全文获取类型
收费全文 | 701篇 |
免费 | 26篇 |
专业分类
化学 | 451篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 169篇 |
物理学 | 104篇 |
出版年
2023年 | 7篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 19篇 |
2017年 | 19篇 |
2016年 | 30篇 |
2015年 | 17篇 |
2014年 | 32篇 |
2013年 | 60篇 |
2012年 | 46篇 |
2011年 | 49篇 |
2010年 | 35篇 |
2009年 | 27篇 |
2008年 | 56篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 47篇 |
2004年 | 35篇 |
2003年 | 21篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1975年 | 3篇 |
1967年 | 1篇 |
1952年 | 3篇 |
1936年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有727条查询结果,搜索用时 31 毫秒
31.
Dr. Györgyi Váradi Prof. Gábor K. Tóth Dr. Zoltán Kele Dr. László Galgóczy Ádám Fizil Prof. Gyula Batta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12684-12692
The folding of disulfide proteins is of considerable interest because knowledge of this may influence our present understanding of protein folding. However, sometimes even the disulfide pattern cannot be unequivocally determined by the available experimental techniques. For example, the structures of a few small antifungal proteins (PAF, AFP) have been disclosed recently using NMR spectroscopy but with some ambiguity in the actual disulfide pattern. For this reason, we carried out the chemical synthesis of PAF. Probing different approaches, the oxidative folding of the synthetic linear PAF yielded a folded protein that has identical structure and antifungal activity as the native PAF. In contrast, unfolded linear PAF was inactive, a result that may have implications concerning its redox state in the mode of action. 相似文献
32.
Rodrigues Ana Luísa Marques Rosa Dias Maria Isabel Prudêncio Maria Isabel Russo Dulce Diniz Mariana Martins Andrea Neves César Kasztovszky Zsolt Harsányi Ildiko Szilágyi Veronika Kovács Imre Szőkefalvi-Nagy Zoltán 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(9):3887-3903
Journal of Radioanalytical and Nuclear Chemistry - A contribution to the discussion about Vila Nova de São Pedro (VNSP) as a production centre of symbolic lithic artefacts, the origin of raw... 相似文献
33.
Szentmihályi Klára May Zoltán Bódis Eszter Tóth Judit Trif László Klébert Szilvia Feczkó Tivadar Károly Zoltán 《Journal of Thermal Analysis and Calorimetry》2022,147(21):11777-11786
Journal of Thermal Analysis and Calorimetry - Spray freeze-drying (SFD) is an effective method for reducing the size of thermosensitive organic substances that are sparingly soluble in water.... 相似文献
34.
Mahitha Udayakumar Bilal El Mrabate Tamás Koós Katalin Szemmelveisz Ferenc Kristály Máté Leskó Ádám Filep Róbert Géber Mateusz Schabikowski Péter Baumli János Lakatos Pál Tóth Zoltán Németh 《Arabian Journal of Chemistry》2021,14(7):103214
Carbon foams have gained significant attention due to their tuneable properties that enable a wide range of applications including catalysis, energy storage and wastewater treatment. Novel synthesis pathways enable novel applications via yielding complex, hierarchical material structure. In this work, activated carbon foams (ACFs) were produced from waste polyurethane elastomer templates using different synthesis pathways, including a novel one-step method. Uniquely, the produced foams exhibited complex structure and contained carbon microspheres. The ACFs were synthesized by impregnating the elastomers in an acidified sucrose solution followed by direct activation using CO2 at 1000 ℃. Different pyrolysis and activation conditions were investigated. The ACFs were characterized by a high specific surface area (SBET) of 2172 m2/g and an enhanced pore volume of 1.08 cm3/g. Computer tomography and morphological studies revealed an inhomogeneous porous structure and the presence of numerous carbon spheres of varying sizes embedded in the porous network of the three-dimensional carbon foam. X-ray diffraction (XRD) and Raman spectroscopy indicated that the obtained carbon foam was amorphous and of turbostratic structure. Moreover, the activation process enhanced the surface of the carbon foam, making it more hydrophilic via altering pore size distribution and introducing oxygen functional groups. In equilibrium, the adsorption of methylene blue on ACF followed the Langmuir isotherm model with a maximum adsorption capacity of 592 mg/g. Based on these results, the produced ACFs have potential applications as adsorbents, catalyst support and electrode material in energy storage systems. 相似文献
35.
Alexander A. Kamnev Roman L. Dykman Krisztina Kovács Alexei N. Pankratov Anna V. Tugarova Zoltán Homonnay Ernő Kuzmann 《Structural chemistry》2014,25(2):649-657
Iron(III)-containing aqueous solutions of 5-methylresorcinol (5-MR), 5-n-propylresorcinol (5-n-PR) and 4-n-hexylresorcinol (4-n-HR) at pH ~ 3 were studied by means of 57Fe transmission Mössbauer spectroscopy. Kinetic considerations were applied to the redox reactions. Density Functional Theory (DFT) calculations were performed for the alkylresorcinol (AR) molecules and their non-alkylated analogue (resorcinol). Mössbauer spectra consisted of quadrupole doublets assigned to high-spin Fe(III) and Fe(II) species. From changes in their relative spectral areas, a gradual reduction of Fe(III) by all the ARs studied was observed. However, significant differences were found for the reduction rates among the ARs. The following series of the reduction rates was established by means of Mössbauer spectroscopy: 4-n-HR ? 5-MR > 5-n-PR, supplemented by rate constants calculated using a kinetic model. DFT calculations resulted in the following series: 4-n-HR ? 5-n-PR > 5-MR ? resorcinol (the latter is not oxidised under the conditions applied). The reversed order of the experimentally observed 5-MR and 5-n-PR oxidation rates may be explained in terms of their different kinetic parameters related to their structure. 相似文献
36.
Dr. Dominikus Heift Dr. Zoltán Benkő Prof. Dr. Hansjörg Grützmacher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11326-11330
Unsaturated phosphorus compounds, such as phosphaalkenes and phosphaalkynes, show a versatile reactivity in cycloadditions. Although phosphaketenes (R?P?C?O) have been known for three decades, their chemistry has remained limited. Herein, we show that heteroatom‐substituted phosphaketenes, R3E?P?C?O (E=Si, Sn), are building blocks for silyl‐ and stannyl‐substituted five‐membered heterocycles containing three phosphorous atoms. The structure of the heterocyclic anion depends on the nature of the tetrel atom involved. Although the silyl analogue [P3C2(OSiR3)2]? is an aromatic 1,2,4‐triphospholide, the stannyl compound [P(CO)2(PSnR3)2]? is a 1,2,4‐triphosphacyclopenta‐3,5‐dionate with a delocalized OCPCO fragment. Because of their anionic character, these compounds can easily be used as building blocks, for example, in the preparation of a silyl‐functionalized hexaphosphaferrocene or the parent 1,2,4‐triphosphacyclopenta‐3,5‐dionate [P(CO)2(PH)2]?. NMR spectroscopic investigations and computations have shown that the heterocycle‐formation reactions presented herein are remarkably complex. 相似文献
37.
A method is presented for the simultaneous determination of Cr(III) and Cr(VI) in yeast using species-specific double-spike
isotope dilution (SSDSID) with anion-exchange liquid chromatography (LC) separation and sector field inductively coupled plasma
mass spectrometric (SF-ICP-MS) detection. Total Cr is quantitated using ID SF-ICP-MS. Samples were digested on a hot plate
at 95±2 °C for 6 h in an alkaline solution of 0.5 M NaOH and 0.28 M Na2CO3 for the determination of Cr(III) and Cr(VI), whereas microwave-assisted decomposition with HNO3 and H2O2 was used for the determination of total Cr. Concentrations of 2,014±16, 1,952±103 and 76±48 mg kg−1 (one standard deviation, n=4, 3, 3), respectively were obtained for total Cr, Cr(III) and Cr(VI) in the yeast sample. Significant oxidation of Cr(III)
to Cr(VI) (24.2±7.6% Cr(III) oxidized, n=3) and reduction of Cr(VI) to Cr(III) (37.6±6.5% Cr(VI) reduced, n=3 ) occurred during alkaline extraction and subsequent chromatographic separation at pH 7. Despite this significant bidirectional
redox transformation, quantitative recoveries for both Cr(III) and Cr(VI) were achieved using the SSDSID method. In addition,
mass balance between total Cr and the sum of Cr(III) and Cr(VI) concentrations was achieved. Method detection limits of 0.3,
2 and 30 mg kg−1 were obtained for total Cr, Cr(VI) and Cr(III), respectively, based on a 0.2-g sub-sample. 相似文献
38.
The molecular geometries and vibrational frequencies of aluminum oxyhalides, AlOX, and their dimers, (AlOX)2, have been calculated by MP2 and density functional methods. The monomeric molecules are linear while the dimers have a D
2h
-symmetry geometry with a four-membered ring, in which the oxygen atoms serve as bridging ligands. Different thermodynamic
properties have been calculated; for AlOBr and AlOI for the first time. 相似文献
39.
n-Hexane andn-nonane were reacted on Pt black, 6% Pt/SiO2, 0.8% Pt/KL zeolite and a 0.6% industrial Pt/Al2O3 catalyst. Selectivities were compared at ∼10% conversion. After reaction, the catalyst was exposed to H2 and the hydrocarbons leaving the catalysts were analyzed. The amount of hydrocarbons left the catalysts decreased in the
sequence Pt black>Pt/SiO2>Pt/KL>Pt/Al2O3. The composition of removed hydrocarbons gave important—although indirect—information on the possible state of “hydrocarbonaceous
deposits” during catalysis. 相似文献
40.