全文获取类型
收费全文 | 415篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
化学 | 340篇 |
晶体学 | 3篇 |
力学 | 5篇 |
数学 | 27篇 |
物理学 | 57篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 14篇 |
2015年 | 18篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 43篇 |
2011年 | 39篇 |
2010年 | 20篇 |
2009年 | 14篇 |
2008年 | 25篇 |
2007年 | 26篇 |
2006年 | 26篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 16篇 |
2002年 | 23篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 4篇 |
1980年 | 2篇 |
排序方式: 共有432条查询结果,搜索用时 31 毫秒
291.
Hetero‐Epitaxial Approach by Using Labile Coordination Sites to Prepare Catenated Metal–Organic Frameworks with High Surface Areas
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. Nianyong Zhu Matthew J. Lennox Gerard Tobin Lisa Goodman Dr. Tina Düren Prof. Wolfgang Schmitt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3595-3599
A solid‐state approach that takes advantage of the ordered 3D arrangement of active secondary building units allows the preparation of new interlocked MOFs that grow hetero‐epitaxially on the crystal faces of a precursor phase that acts as a “topological blueprint”. The synthetic strategy is exemplified by using rigid acetylene‐based ligands to produce highly augmented CuII acetate‐based MOFs. 相似文献
292.
Patrick Kempe Dr. Tina Löschner Prof. Alexander A. Auer Dr. Andreas Seifert Dr. Gerhard Cox Prof. Dr. Stefan Spange 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8040-8053
The twin monomer 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] ( 1 ) can be polymerized to nanostructured SiO2/phenolic‐resin composite material by thermally induced twin polymerization. Thermally induced twin polymerization represents a way to produce nanocomposites simply by thermal induction of twin monomers. Besides 1 , the thermal reaction of several related salicylic (2‐oxybenzylic) silicon molecules has been investigated. The thermal cleavage of the molecules is studied by using several trapping reagents (e.g., vinyl compounds). A significant occurrence of quinone methide adducts indicates that the thermal mechanism proceeds not only by a ring opening at the oxymethylene position, but also with the ortho‐quinone methide as a central or alternative intermediate. This is supported by product analyses of thermally initialized reactions of 1 and its substituted analogues as well as by quantum chemical calculations. 相似文献
293.
Gui-Zhong Xin Bin Hu Zi-Qi Shi Yin Ching Lam Tina Ting-Xia Dong Ping Li Zhong-Ping Yao Karl W.K. Tsim 《Analytica chimica acta》2014
The counterfeit plant products, especially by using incorrect plant materials in pharmaceutical industry, have become a global problem. The plant materials belonging to closely related species but differing in medicinal properties are difficult to be identified. Here, a novel and generally applicable approach to identify the sources of plant materials was developed, which was based on the use of wooden-tip electrospray ionization mass spectrometry (wooden-tip ESI-MS) and multivariate statistical analysis of unidentified MS features (non-targeted). Using this approach, six officinal species of Fritillariae Cirrhosae Bulbus had been successfully differentiated. In addition, Fritillariae Pallidiflorae Bulbus, a common adulterant of Fritillariae Cirrhosae Bulbus, was also identified by using the strategy reported here. Compared with DNA phylogenetic trees, our approach provided finer resolution in distinguishing the closely related Fritillaria species. By combining wooden-tip ESI-MS and multivariate statistical analysis, a useful method was developed here for rapid identification of the sources of herbs, which showed promising perspectives in tracking the supply chain of pharmaceutical suppliers. 相似文献
294.
Simin D. Maleknia Teresa M. Vail Robert B. Cody David O. Sparkman Tina L. Bell Mark A. Adams 《Rapid communications in mass spectrometry : RCM》2009,23(15):2241-2246
A method is described for the rapid identification of biogenic, volatile organic compounds (VOCs) emitted by plants, including the analysis of the temperature dependence of those emissions. Direct analysis in real time (DART) enabled ionization of VOCs from stem and leaf of several eucalyptus species including E. cinerea, E. citriodora, E. nicholii and E. sideroxylon. Plant tissues were placed directly in the gap between the DART ionization source skimmer and the capillary inlet of the time‐of‐flight (TOF) mass spectrometer. Temperature‐dependent emission of VOCs was achieved by adjusting the temperature of the helium gas into the DART ionization source at 50, 100, 200 and 300°C, which enabled direct evaporation of compounds, up to the onset of pyrolysis of plant fibres (i.e. cellulose and lignin). Accurate mass measurements facilitated by TOF mass spectrometry provided elemental compositions for the VOCs. A wide range of compounds was detected from simple organic compounds (i.e. methanol and acetone) to a series of monoterpenes (i.e. pinene, camphene, cymene, eucalyptol) common to many plant species, as well as several less abundant sesquiterpenes and flavonoids (i.e. naringenin, spathulenol, eucalyptin) with antioxidant and antimicrobial properties. The leaf and stem tissues for all four eucalypt species showed similar compounds. The relative abundances of methanol and ethanol were greater in stem wood than in leaf tissue suggesting that DART could be used to investigate the tissue‐specific transport and emissions of VOCs. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
295.
Philipp C. Kohler Tina Ritschel W. Bernd Schweizer Dr. Gerhard Klebe Prof. Dr. François Diederich Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(41):10809-10817
The tRNA‐modifying enzyme tRNA–guanine transglycosylase (TGT) is essential for the pathogenic mechanism of Shigella flexneri, the causing agent of the bacterial diarrheal disease shigellosis. Herein, the synthesis of a new class of rationally designed 6‐amino‐imidazo[4,5‐g]quinazolin‐8(7H)‐one‐ (lin‐benzoguanine) based inhibitors of TGT are reported. In order to accommodate a small hydrophobic crevice opening near the binding site of ribose‐34, 2‐aminoethyl substituents were introduced in position 4 of the heterocyclic scaffold. For this purpose, a synthetic sequence consisting of iodination, Suzuki cross‐coupling, hydroboration, Mitsunobu reaction, and Gabriel synthesis was employed, furnishing a primary amine that served as a common intermediate for the preparation of a series of derivatives. The resulting ligands displayed very low inhibition constants, down to Ki=2 nM . Substantial additional inhibitory potency is gained by interaction of terminal lipophilic groups attached to the substituent at position 4 with the hydrophobic crevice shaped by Val45 and Leu68. At the same time, the secondary ammonium center in the substituent displaces a cluster of water molecules, solvating the catalytic residues Asp102 and Asp280, without loss in binding affinity. In addition, a synthetic intermediate with an unusual 3,6,7,8,9,10‐hexahydroimidazo[4,5‐g][1,3]benzodiazepine core, as confirmed by X‐ray analysis, is reported. 相似文献
296.
Tina M. Kouri John D. Crabtree Lam Huynh Anthony M. Dean Dinesh P. Mehta 《国际化学动力学杂志》2013,45(2):125-139
Detailed chemical kinetic modeling of gas‐phase reactions can result in automatically generated mechanisms that contain thousands of reactions. In this paper, we describe the development of a rule‐based expert system tool that organizes these reactions into classes such as hydrogen abstraction and beta scission. We have developed 29 simple classification rules, 20 complex (well‐skipping) classification rules, and four second‐stage classification rules. This greatly simplifies the task of the chemical kineticist who wishes to verify, analyze, and gain insights into the reactions comprising the mechanism. This system, which is based on the automated identification of the bonds that break and form in a chemical reaction (the reaction mapping problem), is used to classify reactions in three different mechanisms. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 125–139, 2013 相似文献
297.
298.
Nikolai Kuhnert Rakesh Jaiswal Marius Febi Matei Tina Sovdat Sagar Deshpande 《Rapid communications in mass spectrometry : RCM》2010,24(11):1575-1582
All four regioisomers of feruloyl quinic acid and isoferuloyl quinic acid were synthesized and a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method developed that resolves all eight regioisomers. All eight regioisomers can be readily distinguished by their MS/MS spectra in the negative ion mode, illustrating the power of tandem mass spectrometry to elucidate the structures of regioisomeric compounds. Compound identification is possible, either by direct comparison of spectral fingerprints or by rational probing of diagnostic fragment ions, thus allowing the identification of these important classes of natural products and potential human metabolites. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
299.
Protection of aliphatic and aromatic aldehydes as 1,1‐diacetates using VSO4.5H2O under solvent‐free conditions is carried out. The products are obtained in good to excellent yields. Ketones are not affected under these conditions. 相似文献
300.
Shi X Hebrault D Humora M Kiesman WF Peng H Talreja T Wang Z Xin Z 《The Journal of organic chemistry》2012,77(2):1154-1160
Mild reaction conditions for Petasis reactions of substituted salicylaldehydes with various amines and arylboronic acids in the presence of molecular sieves were developed. Molecular sieves (MS) significantly accelerated the reaction rates and drove the reactions to high conversions. The conditions were applied to the synthesis of the core structure of BIIB042, a γ-secretase modulator, without stereochemical erosion of a stereogenic center in the salicylaldehyde intermediate. 相似文献