全文获取类型
收费全文 | 250篇 |
免费 | 7篇 |
专业分类
化学 | 184篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 13篇 |
物理学 | 53篇 |
出版年
2024年 | 7篇 |
2022年 | 9篇 |
2021年 | 20篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 16篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 23篇 |
2011年 | 13篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 11篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有257条查询结果,搜索用时 15 毫秒
201.
Gaber El-Saber Batiha Nosheen Akhtar Abdulrahman A. Alsayegh Wafaa Fouzi Abusudah Najlaa Hamed Almohmadi Hazem M. Shaheen Thakur Gurjeet Singh Michel De Waard 《Molecules (Basel, Switzerland)》2022,27(21)
Plants are a promising source of bioactive compounds that can be used to tackle many emerging diseases both infectious and non-infectious. Among different plants, Acacia is a very large genus and exhibits a diverse array of bioactive agents with remarkable pharmacological properties against different diseases. Acacia, a herb found all over the world, contains approximately more than 1200 species of the Fabaceae family. In the present review, we have collected detailed information on biochemical as well as pharmacological properties. The data were retrieved using different databases, such as Elsevier, PubMed, Science Direct, Google Scholar, and Scopus, and an extensive literature survey was carried out. Studies have shown that Acacia possesses several secondary metabolites, including amines, cyanogenic glycosides, flavonoids, alkaloids, seed oils, cyclitols, fluoroacetate, gums, non-protein amino acids, diterpenes, fatty acids, terpenes, hydrolyzable tannins, and condensed tannins. These compounds exhibit a wide range of pharmaceutical applications such as anti-inflammatory, antioxidant, antidiarrheal, antidiabetic, anticancer, antiviral, liver protective effects, and so on. Thus, the literature shows the tremendous phytochemical impact of the genus Acacia in medicine. Overall, we recommend that more research should be conducted on the medicinal value and isolation and purification of the effective therapeutic agents from Acacia species for the treatment of various ailments. 相似文献
202.
Syed Tasqeeruddin Yahya I. Asiri Syeda Shaheen 《Journal of heterocyclic chemistry》2021,58(2):630-635
An efficient, a hitherto unreported, sustainable, and environmentally friendly microwave-assisted synthesis of 2,3-disubstituted quinolines by reductive cyclization of 2-nitrobenzaldehydes and various active methylene compounds via tandem Knoevenagel condensation promoted by an efficient eco-friendly, chemoselective reducing catalyst ammonium chloride (NH4Cl) and zinc powder was developed. This present methodology is a mild, green, efficient, and environmentally benign process as it eliminates the harsh reaction conditions, non-volatile solvents, relatively expensive reagents, high catalyst loading, and also provides a number of other benefits like fast synthesis, simple reaction set-up, and good to the excellent yield of the products. 相似文献
203.
This article summarizes the preparation and applications of carbon derived from jute sticks and fibers that are low‐cost, widely available, renewable, and environmentally friendly. Both the fibers and sticks are considered ideal candidates of carbon preparation because they are composed of cellulose, hemicelluloses, and lignin, and contain negligible ash content. Various carbon preparation methods including simple pyrolysis, pyrolysis with chemical and physical activations are discussed. The impacts of several parameters including types of activating agents, impregnation ratio, and temperature on their morphology, surface area, pore size, crystallinity, and surface functional groups are also emphasized. Various treatments to endow functionalization for increasing the practical applicability, such as chemical, physical, and physico‐chemical methods, are discussed. In addition, applications of jute‐derived carbon in various practical areas, including energy storage, water treatment, and sensors, are also highlighted in this report. Due to the porous fine structure and a large specific surface area, the jute‐derived carbon could be considered as a powerful candidate material for various industrial applications. Finally, possible future prospects of jute‐derived carbon for various applications are pointed out. 相似文献
204.
Syed Shaheen Shah Sulayman Oladepo Muhammad Ali Ehsan Wissam Iali Asem Alenaizan Mohammad Nahid Siddiqui Munetaka Oyama Abdul-Rahman Al-Betar Md. Abdul Aziz 《Chemical record (New York, N.Y.)》2024,24(1):e202300105
Polyaniline (PANI) has piqued the interest of nanotechnology researchers due to its potential as an electrode material for supercapacitors. Despite its ease of synthesis and ability to be doped with a wide range of materials, PANI′s poor mechanical properties have limited its use in practical applications. To address this issue, researchers investigated using PANI composites with materials with highly specific surface areas, active sites, porous architectures, and high conductivity. The resulting composite materials have improved energy storage performance, making them promising electrode materials for supercapacitors. Here, we provide an overview of recent developments in PANI-based supercapacitors, focusing on using electrochemically active carbon and redox-active materials as composites. We discuss challenges and opportunities of synthesizing PANI-based composites for supercapacitor applications. Furthermore, we provide theoretical insights into the electrical properties of PANI composites and their potential as active electrode materials. The need for this review stems from the growing interest in PANI-based composites to improve supercapacitor performance. By examining recent progress in this field, we provide a comprehensive overview of the current state-of-the-art and potential of PANI-based composites for supercapacitor applications. This review adds value by highlighting challenges and opportunities associated with synthesizing and utilizing PANI-based composites, thereby guiding future research directions. 相似文献
205.
Farkhanda Shaheen Amin Badshah Gianluca Croce Dick de Vos 《Journal of organometallic chemistry》2010,695(3):315-322
Metallacyclic palladium(II) complexes [Pd(L)(R3P)Cl], L = TIQDTC (1,2,3,4-tetrahydroisoquinolinedithiocarbamate), 4MpipDTC (4-methylpipradinedithiocarbamate), MPizDTC (N-methylpiperazinedithiocarbamate), R3P = Ph3P, (o-tolyl)3P, Ph2ClP, were synthesized in a 1:1 molar metal-ligand ratio. These complexes were characterized by elemental analyses, FT-IR, multinuclear (1H, 13C and 31P) NMR. The X-ray crystal structures of [Pd(TIQDTC)(Ph3P)Cl] and [Pd(TIQDTC)((o-tolyl)3P)Cl] show a slightly distorted square planar environment around the Pd(II) ion with S-Pd-S and P-Pd-Cl average bond angles of 74.51 and 92.41, respectively. These complexes were screened for cytotoxic, antifungal, anti-inflammatory and antibacterial activity. Some complexes exhibit a significant activity against fungi. 相似文献
206.
In this paper, the steady flow and heat transfer of a magnetohydrodynamic fluid is studied. The fluid is assumed to be electrically conducting in the presence of a uniform magnetic field and occupies the porous space in annular pipe. The governing nonlinear equations are modeled by introducing the modified Darcy's law obeying the Sisko model. The system is solved using the homotopy analysis method (HAM), which yields analytical solutions in the form of a rapidly convergent infinite series. Also, HAM is used to obtain analytical solutions of the problem for noninteger values of the power index. The resulting problem for velocity field is then numerically solved using an iterative method to show the accuracy of the analytic solutions. The obtained solutions for the velocity and temperature fields are graphically sketched and the salient features of these solutions are discussed for various values of the power index parameter. We also present a comparison between Sisko and Newtonian fluids. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
207.
Syed Shaheen Shah Md. Abdul Aziz Munetaka Oyama Abdul‐Rahman F. Al‐Betar 《Chemical record (New York, N.Y.)》2021,21(1):204-238
Due to their potential applications in industry and potent toxicity to the environment, sulfides and their detection have attracted the attention of researchers. To date, a large number of controlled‐potential techniques for electrochemical sulfide sensors have been developed, thanks to their simplicity, reasonable limit of detection (LOD), and good selectivity. Different researchers have applied different strategies for developing selective and sensitive sulfide sensors. However, there has been no systematic review on controlled‐potential techniques for sulfide sensing. In light of this absence, the main aim of this review article is to summarize various strategies for detecting sulfide in different media. The efficiencies of the developed sulfide sensors for detecting sulfide in its various forms are determined, and the essential parameters, including sensing strategies, working electrodes, detection media, pH, LOD, sensitivity, and linear detection range, are emphasized in particular. Future research in this area is also recommended. It is expected that this review will act as a basis for further research on the fabrication of sulfide sensors for practical applications. 相似文献
208.
Extraction of penicillin G from aqueous solution using a membrane contactor: Numerical investigation
Yan Cao Afrasyab Khan Shaheen Sarkar Ahmad B. Albadarin 《Arabian Journal of Chemistry》2021,14(7):103230
In the current study, the treatment of pharmaceutical wastewater containing penicillin G treatment using a hollow fibre membrane contactor was investigated. A mathematical model based on the finite element method was developed. The extraction was performed using Shellsol TK as organic solvent containing 5% Aliquat 336. The effect of feed pH, flow rate and temperature were examined for the extraction of penicillin G from aqueous solution. The results showed that there is reasonable good agreement between experimental data and modelling values. It was found that increasing temperature from 10 °C to 30 °C increases the penicillin G extraction from 33% to 54%. Also, penicillin G extraction was decreased from 34.7% to 25.1% with increasing pH from 5.5 to 6.5 while it grew to 45.8% when the pH of feed solution was 7. Furthermore, the results showed the diffusive flux is favourable for the system and penicillin G extraction but the convective flux has negative impact on the system in terms of penicillin G extraction. It was concluded that a hollow fibre membrane contactor has the potential for use in wastewater treatment through it is important to improve diffusive flux in the system to enhance penicillin G extraction. 相似文献
209.
In this article, a system of two two-level atoms interacting with a single-mode quantized electromagnetic field in a lossless resonant cavity via a multi-photon transition is considered. The quantum Fisher information, negativity, classical Fisher information, and reduced von Neumann entropy for the two atoms are investigated. We found that the number of photon transitions plays an important role in the dynamics of different information quantifiers in the cases of two symmetric and two asymmetric atoms. Our results show that there is a close relationship between the different quantifiers. Also, the quantum and classical Fisher information can be useful for studying the properties of quantum states which are important in quantum optics and information. 相似文献
210.
Energy transfer from both Coumarin 120 (C120) and p-Bis(o-methylstyryl)-benzene (Bis-MSB), energy donors, to coumarin 7(C7) (acceptor) individually has been studied by steady-state emission measurements in methanol. The dye laser characteristics of the above-mentioned dyes have also been studied with respect to the energy transfer mechanism in the same solvent using a pulsed nitrogen laser as a pumping source. The large values of the critical transfer distances, R0, indicate that the dominant mechanism responsible for energy transfer is due to long-range dipole–dipole interaction between the excited donor and ground state acceptor molecule. Both photophysical and photochemical stability of the donors has been examined under the effect of N2 laser pumping. 相似文献