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排序方式: 共有1074条查询结果,搜索用时 93 毫秒
951.
Zahra BAGHERI 《数学年刊B辑(英文版)》2022,43(2):175-194
Recently, some concepts such as Hom-algebras, Hom-Lie algebras, Hom-Lie admissible algebras, Hom-coalgebras are studied and some classical properties of algebras and some geometric objects are extended on them. In this paper by recalling the concept of Hom-ρ-commutative algebras, the authurs intend to develop some of the most classical results in Riemannian geometry such as metric, connection, torsion tensor, curvature tensor on it and also they discuss about differential operators and get some ... 相似文献
952.
In this study, the oxidation of thiols to sulfonic acids and sulfides to sulfoxides and sulfones was carried out in the presence of Fe3O4/H2O2 as an efficient heterogeneous Fenton system. The products were obtained in good to excellent yields and short reaction times. Further results showed that the heterogeneous catalyst could be recovered easily using an external magnetic field and reused several times without any loss of its catalytic activity. 相似文献
953.
Ali Pourjavadi Zahra Mazaheri Tehrani Alireza Shakerpoor 《Supramolecular chemistry》2016,28(7-8):624-633
In the present research, two types of drug carriers based on mesoporous silica-coated magnetic graphene oxide, Fe3O4@GO@mSiO2, were synthesised and the pH-responsive behaviour for doxorubicin release was investigated. One type of the carrier was dendrimer-like multi ethylene amine grafted on Fe3O4@GO@mSiO2 and the other was dendrimer-like supramolecular polypseudorotaxane. Herein, α-cyclodextrin was used in the structure of supramolecular nanoparticles as a gatekeeper to inhibit the drug from escaping at neutral pH (the pH of healthy tissue). The drug release profile showed that the supramolecular nanocarrier was more sensitive to the pH changes. The content of drug release was about 100% at pH 5.5 (endosomal pH) during 48 h; but it was zero at pH 7.4. Also, the dendrimer structure facilitated the triggered release of doxorubicin. 相似文献
954.
Lewis acids are important and interesting catalysts in most organic transformations. Among different Lewis acids, Zr(IV) species such as ZrCl4 and ZrOCl2·8H2O are allocated special attention because of their low toxicity, availability and handling, moisture stability, and low cost in comparison to some of their corresponding compounds. During recent decades, Lewis acids have been used to promote different types of organic reactions because they naturally possess mild acidity properties and, as such, can catalyze reactions selectively. This means that in the presence of various functional groups, they can operate on a specific group to produce the objective product. In this review we have focused on the reactions which have been progressed in the presence of ZrCl4 and ZrOCl2·8H2O. The study has been ordered based on the number of the reaction components and their solvent media. 相似文献
955.
Mohammad Saeid Hosseini Zahra Hashemi-Pour Navid Hosseini 《International journal of environmental analytical chemistry》2016,96(10):945-958
In this study, a new sensitised spectrofluorometric method was presented as a probe sensor for hypochlorite analysis in oral and tap water samples. By capping L-tyrosine (Tyr) on ZnSe nanoparticles, stable quantum dots (QDs) were obtained. In comparison with Tyr, the fluorescence (FL) emission of Tyr-capped ZnSe is enhanced and shifted to greater wavelength, which causes to enhance the sensitivity for the determination of hypochlorite. Based on the FL quenching of the Tyr-capped ZnSe QDs, hypochlorite concentration was detected at buffering pH of 7 in the range of 5.15 × 10?5?2.57 × 10?2 g L?1. Relative standard deviation and detection limit were found to be 0.83% and 2.06 × 10?5 g L?1, respectively. In comparison with the other methods of hypochlorite determination, this method is simple, fast and inexpensive, with low sample volume consumption. It also exhibits a good selectivity. 相似文献
956.
Kazem Karami Mahboubeh Hosseini-Kharat Zahra Shirani-Sarmazeh Reza Zahedi-Nasab Corrado Rizzoli Janusz Lipkowski 《Journal of Coordination Chemistry》2016,69(5):763-778
Six secondary amine palladacycles bearing monodentate ligands (1a, 2a), 1,2-bis(diphenylphosphino)ethane (dppe) and 1,3-bis(diphenylphosphino)propane (dppp) containing bridging and bidentate ligands (1b, 2b–d), and four C,C-type phosphorus ylide complexes containing thiourea (tu) (3a), phenyl isothiocyanate (4a), and bridging and terminal azide groups (5 and 5a) have been synthesized. Resulting complexes have been characterized by elemental analyses, IR, 1H-, 13C{1H}-, and 31P{1H}-NMR spectroscopy with single crystal X-ray structure determination of 1a and 2a. The Pd in 1a and 2a occupies the center of a slightly distorted square planar environment formed by Caryl, Namine, Npyridine, and Cl. The catalytic efficiency of complexes showed that in most cases, amine palladacycles display better catalytic activities than the phosphorus ylide Pd(II) complexes. Comparison between bidentate and bridging dppe complexes showed that dppe-bridged dimer 2d has higher catalytic activity than dppe bidentate complex. 相似文献
957.
Preparation of a novel sorptive stir bar based on vinylpyrrolidone‐ethylene glycol dimethacrylate monolithic polymer for the simultaneous extraction of diazepam and nordazepam from human plasma
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Mahsa Torabizadeh Zahra Talebpour Nuoshin Adib Hassan Y. Aboul‐Enein 《Journal of separation science》2016,39(7):1316-1325
A new monolithic coating based on vinylpyrrolidone‐ethylene glycol dimethacrylate polymer was introduced for stir bar sorptive extraction. The polymerization step was performed using different contents of monomer, cross‐linker and porogenic solvent, and the best formulation was selected. The quality of the prepared vinylpyrrolidone‐ethylene glycol dimethacrylate stir bars was satisfactory, demonstrating good repeatability within batch (relative standard deviation < 3.5%) and acceptable reproducibility between batches (relative standard deviation < 6.0%). The prepared stir bar was utilized in combination with ultrasound‐assisted liquid desorption, followed by high‐performance liquid chromatography with ultraviolet detection for the simultaneous determination of diazepam and nordazepam in human plasma samples. To optimize the extraction step, a three‐level, four‐factor, three‐block Box–Behnken design was applied. Under the optimum conditions, the analytical performance of the proposed method displayed excellent linear dynamic ranges for diazepam (36–1200 ng/mL) and nordazepam (25–1200 ng/mL), with correlation coefficients of 0.9986 and 0.9968 and detection limits of 12 and 10 ng/mL, respectively. The intra‐ and interday recovery ranged from 93 to 106%, and the relative standard deviations were less than 6%. Finally, the proposed method was successfully applied to the analysis of diazepam and nordazepam at their therapeutic levels in human plasma. The novelty of this study is the improved polarity of the stir bar coating and its application for the simultaneous extraction of diazepam and its active metabolite, nordazepam in human plasma sample. The method was more rapid than previously reported stir bar sorptive extraction techniques based on monolithic coatings, and exhibited lower detection limits in comparison with similar methods for the determination of diazepam and nordazepam in biological fluids. 相似文献
958.
Zahra Nazemi Esmaeil Shams Mohamad Kazem Amini 《Journal of Solid State Electrochemistry》2016,20(2):429-438
In this study, a new procedure for the fabrication of biosensors was developed. The method is based on the covalent attachment of nitrophenyl groups to the electrode surface via diazonium salt reaction followed by their conversion to amine moieties through electrochemical reduction and electrostatic layer-by-layer (LbL) assembly technique. In this procedure, highly stable iron oxide (Fe3O4) nanoparticles (IONPs), chitosan (CHIt), GOx, and Nile blue (NB) were assembled on the surface of aminophenyl modified glassy carbon electrode (AP/GCE) by LbL assembly technique. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the interfaces. The surface coverage of the active GOx and Michaelis–Menten constant (K M) of the immobilized GOx were Γ?=?3.38?×?10?11 mol cm?2 and 2.54 mM, respectively. The developed biosensor displayed a well-defined amperometric response for glucose determination with high sensitivity (8.07 μA mM?1) and low limit of detection (LOD) of 19.0 μM. The proposed approach allows simple biointerface regeneration by increasing pH which causes disruption of the ionic interactions and release of the electrostatic attached layers. The biosensor can then be reconstructed again using fresh enzyme. Simple preparation, good chemical and mechanical stabilities, and easy surface renewal are remarkable advantages of the proposed biosensor fabrication procedure. 相似文献
959.
Zahra S. Kardar Mostafa H. Beyki 《International journal of environmental analytical chemistry》2016,96(13):1276-1289
In the present work, titanium dioxide nanowires (TNWs) were synthesised via hydrothermal method. Insertion of ZnFe2O4 nanoparticles to the surface of TNWs was done by sol gel combustion synthesis of the nanoparticles in the presence of the nanowires. The surface of prepared magnetic TNWs was modified by p-phenylendiamine and then it was used in preconcentration of Cu2+ ion prior to their determination by flame atomic absorption spectroscopy. The sorbent was characterised by Fourier transform infrared spectra, EDX, FE-SEM and VSM techniques. We investigated and optimised various parameters influencing the preconcentration efficiency, such as the media pH, adsorbent quantity, contact time, sample volume and elution conditions. Under optimum conditions, the analytical performance of the method was evaluated. The calibration curve was found to be linear from 10.0 to 150 μg L?1 (R2 = 0.996). Calculated limit of detection was 0.43 μg L?1 (n = 5). The estimated relative standard deviation was 2.50% (n = 5). Moreover, the maximum adsorption capacity of the sorbent was 51.5 mg g?1 and preconcentration factor was 125. Capability of developed method was proved by applying it for preconcentration of Cu2+ ion from food and water samples. 相似文献
960.
Surface Charge‐Transfer Doping of Graphene Nanoflakes Containing Double‐Vacancy (5‐8‐5) and Stone–Wales (55‐77) Defects through Molecular Adsorption
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The adsorption of six electron donor–acceptor (D/A) organic molecules on various sizes of graphene nanoflakes (GNFs) containing two common defects, double‐vacancy (5‐8‐5) and Stone–Wales (55‐77), are investigated by means of ab initio DFT [M06‐2X(‐D3)/cc‐pVDZ]. Different D/A molecules adsorb on a defect graphene (DG) surface with binding energies (ΔEb) of about ?12 to ?28 kcal mol?1. The ΔEb values for adsorption of molecules on the Stone–Wales GNF surface are higher than those on the double vacancy GNF surface. Moreover, binding energies increase by about 10 % with an increase in surface size. The nature of cooperative weak interactions is analyzed based on quantum theory of atoms in molecules, noncovalent interactions plot, and natural bond order analyses, and the dominant interaction is compared for different molecules. Electron density population analysis is used to explain the n‐ and p‐type character of defect graphene nanoflakes (DGNFs) and also the change in electronic properties and reactivity parameters of DGNFs upon adsorption of different molecules and with increasing DGNF size. Results indicate that the HOMO–LUMO energy gap (Eg) of DGNFs decreases upon adsorption of molecules. However, by increasing the size of DGNFs, the Eg and chemical hardness of all complexes decrease and the electrophilicity index increases. Furthermore, the values of the chemical potential of acceptor–DGNF complexes decrease with increasing size, whereas those of donor–DGNF complexes increase. 相似文献