全文获取类型
收费全文 | 4589篇 |
免费 | 203篇 |
国内免费 | 19篇 |
专业分类
化学 | 3185篇 |
晶体学 | 22篇 |
力学 | 199篇 |
数学 | 775篇 |
物理学 | 630篇 |
出版年
2022年 | 19篇 |
2021年 | 58篇 |
2020年 | 76篇 |
2019年 | 90篇 |
2018年 | 61篇 |
2017年 | 44篇 |
2016年 | 126篇 |
2015年 | 87篇 |
2014年 | 135篇 |
2013年 | 235篇 |
2012年 | 312篇 |
2011年 | 362篇 |
2010年 | 186篇 |
2009年 | 190篇 |
2008年 | 293篇 |
2007年 | 325篇 |
2006年 | 298篇 |
2005年 | 312篇 |
2004年 | 255篇 |
2003年 | 224篇 |
2002年 | 152篇 |
2001年 | 47篇 |
2000年 | 48篇 |
1999年 | 41篇 |
1998年 | 27篇 |
1997年 | 41篇 |
1996年 | 53篇 |
1995年 | 55篇 |
1994年 | 51篇 |
1993年 | 36篇 |
1992年 | 31篇 |
1991年 | 26篇 |
1990年 | 30篇 |
1989年 | 24篇 |
1988年 | 22篇 |
1987年 | 22篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 26篇 |
1981年 | 20篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1978年 | 25篇 |
1977年 | 25篇 |
1976年 | 32篇 |
1975年 | 23篇 |
1974年 | 18篇 |
1973年 | 23篇 |
1972年 | 15篇 |
排序方式: 共有4811条查询结果,搜索用时 218 毫秒
1.
Massoumi Sina Challamel Noël Lerbet Jean Wautier Antoine Nicot François Darve Félix 《Meccanica》2022,57(8):2043-2066
Meccanica - This study is an attempt towards a better understanding of the length scale effects on the bending response of the granular beams. To this aim, a unidimensional discrete granular chain... 相似文献
2.
Journal of Statistical Physics - We study mathematically the equilibrium properties of the Bose–Hubbard Hamiltonian in the limit of a vanishing hopping amplitude. This system conserves the... 相似文献
3.
Foundations of Computational Mathematics - We present a finite element variational integrator for compressible flows. The numerical scheme is derived by discretizing, in a structure-preserving way,... 相似文献
4.
Measurement of emerging dechloranes in human serum using modulated gas chromatography coupled to electron capture negative ionization time‐of‐flight mass spectrometry 下载免费PDF全文
5.
François N. Miros Guangxi Huang Yingjie Zhao Naomi Sakai 《Supramolecular chemistry》2015,27(5-6):303-309
Catalysis with anion–π interactions is emerging as an important topic in supramolecular chemistry. Among the reactions explored so far on π-acidic surfaces, coumarin synthesis stands out as a cascade process with several coupled anionic transition states. Increasing π-acidity has been shown in a different context to increase transition-state stabilisation and thus catalytic activity. In this report, we explore the possible use of macrocycles to accelerate coumarin synthesis between two π-acidic surfaces. To our disappointment, we found that compared to monomeric π-acids, coumarin synthesis within divalent macrocycles is clearly slower. Hindered access to an overly confined active site within the macrocycles could possibly account for this loss in activity, but several other explanations are certainly possible. However, operational coumarin synthesis on monomeric π-acidic surfaces is shown to tolerate structural modifications. Best results are obtained with structures that aim for proximity without obstructing transition-state stabilisation on the π-acidic surface. 相似文献
6.
Sorin‐Claudiu Roşca Dr. Chiara Dinoi Dr. Elsa Caytan Dr. Vincent Dorcet Prof. Dr. Michel Etienne Prof. Dr. Jean‐François Carpentier Dr. Yann Sarazin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(19):6505-6509
Strontium and calcium (alkaline earth: Ae) olefin complexes stabilised by secondary Ae???F?C and β‐agostic Ae???H?Si interactions are presented. Olefin coordination onto the alkaline earths is plain in the solid state, and it is thermodynamically favoured over the coordination of THF. The existence of the Ae???olefin interactions is corroborated by solution NMR data and DFT computations. The coordination mode of the olefin varies with steric effects and, if enforced, olefin dissociation can be compensated by the other non‐covalent interactions, as supported by DFT computations. 相似文献
7.
Apidopoulos Vassilis Aujol Jean-François Dossal Charles 《Mathematical Programming》2020,180(1-2):137-156
Mathematical Programming - In this paper we study the convergence of an Inertial Forward–Backward algorithm, with a particular choice of an over-relaxation term. In particular we show that... 相似文献
8.
9.
Yannick Geiger Thierry Achard Aline Maisse-Franois Stphane Bellemin-Laponnaz 《Chemical science》2020,11(46):12453
The chiral ligand N-methylephedrine (NME) was found to catalyse the addition of dimethylzinc to benzaldehyde in an enantiodivergent way, with a monomeric and a homochiral dimeric complex both catalysing the reaction at a steady state and giving opposite product enantiomers. A change in the sign of the enantiomeric product was thus possible by simply varying the catalyst loading or the ligand ee, giving rise to an enantiodivergent non-linear effect. Simulations using a mathematical model confirmed the possibility of such behaviour and showed that this can lead to situations where a reaction gives racemic products, although the system is composed only of highly enantioselective individual catalysts. Furthermore, depending on the dimer''s degree of participation in the catalytic conversion, enantiodivergence may or may not be observed experimentally, which raises questions about the possibility of enantiodivergence in other monomer/dimer-catalysed systems. Simulations of the reaction kinetics showed that the observed kinetic constant kobs is highly dependent on user-controlled parameters, such as the catalyst concentration and the ligand ee, and may thus vary in a distinct way from one experimental setup to another. This unusual dependency of kobs allowed us to confirm that a previously observed U-shaped catalyst order vs. catalyst loading-plot is linked to the simultaneous catalytic activity of both monomeric and dimeric complexes.An asymmetric reaction consisting of competing monomeric and dimeric catalysts may explain enantiodivergent non-linear effects. 相似文献
10.