全文获取类型
收费全文 | 678篇 |
免费 | 100篇 |
国内免费 | 333篇 |
专业分类
化学 | 996篇 |
晶体学 | 11篇 |
力学 | 2篇 |
综合类 | 1篇 |
数学 | 1篇 |
物理学 | 100篇 |
出版年
2024年 | 16篇 |
2023年 | 55篇 |
2022年 | 131篇 |
2021年 | 136篇 |
2020年 | 94篇 |
2019年 | 80篇 |
2018年 | 48篇 |
2017年 | 44篇 |
2016年 | 40篇 |
2015年 | 22篇 |
2014年 | 30篇 |
2013年 | 114篇 |
2012年 | 35篇 |
2011年 | 32篇 |
2010年 | 28篇 |
2009年 | 22篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 14篇 |
2005年 | 14篇 |
2004年 | 20篇 |
2003年 | 15篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 7篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 11篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有1111条查询结果,搜索用时 15 毫秒
41.
将光响应分子甲基螺吡喃SP-CH3引入UiO-66的非极性孔笼中,构筑吸附活性位可光控调节的光响应吸附剂。SP-CH3功能化的吸附剂完好保留了载体UiO-66的骨架和孔道结构。以阴离子染料甲基橙为探针,研究了吸附剂在不同光照条件下的吸附和解吸性能。结果表明,经紫外光照后,吸附剂对甲基橙的吸附量为41.99 mg·g-1,相较于可见光照后样品的吸附量提升57.56%,吸附作用增强;经可见光照后,甲基橙的脱附量为81.6%。本策略通过光照刺激改变UiO-66孔笼中SP-CH3的构型及表面电荷性质,即对吸附活性位进行光控调节,在不同光照条件下实现对吸附质的高效吸附和有效脱附。 相似文献
42.
选择具有强给电子能力的1,2,4-三唑为配体,成功合成了银基金属有机骨架材料(Ag-MOF)并用于电催化还原CO2反应(CO2RR)。借助粉末X射线衍射、透射电子显微镜、扫描电子显微镜、计时电流法等表征手段对材料的晶体结构、形貌和电催化CO2RR性能进行了系统的研究。与商品化的纳米Ag颗粒对比,Ag-MOF展现出更优异的电催化CO2RR产物选择性、催化活性和稳定性,在-0.9 V (vs RHE)时,CO的法拉第效率高达96.1%。当电压为-1.1 V (vs RHE)时,电流密度可达17 mA·cm-2,且电极可以稳定运行300 min。这说明通过选择合适的配体结构,可以改变催化位点周围的化学环境,从而高效将CO2转化为目标产物。 相似文献
43.
采用简单的热解-硫化两步法成功制备了一种新型的富氮掺杂碳空心纳米笼(NC)负载双元金属硫化物纳米颗粒(CoNixSy)的复合材料 CoNixSy/NC。该策略以丁二酮肟镍为镍源,增加了活性位点,同时前驱体 ZIF-8@Ni-ZIF-67的核壳结构为空心碳纳米笼的构建提供了可能性。这种独特的负载多金属硫化物纳米颗粒的中空结构使CoNixSy/NC作为电极材料时具有更多的活性位点、更高的导电性和结构稳定性,从而使其具有较高的比容量(1 A·g-1时比容量为629.2 F·g-1),优异的循环稳定性(1 A·g-1下1 000次循环测试后容量保持率为93.4%)。当将其进一步组装成对称超级电容器后,在1 A·g-1下可提供207.2 F·g-1的比电容,1 000圈循环稳定后的容量保持率为85.36%。 相似文献
44.
B. S. Randhawa K. J. Sweety Manpreet Kaur J. M. Greneche 《Journal of Thermal Analysis and Calorimetry》2004,75(1):101-111
Thermal analysis of some transition metal ferrimaleate precursors, M3[Fe(mal)3]2·xH2O (M=Mn, Co, Ni, Cu) has been studied in static air atmosphere from ambient to 600°C. Various physico-chemical techniques, i.e. TG, DTG, DTA, XRD, IR, Mössbauer spectrometry, have been employed to characterize both the intermediates and final products. After dehydration the anhydrous precursors undergo decomposition to yield an iron(II) intermediate, M[FeII(mal)2] (M=Mn, Co, Ni, Cu) in the temperature range 160-275°C. A subsequent oxidative decomposition of iron(II) species leads to the formation of -Fe2O3 and MO in the successive stages. Finally a solid-state reaction occurs between the oxides above 400°C resulting in the formation of transition metal ferrites, MFe2O4. The ferrites have been obtained at much lower temperature and in less time than in the conventional ceramic method.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
45.
金属-有机框架材料在气体吸附/分离方面具有广泛的应用, 因而引起国内外学者的广泛关注。本文以6种代表性的MOFs为例简单介绍了利用理论工具研究MOFs孔结构的方法。 相似文献
46.
Mesoporous molecular sieves were synthesized from Beta and Fau zeolite precursors through S+X−I+ route under extremely acidic conditions in parallel (designated as MBeta and MFau, respectively). The textural properties of MFau were different from its MBeta counterpart but resembled normal MCM-41 silica from TEOS. Al content in MBeta was almost equivalent to that in the initial Beta zeolite precursors, whereas only trace Al species was present in MFau from elemental analysis results. The hydrothermal stability of MBeta after post-synthesis ammonia treatment was considerably improved compared with normal MCM-41 aluminosilicates, whereas the MFau after the same procedure was as unstable as normal MCM-41 silica. Thus, the assembly behaviors of Beta and Fau zeolite precursors were comparatively studied based on these results. The microstructure of Fau zeolite precursors were degraded by the extremely acidic condition, and Al species was dissolved into the synthesis mixture. However, Beta zeolite precursors survived the chemical attack of extremely acidic media and were incorporated into mesostructured framework as primary building units. 相似文献
47.
A new and convenient route is developed to synthesize CdSe and core-shell CdSe/CdS quantum dots(QDs) in aqueous solution.The gaseous precursors,H2Se and H2S,generated on-line by reducing SeO 3 2à with NaBH 4 and the reaction between Na 2 S and diluted H2SO 4,are used to form high-quality CdSe and CdSe/CdS QDs,respectively.The synthesized water-soluble CdSe and CdSe/CdS QDs possess high quantum yield(3% and 20%) and narrow full-width-at-half-maximum(43 nm and 38 nm).The synthesis process is easily reproducible with simple apparatus and low-toxic chemicals,and can be readily extended to the large-scale aqueous synthesis of QDs. 相似文献
48.
R. P. Litvinovskaya N. V. Koval' V. A. Khripach 《Chemistry of Heterocyclic Compounds》2000,36(2):190-194
Modified vitamin D precursors with oxygen-containing substituents at various positions in the side-chain were obtained using previously synthesized 20-isoxazolin-3-yl-and 20-isoxazolin-5-ylsteroids.Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, 220141 Minsk, Belarus;Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 230–235, February, 2000. 相似文献
49.
近年来金属有机骨架(MOF)以其独特的结构特点(高比表面积、织构性质可调以及暴露的金属离子可以100%利用)引起了催化学者的极大重视,本文评述了与传统催化材料(如分子筛)相比,金属有机骨架作为催化材料的优点与不足,针对多数MOF中处于节点的金属离子被配体配位饱和而不具备催化活性这一弊端,本文基于对这一问题的最新研究进展总结了在MOF上创立催化活性位的4种方法:即前合成法、后合成共价修饰法、浸渍法以及沉淀法,讨论了这4种方法各自的优缺点,并详细介绍了这些方法在催化反应中的探索和应用,指出了MOF在催化领域需要重视的问题和未来的研究方向,以期对MOF在催化领域的研究和开发提供参考。 相似文献
50.
Laura Montanaro K. Belgacem P. Llewellyn F. Rouquerol F. Merlo Paola Palmero 《Journal of Thermal Analysis and Calorimetry》2007,88(3):789-793
Wet chemical synthesis of precursor oxide ceramics is a method to obtain small particulate powders. Such powders are far more
prone to ageing in air than more traditional precursors. Thermogravimetric analysis is used to highlight the species responsible
for the ageing of ceramic precursors. Indeed water and carbon dioxide are observed to evolve from aged powders. Ceramics obtained
from aged precursors can reach a very low final density with respect to the theoretical value. A large degree of the original
sintering properties can be recovered after washing the aged powders with ethanol in a basic medium. 相似文献