全文获取类型
收费全文 | 1168篇 |
免费 | 140篇 |
国内免费 | 120篇 |
专业分类
化学 | 939篇 |
晶体学 | 40篇 |
力学 | 48篇 |
综合类 | 4篇 |
数学 | 145篇 |
物理学 | 252篇 |
出版年
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 28篇 |
2020年 | 17篇 |
2019年 | 31篇 |
2018年 | 21篇 |
2017年 | 25篇 |
2016年 | 50篇 |
2015年 | 56篇 |
2014年 | 62篇 |
2013年 | 86篇 |
2012年 | 81篇 |
2011年 | 92篇 |
2010年 | 48篇 |
2009年 | 40篇 |
2008年 | 76篇 |
2007年 | 58篇 |
2006年 | 60篇 |
2005年 | 49篇 |
2004年 | 56篇 |
2003年 | 44篇 |
2002年 | 61篇 |
2001年 | 47篇 |
2000年 | 30篇 |
1999年 | 28篇 |
1998年 | 22篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1974年 | 7篇 |
1971年 | 6篇 |
1970年 | 4篇 |
1968年 | 4篇 |
1967年 | 4篇 |
排序方式: 共有1428条查询结果,搜索用时 15 毫秒
61.
Qiang Fu Xianjie Wang Jiecai Han Jun Zhong Tongrui Zhang Tai Yao Chengyan Xu Tangling Gao Shibo Xi Ce Liang Lingling Xu Ping Xu Bo Song 《Angewandte Chemie (International ed. in English)》2021,60(1):259-267
To ensure sustainable hydrogen production by water electrolysis, robust, earth‐abundant, and high‐efficient electrocatalysts are required. Constructing a hybrid system could lead to further improvement in electrocatalytic activity. Interface engineering in composite catalysts is thus critical to determine the performance, and the phase‐junction interface should improve the catalytic activity. Here, we show that nickel diphosphide phase junction (c‐NiP2/m‐NiP2) is an effective electrocatalyst for hydrogen production in alkaline media. The overpotential (at 10 mA cm?2) for NiP2‐650 (c/m) in alkaline media could be significantly reduced by 26 % and 96 % compared with c‐NiP2 and m‐NiP2, respectively. The enhancement of catalytic activity should be attributed to the strong water dissociation ability and the rearrangement of electrons around the phase junction, which markedly improved the Volmer step and benefited the reduction process of adsorbed protons. 相似文献
62.
Balancing the Rate of Cluster Growth and Etching for Gram‐Scale Synthesis of Thiolate‐Protected Au25 Nanoclusters with Atomic Precision
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xun Yuan Bin Zhang Zhentao Luo Qiaofeng Yao Prof. David Tai Leong Prof. Ning Yan Prof. Jianping Xie 《Angewandte Chemie (International ed. in English)》2014,53(18):4623-4627
We report a NaOH‐mediated NaBH4 reduction method for the synthesis of mono‐, bi‐, and tri‐thiolate‐protected Au25 nanoclusters (NCs) with precise control of both the Au core and thiolate ligand surface. The key strategy is to use NaOH to tune the formation kinetics of Au NCs, i.e., reduce the reduction ability of NaBH4 and accelerate the etching ability of free thiolate ligands, leading to a well‐balanced reversible reaction for rapid formation of thermodynamically favorable Au25 NCs. This protocol is facile, rapid (≤3 h), versatile (applicable for various thiolate ligands), and highly scalable (>1 g Au NCs). In addition, bi‐ and tri‐thiolate‐protected Au25 NCs with adjustable ratios of hetero‐thiolate ligands were easily obtained. Such ligand precision in molecular ratios, spatial distribution and uniformity resulted in richly diverse surface landscapes on the Au NCs consisting of multiple functional groups such as carboxyl, amine, and hydroxy. Analysis based on NMR spectroscopy revealed that the hetero‐ligands on the NCs are well distributed with no ligand segregation. The unprecedented synthesis of multi‐thiolate‐protected Au25 NCs may further promote the practical applications of functional metal NCs. 相似文献
63.
水杨羟肟酸对氟碳铈矿的捕收机制研究 总被引:2,自引:0,他引:2
以水杨羟肟酸为捕收剂,通过浮选试验、溶液化学计算、动电位和红外光谱检测分析研究了氟碳铈矿的可浮性及药剂与矿物的作用机制。当水杨羟肟酸浓度为5×10-4mol·L-1时,氟碳铈矿在pH=7~10较宽的范围内有较好的可浮性,与矿物表面的稀土阳离子的水解产物种类及其浓度有关。pH=8~9范围内,稀土阳离子水解优势组分RE(OH)2+和RE(OH)+2吸附在氟碳铈矿表面是主要的正活性质点,有利于药剂的化学吸附。在pH=8.3时,水杨羟肟酸对氟碳铈矿捕收是化学吸附作用生成五元环螯合物的结果。 相似文献
64.
Dynamic and Quantitative Control of the DNA‐Mediated Growth of Gold Plasmonic Nanostructures
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Jianlei Shen Lifeng Xu Dr. Chunpeng Wang Dr. Hao Pei Prof.Dr. Renzhong Tai Prof.Dr. Shiping Song Prof.Dr. Qing Huang Prof.Dr. Chunhai Fan Prof.Dr. Gang Chen 《Angewandte Chemie (International ed. in English)》2014,53(32):8338-8342
Reproducible and controllable growth of nanostructures with well‐defined physical and chemical properties is a longstanding problem in nanoscience. A key step to address this issue is to understand their underlying growth mechanism, which is often entangled in the complexity of growth environments and obscured by rapid reaction speeds. Herein, we demonstrate that the evolution of size, surface morphology, and the optical properties of gold plasmonic nanostructures could be quantitatively intercepted by dynamic and stoichiometric control of the DNA‐mediated growth. By combining synchrotron‐based small‐angle X‐ray scattering (SAXS) with transmission electron microscopy (TEM), we reliably obtained quantitative structural parameters for these fine nanostructures that correlate well with their optical properties as identified by UV/Vis absorption and dark‐field scattering spectroscopy. Through this comprehensive study, we report a growth mechanism for gold plasmonic nanostructures, and the first semiquantitative revelation of the remarkable interplay between their morphology and unique plasmonic properties. 相似文献
65.
Jong Young Joung Ha Yeon Lee Jongil Park Jee-Young Lee Byung Ha Chang Kyoung Tai No Ky-Youb Nam Jae Sung Hwang 《Applied biochemistry and biotechnology》2014,172(4):1882-1897
Melanocytes are unique cells that produce specific melanin-containing intracellular organelles called melanosomes. Melanosomes are transported from the perinuclear area of melanocytes toward the plasma membrane as they become more melanized in order to increase skin pigmentation. In this vesicular trafficking of melanosomes, Rab27a, melanophilin, and myosin Va play crucial roles in linking melanosomes to actin-based motors. To identify novel compounds to inhibit binding interface between Rab27a and melanophilin, a pharmacophore model was built based on a modeled 3D structure of the protein complex that describes the essential binding residues in the intermolecular interaction. A pharmacophore model was employed to screen a chemical library database. Finally, 25 virtual hits were selected for biological evaluations. The biological activities of 11 analogues were evaluated in a second assay. Two compounds were identified as having concentration-dependent inhibitory activity. By analyzing structure–activity relationships of derivatives of BMD-20, two hydroxyl functional groups were found to be critical for blocking the intermolecular binding between Rab27a and melanophilin. 相似文献
66.
Chin-Kuen Tai Pao-Ling Yeh Chun-Chi Chang Wen-Hao Chen Rong-Hou Wu Yu-Ma Chou Bo-Cheng Wang 《Research on Chemical Intermediates》2014,40(6):2355-2362
Recently, the organic synthesis and electronic device applications of π-conjugated polymer-based materials with low energy band gap (below 2 eV) and high values of incident photon to current efficiency have been presented. In the present study, the physical properties of polythiophene (PTH) and its derivative systems (PTs) were investigated as π-conjugated low energy band gap polymers. Density functional theory with periodic boundary condition (PBC), the B3LYP functional, and the 6-31G(d) basis set was applied to determine their geometric and electronic structures and corresponding energies (E HOMO, E LUMO, and E g = E LUMO ? E HOMO) from the monomer of thiophene and its derivatives for one-dimensional (1D) extension to polymer. The effects of 3-substitution in PTs including electron-donating (CH3–, C6H13–, OH–, Cl–, OCH3–, and CHO–) and electron-withdrawing groups (Cl–, CHO–, CN–, NO2–, CF3–, and COOH–) compared with PTH were investigated. According to the calculation results, PTs with electron-donating and electron-withdrawing substituents should exhibit red- and blue-shifts, respectively, compared with PTH. These calculation results show good agreement with experimental data and provide further information for molecular design considerations. 相似文献
67.
A new tripodal ligand, N,N′,N″-tri(salicylaldehyde)triaminotriethylamine (1) has been synthesized and characterized by elemental analysis, IR and UV spectroscopy, MS, and X-ray crystallography. X-ray diffraction analysis reveals that the three chains of the ligand form a cup-like structure. The ligand’s magnesium(II) complex has been synthesized and characterized by elemental analysis, conductivity, and IR and UV spectroscopy. The luminescence properties of the ligand and its magnesium(II) complex were investigated in DMF, CH3OH, and CH3CH2OH solution and in the solid state at room temperature. 相似文献
68.
Sahar Pakbaten Toopkanloo Tai Boon Tan Faridah Abas Mohammad Azam Imededdine Arbi Nehdi Chin Ping Tan 《Molecules (Basel, Switzerland)》2020,25(24)
In order to improve the membrane lipophilicity and the affinity towards the environment of lipid bilayers, squalene (SQ) could be conjugated to phospholipids in the formation of liposomes. The effect of membrane composition and concentrations on the degradation of liposomes prepared via the extrusion method was investigated. Liposomes were prepared using a mixture of SQ, cholesterol (CH) and Tween80 (TW80). Based on the optimal conditions, liposome batches were prepared in the absence and presence of SQ. Their physicochemical and stability behavior were evaluated as a function of liposome constituent. From the optimization study, the liposomal formulation containing 5% (w/w) mixed soy lecithin (ML), 0.5% (w/w) SQ, 0.3% (w/w) CH and 0.75% (w/w) TW80 had optimal physicochemical properties and displayed a unilamellar structure. Liposome prepared using the optimal formulation had a low particle size (158.31 ± 2.96 nm) and acceptable %increase in the particle size (15.09% ± 3.76%) and %trolox equivalent antioxidant capacity (%TEAC) loss (35.69% ± 0.72%) against UV light treatment (280–320 nm) for 6 h. The interesting outcome of this research was the association of naturally occurring substance SQ for size reduction without the extra input of energy or mechanical procedures, and improvement of vesicle stability and antioxidant activity of ML-based liposome. This study also demonstrated that the presence of SQ in the membrane might increase the acyl chain dynamics and decrease the viscosity of the dispersion, thereby limiting long-term stability of the liposome. 相似文献
69.
Katsuhiko Ariga Xiaofang Jia Jingwen Song Jonathan P. Hill David Tai Leong Yi Jia Junbai Li 《Angewandte Chemie (International ed. in English)》2020,59(36):15424-15446
Incorporation of non‐equilibrium actions in the sequence of self‐assembly processes would be an effective means to establish bio‐like high functionality hierarchical assemblies. As a novel methodology beyond self‐assembly, nanoarchitectonics, which has as its aim the fabrication of functional materials systems from nanoscopic units through the methodological fusion of nanotechnology with other scientific disciplines including organic synthesis, supramolecular chemistry, microfabrication, and bio‐process, has been applied to this strategy. The application of non‐equilibrium factors to conventional self‐assembly processes is discussed on the basis of examples of directed assembly, Langmuir–Blodgett assembly, and layer‐by‐layer assembly. In particular, examples of the fabrication of hierarchical functional structures using bio‐active components such as proteins or by the combination of bio‐components and two‐dimensional nanomaterials, are described. Methodologies described in this review article highlight possible approaches using the nanoarchitectonics concept beyond self‐assembly for creation of bio‐like higher functionalities and hierarchical structural organization. 相似文献
70.
以三聚氰胺和硼酸为原料在水溶液中反应合成出了一种新的BCN化合物先驱体C3N6H6(H3BO3)2。XRD表征结果表明三聚氰胺和硼酸的最佳配比为1∶3(物质的量比)。用单晶X-射线衍射分析法测定了该化合物的晶体结构。该化合物属单斜晶系,空间群为P21/C,晶胞参数为a=0.3597(7)nm,b=2.0105(4)nm,c=1.4112(3)nm,α=90,°β=92.07(3),°γ=90,°V=1.0199(3)nm3,Z=4,D c=1.627g.cm-3,μ(MoKα)=0.144mm-1,F(000)=520。晶体结构经全矩阵最小二乘法修正,最终可靠因子R1=0.0519,wR2=0.1361。该化合物是由C3N6H6分子和H3BO3分子通过氢键加合组装形成的三维超分子结构化合物。 相似文献