全文获取类型
收费全文 | 4572篇 |
免费 | 175篇 |
国内免费 | 17篇 |
专业分类
化学 | 3743篇 |
晶体学 | 20篇 |
力学 | 57篇 |
数学 | 491篇 |
物理学 | 453篇 |
出版年
2024年 | 2篇 |
2023年 | 33篇 |
2022年 | 88篇 |
2021年 | 203篇 |
2020年 | 121篇 |
2019年 | 151篇 |
2018年 | 124篇 |
2017年 | 102篇 |
2016年 | 177篇 |
2015年 | 168篇 |
2014年 | 148篇 |
2013年 | 313篇 |
2012年 | 351篇 |
2011年 | 354篇 |
2010年 | 231篇 |
2009年 | 177篇 |
2008年 | 283篇 |
2007年 | 319篇 |
2006年 | 269篇 |
2005年 | 226篇 |
2004年 | 196篇 |
2003年 | 163篇 |
2002年 | 130篇 |
2001年 | 47篇 |
2000年 | 50篇 |
1999年 | 39篇 |
1998年 | 45篇 |
1997年 | 29篇 |
1996年 | 35篇 |
1995年 | 17篇 |
1994年 | 23篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1985年 | 6篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1937年 | 1篇 |
排序方式: 共有4764条查询结果,搜索用时 15 毫秒
181.
182.
Olga Mezentseva Galina Slepchenko Victor Filimonov Elena Mikheeva Galina Arbit 《Electroanalysis》2019,31(8):1477-1483
The electrochemical behavior of a number of benzoyl barbiturates was studied using a glassy carbon electrode (GCE). The kinetics of the electrode process is determined, the contribution of physical adsorption to the electrochemical process is estimated, and the mechanism of the possible electrochemical reaction is proposed. It is shown that the electrochemical reduction potentials of benzoyl phenobarbital derivatives are determined by the LUMO energies, calculated by the B3LYP 6‐311+G method. It is established that the process is quasi‐reversible, complicated by adverse reactions. The influence of halogen type and its position in the benzoyl residue of the studied substances on the analytical signal is established. The effective values of the dissociation constants of various forms of benzoyl derivatives were calculated using the example of halonal, for which the values 3.16 ? 10?8 and 6.31 ? 10?12, respectively, were found. 相似文献
183.
Manon Catherin Olatz Uranga-Barandiaran Arnaud Brosseau Dr. Rémi Métivier Dr. Gabriel Canard Dr. Anthony D'Aléo Dr. David Casanova Prof. Frédéric Castet Dr. Elena Zaborova Prof. Frédéric Fages 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3818-3828
We describe the synthesis of a series of covalently linked dimers of quadrupolar curcuminoid-BF2 dyes and the detailed investigation of their solvent-dependent spectroscopic and photophysical properties. In solvents of low polarity, intramolecular folding induces the formation of aggregated chromophores, the UV/Vis absorption spectra of which display the optical signature characteristic of weakly-coupled H-aggregates. The extent of folding and, in turn, of ground-state aggregation is strongly dependent on the nature of the flexible linker. Steady-state and time-resolved fluorescence emission spectroscopies show that the Frenkel exciton relaxes into a fluorescent symmetrical excimer state with a long lifetime. Furthermore, our in-depth studies show that a weakly emitting excimer lies on the pathway toward a photocyclomer. Two-dimensional 1H NMR spectroscopy and density functional theory (DFT) allowed the structure of the photoproduct to be established. To our knowledge, this represents the first example of a [2π+2π] photodimerization of the curcuminoid chromophore. 相似文献
184.
Monika Kořenková Dr. Ing. Martin Hejda Prof. Milan Erben Dr. Ing. Robert Jirásko Prof. Dr. Roman Jambor Prof. Aleš Růžička Dr. Elena Rychagova Prof. Sergey Ketkov Prof. Libor Dostál 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(56):12884-12888
The reaction of N,C,N-chelated stibinidene ArSb ( 1 ) (Ar=C6H3-2,6-(CH=NtBu)2) with selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing an antimony atom at the bridgehead position, fused with a 6-membered benzene and a 5-membered N-alkyl/aryl-pyrrolidine ring. These compounds were completely characterized. More importantly, additional studies showed that these reactions are reversible in solution, thereby representing an unprecedented reversible activation of a C=C bond by an antimony(I) compound. 相似文献
185.
186.
187.
Sergey V. Nikitin Dmitriy A. Parkhomenko Mariya V. Edeleva Elena G. Bagryanskaya 《Journal of polymer science. Part A, Polymer chemistry》2015,53(21):2546-2556
Simulation on the kinetic scheme of enhanced spin capturing polymerizations (ESCP) were performed to reveal the influence of different parameters, e.g., initiation rate, spin capturing and side reactions on the properties (the monomer conversion, degree of polymerization, polydispersity index, and the fraction of “living” chains) of polymer obtained. The kinetic scheme of ESCP was solved numerically as well as the method of statistical moments of molecular weight distribution was applied to get some numerical expressions for analysis. The simulations showed that fast initiation rate can lead to decrease of living fraction and broadening of molecular weight distribution. Whereas high rate of spin capturing makes the polymer chains shorter but increases living character. And side reactions always decrease livingness of the polymer obtained. Finally in the case of absence of side reaction we were able to formulate criteria for formation of polymer with target molecular weight and quota of living chains via ESCP process. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2546–2556 相似文献
188.
189.
Dr. Julian Brunner Britta Maier Rose Rosenberg Sebastian Sturm Prof. Dr. Helmut Cölfen Dr. Elena V. Sturm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(66):15242-15248
Applications in the fields of materials science and nanotechnology increasingly demand monodisperse nanoparticles in size and shape. Up to now, no general purification procedure exists to thoroughly narrow the size and shape distributions of nanoparticles. Here, we show by analytical ultracentrifugation (AUC) as an absolute and quantitative high-resolution method that multiple recrystallizations of nanocrystals to mesocrystals is a very efficient tool to generate nanocrystals with an excellent and so-far unsurpassed size-distribution (PDIc=1.0001) and shape. Similar to the crystallization of molecular building blocks, nonclassical recrystallization removes “colloidal” impurities (i.e., nanoparticles, which are different in shape and size from the majority) by assembling them into a mesocrystal. In the case of nanocrystals, this assembly can be size- and shape-selective, since mesocrystals show both long-range packing ordering and preferable crystallographic orientation of nanocrystals. Besides the generation of highly monodisperse nanoparticles, these findings provide highly relevant insights into the crystallization of mesocrystals. 相似文献
190.
Elena Molteni Giovanni Onida Giancarlo Cappellini 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(4):98
We study the electronic properties of the Si(001):Uracil, Si(001):Thymine, andSi(001):5-Fluorouracil systems, focusing on the Si dimer-bridging configuration withadsorption governed by carbonyl groups. While the overall structural and electronicproperties are similar, with small differences due to chemical substitutions, much largereffects on the surface band dispersion and bandgap show up as a function of the molecularorientation with respect to the surface. An off-normal orientation of the molecular planesis favored, showing larger bandgap and lower total energy than the upright position. Wealso analyze the localization of gap-edge occupied and unoccupied surface states. 相似文献