全文获取类型
收费全文 | 4736篇 |
免费 | 195篇 |
国内免费 | 25篇 |
专业分类
化学 | 3650篇 |
晶体学 | 16篇 |
力学 | 87篇 |
数学 | 552篇 |
物理学 | 651篇 |
出版年
2023年 | 53篇 |
2022年 | 143篇 |
2021年 | 183篇 |
2020年 | 145篇 |
2019年 | 123篇 |
2018年 | 64篇 |
2017年 | 61篇 |
2016年 | 182篇 |
2015年 | 187篇 |
2014年 | 175篇 |
2013年 | 253篇 |
2012年 | 354篇 |
2011年 | 402篇 |
2010年 | 221篇 |
2009年 | 184篇 |
2008年 | 310篇 |
2007年 | 283篇 |
2006年 | 268篇 |
2005年 | 199篇 |
2004年 | 211篇 |
2003年 | 173篇 |
2002年 | 145篇 |
2001年 | 37篇 |
2000年 | 32篇 |
1999年 | 30篇 |
1998年 | 21篇 |
1997年 | 24篇 |
1996年 | 24篇 |
1995年 | 23篇 |
1994年 | 24篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 15篇 |
1988年 | 9篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 33篇 |
1984年 | 31篇 |
1983年 | 24篇 |
1982年 | 27篇 |
1981年 | 26篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1975年 | 13篇 |
1974年 | 9篇 |
排序方式: 共有4956条查询结果,搜索用时 0 毫秒
91.
Nicolás D. Gómez Violeta D'Accurso V. Mariana Freytes Francisco A. Manzano Jorge Codnia M. Laura Azcárate 《国际化学动力学杂志》2013,45(5):306-313
An experimental setup that coupled IR multiple‐photon dissociation (IRMPD) and laser‐induced fluorescence (LIF) techniques was implemented to study the kinetics of the recombination reaction of dichlorocarbene radicals, CCl2, in an Ar bath. The CCl2 radicals were generated by IRMPD of CDCl3. The time dependence of the CCl2 radicals’ concentration in the presence of Ar was determined by LIF. The experimental conditions achieved allowed us to associate the decrease in the concentration of radicals to the self‐recombination reaction to form C2Cl4. The rate constant for this reaction was determined in both the falloff and the high‐pressure regimes at room temperature. The values obtained were k0 = (2.23 ± 0.89) × 10?29 cm6 molecules?2 s?1 and k∞ = (6.73 ± 0.23) × 10?13 cm3 molecules?1 s?1, respectively. 相似文献
92.
An expeditious synthetic method for the preparation of bis(indollyl)methane derivatives has been developed through a bismuth nitrate-catalyzed reaction of indole with various carbonyl compounds in mortar and pastle under solvent-free conditions. 相似文献
93.
Alternating copolymers of vinyl acetate (VAc) and maleic anhydride (MA) are produced preferentially when VAc and MA are copolymerized at moderate temperatures while random copolymers are produced at temperatures above 90°C. A charge-transfer complex (CTC) of VAc/MA exists at moderate temperatures but does not exist at temperatures above 90°C. 相似文献
94.
Dolores Bellido-Milla Laura Ma Cubillana-Aguilera Mohammed El Kaoutit Ma Purificación Hernández-Artiga José Luis Hidalgo-Hidalgo de Cisneros Ignacio Naranjo-Rodríguez José Ma Palacios-Santander 《Analytical and bioanalytical chemistry》2013,405(11):3525-3539
Graphite powder-based electrodes have the electrochemical performance of quasi-noble metal electrodes with intrinsic advantages related to the possibility of modification to enhance selectivity and their easily renewable surface, with no need for hazardous acids or bases for their cleaning. In contrast with commercial electrodes, for example screen-printed or sputtered-chip electrodes, graphite powder-based electrodes can also be fabricated in any laboratory with the form and characteristics desired. They are also readily modified with advanced materials, with relatively high reproducibility. All these characteristics make them a very interesting option for obtaining a large variety of electrodes to resolve different kinds of analytical problems. This review summarizes the state-of-the-art, advantages, and disadvantages of graphite powder-based electrodes in electrochemical analysis in the 21st century. It includes recent trends in carbon paste electrodes, devoting special attention to the use of emergent materials as new binders and to the development of other composite electrodes. The most recent advances in the use of graphite powder-modified sol–gel electrodes are also described. The development of sonogel–carbon electrodes and their use in electrochemical sensors and biosensors is included. These materials extend the possibilities of applications, especially for industrial technology-transfer purposes, and their development could affect not only electroanalytical green chemistry but other interesting areas also, for example catalysis and energy conversion and storage. 相似文献
95.
Dr. Peter Wick Dr. Anna E. Louw‐Gaume Dr. Melanie Kucki Prof. Harald F. Krug Prof. Kostas Kostarelos Prof. Bengt Fadeel Prof. Kenneth A. Dawson Dr. Anna Salvati Prof. Ester Vázquez Dr. Laura Ballerini Dr. Mauro Tretiach Dr. Fabio Benfenati Dr. Emmanuel Flahaut Dr. Laury Gauthier Prof. Maurizio Prato Dr. Alberto Bianco 《Angewandte Chemie (International ed. in English)》2014,53(30):7714-7718
96.
97.
Dr. Laura Orian Lando P. Wolters Prof. Dr. F. Matthias Bickelhaupt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(40):13337-13347
A mechanistic density functional theory study of acetylene [2+2+2] cyclotrimerization to benzene catalyzed by RhI half metallocenes is presented. The catalyst fragment contains a heteroaromatic ligand, that is, the 1,2‐azaborolyl (Ab) or the 3a,7a‐azaborindenyl (Abi) anions, which are isostructural and isoelectronic to the hydrocarbon cyclopentadienyl (Cp) and indenyl (Ind) anions, respectively, but differ from the last ones on having two adjacent carbon atoms replaced with a boron and a nitrogen atom. The better performance of either the classic hydrocarbon or the heteroaromatic catalysts is found to depend on the different mechanistic paths that can be envisioned for the process. The present analyses uncover and explain general structure–reactivity relationships that may serve as rational design principles. In particular, we provide evidence of a reverse indenyl effect. 相似文献
98.
99.
Solvent‐Controlled Bifurcated Cascade Process for the Selective Preparation of Dihydrocarbazoles or Dihydropyridoindoles 下载免费PDF全文
Dr. Dong‐Liang Mo Dr. Donald J. Wink Dr. Laura L. Anderson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13217-13225
A solvent‐controlled cascade process has been identified for the dual purpose of the preparation of either dihydrocarbazoles or dihydropyridoindoles from identical N‐aryl‐α,β‐unsaturated nitrones and electron‐deficient allene starting materials. These reactions proceed smoothly under mild metal‐free conditions affording a range of two types of skeletally distinct indole‐based heterocycles in high yield and diastereoselectivity. These transformations demonstrate the use of a bifurcated cascade process that hinges on the ring‐opening event of a benzazepine intermediate for the synthesis of skeletally diverse heterocyclic products and rapid access to biologically‐significant, indole‐based structures. 相似文献