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941.
Dr. Xi Wang Yijun Yang Dr. Tianyou Zhai Yeteng Zhong Dr. Zhanjun Gu Prof. Y. Charles Cao Prof. Yuliang Zhao Dr. Ying Ma Prof. Jiannian Yao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(17):5442-5449
We have demonstrated a new and facile bottom‐up protocol for the effective synthesis of oval‐shaped iron oxide/ethylene glycol (FeOx/EG) mesostructured nanosheets. Deprotonated ethylene glycol molecules are intercalated into iron oxide layers to form an interlayer distance of 10.6 Å. These materials display some peculiar magnetic properties, such as the low Morin temperature TM and ferromagnetism below this TM value. CdSe/ZnS nanoparticles can be loaded onto these mesostructured nanosheets to produce nanocomposites that combine both magnetic and fluorescence functions. In addition, iron oxide/propanediol (or butanediol) mesostructured materials with increased interlayer distances can also be synthesized. The developed synthetic strategy may be extended toward the creation of other ultrathin mesostructured nanosheets. 相似文献
942.
Dr. Yan‐Fen Fang Prof. Wan‐Hong Ma Prof. Ying‐Ping Huang Prof. Gen‐Wei Cheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(9):3224-3229
The band structure of multicomponent semiconductor photocatalysts, as well as their reactivity distinction under different wavelengths of light, is still unclear. BiOBr, which is a typical multicomponent semiconductor, may have two possible valence‐band structures, that is, two discrete valence bands constructed respectively from O 2p and Br 4p orbitals, or one valence band derived from the hybridization of these orbitals. In this work, aqueous photocatalytic hydroxylation is applied as the probe reaction to investigate the nature and reactions of photogenerated holes in BiOBr. Three organic compounds (microcystin‐LR, aniline, and benzoic acid) with different oxidation potentials were selected as substrates. Isotope labeling (H218O as the solvent) was used to determine the source of the O atom in the hydroxyl group of the products, which distinguishes the contribution of different hydroxylation pathways. Furthermore, a spin‐trapping ESR method was used to quantify the reactive oxygen species (.OH and .OOH) formed in the reaction system. The different isotope abundances of the hydroxyl O atom of the products formed, as well as the reverse trend of the .OH/.OOH ratio with the oxidative resistance of the substrate under UV and visible irradiation, reveal that BiOBr has two separate valence bands, which have different oxidation ability and respond to UV and visible light, respectively. This study shows that the band structure of semiconductor photocatalysts can be reliably analyzed with an isotope labeling method. 相似文献
943.
Dr. Dongpeng Yan Dr. Dejan‐Krešimir Bučar Dr. Amit Delori Bhavnita Patel Dr. Gareth O. Lloyd Prof. William Jones Prof. Xue Duan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8213-8219
Multi‐component organic nanocrystals that are comprised of two or more supramolecular building blocks can be used to extend the design and assembly scope of solid molecular materials. Herein, we report the use of ultrasonication to prepare halogen‐bonded stilbene‐based nano‐cocrystals that exhibit different photoemission properties, including one‐ and two‐phonon emission and fluorescence lifetimes, relative to those of macrodimensional crystals. The structural transformation from nano‐cocrystals into nanocrystals upon heating results in a luminescence red‐shift from greenish blue to yellow. The temperature‐dependent ratiometric luminescence may allow such nano‐cocrystals to be used as fluorescent sensors and thermosensitive materials. 相似文献
944.
Qian Lei Yawen Wei Dinesh Talwar Prof. Chao Wang Prof. Dong Xue Prof. Jianliang Xiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(12):4021-4029
Reductive amination of various ketones and aldehydes by transfer hydrogenation under aqueous conditions has been developed, by using cyclometallated iridium complexes as catalysts and formate as hydrogen source. The pH value of the solution is shown to be critical for a high catalytic chemoselectivity and activity, with the best pH value being 4.8. In comparison with that in organic solvents, the reductive amination in an aqueous phase is faster, and the molar ratio of the substrate to the catalyst (S/C) can be set as high as 1×105, the highest S/C value ever reported in reductive amination reactions. The catalyst is easy to access and the reaction is operationally simple, allowing a wide range of ketones and aldehydes to react with various amines in high yields. The protocol provides a practical and environmental friendly new method for the synthesis of amine compounds. 相似文献
945.
Feng Huang Ying‐Ying Pei Hui‐Hui Zuo Jia‐Liang Chen Yin Yang Prof. Xun‐Cheng Su 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):17141-17149
Site‐specific labeling of proteins with lanthanide ions offers great opportunities for investigating the structure, function, and dynamics of proteins by virtue of the unique properties of lanthanides. Lanthanide‐tagged proteins can be studied by NMR, X‐ray, fluorescence, and EPR spectroscopy. However, the rigidity of a lanthanide tag in labeling of proteins plays a key role in the determination of protein structures and interactions. Pseudocontact shift (PCS) and paramagnetic relaxation enhancement (PRE) are valuable long‐range structure restraints in structural‐biology NMR spectroscopy. Generation of these paramagnetic restraints generally relies on site‐specific tagging of the target proteins with paramagnetic species. To avoid nonspecific interaction between the target protein and paramagnetic tag and achieve reliable paramagnetic effects, the rigidity, stability, and size of lanthanide tag is highly important in paramagnetic labeling of proteins. Here 4′‐mercapto‐2,2′: 6′,2′′‐terpyridine‐6,6′′‐dicarboxylic acid (4MTDA) is introduced as a a rigid paramagnetic and fluorescent tag which can be site‐specifically attached to a protein by formation of a disulfide bond. 4MTDA can be readily immobilized by coordination of the protein side chain to the lanthanide ion. Large PCSs and RDCs were observed for 4MTDA‐tagged proteins in complexes with paramagnetic lanthanide ions. At an excitation wavelength of 340 nm, the complex formed by protein–4MTDA and Tb3+ produces high fluorescence with the main emission at 545 nm. These interesting features of 4MTDA make it a very promising tag that can be exploited in NMR, fluorescence, and EPR spectroscopic studies on protein structure, interaction, and dynamics. 相似文献
946.
Ying‐Lu Cui Ji‐Long Zhang Prof. Qing‐Chuan Zheng Rui‐Juan Niu Yu Xu Prof. Hong‐Xing Zhang Chia‐Chung Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(2):549-557
Cytochrome P450 (CYP) 7B1 is a steroid cytochrome P450 7α‐hydroxylase that has been linked directly with bile salt synthesis and hereditary spastic paraplegia type 5 (SPG5). The enzyme provides the primary metabolic route for neurosteroids dehydroepiandrosterone (DHEA), cholesterol derivatives 25‐hydroxycholesterol (25‐HOChol), and other steroids such as 5α‐androstane‐3β,17β‐diol (anediol), and 5α‐androstene‐3β,17β‐diol (enediol). A series of investigations including homology modeling, molecular dynamics (MD), and automatic docking, combined with the results of previous experimental site‐directed mutagenesis studies and access channels analysis, have identified the structural features relevant to the substrate selectivity of CYP7B1. The results clearly identify the dominant access channels and critical residues responsible for ligand binding. Both binding free energy analysis and total interaction energy analysis are consistent with the experimental conclusion that 25‐HOChol is the best substrate. According to 20 ns MD simulations, the Phe cluster residues that lie above the active site, particularly Phe489, are proposed to merge the active site with the adjacent channel to the surface and accommodate substrate binding in a reasonable orientation. The investigation of CYP7B1–substrate binding modes provides detailed insights into the poorly understood structural features of human CYP7B1 at the atomic level, and will be valuable information for drug development and protein engineering. 相似文献
947.
Dr. Xiaolong Liang Xiaoda Li Lijia Jing Peng Xue Lingdong Jiang Prof. Qiushi Ren Prof. Dr. Zhifei Dai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(47):16113-16121
This paper reports the facile design and synthesis of a series of lipidic organoalkoxysilanes with different numbers of triethoxysilane headgroups and hydrophobic alkyl chains linked by glycerol and pentaerythritol for the construction of cerasomes with regulated surface siloxane density and controlled release behavior. It was found that the number of triethoxysilane headgroups affected the properties of the cerasomes for encapsulation efficiency, drug loading capacity, and release behavior. For both water‐soluble doxorubicin (DOX) and water‐insoluble paclitaxel (PTX), the release rate from the cerasomes decreased as the number of triethoxysilane headgroups increased. The slower release rate from the cerasomes was attributed to the higher density of the siloxane network on the surface of the cerasomes, which blocks the drug release channels. In contrast to the release results with DOX, the introduction of one more hydrophobic alkyl chain into the cerasome‐forming lipid resulted in a slower release rate of PTX from the cerasomes due to the formation of a more compact cerasome bilayer. An MTT viability assay showed that all of these drug‐loaded cerasomes inhibited proliferation of the HepG2 cancer cell line. The fine tuning of the chemical structure of the cerasome‐forming lipids would foster a new strategy to precisely regulate the release rate of drugs from cerasomes. 相似文献
948.
Dr. Yun Wang Dr. Jin Yang Dr. Ying‐Ying Liu Prof. Dr. Jian‐Fang Ma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(43):14591-14599
Two porous metal–organic frameworks (MOFs), [Zn3(L)(H2O)2] ? 3 DMF ? 7 H2O ( MOF‐1 ) and [(CH3)2NH2]6[Ni3(L)2(H2O)6] ? 3 DMF ? 15 H2O ( MOF‐2 ), were synthesized solvothermally (H6L=1,2,3,4,5,6‐hexakis(3‐carboxyphenyloxymethylene)benzene). In MOF ‐ 1 , neighboring ZnII trimers are linked by the backbones of L ligands to form a fascinating 3D six‐connected framework with the point symbol (412.63) (412.63). In MOF‐2 , eight L ligands bridge six NiII atoms to generate a rhombic‐dodecahedral [Ni6L8] cage. Each cage is surrounded by eight adjacent ones through sharing of carboxylate groups to yield an unusual 3D porous framework. Encapsulation of LnIII cations for tunable luminescence and small drug molecules for efficient delivery were investigated in detail for MOF‐1 . 相似文献
949.
950.