全文获取类型
收费全文 | 233篇 |
免费 | 16篇 |
专业分类
化学 | 204篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 19篇 |
物理学 | 21篇 |
出版年
2023年 | 3篇 |
2022年 | 28篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 11篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 15篇 |
2011年 | 19篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 9篇 |
2007年 | 19篇 |
2006年 | 7篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有249条查询结果,搜索用时 15 毫秒
201.
Asma Nsira Hasan Mtiraoui Sami Chniti Hanan Al-Ghulikah Rafik Gharbi Moncef Msaddek 《Molecules (Basel, Switzerland)》2022,27(13)
Novel 1,2,3-triazolo-linked-1,5-benzodiazepinones were designed and synthesized via a Cu(I)-catalyzed 1,3-dipolar alkyne-azide coupling reaction (CuAAC). The chemical structures of these compounds were confirmed by 1H NMR, 13C NMR, HMBC, HRMS, and elemental analysis. The compounds were screened for their in vitro antibacterial and antifungal activities. Several compounds exhibited good to moderate activities compared to those of established standard drugs. Furthermore, the binding interactions of these active analogs were confirmed through molecular docking. 相似文献
202.
Jehan YAl-Humaidi Foziah AAl-Saif Dalal NB injawhar Hanan ABakhsh Moamen SRefat 《光谱学与光谱分析》2021,41(2):658-664
Te(Ⅳ), Se(Ⅳ), V(Ⅲ), Nb(Ⅴ) and Ta(Ⅴ) complexes of indole-3-acetic acid (IAAH) ligand were synthesized, characterized by elemental analysis and various spectroscopic techniques like, IR, 1H-NMR, X-ray powder diffraction, UV-Visible, thermogravimetry analysis, magnetic measurements, molar conductance and surface morphology using SEM. All the synthesized complexes of IAAH ligand have 1∶2 stoichiometry of the types [Te(IAA)2(NH3)2]·2Cl (Ⅰ), [Se(IAA)2(NH3)2]·2Cl (Ⅱ), [V(IAA)2(NH3)(Cl)] (Ⅲ), [Nb(IAA)2(Cl)3] (Ⅳ), and [Ta(IAA)2(Cl)3] (Ⅴ). Spectral analysis indicates octahedral geometry for the Te(Ⅳ), Se(Ⅳ) and V(Ⅲ) complexes, whereas both Nb(Ⅴ) and Ta(Ⅴ) have a seven-coordination. The bonding sites are the oxygen atoms of carboxylate group for the deprotonated indole-3-acetic acid (IAA) ligand. The thermogravimetry analysis studies gave evidence for the presence of other coordinated molecules (Cl or NH3) in the composition of IAA complexes, which were further supported by IR and micro analytical measurements. The higher molar conductance data of tellurium and selenium (Ⅳ) complexes reveal that these chelates are electrolytes, while low conductivity values for the vanadium(Ⅲ), niobium and tantalum(Ⅴ) chelates indicated a non-electrolytes. To test the antibacterial property of the five complexes in this study, four bacterial strains Klebsiella (G-), Escherichia coli (G-), Staphylococcus aureus (G+) and Staphylococcus epidermidis (G+) were used in the investigation. The effects of the five complexes in the cytotoxicity of Caco-2 and Mcf-7 human cancer cell lines were studied Neutral red uptake assay for the estimation of cell viability/cytotoxicity protocol. 相似文献
203.
Vandana Thotathil Hanan Hosni Rizk Ameena Fakrooh Lakshmaiah Sreerama 《Molecules (Basel, Switzerland)》2022,27(19)
Acacia ehrenbergiana (Hayne), also known as Salam, is a highly drought resistant shrub distributed in North and East Africa, and the Arabian Peninsula. The plant is gathered for its gum and fiber, and is an important legume species for indigenous populations. In this study, the phytochemical analysis, antibacterial, and antioxidant properties of various alcoholic and aqueous extracts of Acacia ehrenbergiana grown in Qatar were investigated. The qualitative phytochemical screening of this species exhibited the presence of glycosides, tannins, flavonoids, terpenoids, saponins, phenol, and anthraquinones in various extracts. The agar diffusion method was performed to check the antibacterial activity. The acetone and ethanol extracts showed 85% antibacterial activity of the control against Gram-negative E. coli, while the acetone extract had 65% activity against the Bacillus Gram-positive species. The highest activity against Staphylococcus aureus was 65% for the butanol extract. The antioxidant capacities were evaluated by the DPPH method. Various extracts exhibited antioxidant activities similar to or higher than standard antioxidants, with the highest percent inhibition of 95% for the acetone and ethanol extracts. The acetone extracts were further purified by reverse phase combiflash chromatography followed by HPLC. Three of the pure compounds isolated were subjected to MS, FTIR, and NMR spectral analysis and were found to be stigmasterol, spinasterol, and theogallin. In conclusion, the observed antibacterial and antioxidant activities as well as the presence of secondary metabolites with potential medicinal activities makes Acacia ehrenbergiana a potent valuable endemic medicinal plant. 相似文献
204.
Ghada Abd‐Elmonsef Mahmoud Amna S.A. Zidan Aref A.M. Aly Hanan K. Mosbah Ahmed B.M. Ibrahim 《应用有机金属化学》2019,33(2)
This paper presents the one‐pot reaction synthesis of coordination calcium and strontium compounds [Ca(L)2(H2O)2 1 and Sr(L)2(H2O)2 2 ] with the 2‐(4‐chlorophenylamino) benzoic acid ligand ( HL = C13H10NO2Cl). The complexes were obtained in good yields, and their structures were corroborated according to their CHN, spectroscopic (IR and UV/Vis.) and solution molar conductivity data as the latter confirmed their molecular nature. Additionally, the powder X‐ray diffraction pattern of the complexes was used to determine the cell parameters and the hkl indices together with their corresponding 2θ values. The microbial resistance against the currently available antifungal agents requires searching for new antifungal compounds. Promising fungicidal activities of these coordination complexes were determined against the Fusarium corn disease as complexes 1 and 2 at 30°C inhibited the grain pathogenicity by 70% and 66%, respectively. Moreover, 1 and 2 retarded the amylase enzymes that are responsible for the pathogenicity by 35.13% and 26.22% at 30°C. 相似文献
205.
Abdul Hanan Mukhtiar Ahmed Muhammad Nazim Lakhan Altaf Hussain Shar Dianxue Cao Ali Asif Amir Ali Mahtab Gul 《印度化学会志》2022,99(5):100442
Because of energy crisis, the hydrogen evolution reaction (HER) limits the feasible utilization of water splitting. Herein, we report reduced graphene-oxide (rGO) with Iron-oxide (Fe3O4) nanostructures as highly active electrocatalyst for HER. As-prepared [email protected]3O4 shows superior electrochemical responses to those of corresponding its monometallic rGO and Fe3O4. The overpotential of [email protected]3O4 has been achieved as 300 mV at 10 mA/cm2 current density with a Tafel slope of 80 mV/dec. The [email protected]3O4 nanostructure has its stability for 24 h to reveal long term electrochemical performance. 相似文献
206.
Antar A. Abdelhamid Hanan A. Salah Adel A. Marzouk 《Journal of heterocyclic chemistry》2020,57(2):676-685
The pyrrolidinium hydrogen sulfate (PHS) was used as an excellent ionic liquid catalyst for the preparation of many imidazoles moiety, which have biologically application via one-pot multicomponent reaction. Imidazoles were afforded through the reaction of equimolar from 1,2-diphenylethane-1,2-dione, ammonium acetate, different aromatic aldehydes, and ethyl glycinate hydrochloride. This method has the advantages of giving excellent yield, shortened reaction times, and ease of establishment. Moreover, the yielded of imidazoles components can be purified and crystallized by a nonchromatographic technique, and the catalyst can be reused. These entire novel synthesized components have been identified by spectral data: IR, NMR and mass spectra. These compounds have an in vivo antioxidant activity on experimental animals (rats). 相似文献
207.
Hanan Aljubran Maxim L. Yattselev 《Journal of Mathematical Analysis and Applications》2019,469(1):428-446
Let be a sequence of orthonormal polynomials on the unit circle with respect to a positive Borel measure μ that is symmetric with respect to conjugation. We study asymptotic behavior of the expected number of real zeros, say , of random polynomials where are i.i.d. standard Gaussian random variables. When μ is the acrlength measure such polynomials are called Kac polynomials and it was shown by Wilkins that admits an asymptotic expansion of the form (Kac himself obtained the leading term of this expansion). In this work we generalize the result of Wilkins to the case where μ is absolutely continuous with respect to arclength measure and its Radon–Nikodym derivative extends to a holomorphic non-vanishing function in some neighborhood of the unit circle. In this case admits an analogous expansion with the coefficients depending on the measure μ for (the leading order term and remain the same). 相似文献
208.
Masood Muhammad Hanan Haleem Noor Shakeel Iqra Jamal Yousuf 《Research on Chemical Intermediates》2020,46(12):5165-5180
Research on Chemical Intermediates - Increased carbon dioxide (CO2) emissions from anthropogenic activities are a contributing factor to the growing global warming worldwide. The economical method... 相似文献
209.
Sheta M. Sheta Said M. El‐Sheikh Mohkles M. Abd‐Elzaher Salem R. Salem Hanan A. Moussa Reda M. Mohamed Ibraheem A. Mkhalid 《应用有机金属化学》2019,33(12)
For the first time, alpha‐fetoprotein (AFP) quantification as an early test for liver cancer diagnosis competing with other interfering analytes and factors based on a novel nano‐magnetic metal–organic framework (MOF) was investigated. The novel nano‐magnetic MOF was synthesized via a simple preparation method, and characterized using various techniques. The X‐ray photoelectron spectrum of the nano‐magnetic MOF shows Cu 2p, O 1s, N 1s and C 1s peaks that evidence the presence of these elements in the sample without any impurities. Scanning and transmission electron microscopy images show the nano‐magnetic MOF with average size between 22 and 43 nm. The results of a photoluminescence study show that the nano‐magnetic MOF exhibits strong emission at 418 nm after excitation at 354 nm. Moreover, a Stern–Völmer graph shows a linear calibration curve over an AFP concentration range 1.0–520 ng ml?1 with a correlation coefficient of 0.997, detection limit of 1.18 ng ml?1 and quantitation limit of 3.58 ng ml?1. According to the marked quenching of the photoluminescence intensity of the nano‐magnetic MOF using various concentrations of AFP, it was successfully used as a biosensor for AFP in serum samples collected from hepatitis patients in addition to healthy males and females. The quenching mechanism was well studied, and found to be a dynamic type. The present work offers a simple, low‐cost, room‐temperature and rapid technique, being non‐time‐consuming, highly accurate, selective and highly sensitive compared with most published methods. 相似文献
210.
Synthesis,spectroscopic, thermal analyses,biological activity and molecular docking studies on mixed ligand complexes derived from Schiff base ligands and 2,6‐pyridine dicarboxylic acid
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)
Two novel Schiff base ligands (La and Lb) were prepared from the condensation of quinoline 2‐aldehyde with 2‐aminopyridine (ligand La) and from the condensation of oxamide with furfural (ligand Lb). Mixed ligand complexes of the type M+2La/b Lc were prepared, where (La and Lb) the primary ligands and Lc was 2,6‐pyridinedicarboxylic acid as secondary ligand. Metal ions used were Fe(II), Co(II), Ni(II) and Zn(II) for mixed ligands La Lc and Fe(II), Co(II), Ni(II), Cu(II), Hg(II) and Zn(II) for LbLc mixed ligands. La and Lb Schiff base ligands were both characterized using elemental analyses, molar conductance, IR, 1H and 13C NMR. Mass spectra for Lb, [Zn(La)LcCl]Cl and [Cu(Lb)LcCl]Cl were also studied. ESR spectrum of the [Cu(Lb) LcCl]Cl complex was also recorded The metal complexes were synthesized and characterized using elemental analyses, spectroscopic (IR, 1H NMR, UV‐visible, diffused reflectance), molar conductance, magnetic moment and thermal studies. The IR and 1H NMR spectral data revealed that 2,6‐pyridinedicarboxalic acid ligand coordinated to the metal ions via pyridyl N and carboxylate O without proton displacement. In addition, the IR data showed that La and Lb ligands behaved as neutral bidentate ligands with N2 donation sites (quinoline N and azomethine N for La and two azomethine N for Lb). Based on spectroscopic studies, an octahedral geometry was proposed for the complexes. The thermal stability and degradation of the metal complexes were investigated by thermogravimetric analysis. The binding modes and affinities of La, Lb and Zn(II) complexes towards receptors of crystal structure of E. coli (PDB ID: 3 t88) and mutant oxidoreductase of breast cancer (PDB ID: 3 hb5) receptors were also studied. The antimicrobial activity against two species of Gram positive, Gram negative bacteria and fungi were tested for the Schiff base ligands, 2,6‐pyridinedicarboxylic acid and the mixed ligand complexes and revealed that the synthesized mixed ligand complexes exhibited higher antimicrobial activity than their free Schiff base ligands. 相似文献