全文获取类型
收费全文 | 11911篇 |
免费 | 643篇 |
国内免费 | 58篇 |
专业分类
化学 | 8738篇 |
晶体学 | 38篇 |
力学 | 295篇 |
数学 | 1857篇 |
物理学 | 1684篇 |
出版年
2023年 | 92篇 |
2022年 | 142篇 |
2021年 | 202篇 |
2020年 | 291篇 |
2019年 | 305篇 |
2018年 | 144篇 |
2017年 | 166篇 |
2016年 | 436篇 |
2015年 | 476篇 |
2014年 | 489篇 |
2013年 | 648篇 |
2012年 | 919篇 |
2011年 | 922篇 |
2010年 | 570篇 |
2009年 | 492篇 |
2008年 | 734篇 |
2007年 | 703篇 |
2006年 | 645篇 |
2005年 | 629篇 |
2004年 | 496篇 |
2003年 | 404篇 |
2002年 | 391篇 |
2001年 | 184篇 |
2000年 | 152篇 |
1999年 | 144篇 |
1998年 | 151篇 |
1997年 | 148篇 |
1996年 | 121篇 |
1995年 | 93篇 |
1994年 | 87篇 |
1993年 | 98篇 |
1992年 | 71篇 |
1991年 | 69篇 |
1990年 | 57篇 |
1989年 | 72篇 |
1988年 | 55篇 |
1987年 | 38篇 |
1986年 | 44篇 |
1985年 | 59篇 |
1984年 | 49篇 |
1983年 | 50篇 |
1982年 | 51篇 |
1981年 | 59篇 |
1980年 | 45篇 |
1979年 | 47篇 |
1978年 | 45篇 |
1977年 | 44篇 |
1976年 | 50篇 |
1975年 | 42篇 |
1973年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Christian Kluger Wolfgang H. Binder 《Journal of polymer science. Part A, Polymer chemistry》2007,45(3):485-499
Block copolymers on basis of poly(oxanorbornenes) bearing functional moieties in their side‐chains are prepared via a combination of ROMP‐methods and 1,3‐dipolar‐“click”‐reactions. Starting from N‐substituted‐ω‐bromoalkyl‐oxanorbornenes and alkyl‐/perfluoroalkyl‐oxanorbornenes, block copolymers with molecular weights up to 25,000 g mol?1 were generated. Subsequent nucleophilic exchange‐reactions yielded the block‐copolymers functionalized with ω‐azidoalkyl‐moieties in one block. The 1,3‐azide/alkine‐“click” reactions with a variety of terminal alkynes in the presence of a catalyst system consisting of tetrakis(acetonitrile)hexafluorophosphate copper(I) and tris(1‐benzyl‐5‐methyl‐1H‐ [1,2,3]triazol‐4‐ylmethyl)‐amine furnished the substituted block copolymers in high yields, as proven by NMR‐spectroscopy. The resulting polymers were investigated via temperature‐dependent SAXS‐methods, revealing their microphase separated structure as well as their temperature‐dependent behavior. The presented method offers the generation of a large set of different block‐copolymers from only a small set of starting materials because of the high versatility of the “click” reaction, thus enabling a simple and complete functionalization after the initial polymerization reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 485–499, 2007 相似文献
74.
Christian Buchgraber Alexander Pogantsch Stefan Kappaun Julia Spanring Wolfgang Kern 《Journal of polymer science. Part A, Polymer chemistry》2006,44(14):4317-4327
Light‐emitting diodes based on organic materials [organic light‐emitting diodes (OLEDs)] have attracted much interest over the past decade. Several different attempts have been made to realize multicolor OLEDs. This article describes a new approach based on energy transfer in a donor/acceptor system. A copolymer containing both donor and acceptor compounds as comonomer units is prepared. The polymer consists of a derivative of a luminescent dye [4‐dicyanmethylene‐2‐methyl‐6‐4H‐pyran (DCM); acceptor compound], which is copolymerized with fluorene (donor compound) to combine the properties of an electroactive polymer with a highly luminescent dye. Photochemical processing is achieved by UV irradiation of this copolymer in the presence of gaseous trialkylsilanes. This reagent selectively saturates the C?C bonds in the DCM comonomer units while leaving the fluorene units essentially unaffected. As a result of the photochemical process, the red electroluminescence of the acceptor compound vanishes, and the blue‐green electroluminescence from the polyfluorene units is recovered. Compared with previous approaches based on polymer blends, this copolymer approach avoids problems associated with phase‐separation phenomena in the active layer of OLEDs. © 2006Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4317–4327, 2006 相似文献
75.
Martin Loeser Lorenzo Occhi Christian Vélez Raffaele Rezzonico Bernd Witzigmann 《Optical and Quantum Electronics》2006,38(12-14):1069-1075
The impact of self-heating and cavity length on the spectral emission properties of SLEDs is investigated using a state-of-the-art simulation tool. Simulated data are compared to measurements for two InP-based benchmark devices operating around 1300 nm, and excellent agreement is achieved in either case. 相似文献
76.
Christian Constanda 《Proceedings of the American Mathematical Society》1998,126(3):827-834
Sommerfeld-type radiation conditions are indicated for the solutions of the system governing the small stationary oscillations in plates with transverse shear deformation, and a uniqueness theorem is proved in the case of the corresponding exterior Dirichlet and Neumann problems.
77.
78.
Christian Maes 《Journal of statistical physics》1990,61(3-4):667-681
An anisotropic lattice gas dynamics is investigated for which particles on
d
jump to empty nearest neighbor sites with (fast) rate –2 in a specified direction and some particular configuration-dependent rates in the other directions. The model is translation and reflection invariant and is particle conserving. The space coordinate in the fast-rate direction is rescaled by –1. It follows that the density field converges in probability, as 0, to the corresponding solution of a nonlinear diffusion-type equation. The microscopic fluctuations about the deterministic macroscopic evolution are determined explicitly and it is found that the stationary fluctuations decay via a power law (1/r
d
) with the direction dependence of a quadrupole field. 相似文献
79.
Joel L. Lebowitz Christian Maes Eugene R. Speer 《Journal of statistical physics》1990,59(1-2):117-170
We investigate the behavior of discrete-time probabilistic cellular automata (PCA), which are Markov processes on spin configurations on ad-dimensional lattice, from a rigorous statistical mechanics point of view. In particular, we exploit, whenever possible, the correspondence between stationary measures on the space-time histories of PCAs on
d
and translation-invariant Gibbs states for a related Hamiltonian on (
d+1). This leads to a simple large-deviation formula for the space-time histories of the PCA and a proof that in a high-temperature regime the stationary states of the PCA are Gibbsian. We also obtain results about entropy, fluctuations, and correlation inequalities, and demonstrate uniqueness of the invariant state and exponential decay of correlations in a high-noise regime. We discuss phase transitions in the low-noise (or low-temperature) regime and review Toom's proof of nonergodicity of a certain class of PCAs. 相似文献
80.