全文获取类型
收费全文 | 583篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 362篇 |
晶体学 | 5篇 |
力学 | 18篇 |
数学 | 97篇 |
物理学 | 110篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 31篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 16篇 |
2017年 | 12篇 |
2016年 | 20篇 |
2015年 | 20篇 |
2014年 | 20篇 |
2013年 | 42篇 |
2012年 | 38篇 |
2011年 | 39篇 |
2010年 | 34篇 |
2009年 | 22篇 |
2008年 | 32篇 |
2007年 | 36篇 |
2006年 | 31篇 |
2005年 | 18篇 |
2004年 | 17篇 |
2003年 | 20篇 |
2002年 | 23篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有592条查询结果,搜索用时 15 毫秒
21.
Dariusz Zagrodny 《Journal of Optimization Theory and Applications》2018,178(2):411-423
In this paper, results on the strong convergence of subgradients of convex functions along a given direction are presented; that is, the relative compactness (with respect to the norm) of the union of subdifferentials of a convex function along a given direction is investigated. 相似文献
22.
Monika Szufla Aleksandra Choroś Dr. Wojciech Nitek Prof. Dariusz Matoga 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(37):e202200835
By using the strategy of pre-assembly chlorosulfonation applied to a linker precursor, the first sulfonated zirconium metal–organic framework ( JUK-14 ) with two-dimensional (2D) structure, was synthesized. Single-crystal X-ray diffraction reveals that the material is built of Zr6O4(OH)4(COO)8 oxoclusters, doubly 4-connected by angular dicarboxylates, and stacked in layers spaced 1.5 nm apart by the presence of sulfonic groups. JUK-14 exhibits excellent hydrothermal stability, permanent porosity confirmed by gas adsorption studies, and shows high (>10−4 S/cm) and low (<10−8 S/cm) proton conductivity under humidified and anhydrous conditions, respectively. Post-synthesis inclusion of imidazole improves the overall conductivity increasing it to 1.7×10−3 S/cm at 60 °C and 90 % relative humidity, and by 3 orders of magnitude at 160 °C. The combination of 2D porous nature with robustness of zirconium MOFs offers new opportunities for exploration of the material towards energy and environmental applications. 相似文献
23.
24.
Regioselective formation of β‐(E)‐ and α‐alkenylsilane moiety attached to silsesquioxane core via Pt‐ and Ru‐based hydrosilylation
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The first attempts to use ethynylsiloxysilsesquioxanes as reagents for hydrosilylation in the presence of Pt‐ and Ru‐based catalysts are reported. The results obtained strongly depend on the catalytic system used. The catalysts are proved to promote regioselective introduction of β‐(E)‐ and α‐fragments of the alkenylsilane group to the silsesquioxane core. The favourable features of these catalytic systems are their high selectivity and the requirement for relatively mild conditions. This methodology was also successfully applied to dihydro‐substituted organosilicon compounds to obtain a new class of silsesquioxane‐based compounds. 相似文献
25.
Dariusz Cal 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):816-824
ω-[(Arylphosphonomethyl)amino]alkylphosphonic and carboxylic acids are prepared in an easy work-up procedure, by addition of diethyl phosphite to in situ–generated arylideneaminoalkylphosphonic or carboxylic acids followed by hydrolysis with hydrochloric acid 相似文献
26.
Dichloroacetylene (C2Cl2) reacts with carbazole and primary amines under phase-transfer catalytic (PTC) conditions to give 1-N-alkylimino-1,2-di(9-carbazolyl)ethanes (I) and 9-((E)-1,2-dichlorovinyl)carbazole (II) in one-step synthesis. Compounds I are formed from the addition of amines to the triple bond of C2Cl2 followed by reactions with carbazole. 相似文献
27.
Paweł Mierczynski Piotr Kaczorowski Agnieszka Ura Waldemar Maniukiewicz Marcin Zaborowski Radoslaw Ciesielski Adam Kedziora Tomasz P. Maniecki 《Central European Journal of Chemistry》2014,12(2):206-212
Ternary CuO-ZrO2-Al2O3 catalysts promoted by palladium or gold were prepared and tested in CO hydrogenation reaction at 260°C under elevated pressure (4.8 MPa). The promotion effect of palladium or gold addition on the physicochemical and catalytical properties of CuO-ZrO2-Al2O3 catalysts in methanol synthesis (MS) was studied. The catalysts were characterized by BET, XRD, TPR-H2, TPD-NH3 methods. The BET results showed that the ternary system CuO-ZrO2-Al2O3 had the largest specific surface area, cumulative pore volume and average pore size in comparison with the promoted catalysts. The yield of methanol can be given through the following sequence: 5%Pd/CuO-ZrO2-Al2O3 > CuO-ZrO2-Al2O3 > 2%Au/CuO-ZrO2-Al2O3. We also found that the presence of gold or palladium on catalyst surface has strong influence on the reaction selectivity. The high selectivity of gold doped ternary catalyst is explained by the gold-oxide interface sites created on the catalyst surface and the acidity of those systems. The higher selectivity to methanol in the case of the palladium catalyst is explained by the spillover effect between Pd and CuO. 相似文献
28.
Andrzej Jóźwiak Paweł Tokarz Piotr M. Zagórski Róża Hamera Dariusz Cal Grzegorz Satała Andrzej J. Bojarski 《Heteroatom Chemistry》2015,26(4):290-298
Syntheses of a series of compounds bearing a 1‐(fluorophenyl)piperazin‐4‐ylmethyl moiety, namely dialkyl 1‐(fluorophenyl)piperazin‐4‐ylmethyl phosphonates 3a–f , diethyl 2‐[1‐(fluorophenyl)piperazin‐4‐yl]‐ethyl phosphonates 4a,b , diethyl 3‐[1‐(4‐fluorophenyl)‐piperazin‐4‐yl]‐propyl phosphonate 5 , and di[1‐(fluorophenyl)piperazin‐4‐yl]methanes 6a,b were performed, and some of them were screened for their affinity for serotonin 5‐HT1A, 5‐HT6, and 5‐HT7 receptors. Moderate interactions with these receptors were demonstrated. 相似文献
29.
Micha P. Maliski Jaromir Budzianowski Magorzata Kikowska Monika Derda Marcelina M. Jaworska Dariusz T. Mlynarczyk Marta Szukalska Ewa Florek Barbara Thiem 《Molecules (Basel, Switzerland)》2021,26(4)
Genetically uniform plant material, derived from Lychnis flos-cuculi propagated in vitro, was used for the isolation of 20-hydroxyecdysone and polypodine B and subjected to an evaluation of the antifungal and antiamoebic activity. The activity of 80% aqueous methanolic extracts, their fractions, and isolated ecdysteroids were studied against pathogenic Acanthamoeba castellani. Additionally, a Microtox® acute toxicity assay was performed. It was found that an 80% methanolic fraction of root extract exerts the most potent amoebicidal activity at IC50 of 0.06 mg/mL at the 3rd day of treatment. Both ecdysteroids show comparable activity at IC50 of 0.07 mg/mL. The acute toxicity of 80% fractions at similar concentrations is significantly higher than that of 40% fractions. Crude extracts exhibited moderate antifungal activity, with a minimum inhibitory concentration (MIC) within the range of 1.25–2.5 mg/mL. To the best of our knowledge, the present report is the first to show the biological activity of L. flos-cuculi in terms of the antifungal and antiamoebic activities and acute toxicity. It is also the first isolation of the main ecdysteroids from L. flos-cuculi micropropagated, ecdysteroid-rich plant material. 相似文献
30.
Dariusz?BochenekEmail author Przemys?aw?Niemiec Izabela?Szafraniak-Wiza Ma?gorzata?Adamczyk Ryszard?Skulski 《The European Physical Journal B - Condensed Matter and Complex Systems》2015,88(10):277
In the paper the influence of mechanical activation of the powder on the final dielectric properties lead-free Ba(Fe1/2Nb1/2)O3 (BFN) ceramic was examined. The BFN ceramics were obtained by 3-steps route. Firstly, the substrates were pre-homogenized in a planetary ball mill. Than, the powder was activated in vibratory mill (the shaker type SPEX 8000 Mixer Mill) for different duration between 25 h and 100 h. The influence of the milling time on the BFN powder was monitored by X-ray diffraction. The diffraction data confirmed that the milling process of the starting components is accompanied by partial synthesis of the BFN materials. The longer of the high-energy milling duration the powders results in increasing the amount of amorphous/nanocrystalline content. The mechanically activated materials were sintered in order to obtain the ceramic samples. During this temperature treatment the final crystallisation of the powder appeared what was confirmed by XRD studies. The performed dielectric measurements have revealed the reduction of the dielectric loss of the BFN ceramics compared to materials obtained by classic methods. 相似文献