全文获取类型
收费全文 | 2985篇 |
免费 | 173篇 |
专业分类
化学 | 2177篇 |
晶体学 | 8篇 |
力学 | 65篇 |
数学 | 435篇 |
物理学 | 473篇 |
出版年
2024年 | 2篇 |
2023年 | 23篇 |
2022年 | 19篇 |
2021年 | 25篇 |
2020年 | 37篇 |
2019年 | 40篇 |
2018年 | 64篇 |
2017年 | 45篇 |
2016年 | 116篇 |
2015年 | 108篇 |
2014年 | 101篇 |
2013年 | 207篇 |
2012年 | 233篇 |
2011年 | 248篇 |
2010年 | 143篇 |
2009年 | 125篇 |
2008年 | 192篇 |
2007年 | 194篇 |
2006年 | 142篇 |
2005年 | 153篇 |
2004年 | 146篇 |
2003年 | 104篇 |
2002年 | 92篇 |
2001年 | 81篇 |
2000年 | 86篇 |
1999年 | 63篇 |
1998年 | 39篇 |
1997年 | 11篇 |
1996年 | 35篇 |
1995年 | 23篇 |
1994年 | 28篇 |
1993年 | 24篇 |
1992年 | 25篇 |
1991年 | 30篇 |
1990年 | 21篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有3158条查询结果,搜索用时 31 毫秒
141.
Dr. Israel Fernández Prof. Dr. Miquel Solà Prof. Dr. F. Matthias Bickelhaupt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7416-7422
The origin of the experimentally known preference for [6,6] over [5,6] bonds in cycloaddition reactions involving C60 has been computationally explored. To this end, the Diels–Alder reaction between cyclopentadiene and C60 has been analysed by means of the recently introduced activation strain model of reactivity in combination with the energy decomposition analysis method. Other issues, such as the aromaticity of the corresponding transition states, have also been considered. These results indicate that the major factor controlling the observed regioselectivity is the more stabilising interaction between the deformed reactants in the [6,6] reaction pathway along the entire reaction coordinate. 相似文献
142.
143.
144.
A One‐Pot Synthesis of N‐Aryl‐2‐Oxazolidinones and Cyclic Urethanes by the Lewis Base Catalyzed Fixation of Carbon Dioxide into Anilines and Bromoalkanes
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)
Teemu Niemi Dr. Jesus E. Perea‐Buceta Dr. Israel Fernández Otto‐Matti Hiltunen Vili Salo Sari Rautiainen Dr. Minna T. Räisänen Prof. Timo Repo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10355-10359
The multicomponent assembly of pharmaceutically relevant N‐aryl‐oxazolidinones through the direct insertion of carbon dioxide into readily available anilines and dibromoalkanes is described. The addition of catalytic amounts of an organosuperbase such as Barton's base enables this transformation to proceed with high yields and exquisite substrate functional‐group tolerance under ambient CO2 pressure and mild temperature. This report also provides the first proof‐of‐principle for the single‐operation synthesis of elusive seven‐membered ring cyclic urethanes. 相似文献
145.
Begoña Pons Miguel A. Fernández-Torroba Gustavo Ortiz María Teresa Tena 《International journal of environmental analytical chemistry》2013,93(6):495-506
VOCs were detected and identified in the water of several wells in the area of Nájera (La Rioja). The past uncontrolled spills from an important painting and varnishing industry and from other smaller ones devoted to the manufacture of furniture and varnishing activities were the sources of the VOCs plume detected in this aquifer. This article shows the results obtained in the monitoring and assessment of the pollution at 18 sampling points for more than a year. It has allowed us to study the evolution of the different pollutants and the influence of a remediation process applied by the company in the main pollution source. The analytical method is based on headspace-solid-phase microextraction (SPME) using a 75-μm carboxen-polydimethylsiloxane fibre. Quantification was carried out by gas chromatography with flame ionization detection. This method has allowed us to determine the 13 VOCs identified in the polluted underground samples providing good sensitivity (LOD between 0.1 and 6.0 ng/mL) and reproducibility (r.s.d. less than 10%). 相似文献
146.
J. M. Fernández-Pradas D. Comas J. L. Morenza P. Serra 《Applied Physics A: Materials Science & Processing》2013,111(1):203-207
We report a novel resistive random access memory using tri-layer dielectrics of GeO x /nano-crystal TiO2/TaON and low cost top Ni and bottom TaN electrodes. Excellent device performance of ultra-low 720 fJ switching energy, tight distributions of set/reset currents, and exceptionally long endurance of 5×109 cycles were achieved simultaneously. Such excellent endurance may create new applications such as those used for Data Centers that are ascribed to the higher-κ nano-crystal TiO2, hopping pass via grain boundaries, and fast switching speed of 100 ns to improve the dielectric fatigue during endurance stress. 相似文献
147.
Alberto Fernández-Alarcón Dr. José Manuel Guevara-Vela José Luis Casals-Sainz Dr. Aurora Costales Dr. Evelio Francisco Dr. Ángel Martín Pendás Dr. Tomás Rocha Rinza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17035-17045
The development of chemical intuition in photochemistry faces several difficulties that result from the inadequacy of the one-particle picture, the Born–Oppenheimer approximation, and other basic ideas used to build models. It is shown herein how real-space approaches can be efficiently used to gain valuable insights in photochemistry through a simple example of red and blue shift effects: the double hypso- and bathochromic shifts in the low-lying valence excited states of (H2O)2. It is demonstrated that 1) the use of these techniques allows the perturbative language used in the theory of intermolecular interactions, even in the strongly interacting short-range regime, to be maintained; 2) one and only one molecule is photoexcited in each of the addressed excited states and 3) the electrostatic interaction between the in-the-cluster molecular dipoles provides a fairly intuitive rationalisation of the observed batho- and hypsochromism. The methods exploited and illustrated herein are able to maintain the individuality and properties of the interacting entities in a molecular aggregate, and thereby they allow chemical intuition in general states, at any geometry and using a broad variety of electronic structure methods to be kept and built. 相似文献
148.
Prof. Dr. Javier A. Cabeza Dr. Israel Fernández Dr. José M. Fernández-Colinas Dr. Pablo García-Álvarez Carlos J. Laglera-Gándara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(53):12423-12430
An efficient synthesis of 2-di-tert-butylphosphanylmethylpyrrole (HpyrmPtBu2), by treating 2-dimethylaminomethylpyrrole (HpyrmNMe2) with tBu2PH at 135 °C in the absence of any solvent, has allowed the preparation of the new PGeP germylene Ge(pyrmPtBu2)2 ( 1 ), by treating [GeCl2(dioxane)] with LipyrmPtBu2, in which the Ge atom is stabilized by intramolecular interactions with one (solid state) or both (solution) of its phosphane groups. Reactions of germylene 1 with Group 10 metal dichlorido complexes containing easily displaceable ligands have led to [MCl{κ3P,Ge,P-GeCl(pyrmPtBu2)2}] [M=Ni ( 2 ), Pd ( 3 ), Pt ( 4 )], which have an unflawed square-planar metal environment. Treatment of germylene 1 with [AuCl(tht)] (tht=tetrahydrothiophene) rendered [Au{κ3P,Ge,P-GeCl(pyrmPtBu2)2}] ( 5 ), which is a rare case of a T-shaped gold(I) complex. The hydrolysis of 5 gave the linear gold(I) derivative [Au(κP-HpyrmPtBu2)2]Cl ( 6 ). Complexes 2 – 5 contain a PGeP pincer chloridogermyl ligand that arises from the insertion of the Ge atom of germylene 1 into a M−Cl bond of the corresponding metal reagent. The bonding in these molecules has been studied by DFT/NBO/QTAIM calculations. These results demonstrate that the great flexibility of germylene 1 makes it a better precursor to PGeP pincer complexes than the previously known germylenes of this type. 相似文献
149.
Dr. Yago García-Rodeja Prof. Dr. Israel Fernández 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9771-9779
The influence of the replacement of C=C bonds by isoelectronic B−N moieties on the reactivity of π-curved polycyclic aromatic hydrocarbons has been computationally explored by means of density functional theory calculations. To this end, we selected the Diels–Alder cycloaddition reactions of the parent corannulene and its BN-doped counterparts with either cyclopentadiene or maleic anhydride. In addition, the analogous reactions involving larger buckybowls, such as BN-hemifullerene, BN-circumtrindene, and BN-fullerene, have been also considered. It has been found that whereas corannulene behaves as a dienophile, its BN counterpart better acts as a diene. In contrast, the larger BN-curved systems cannot be used as dienes in Diels–Alder reactions, but undergo facile (i.e., low barrier) cycloaddition reactions with cyclopentadiene. The observed trends in reactivity, which cannot be directly explained by using typical frontier molecular orbital arguments, are quantitatively described in detail by means of state-of-the-art computational methods, namely the activation strain model of reactivity combined with the energy decomposition analysis method. The results of our calculations highlight the crucial role of the curvature of the system on the reactivity and its influence on the strength of the orbital interactions between the deformed reactants during their transformations. 相似文献
150.