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101.
Abdurrahman Özhan Ömer Şahin Mehmet Maşuk Küçük Cafer Saka 《Cellulose (London, England)》2014,21(4):2457-2467
In this work, activated carbon prepared from pine cone (PCAC) with ZnCl2 as an activation agent under microwave radiation was investigated. The activation step was performed at the microwave input power of 400 W and radiation time of 5 min. The properties of activated carbon were characterized by N2 adsorption Brunauer–Emmett–Teller (BET), scanning electron microscopy and Fourier transform infrared spectroscopy. Results showed that the BET surface area, Langmuir surface area, and total pore volume of PCAC were 939, 1,486 m2/g and 0.172 cm3/g, respectively. Adsorption capacity was demonstrated by the iodine numbers. The adsorptive property of PCAC was tested using methylene blue dye. Equilibrium data was best fitted by the Langmuir isotherm model, showing a monolayer adsorption capacity of 60.97 mg/g. The pseudo-first- and pseudo-second-order kinetic models were examined to evaluate the kinetic data, and the rate constants were calculated. Adsorption of the dyes followed pseudo-first order kinetics. Thermodynamic parameters such as free energy, enthalpy and entropy of dye adsorption were obtained. 相似文献
102.
Yoldas Seki Aylin Altinisik Başak Demircioğlu Caner Tetik 《Cellulose (London, England)》2014,21(3):1689-1698
A novel carboxymethylcellulose (CMC)–hydroxyethylcellulose (HEC)-based hydrogel with sensitivity to environmental changes, pH and salts was synthesized by using fumaric acid and malic acid at various concentrations. Water uptake capacity of hydrogels was investigated in distilled water, various salt and pH solutions. From pH-dependent studies, it was found that greater water uptake values were observed at greater pH values (7.4), and reversible pH responsiveness of CMC–HEC based hydrogels was obtained. Decreasing the water uptake capacity with increasing of the charge of the metal cation (Al3+ < Ca2+ < Na+) demonstrated metal ion responsiveness of CMC–HEC-based hydrogels. From tensile tests of the hydrogels, a greater crosslinker concentration led to greater tensile strength values. Thermogravimetric analysis and scanning electron microscopy images were used to determine the thermal stability and to observe morphological properties of the samples, respectively. 相似文献
103.
Hüseyin Aksel Eren Ozan Avinc Burcu Erişmiş Semiha Eren 《Cellulose (London, England)》2014,21(6):4643-4658
In this study, the effects of ultrasound on ozone treatment processes for bleaching cotton fabrics were investigated and compared with the conventional hydrogen peroxide bleaching process (60 °C over 90 min). Two ultrasonic + ozone treatments of cotton fabric samples were carried out: (1) ozone in an ultrasonic homogenizer (UH) and (2) ozone in an ultrasonic bath. Ozone dosages, temperature and time variations were determined with both ozone-ultrasonic bleaching processes. Whiteness, yellowness, weight, tensile strength properties, FTIR (ATR) spectra and visual appearance, via scanning electron microscopy of treated cotton fabrics as well as chemical oxygen demand (COD) of bleaching effluents, were investigated. It was concluded that the ozone + UH process, conducted for 30 min at 30 °C, produced closely equivalent values of cotton fabric whiteness and yellowness to the classic peroxide bleaching process, with slightly less weight loss, dramatically less COD in the process effluent (29 mg/l for ozone-UH vs. 4,316 mg/l for classical peroxide treatment), and without causing any adverse and/or detrimental effects on loss of fabric strength or elongation of the cotton fabrics. The ozone-UH process also leads to time and energy savings with much less environmental impact. Consequently, the combination of ozonation plus UH carried out at 30 °C over 30 min can be used successfully for cotton bleaching instead of the classic hydrogen peroxide bleaching process. 相似文献
104.
Ayşegül Doğan Selami Demirci Ali Özhan Aytekin Fikrettin Şahin 《Applied biochemistry and biotechnology》2014,174(1):28-42
Saccharomyces cerevisiae, industrial yeast isolate, has been of great interest in recent years for fuel ethanol production. The ethanol yield and productivity depend on many inhibitory factors during the fermentation process such as temperature, ethanol, compounds released as the result of pretreatment procedures, and osmotic stress. An ideal strain should be able to grow under different stress conditions occurred at different fermentation steps. Development of tolerant yeast strains can be achieved by reprogramming pathways supporting the ethanol metabolism by regulating the energy balance and detoxicification processes. Complex gene interactions should be solved for an in-depth comprehension of the yeast stress tolerance mechanism. Genetic engineering as a powerful biotechnological tool is required to design new strategies for increasing the ethanol fermentation performance. Upregulation of stress tolerance genes by recombinant DNA technology can be a useful approach to overcome inhibitory situations. This review presents the application of several genetic engineering strategies to increase ethanol yield under different stress conditions including inhibitor tolerance, ethanol tolerance, thermotolerance, and osmotolerance. 相似文献
105.
The inhibiting effect of (NE)-4-phenoxy-N-(3-phenylallylidene) aniline (PAC) on the corrosion of mild steel in 1.0 M HCl has been studied by electrochemical impedance spectroscopy, and Tafel polarization measurements. The corrosion rate was also calculated theoretically in terms of mm per year and mil per year, using current density values of mild steel in 1.0 M HCl medium. It was found that PAC has a remarkable inhibition efficiency on the corrosion of mild steel especially at high temperatures. The values of E a obtained in presence of a Schiff base were found to be lower than those obtained in the inhibitor-free solution. The increase of inhibition efficiency percent with temperature increase was associated with the transformation of physical adsorption into chemical adsorption. The thermodynamic functions of adsorption processes have been evaluated and discussed at each temperature. Scanning electron microscope observations of the electrode surface confirmed the existence of a protective adsorbed film of the inhibitor on the electrode surface. 相似文献
106.
Eymen Akşener Aysel Kantürk Figen Sabriye Pişkin 《Research on Chemical Intermediates》2014,40(5):2103-2117
In this study, the synthesis of barium metaborate powder (BaB2O4) was carried out by ultrasound-assisted precipitation using different borate solutions. Different solutions such as borax (Na2B4O7, BD), boric acid (H3BO3, BA), and sodium metaborate (NaBO2, SMB) were used in the synthesis and an ultrasonic immersion horn probe was used as the major source of ultrasound. The effect of reaction temperature and time, pH, and crystallization time on the BaB2O4 yield (%) was investigated. The ultrasound-assisted synthesis up to 90 % yield could be achieved using a 0.2 M BD solution at 80 °C, reacting for 5 min at pH 13 followed by 2 h of crystallization. Following crystallization, the obtained powder was heated up to 140, 250, 650, and 750 °C for 2.5 h, and it was shown that β-BaB2O4 nanometric powders were obtained after the 750 °C heat treatment. 相似文献
107.
Selami Ercan Ercan Çınar Cihat Özaydın Nuriye Efe Ertürk Reşit Çakmak 《Journal of heterocyclic chemistry》2020,57(7):2875-2888
Designing new inhibitors having less side effects is a need which also could reduce cholesterol levels. To fulfill this aim, we have carried out a molecular docking study toward 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase. A set of designed structural derivatives of statin drugs, eight ligands which are used as HIV-1 integrase inhibitor candidates, a set of terpenoids, and ligands downloaded from Zinc15 database were docked to HMG-CoA reductase enzyme which contains atorvastatin in crystal structure. The analysis of docking studies revealed that statin derivative ligands are more appropriate for inhibition of HMG-CoA reductase. To define the contribution of the molecular properties to the binding of ligands to enzyme structure; the highest occupied molecular orbitals-lowest unoccupied molecular orbitals, hardness, electronegativity, and chemical potential properties of ligands have best score in their sets calculated by quantum mechanical tools. 相似文献
108.
Gülhan Turan Begüm Nurpelin Sağlik Ulviye Acar Çevik Serkan Levent Betül Kaya Çavuşoğlu 《Phosphorus, sulfur, and silicon and the related elements》2020,195(6):491-497
AbstractIn this study, a novel series of benzothiazole-thiazolylhydrazine (3a–3i) was synthesized and their structures were characterized by 1H-NMR, 13C-NMR spectrometry, and mass spectroscopy. These compounds were evaluated as inhibitors of type A and type B monoamine oxidase (MAO) enzymes. The most active compound 3b (2-((2-(2-(4-(4-Nitrophenyl)thiazol-2-yl)hydrazineylidene)-2-phenylethyl)thio)benzothiazole) showed strong inhibitory activity at hMAO-A (IC50 of 0.095?±?0.004?µM). Furthermore, compound 3i (2-((2-(2-(4-(2,4-dichlorophenyl)thiazol-2-yl)hydrazineylidene)-2-phenylethyl)thio)benzothiazole) showed significant inhibition profile on hMAO-A with the IC50 values 0.141?±?0.006?µM. 相似文献
109.
This paper in concerned with the linear theory of materials with memory that possess a double porosity structure. First, the formulation of the initial-boundary-value problem is presented. Then, a uniqueness result is established. The semigroup theory of linear operators is used to prove existence and continuous dependence of solutions. A minimum principle for the dynamical theory is also derived. 相似文献
110.
We report on the application of a simple and versatile antioxidant capacity assay for dietary polyphenols, vitamin C and vitamin
E utilizing the copper(II)-neocuproine (Cu(II)-Nc) reagent as the chromogenic oxidant, which we term the CUPRAC (cupric reducing
antioxidant capacity) method. It involves mixing the antioxidant solution (directly or after acid hydrolysis) with solutions
of CuCl2, neocuproine, and ammonium acetate at pH 7, and measuring the absorbance at 450 nm after 30 min. Slowly reacting antioxidants
required an incubation at 50 °C for 20 min for color development. The flavonoid glycosides were hydrolyzed to their corresponding
aglycones by refluxing in 1.2 M HCl-containing 50% MeOH for fully exhibiting their antioxidant potencies. Certain compounds
also needed incubation after acid hydrolysis for color development. The CUPRAC absorbances of mixture constituents were additive,
indicating lack of chemical deviations from Beer’s law. The CUPRAC antioxidant capacities of a wide range of polyphenolics
are reported in this work and compared to those found by ABTS/persulfate and Folin assays. The trolox-equivalent capacities
of the antioxidants were linearly correlated (r = 0.8) to those found by ABTS but not to those of Folin. The highest antioxidant capacities in the CUPRAC method were observed
for epicatechin gallate, epigallocatechin gallate, quercetin, fisetin, epigallocatechin, catechin, caffeic acid, epicatechin,
gallic acid, rutin, and chlorogenic acid in this order, in accordance with theoretical expectations. The experiences of other
CUPRAC users also are summarized.
Correspondence: Reşat Apak, Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar, TR-34320 Istanbul,
Turkey 相似文献