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421.
Hinrichs M Hofbauer FR Klüfers P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(17):4675-4683
With the [Re(CO)(3)Br(3)](2-) ion as a precursor for the Re(I)(CO)(3) fragment, the diols (1R,2R)-cyclohexane-1,2-diol [(1R,2R)-Chxd], anhydroerythritol (AnEryt), and (1S,2S)-cyclopentane-1,2-diol [(1S,2S)-Cptd] form dinuclear monoanions in the salts (NBu(4))[(Re(2)(CO)(6){mu-(1R,2R)-ChxdH(-1)}(3)] (1), [K([18]crown-6)][Re(2)(CO)(6)(mu-OMe)(2)(mu-AnErytH(-1))] (2) and (NBu(4))[Re(2)(CO)(6){mu-(1S,2S)-CptdH(-1)}(3)] (3). The monoanionic diolato ligands in these triply bridged dirhenates(I) are monodentate. Bridging triolato ligation in the trirhenates(I) is supported by the anions of glycerol (Glyc) and methyl beta-D-ribopyranoside (Me-beta-D-Ribp), the latter binding in its (1)C(4) conformation, in (DBUH)(2)[Re(3)(CO)(9)(mu(3)-O)(mu(3)-GlycH(-3))]0.5 MeCN (4 a), (NEt(4))[Re(3)(CO)(9)(mu(3)-OMe)(mu(3)-GlycH(-3))] (4 b) and (DBUH)[Re(3)(CO)(9)(mu(3)-OMe)(mu(3)-(1)C(4)-Me-beta-D-Ribp2,3,4H(-3))] (5). The chiral sugar alcohols L-threitol (L-Thre) and D-arabitol (D-Arab) act as tetra- and pentadentate ligands, respectively, in (NEt(4))[Re(2)(CO)(6)(L-ThreH(-3))]MeCN (6) and (NEt(4))(2)(DBUH)(2)[Re(6)(CO)(18)(D-ArabH(-5))(2)] (7). Complexes 6 and 7 are free of supporting oxo or methoxo ligands and use solely the O-atom pattern of the polyol for the connection of the Re(I)(CO)(3) moieties. 相似文献
422.
Labeling the planar face of crystalline cellulose using quantum dots directed by type-I carbohydrate-binding modules 总被引:1,自引:1,他引:0
Qi Xu Melvin P. Tucker Phil Arenkiel Xin Ai Garry Rumbles Junji Sugiyama Michael E. Himmel Shi-You Ding 《Cellulose (London, England)》2009,16(1):19-26
We report a new method for the direct labeling and visualization of crystalline cellulose using quantum dots (QDs) directed
by carbohydrate-binding modules (CBMs). Two type-I (surface binding) CBMs belonging to families 2 and 3a were cloned and expressed
with dual histidine tags at the N- and C-termini. Semiconductor (CdSe)ZnS QDs were used to label these CBMs following their binding to Valonia cellulose crystals. Using this approach, we demonstrated that QDs are linearly arrayed on cellulose, which implies that these
CBMs specifically bind to a planar face of cellulose. Direct imaging has further shown that different sizes (colors) of QDs
can be used to label CBMs bound to cellulose. Furthermore, the binding density of QDs arrayed on cellulose was modified predictably
by selecting from various combinations of CBMs and QDs of known dimensions. This approach should be useful for labeling and
imaging cellulose-containing materials precisely at the molecular scale, thereby supporting studies of the molecular mechanisms
of lignocellulose conversion for biofuels production. 相似文献
423.
424.
采用近红外飞秒激光辐照浸泡在硫酸溶液中的N型单晶硅片,激光波长800 nm,脉宽200 fs,重频1 kHz,平均功率为100 mW,而硫酸溶液的质量分数分别选择为0.1%和1%。辐照后硅表面呈直径为5~8 mm,高度15 mm的柱型结构。分析其荧光特性,并通过比较硅材料表面微结构与激光光源、扫描参数、硅片背景环境的关系,确定最佳辐照条件为激光扫描速度750 mm/s,扫描间距5 mm/s。最终在厚度0.5 mm、直径26 mm的硅片上获得10 mm×10 mm的方形扫描区域,荧光光谱显示激光扫描后的区域在700 nm附近有很强的荧光发射。分析结果表明飞秒激光扫描改变了样品的表面微结构尺寸,增大了吸收面积,扩展了荧光激发波长,有效提高了样品的吸收效率和荧光发光相对强度(超过扫描前发光相对强度的2倍),荧光发射谱的变化是由量子限制效应和表面态模型共同作用的结果。 相似文献
425.
Sreehari Surendran Rajasree Jierui Yu Dr. H. Christopher Fry Ryther Anderson Dr. Wenqian Xu Riya Krishnan Jiaxin Duan Dr. Subhadip Goswami Prof. Dr. Diego A. Gómez-Gualdrón Prof. Dr. Pravas Deria 《Angewandte Chemie (International ed. in English)》2023,62(38):e202305323
High quantum yield triplets, populated by initially prepared excited singlets, are desired for various energy conversion schemes in solid working compositions like porous MOFs. However, a large disparity in the distribution of the excitonic center of mass, singlet-triplet intersystem crossing (ISC) in such assemblies is inhibited, so much so that a carboxy-coordinated zirconium heavy metal ion cannot effectively facilitate the ISC through spin-orbit coupling. Circumventing this sluggish ISC, singlet fission (SF) is explored as a viable route to generating triplets in solution-stable MOFs. Efficient SF is achieved through a high degree of interchromophoric coupling that facilitates electron super-exchange to generate triplet pairs. Here we show that a predesigned chromophoric linker with extremely poor ISC efficiency (kISC) but form triplets in MOF in contrast to the frameworks that are built from linkers with sizable kISC but . This work opens a new photophysical and photochemical avenue in MOF chemistry and utility in energy conversion schemes. 相似文献
426.
Dr. Guolong Xing Shuai Zhang Prof. Weidong Zhu Prof. Teng Ben 《Angewandte Chemie (International ed. in English)》2023,62(8):e202215074
White et al., in a recent Correspondence, provided additional structural data to illustrate that CPOS-6 undergoes a single-crystal-to-single-crystal transformation during water adsorption/desorption. This finding gave a better understanding of the relevant experimental phenomena from the perspective of structural transformation and is a good complement to our previous results. However, we wish to emphasize that our research focuses on the kinetic behavior of water during ultrafast adsorption/desorption in nano-confined channels. Herein, we further interpret the rapid transport of water molecules in the nano-confined channels from the perspective of superfluidity. 相似文献
427.
Lingjuan Hu Qin Li Yunjun Luo Bixin Jin Shumeng Chi Xiaoyu Li 《Angewandte Chemie (International ed. in English)》2023,62(42):e202310022
The fabrication of uniform cylindrical nanoobjects from soft materials has attracted tremendous research attention from both fundamental research and practical application points of view but has also posed outstanding challenges in terms of their preparation. Herein, we report a one-step method to assemble cylindrical micelles (CMs) with highly controllable lengths from a single liquid crystalline block copolymer by an in situ nucleation-growth strategy. By adjusting the assembly conditions, the lengths of the CMs are controlled from hundreds of nanometers to micrometers. Several influencing factors are systematically investigated to comprehensively understand the process. Particularly, the solvent quality is found determinative in either enhancing or suppressing the nucleation process to produce shorter and longer CMs, respectively. Taking advantage of this strategy, the lengths of CMs can be nicely controlled over a wide concentration range of four orders of magnitude. Lastly, CMs are produced on decent scales and applied as additives to dramatically toughen glassy plastic matrix, revealing an unprecedented length-dependent toughening effect. 相似文献