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211.
Mohamed A. Yassin Bassam Tawabini Abdulaziz Al-Shaibani John Adedapo Adetoro Mohammed Benaafi Ahmed M. AL-Areeq A. G. Usman S. I. Abba 《Molecules (Basel, Switzerland)》2022,27(13)
Unconsolidated earthen surface materials can retain heavy metals originating from different sources. These metals are dangerous to humans as well as the immediate environment. This danger leads to the need to assess various geochemical conditions of the materials. In this study, the assessment of topsoil materials’ contamination with heavy metals (HMs) was conducted. The material’s representative spatial samples were taken from various sources: agricultural, industrial, and residential areas. The materials include topsoil, eolian deposits, and other unconsolidated earthen materials. The samples were analyzed using the ICP-OES. The obtained results based on the experimental procedure indicated that the average levels of the heavy metals were: As (1.21 ± 0.69 mg/kg), Ba (110.62 ± 262 mg/kg), Hg (0.08 ± 0.18 mg/kg), Pb (6.34 ± 14.55 mg/kg), Ni (8.95 ± 5.66 mg/kg), V (9.98 ± 6.08 mg/kg), Cd (1.18 ± 4.33 mg/kg), Cr (31.79 ± 37.9 mg/kg), Cu (6.76 ± 12.54 mg/kg), and Zn (23.44 ± 84.43 mg/kg). Subsequently, chemometrics modeling and a prediction of Cr concentration (mg/kg) were performed using three different modeling techniques, including two artificial intelligence (AI) techniques, namely, generalized neural network (GRNN) and Elman neural network (Elm NN) models, as well as a classical multivariate statistical technique (MST). The results indicated that the AI-based models have a superior ability in estimating the Cr concentration (mg/kg) than MST, whereby GRNN can enhance the performance of MST up to 94.6% in the validation step. The concentration levels of most metals were found to be within the acceptable range. The findings indicate that AI-based models are cost-effective and efficient tools for trace metal estimations from soil. 相似文献
212.
Muhammad Ashraf Syed Shaheen Shah Dr. Ibrahim Khan Dr. Md. Abdul Aziz Prof. Nisar Ullah Dr. Mujeeb Khan Dr. Syed Farooq Adil Zainab Liaqat Dr. Muhammad Usman Prof. Wolfgang Tremel Dr. Muhammad Nawaz Tahir 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(23):6973-6984
Tungsten oxide/graphene hybrid materials are attractive semiconductors for energy-related applications. Herein, we report an asymmetric supercapacitor (ASC, HRG//m-WO3 ASC), fabricated from monoclinic tungsten oxide (m-WO3) nanoplates as a negative electrode and highly reduced graphene oxide (HRG) as a positive electrode material. The supercapacitor performance of the prepared electrodes was evaluated in an aqueous electrolyte (1 m H2SO4) using three- and two-electrode systems. The HRG//m-WO3 ASC exhibits a maximum specific capacitance of 389 F g−1 at a current density of 0.5 A g−1, with an associated high energy density of 93 Wh kg−1 at a power density of 500 W kg−1 in a wide 1.6 V operating potential window. In addition, the HRG//m-WO3 ASC displays long-term cycling stability, maintaining 92 % of the original specific capacitance after 5000 galvanostatic charge–discharge cycles. The m-WO3 nanoplates were prepared hydrothermally while HRG was synthesized by a modified Hummers method. 相似文献
213.
In this paper we obtain sharp Lieb–Thirring inequalities for a Schrödinger operator on semiaxis with a matrix potential and show how they can be used to other related problems. Among them are spectral inequalities on star graphs and spectral inequalities for Schrödinger operators on half-spaces with Robin boundary conditions. 相似文献
214.
Ibrahim Abdul Razak Anwar Usman Hoong‐Kun Fun Bohari M. Yamin Goh Wooi Keat 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):m122-m123
In the title compound, [SbCl2(C4H8N2S)2]Cl, the coordination around the Sb atom can be described as distorted pseudo‐octahedral. Both rings of the trimethylenethiourea ligands [alternatively 3,4,5,6‐tetrahydropyrimidine‐2(1H)‐thione] adopt an envelope conformation. The molecules are connected into dimers in the ab plane by two intermolecular hydrogen bonds. The dimers are arranged into infinite one‐dimensional chains along the a axis as a result of the Cl? ions forming intermolecular hydrogen bonds with three NH groups. 相似文献
215.
Muhammad?Nasir Mian?Hasnain?Nawaz Usman?Latif Mustansara?Yaqub Akhtar?HayatEmail author Abdur?RahimEmail author 《Mikrochimica acta》2017,184(2):323-342
Various kinds of nanomaterials have been described in recent years that represent stable and low-cost alternatives to biomolecules (such as enzymes) for use in (bio)analytical methods. The materials typically include, metal/metal oxides, metal complexes, nanocomposites, porphyrins, phthalocyanines, smart polymers, and carbonaceous nanomaterials. Due to their biomimetic and other properties, such nano-materials may replace natural enzymes in chemical sensors, biosensors, and in various kinds of bioassays. This overview (with 252 references) highlights the analytical potential of such nanomaterials. It is divided into sections on (a) the types of nanomaterials according to their intrinsic nature, (b) non-enzymatic sensor designs (including electrochemical, colorimetric, fluorescent and chemiluminescent methods), and (c), applications of non-enzymatic sensors in the biomedical, environmental and food analysis fields. We finally address current challenges and future directions. 相似文献
216.
Sheng‐Li Li Anwar Usman Ibrahim A. Razak Hoong‐Kun Fun Jie‐Ying Wu Yu‐Peng Tian Min‐Hua Jiang Zu‐Yao Chen 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(5):m181-m183
In the title compound, [Ni(CH5N3S)2(H2O)2](C4H3O4)2·2H2O, the Ni atom lies on a center of symmetry and is coordinated by N and S atoms from two thiosemicarbazide ligands and the O atoms of two water molecules in a distorted octahedral geometry. In the asymmetric unit, the three components are linked together by one O—H⋯O and two N—H⋯O hydrogen bonds. The packing is built from molecular ribbons parallel to the b direction, stabilized by intramolecular hydrogen bonds, and by one N—H⋯S and two N—H⋯O intermolecular hydrogen bonds. The ribbons are further connected into columns by N—H⋯O interactions and then into a three‐dimensional network by three O—H⋯O hydrogen bonds. 相似文献
217.
In this article, flow and heat transfer inside a corrugated cavity is analyzed for natural convection with a heated inner obstacle. Thermal performance is analyzed for Cu O–water inside a partially heated domain by defining the constraint along the boundaries. For nanofluid analysis, the Koo and Kleinstreuer Li(KKL) model is implemented to deal with the effective thermal conductivity and viscosity. A heated thin rod is placed inside the corrugated cavity and the bottom portion of the corrugated cavity is partially heated. The dimensionless form of nonlinear partial differential equations are obtained through the compatible transformation along with the boundary constraint. The finite element method is executed to acquire the numerical solution of the obtained dimensional system. Streamlines, isotherms and heat transfers are analyzed for the flow field and temperature distribution. The Nusselt number is calculated at the surface of the partially heated domain for various numerical values of emerging parameters by considering the inner obstacle at cold, adiabatic and heated conditions. The computational simulation was performed by introducing various numerical values of emerging parameters. Important and significant results have been attained for temperature and velocities(in both x-and y-directions) at the vertically and horizontally mean positions of the corrugated duct. 相似文献
218.
Hai‐Liang Zhu Xiu‐Ying Liu Xian‐Jiang Wang Feng Yang Anwar Usman Hoong‐Kun Fun 《无机化学与普通化学杂志》2003,629(11):1986-1990
Three polymeric silver(I) complexes with terephthalate anions as counterions or ligands, [Ag(pren)]2(tp)·2H2O ( 1 ), [Ag(en)][Ag(μ2‐tp)]·H2O ( 2 ), and [Ag2(μ4‐tp)(apy)2] ( 3 ) (where pren = 1, 2‐propylenediamine, tp =terephthalate dianion, en = ethylenediamine, and apy = 2‐aminopyridine) were synthesized and characterized by X‐ray single crystal analysis and infrared spectroscopy. 1 crystallizes in the monoclinic space group P211/c with a = 11.3221(5), b = 7.1522(3), c = 14.8128(5)Å, V = 1015.77(7)Å3, β = 122.132(2), and Z = 2. 2 crystallizes in the orthorhombic space group Pnma with a = 9.6144(6), b = 11.3465(7), c = 11.4810(7)Å, V = 1252.5(1)Å3, and Z = 4. 3 crystallizes in the monoclinic space group P21/n with a = 8.2003(5), b = 5.8869(4), c = 18.3769(11)Å, β = 92.593(1), V = 886.2(1)Å3, and Z = 4. Terephthalate dianions are not coordinated to the metal atoms in 1 , but act as a μ2‐bridging ligand in 2 and as a μ4‐bridging ligand in 3 . 相似文献
219.
John RP Sreekanth A Prathapachandra Kurup MR Usman A Ibrahim AR Fun HK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(6):1349-1358
The spectral studies and structure of a ternary complex of copper(II) with 2-hydroxyacetophenone 3-hexamethyliminylthiosemicarbazonate (L(2-)) and 1,10-phenanthroline (phen) are reported. The thiosemicarbazone binds to the metal as a dianionic ONS-donor (L(2-)) ligand, and forms a complex of the stoichiometry [CuLphen]. The copper(II) complex was characterized by IR and UV/Vis spectroscopies, as well as by solid state room-temperature magnetic susceptibility. Spin Hamiltonian and bonding parameters of the compound are calculated from the EPR spectra. Computer simulation of EPR spectrum in DMF at 77 K aided the calculation of magnetic and bonding parameters of the compound. The structure of the compound is solved by single crystal X-ray diffraction. The geometry around copper is distorted square pyramidal. 相似文献
220.
Zhang Ze Liu Qing-Liang Yang Jia-Xiang Wu Jie-Ying Tian Yu-Peng Jin Bao-kang Fun Hoong-Kun Chantrapromma Suchada Usman Anwar 《Transition Metal Chemistry》2003,28(8):930-934
The title complex [Mn2(phen)4(FCA)2](ClO4)2·H2O (1) (FCA = dianion of 3-ferrocenyl-2-crotonic acid, phen = 1,10-phenanthroline) has been prepared, and its structure determined by single crystal X-ray diffraction analysis. The structure consists of a dinuclear cation [Mn2(phen)4(FCA)2]2+, non-coordinated perchlorate anions and a water molecule. The two MnII ions are separated by 4.374 Å in the cation and are dicarboxylate-bridged by carboxylate ligands containing ferrocenyl units. Each FCA is bound to two MnII ions through carboxylate oxygens with the syn–anti bridging mode. The MnII ion is coordinated in an octahedral N4O2 geometry by two chelate phen ligands and two -carboxylate oxygen atoms. Electrochemical properties of (1) are discussed. 相似文献