全文获取类型
收费全文 | 506篇 |
免费 | 15篇 |
国内免费 | 3篇 |
专业分类
化学 | 410篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 54篇 |
物理学 | 54篇 |
出版年
2023年 | 4篇 |
2022年 | 46篇 |
2021年 | 53篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 14篇 |
2017年 | 15篇 |
2016年 | 25篇 |
2015年 | 20篇 |
2014年 | 30篇 |
2013年 | 33篇 |
2012年 | 41篇 |
2011年 | 31篇 |
2010年 | 39篇 |
2009年 | 20篇 |
2008年 | 22篇 |
2007年 | 22篇 |
2006年 | 13篇 |
2005年 | 15篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有524条查询结果,搜索用时 0 毫秒
91.
Incorporation of a Phenanthrene Subunit into a Sapphyrin Framework: Synthesis of Expanded Aceneporphyrinoids 下载免费PDF全文
Dr. Bartosz Szyszko Marcin Małecki Dr. Anna Berlicka Michał J. Białek Dr. Agata Białońska Kamil Kupietz Dr. Ewa Pacholska‐Dudziak Prof. Lechosław Latos‐Grażyński 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7602-7608
32‐Hetero‐5,6‐dimethoxyphenanthrisapphyrins—macrocycles that link structural features of polycylic aromatic hydrocarbons and expanded porphyrins—were obtained in a straightforward [3+1] condensation reaction of dimethoxyphenanthritripyrrane and 2,5‐bis(arylhydroxymethyl)heterocyclopentadienes. The highly folded conformation of formally 4 n π‐electron macrocycles causes them to manifest only limited macrocyclic π conjugation as explored by means of NMR spectroscopic and X‐ray structural analyses, and supported by DFT calculations. Although protonation does not change their π‐conjugation characteristics, the cleavage of ether groups at the phenanthrenylene moiety yields nonaromatic 32‐hetero‐5,6‐dioxophenanthrisapphyrins. 相似文献
92.
Fyodor S. Kot Vladimir L. Rapoport Galina V. Kharitonova 《Central European Journal of Chemistry》2007,5(3):846-857
The results of the laboratory pot experiments on soil mercury (Hg) immobilisation with a non-toxic and price-reasonable agent
— colloidal sulphur (S) water suspension, are presented. It was shown that fertilisation with small agrochemical doses of
colloidal S reduces excess Hg effectively as follows: in interstitial waters by a factor 2 – 12 times for total Hg, and 22–
680 times for “reactive” Hg; in stems and leaves of oats – 7 – 22 times; and in moss bags, reflecting soil Hg degassing, 7
– 15 times, for the most heavily Hg-spiked soils. The results obtained allowed to conclude that the immobilization of Hg occurs
through Hg binding to the newly formed S-bearing functional groups in humic acids and/or sulphides.
相似文献
93.
Katarzyna Kucwaj-Brysz Anna Dela Sabina Podlewska Marek Bednarski Agata Siwek Grzegorz Sataa Kinga Czarnota Jadwiga Handzlik Katarzyna Kie-Kononowicz 《Molecules (Basel, Switzerland)》2021,26(22)
Several studies confirmed the reciprocal interactions between adrenergic and serotoninergic systems and the influence of these phenomena on the pathogenesis of anxiety. Hence, searching for chemical agents with a multifunctional pharmacodynamic profile may bring highly effective therapy for CNS disorders. This study presents a deep structural insight into the hydantoin-arylpiperazine group and their serotonin/α-adrenergic activity. The newly synthesized compounds were tested in the radioligand binding assay and the intrinsic activity was evaluated for the selected derivatives. The computer-aided SAR analysis enabled us to answer questions about the influence of particular structural fragments on selective vs. multifunctional activity. As a result of the performed investigations, there were two leading structures: (a) compound 12 with multifunctional adrenergic-serotonin activity, which is a promising candidate to be an effective anxiolytic agent; (b) compound 14 with high α1A/α1D affinity and selectivity towards α1B, which is recommended due to the elimination of probable cardiotoxic effect. The structural conclusions of this work provide significant support for future lead optimization in order to achieve the desired pharmacodynamic profile in searching for new CNS-modulating agents. 相似文献
94.
We try to establish the commonalities and leadership in the cryptocurrency markets by examining the mutual information and lead-lag relationships between Bitcoin and other cryptocurrencies from January 2019 to June 2021. We examine the transfer entropy between volatility and liquidity of seven highly capitalized cryptocurrencies in order to determine the potential direction of information flow. We find that cryptocurrencies are strongly interrelated in returns and volatility but less in liquidity. We show that smaller and younger cryptocurrencies (such as Ripple’s XRP or Litecoin) have started to affect the returns of Bitcoin since the beginning of the pandemic. Regarding liquidity, the results of the dynamic time warping algorithm also suggest that the position of Monero has increased. Those outcomes suggest the gradual increase in the role of privacy-oriented cryptocurrencies. 相似文献
95.
Priti Tagde Pooja Tagde Fahadul Islam Sandeep Tagde Muddaser Shah Zareen Delawar Hussain Md. Habibur Rahman Agnieszka Najda Ibtesam S. Alanazi Mousa O. Germoush Hanan R. H. Mohamed Mardi M. Algandaby Mohammed Z. Nasrullah Natalia Kot Mohamed M. Abdel-Daim 《Molecules (Basel, Switzerland)》2021,26(23)
Curcumin is the primary polyphenol in turmeric’s curcuminoid class. It has a wide range of therapeutic applications, such as anti-inflammatory, antioxidant, antidiabetic, hepatoprotective, antibacterial, and anticancer effects against various cancers, but has poor solubility and low bioavailability. Objective: To improve curcumin’s bioavailability, plasma concentration, and cellular permeability processes. The nanocurcumin approach over curcumin has been proven appropriate for encapsulating or loading curcumin (nanocurcumin) to increase its therapeutic potential. Conclusion: Though incorporating curcumin into nanocurcumin form may be a viable method for overcoming its intrinsic limitations, and there are reasonable concerns regarding its toxicological safety once it enters biological pathways. This review article mainly highlights the therapeutic benefits of nanocurcumin over curcumin. 相似文献
96.
97.
98.
Roksana Kordala-Markiewicz Hubert Rodak Bartosz Markiewicz Filip Walkiewicz Agata Sznajdrowska Katarzyna Materna Katarzyna Marcinkowska Tadeusz Praczyk Juliusz Pernak 《Tetrahedron》2014
Ammonium ionic liquids with the 4-chloro-2-methylphenoxyacetate anion were synthesized and characterized. Physicochemical properties, such as thermal stability, phase transition temperatures, viscosity, density, refractive index, as well as surface activity and herbicidal activity were determined. Improved physicochemical properties suggest a reduced environmental impact of newly formed group of herbicidal ionic liquids (HILs). HILs with a longer substituent can be characterized with better herbicidal activity in comparison with commercial products. 相似文献
99.
100.
Agata Siwek Joanna Stefaska Irena Wawrzycka‐Gorczyca Monika Wujec 《Heteroatom Chemistry》2010,21(3):131-138
A series of s‐triazoles and thiohydantoines were synthesized by dehydrocyclization of 1‐substituted‐4‐ethoxycarbonylmethylthiosemicarbazides. The molecular structure proposed for s‐triazoles was confirmed by the X‐ray crystal structure analysis of one compound that was prone to crystallization. All compounds were tested in vitro for their antibacterial activity. Some of them showed low levels of activity against Gram‐positive species, MIC range 100–400 μg/mL or higher. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:131–138, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20597 相似文献