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921.
3-Cyanomethylidene oxindole derivatives were prepared in excellent yields utilizing DBU-promoted Knoevenagel condensation of isatin derivatives with active methylene reagents. The isolated products were then reacted with azaenamines via a DBU-promoted Michael addition to yield spirocyclic 2-oxindole derivatives with incorporated 6-amino-4H-pyridazines and their fused derivatives. 相似文献
922.
Essam S. Zakaria Ismail M. Ali Hisham F. Aly 《Journal of colloid and interface science》2009,338(2):346-352
Magnesium titano-antimonate (MgTi5Sb2O16·12.5H2O) and cerium titano-antimonate (Ce2.7Ti5Sb2O19·15.0H2O) were synthesized as new cation exchangers using the in situ precipitation technique. Physico-chemical investigations showed different behaviors for the obtained materials. The materials have significant stability at high acid concentration and temperature. The ion exchange capacity for Cs+ in the presence of different alcoholic solvents was found to increase and generally obey the order C2H5OH > CH3OH > H2O. Diffusion coefficients (Di) and thermodynamic parameters of Cs+ exchange in both magnesium and cerium titano-antimonates in aqueous and alcoholic solutions were calculated. The swelling ratios of the materials were predicted by applying modified calculations at constant values of Di. The results showed insignificant swelling behavior in the presence of organic solvents. 相似文献
923.
Elbashir AA Saad B Ali AS Saleh MI Aboul-Enein HY 《Biomedical chromatography : BMC》2009,23(3):295-301
A capillary electrophoretic (CE) method for the baseline separation of the enantiomers of primaquine diphosphate (PQ) and quinocide (QC) (a major contaminant) in pharmaceutical formulations is proposed. Both components were separated under the following conditions: 50 mm tris phosphate buffer (pH 3.0) containing 15 mm hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as background electrolyte; applied voltage, 16 kV; capillary temperature, 25 degrees C; detection wavelength, 254 nm; hydrostatic injection, 10 s. The separations were conducted using a 35 cm length and 50 microm i.d. uncoated fused silica capillary column. Under the optimized conditions, the components were successfully separated in about 5 min. Intraday precision of migration time and corrected peak areas when expressed as relative standard deviation ranged from 0.17 to 0.45 and 2.60 to 3.94%, respectively, while the interday precision ranged from 2.59 to 4.20 and 3.15 to 4.21%, respectively. After the validation exercise, the proposed method was applied for the determination of QC impurity in PQ formulations. 相似文献
924.
Nabila A. Mazied Sahar A. Ismail Manal F. Abou Taleb 《Radiation Physics and Chemistry》2009,78(11):899-905
The use of hydrogels as carriers for anticancer delivery has been a subject of significant recent research. In our recent work, we have shown that diffusion-controlled delivery of flutamide from hydrogels containing poly (dimethylaminoethyl methacrylate (DMAEMA)/ethyleneglycol dimethacrylate (EGDMA)) can be possible and controlled by the three-dimensional structure. Hydrogels based essentially on dimethylaminoethyl methacrylate and different ratios of ethyleneglycol dimethacrylate monomers were synthesized using gamma radiation copolymerization. The influence of copolymer composition and pH value of the surrounding medium on swelling behavior into the glassy polymer were discussed. The results showed that the ratio of EGDMA in the comonomer feeding solution has a great effect on the gel fraction and water content in the final hydrogel. In this regard, it was observed that the increase of EGDMA ratio decreased these properties. The ability of the prepared copolymer to be used as drug carrier for anticancer drug-delivery system was estimated using flutamide as a model drug. In vitro drug-release studies in different buffer solutions show that the basic parameters affecting the drug release behavior of hydrogel are the pH of the solution and DMAEMA content of hydrogel. 相似文献
925.
Capitalizing on the company’s crucial knowledge is an important operation for company’s success. The first step in knowledge capitalizing is to identify the crucial knowledge for which capitalizing operation is required. The crucial knowledge identification is an ill-structured and multi-criteria problem. In this paper, the crucial knowledge identification problem is structured according to the well-known Simon’s decision making process. Then, a decision support system (DSS), called K-DSS, is developed to support this decision process. The main objectives of this paper are to introduce the crucial knowledge identification decision process, to present the conceptual and functional architectures of K-DSS and to illustrate its utility through a real-world case study conducted in an automobile company. 相似文献
926.
927.
Fyaz M. D. Ismail Michael G. B. Drew Suppiah Navaratnam Roger H. Bisby 《Research on Chemical Intermediates》2009,35(4):363-377
Free radicals from one-electron oxidation of the antimalarial drug pyronaridine have been studied by pulse radiolysis. The
results show that pyronaridine is readily oxidised to an intermediate semi-iminoquine radical by inorganic and organic free
radicals, including those derived from tryptophan and acetaminophen. The pyronaridine radical is rapidly reduced by both ascorbate
and caffeic acid. The results indicate that the one-electron reduction potential of the pyronaridine radical at neutral pH
lies between those of acetaminophen (707 mV) and caffeic acid (534 mV). The pyronaridine radical decays to produce the iminoquinone,
detected by electrospray mass spectrometry, in a second-order process that density functional theory (DFT) calculations (UB3LYP/6-31+G*)
suggest is a disproportionation reaction. Important calculated dimensions of pyronaridine, its phenoxyl and aminyl radical,
as well as the iminoquinone, are presented.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
928.
Ismail Yilmaz Salih Ilhan Hamdi Temel Ahmet Kilic 《Journal of inclusion phenomena and macrocyclic chemistry》2009,63(1-2):163-169
Four macrocyclic Schiff-base cobalt complexes, [CoL1][NO3]2 · 3H2O, [CoL2][NO3]2 · 4H2O, [CoL3][NO3]2 · 4H2O and [CoL4][NO3]2 · 2H2O, were synthesized by reaction of salicylaldehyde derivatives with 1,4-bis(3-aminopropoxy)butane or (±)-trans-1,2-diaminocyclohexane and Co(NO3)2 · 6H2O by template effect in methanol. The metals to ligand ratio of the complexes were found to be 1:1. The Co(II) complexes are proposed to be tetrahedral geometry. The macrocyclic Co(II) complexes are 1:2 electrolytes as shown by their molar conductivities (ΛM) in DMF (dimethyl formamide) at 10?3 M. The structure of Co(II) complexes is proposed from elemental analysis, Ft-IR, UV–visible spectra, magnetic susceptibility, molar conductivity measurements and mass spectra. Electrochemical and thin-layer spectroelectrochemical studies of the complexes were comparatively studied in the same experimental conditions. The electrochemical results revealed that all complexes displayed irreversible one reduction processes and their cathodic peak potential values (E pc) were observed in around of ?1.14 to 0.95 V. It was also seen that [CoL1][NO3]2 · 3H2O and [CoL2][NO3]2 · 4H2O exhibited one cathodic wave without corresponding anodic wave but, [CoL3][NO3]2 · 4H2O and [CoL4][NO3]2 · 2H2O showed one cathodic wave with corresponding anodic wave, probably due to the presence of different ligand nature even if the complexes have the same N2O2 donor set. In view of spectroelectrochemical studies [CoL3][NO3]2 · 4H2O showed distinctive spectral changes in which the intensity of the band (λ = at 316 nm, assigned to n → π* transitions) decreased and a new broad band in a low intensity about 391 nm appeared as a result of the reduction process based on the cobalt center in the complex. 相似文献
929.
Sameh M.I. Saad Zdenka Policova Andrew Dang Edgar J. Acosta Michael L. Hair A. Wilhelm Neumann 《Colloids and surfaces. B, Biointerfaces》2009,73(2):365-375
This paper presents a continuation of the development of a drop shape method for film studies, ADSA-CSD (Axisymmetric Drop Shape Analysis-Constrained Sessile Drop). ADSA-CSD has certain advantages over conventional methods. The development presented here allows complete exchange of the subphase of a spread or adsorbed film. This feature allows certain studies relevant to lung surfactant research that cannot be readily performed by other means. The key feature of the design is a second capillary into the bulk of the drop to facilitate addition or removal of a secondary liquid. The development will be illustrated through studies concerning lung surfactant inhibition. After forming a sessile drop of a basic lung surfactant preparation, the bulk phase can be removed and exchanged for one containing different inhibitors. Such studies mimic the leakage of plasma and blood proteins into the alveolar spaces altering the surface activity of lung surfactant in a phenomenon called surfactant inhibition. The resistance of the lung surfactant to specific inhibitors can be readily evaluated using the method. The new method is also useful for surfactant reversal studies, i.e. the ability to restore the normal surface activity of an inhibited lung surfactant film by using special additives. Results show a distinctive difference between the inhibition when an inhibitor is mixed with and when it is injected under a preformed surfactant film. None of the inhibitors studied (serum, albumin, fibrinogen, and cholesterol) were able to penetrate a preexisting film formed by the basic preparation (BLES and protasan), while all of them can alter the surface activity of such preparation when mixed with the preparation. Preliminary results show that reversal of serum inhibition can be easily achieved and evaluated using the modified methodology. 相似文献
930.
Sleep-mode ready,area efficient capacitor-free low-dropout regulator with input current-differencing
John Hu Wei Liu Mohammed Ismail 《Analog Integrated Circuits and Signal Processing》2010,63(1):107-112
This paper proposes an input current-differencing technique in designing a capacitor-free low-dropout regulator to simultaneously
achieve sleep-mode efficiency and silicon real estate saving. With no minimum output current required to be stable, the regulator
could greatly improve SoC efficiency during standby, which is extremely attractive for battery powered applications. Designed
in TSMC 0.18-μm CMOS technology, it regulates 1.8–1.2 V supply down to 1 V with 100 mA maximum output current and can drive
up to 100 pF of load parasitic capacitance. Compared with prior arts with the same sleep-mode compatibility and similar output
current range, it reduces the on-chip compensation capacitance from 21 to 4.5 pF. 相似文献