全文获取类型
收费全文 | 4128篇 |
免费 | 742篇 |
国内免费 | 258篇 |
专业分类
化学 | 3196篇 |
晶体学 | 257篇 |
力学 | 18篇 |
综合类 | 15篇 |
数学 | 506篇 |
物理学 | 1136篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 33篇 |
2021年 | 21篇 |
2020年 | 31篇 |
2019年 | 82篇 |
2018年 | 112篇 |
2017年 | 124篇 |
2016年 | 131篇 |
2015年 | 311篇 |
2014年 | 313篇 |
2013年 | 391篇 |
2012年 | 360篇 |
2011年 | 366篇 |
2010年 | 373篇 |
2009年 | 400篇 |
2008年 | 333篇 |
2007年 | 276篇 |
2006年 | 247篇 |
2005年 | 164篇 |
2004年 | 162篇 |
2003年 | 171篇 |
2002年 | 131篇 |
2001年 | 128篇 |
2000年 | 114篇 |
1999年 | 105篇 |
1998年 | 79篇 |
1997年 | 46篇 |
1996年 | 31篇 |
1995年 | 13篇 |
1994年 | 19篇 |
1993年 | 24篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有5128条查询结果,搜索用时 7 毫秒
101.
Influence of higher harmonics of the undulator in X‐ray polarimetry and crystal monochromator design 下载免费PDF全文
Berit Marx‐Glowna Kai S. Schulze Ingo Uschmann Tino Kämpfer Günter Weber Christoph Hahn Hans‐Christian Wille Kai Schlage Ralf Röhlsberger Eckhart Förster Thomas Stöhlker Gerhard G. Paulus 《Journal of synchrotron radiation》2015,22(5):1151-1154
The spectrum of the undulator radiation of beamline P01 at Petra III has been measured after passing a multiple reflection channel‐cut polarimeter. Odd and even harmonics up to the 15th order, as well as Compton peaks which were produced by the high harmonics in the spectrum, could been measured. These additional contributions can have a tremendous influence on the performance of the polarimeter and have to be taken into account for further polarimeter designs. 相似文献
102.
On semipolar epitaxial ZnO grown by chemical vapor deposition consists of two distinct orientations as evidenced by transmission electron microscopy and X‐ray diffraction. The initially grown ZnO on GaN follows the GaN lattice with the epitaxial relationship of // and The other oriented ZnO domains then grow on faceted with and with good coherency with the ‐oriented grains. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
103.
Structure‐Based Design of Inhibitors of the Aspartic Protease Endothiapepsin by Exploiting Dynamic Combinatorial Chemistry 下载免费PDF全文
Milon Mondal Nedyalka Radeva Dr. Helene Köster Dr. Ahyoung Park Dr. Constantinos Potamitis Dr. Maria Zervou Prof. Dr. Gerhard Klebe Dr. Anna K. H. Hirsch 《Angewandte Chemie (International ed. in English)》2014,53(12):3259-3263
Structure‐based design (SBD) can be used for the design and/or optimization of new inhibitors for a biological target. Whereas de novo SBD is rarely used, most reports on SBD are dealing with the optimization of an initial hit. Dynamic combinatorial chemistry (DCC) has emerged as a powerful strategy to identify bioactive ligands given that it enables the target to direct the synthesis of its strongest binder. We have designed a library of potential inhibitors (acylhydrazones) generated from five aldehydes and five hydrazides and used DCC to identify the best binder(s). After addition of the aspartic protease endothiapepsin, we characterized the protein‐bound library member(s) by saturation‐transfer difference NMR spectroscopy. Cocrystallization experiments validated the predicted binding mode of the two most potent inhibitors, thus demonstrating that the combination of de novo SBD and DCC constitutes an efficient starting point for hit identification and optimization. 相似文献
104.
Stephanie M. Barbon Pauline A. Reinkeluers Dr. Jacquelyn T. Price Prof. Dr. Viktor N. Staroverov Prof. Dr. Joe B. Gilroy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11340-11344
The straightforward synthesis of a series of 3‐cyanoformazanate boron difluoride dyes is reported. Phenyl, 4‐methoxyphenyl and 4‐cyanophenyl N‐substituted derivatives were isolated and characterized by single‐crystal X‐ray crystallography, cyclic voltammetry, and UV/Vis spectroscopy. The compounds were demonstrated to possess tunable, substituent‐dependent absorption, emission, and electrochemical properties, which were rationalized through electronic structure calculations. 相似文献
105.
106.
Cover Picture: Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets (Chem. Eur. J. 6/2014) 下载免费PDF全文
107.
Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets 下载免费PDF全文
Dr. Miguel Clemente‐León Prof. Eugenio Coronado Prof. Carlos J. Gómez‐García Dr. Maurici López‐Jordà Dr. Agustín Camón Ana Repollés Dr. Fernando Luis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1669-1676
The insertion of the single‐molecule magnet (SMM) [MnIII(salen)(H2O)]22+ (salen2?=N,N′‐ethylenebis‐(salicylideneiminate)) into a ferromagnetic bimetallic oxalate network affords the hybrid compound [MnIII(salen)(H2O)]2[MnIICrIII(ox)3]2 ? (CH3OH) ? (CH3CN)2 ( 1 ). This cationic Mn2 cluster templates the growth of crystals formed by an unusual achiral 3D oxalate network. The magnetic properties of this hybrid magnet are compared with those of the analogous compounds [MnIII(salen)(H2O)]2[ZnIICrIII(ox)3]2 ? (CH3OH) ? (CH3CN)2 ( 2 ) and [InIII(sal2‐trien)][MnIICrIII(ox)3] ? (H2O)0.25 ? (CH3OH)0.25 ? (CH3CN)0.25 ( 3 ), which are used as reference compounds. In 2 it has been shown that the magnetic isolation of the Mn2 clusters provided by their insertion into a paramagnetic oxalate network of CrIII affords a SMM behavior, albeit with blocking temperatures well below 500 mK even for frequencies as high as 160 kHz. In 3 the onset of ferromagnetism in the bimetallic MnIICrIII network is observed at Tc=5 K. Finally, in the hybrid compound 1 the interaction between the two magnetic networks leads to the antiparallel arrangement of their respective magnetizations, that is, to a ferrimagnetic phase. This coupling induces also important changes on the magnetic properties of 1 with respect to those of the reference compounds 2 and 3 . In particular, compound 1 shows a large magnetization hysteresis below 1 K, which is in sharp contrast with the near‐reversible magnetizations that the SMMs and the oxalate ferromagnetic lattice show under the same conditions. 相似文献
108.
Synthesis and Biological Evaluation of a Class of Mitochondrially‐Targeted Gadolinium(III) Agents 下载免费PDF全文
Dr. Daniel E. Morrison Dr. Jade B. Aitken Dr. Martin D. de Jonge Dr. Fatiah Issa Prof. Hugh H. Harris Prof. Louis M. Rendina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16602-16612
A structure–activity relationship study of a library of novel bifunctional GdIII complexes covalently linked to arylphosphonium cations is reported. Such complexes have been designed for potential application in binary cancer therapies such as neutron capture therapy and photon activation therapy. A positive correlation was found between lipophilicity and cytotoxicity of the complexes. Mitochondria uptake was determined by means of inductively coupled plasma mass spectrometry (ICP‐MS), and Gd uptake was determined by means of quantification using synchrotron X‐ray fluorescence (XRF) imaging. A negative correlation between lipophilicity and tumour selectivity of the GdIII complexes was demonstrated. This study highlights the delicate balance required to minimise in vitro cytotoxicity and optimise in vitro tumour selectivity and mitochondrial localisation for this new class of mitochondrially‐targeted binary therapy agents. We also report the highest in vitro tumour selectivity for any Gd agent reported to date, with a T/N (tumour/normal cell) ratio of up to 23.5±6.6. 相似文献
109.
Unraveling the Crystal Structure of Lanthanide–Murexide Complexes: Use of an Ancient Complexometry Indicator as a Near‐Infrared‐Emitting Single‐Ion Magnet 下载免费PDF全文
Xiaohui Yi Dr. Kevin Bernot Vincent Le Corre Dr. Guillaume Calvez Dr. Fabrice Pointillart Dr. Olivier Cador Dr. Boris Le Guennic Julie Jung Dr. Olivier Maury Dr. Virginie Placide Dr. Yannick Guyot Dr. Thierry Roisnel Dr. Carole Daiguebonne Prof. Olivier Guillou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1569-1576
Herein, we provide some structural evidence of the complexation color‐change of murexide solutions in presence of lanthanide, which has been used for decades in complexometric studies. For Ln=Sm to Lu and Y, the compounds crystallize as monomeric [Ln(Murex)3] ? 11 H2O with an N3O6 tricapped square‐antiprism environment, which are stable up to 250 °C. Single‐ion magnet (SIM) behavior is then observed on the YbIII derivative in an original nine‐coordinated environment. In‐field slow relaxation (Δ=(15.6±1) K; τ0=2.73×10?6 s) is observed with a very narrow distribution of the relaxation time (αmax=0.09). Magnetic and photophysical properties can be correlated. On one hand the analysis of NIR emission spectrum permits to have access to crystal field parameters and to compare them with those extracted from dc measurements. On the other hand, magnetic measurements permit to identify the nature of the M J states involved in the 2F5/2→2F7/2 luminescence spectrum. The gap between the low‐lying states is in agreement with the energy barrier obtained from magnetic slow‐relaxation measurement. 相似文献
110.
Coverage‐ and Temperature‐Dependent Metalation and Dehydrogenation of Tetraphenylporphyrin on Cu(111) 下载免费PDF全文
Michael Röckert Matthias Franke Quratulain Tariq Stefanie Ditze Michael Stark Patrick Uffinger Daniel Wechsler Upendra Singh Dr. Jie Xiao Dr. Hubertus Marbach Prof. Dr. Hans‐Peter Steinrück Dr. Ole Lytken 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):8948-8953
Using temperature‐programmed desorption, supported by X‐ray photoelectron spectroscopy and scanning tunneling microscopy, a comprehensive overview of the main reactions of 5,10,15,20‐tetraphenyl‐21H,23H‐porphyrin (2HTPP) on Cu(111) as a function of coverage and temperature is obtained. Three reactions were identified: metalation with Cu substrate atoms, stepwise partial dehydrogenation, and finally complete dehydrogenation. At low coverage the reactions are independent of coverage, but at higher coverage metalation becomes faster and partial dehydrogenation slower. This behavior is explained by a weaker interaction between the iminic nitrogen atoms and the Cu(111) surface in the high‐coverage checkerboard structure, leading to faster metalation, and the stabilizing effect of T‐type interactions in the CuTPP islands formed at high coverage after metalation, leading to slower dehydrogenation. Based on the amount of hydrogen released and the appearance in STM, a structure of the partially dehydrogenated molecule is suggested. 相似文献