of both the diblock copolymers and the host homopolymers on the segregation isotherm is investigated. When the degree of polymerization of the homopolymer is much larger than that of the diblock copolymer, the normalized interfacial excess (zi*/Rg), where Rg is the radius of gyration of an isolated block copolymer chain, is a universal function of that portion of the block copolymer chemical potential due to chain stretching. The existence of such a universal function is predicted by theory and its form is in good agreement with self-consistent mean field calculations. Using these results, one can predict important aspects of the block copolymer segregation (e.g., the saturation interfacial excess) without recourse to the time-consuming numerical calculations. © 1994 John Wiley & Sons, Inc. 相似文献
8.
9.
10.
Radu Ioan Boţ Ioan Bogdan Hodrea Gert Wanka 《Nonlinear Analysis: Theory, Methods & Applications》2007
Considering a constrained fractional programming problem, within the present paper we present some necessary and sufficient conditions, which ensure that the optimal objective value of the considered problem is greater than or equal to a given real constant. The desired results are obtained using the Fenchel–Lagrange duality approach applied to an optimization problem with convex or difference of convex (DC) objective functions and finitely many convex constraints. These are obtained from the initial fractional programming problem using an idea due to Dinkelbach. We also show that our general results encompass as special cases some recently obtained Farkas-type results. 相似文献