全文获取类型
收费全文 | 551篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
化学 | 382篇 |
晶体学 | 6篇 |
力学 | 21篇 |
数学 | 122篇 |
物理学 | 36篇 |
出版年
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 27篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 21篇 |
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 30篇 |
2012年 | 25篇 |
2011年 | 33篇 |
2010年 | 18篇 |
2009年 | 23篇 |
2008年 | 29篇 |
2007年 | 27篇 |
2006年 | 18篇 |
2005年 | 39篇 |
2004年 | 26篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有567条查询结果,搜索用时 5 毫秒
91.
For a (co)monad T
l
on a category , an object X in , and a functor , there is a (co)simplex in . The aim of this paper is to find criteria for para-(co)cyclicity of Z
*. Our construction is built on a distributive law of T
l
with a second (co)monad T
r
on , a natural transformation , and a morphism in . The (symmetrical) relations i and w need to satisfy are categorical versions of Kaygun’s axioms of a transposition map. Motivation comes from the observation
that a (co)ring T over an algebra R determines a distributive law of two (co)monads and on the category of R-bimodules. The functor Π can be chosen such that is the cyclic R-module tensor product. A natural transformation is given by the flip map and a morphism is constructed whenever T is a (co)module algebra or coring of an R-bialgebroid. The notion of a stable anti-Yetter-Drinfel’d module over certain bialgebroids, the so-called ×
R
-Hopf algebras, is introduced. In the particular example when T is a module coring of a ×
R
-Hopf algebra and X is a stable anti-Yetter-Drinfel’d -module, the para-cyclic object Z
* is shown to project to a cyclic structure on . For a -Galois extension , a stable anti-Yetter-Drinfel’d -module T
S
is constructed, such that the cyclic objects and are isomorphic. This extends a theorem by Jara and Ştefan for Hopf Galois extensions. As an application, we compute Hochschild
and cyclic homologies of a groupoid with coefficients in a stable anti-Yetter-Drinfel’d module, by tracing it back to the
group case. In particular, we obtain explicit expressions for (coinciding relative and ordinary) Hochschild and cyclic homologies
of a groupoid. The latter extends results of Burghelea on cyclic homology of groups. 相似文献
92.
Colloidal Surface Active Maghemite Nanoparticles for Biologically Safe CrVI Remediation: from Core‐Shell Nanostructures to Pilot Plant Development
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Massimiliano Magro Dr. Stefania Domeneghetti Davide Baratella Dr. Petr Jakubec Prof. Dr. Gabriella Salviulo Dr. Emanuela Bonaiuto Dr. Paola Venier Ondřej Malina Dr. Jiří Tuček Dr. Václav Ranc Dr. Giorgio Zoppellaro Prof.Dr. Radek Zbořil Prof. Dr. Fabio Vianello 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14219-14226
The present study is aimed at the exploration of achievable improvements for CrVI ex situ and in situ water remediation by using novel naked colloidal maghemite (γ‐Fe2O3) nanoparticles (surface active maghemite nanoparticles, SAMNs). The reliability of SAMNs for CrVI binding and removal was demonstrated, and SAMN@CrVI complex was characterized, as well as the covalent nature of the absorption was unequivocally proved. SAMNs were structurally and magnetically well conserved after CrVI binding. Thus, in consideration of their affinity for CrVI, SAMNs were exploited in a biological model system, mimicking a real in situ application. The assay evidenced a progressive reduction of revertant colonies of Salmonella typhimurium TA100 strain, as maghemite nanoparticles concentration increased, till the complete suppression of CrVI mutagen effect. Finally, an automatic modular pilot system for continuous magnetic removal and recovery of CrVI from water is proposed. SAMNs, thanks to their colloidal, binding, and catalytic properties, represent a promising tool as a reliable nanomaterial for water remediation by CrVI. 相似文献
93.
94.
Magyari Jzef Barta Holl Berta Rodi Marko V. Jovanovi Ljiljana S. Mszros Szcsnyi Katalin Ferenc Wiesawa Osypiuk Dariusz Mosolyg Tmea Kincses Annamria Spengler Gabriella 《Journal of Thermal Analysis and Calorimetry》2022,147(1):229-242
Journal of Thermal Analysis and Calorimetry - New coordination compounds have been synthesized by reacting Zn(II) and Co(II) nitrate or acetate in the presence of triethylamine with Schiff-base... 相似文献
95.
Franco Benetollo Gabriella Bombieri Giuseppe Alonzo Nuccio Bertazzi 《Journal of chemical crystallography》1995,25(2):89-92
The synthesis and the crystal and molecular structure of the difluoro(hydroxodi-2-pyridylmethoxo-NNO) antimony(III) compound determined by single crystal X-ray diffraction analysis are reported. Crystals are orthorhombic, space group Pbcn,a=12.732(2),b=12.165(2),c=15.936(2) Å. Refinement based on 1516 observed reflections led to a finalR value of 0.025 (Rw=0.028). In the crystal the di-2-pyridyl ketone behaves asfacial-(NNO)-terdentate in the Sb coordination, the square pyramid geometry around the metal is completed by the coordination of two fluorine atoms. 相似文献
96.
Markt P McGoohan C Walker B Kirchmair J Feldmann C De Martino G Spitzer G Distinto S Schuster D Wolber G Laggner C Langer T 《Journal of chemical information and modeling》2008,48(8):1693-1705
The cysteine protease cathepsin S (CatS) is involved in the pathogenesis of autoimmune disorders, atherosclerosis, and obesity. Therefore, it represents a promising pharmacological target for drug development. We generated ligand-based and structure-based pharmacophore models for noncovalent and covalent CatS inhibitors to perform virtual high-throughput screening of chemical databases in order to discover novel scaffolds for CatS inhibitors. An in vitro evaluation of the resulting 15 structures revealed seven CatS inhibitors with kinetic constants in the low micromolar range. These compounds can be subjected to further chemical modifications to obtain drugs for the treatment of autoimmune disorders and atherosclerosis. 相似文献
97.
98.
Siani G Angelini G De Maria P Fontana A Pierini M 《Organic & biomolecular chemistry》2008,6(22):4236-4241
The rates of tautomerization of 2-nitrocyclohexanone (2-NCH) have been measured spectrophotometrically at 25.0 +/- 0.1 degrees C in several organic aprotic solvents and their binary mixtures. In cyclohexane the reaction is effectively catalyzed by bases and inhibited by acids while the so-called "spontaneous reaction" appears essentially due to autocatalysis. Apparent second order rate constants (k(app)(B)) for the reaction catalyzed by triethylamine (TEA) and pyridine (Pyr) have been obtained. From the experimental k(app)(B) values rate constants for the enolization (k(1)(B)) and ketonization (k(-1)(B)) reactions have been calculated. A Kamlet-Taft type linear solvation energy relationship (LSER) adequately accounts for the observed solvent effects. Activation parameters for both reactions show that solvent effects are mainly entropic in origin and that there is a shift of the transition state from a ketone-like to an enol-like structure on passing from less to more polar solvents. 相似文献
99.
Yasser M. Loksha Daniel Globisch Erik B. Pedersen Paolo La Colla Gabriella Collu Roberta Loddo 《Journal of heterocyclic chemistry》2008,45(4):1161-1166
100.
Onel L Bourceanu G Wittmann M Noszticzius Z Szabó G 《The journal of physical chemistry. A》2008,112(46):11649-11655
A recent report on an intense CO 2 and CO evolution in the Briggs-Rauscher (BR) reaction revealed that iodination of malonic acid (MA) is not the only important organic reaction in the classical BR oscillator. To disclose the source of the gas evolution, iodomalonic (IMA) and diiodomalonic (I2MA) acids were prepared by iodinating MA with nascent iodine in a semibatch reactor. The nascent iodine was generated by an iodide inflow into the reactor, which contained a mixture of MA and acidic iodate. Some CO2 and a minor CO production was observed during these iodinations. It was found that in an aqueous acidic medium the produced I2MA is not stable but decomposes slowly to diiodoacetic acid and CO2. The first-order rate constant of the I 2MA decarboxylation at 20 degrees C was found to be k1 = 9 x 10(-5) s(-1), which is rather close to the rate constant of the analogous decarboxylation of dibromomalonic acid under similar conditions (7 x 10(-5)s(-1)). From the rate of the CO2 evolution, the I2MA concentration can be calculated in a MA-IMA-I2MA mixture as only I2MA decarboxylates spontaneously but MA and IMA are stable. Following CO2 evolution rates, it was proven that I2MA can react with MA in the reversible reaction I2MA + MA <--> 2 IMA. The equilibrium constant of this reaction was calculated as K = 380 together with the rate constants of the forward k 2 = 6.2 x 10 (-2) M (-1)s(-1) and backward k-2 = 1.6 x 10(-4) M(-1)s(-1) reactions. The probable mechanism of the reaction is I(+1) transfer from I2MA to MA. The presence of I(+1) in a I2MA solution is demonstrated by its reduction with ascorbic acid. To estimate the fraction of CO2 coming from the decarboxylation of I2MA in an oscillatory BR reaction, the oscillations were inhibited by resorcinol. Unexpectedly, all CO2 and CO evolution was interrupted for more than one hour after injecting a small amount of resorcinol (10(-5) M initial concentration in the reactor). Finally, some implications of the newly found I(+1) transfer reactions and the surprisingly effective inhibition by resorcinol regarding the mechanism of the oscillatory BR reaction are discussed. The latter is explained by the ability of resorcinol to scavenge free radicals including iodine atoms without producing iodide ions. 相似文献