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排序方式: 共有239条查询结果,搜索用时 15 毫秒
101.
Sibel Gunes Veysel Ozceyhan Orhan Buyukalaca 《Experimental Thermal and Fluid Science》2010,34(6):684-691
The heat transfer and pressure drop were experimentally investigated in a coiled wire inserted tube in turbulent flow regime. The coiled wire has equilateral triangular cross section and was inserted separately from the tube wall. The experiments were carried out with three different pitch ratios (P/D = 1, 2 and 3) and two different ratio of equilateral triangle length side to tube diameter (a/D = 0.0714 and 0.0892) at a distance (s) of 1 mm from the tube wall in the range of Reynolds number from 3500 to 27,000. Uniform heat flux was applied to the external surface of the tube and air was selected as fluid. The experimental results obtained from a smooth tube were compared with those from the studies in literature for validation of experimental set-up. The use of coiled wire inserts leads to a considerable increase in heat transfer and pressure drop over the smooth tube. The Nusselt number rises with the increase of Reynolds number and wire thickness and the decrease of pitch ratio. The highest overall enhancement efficiency of 36.5% is achieved for the wire with a/D = 0.0892 and P/D = 1 at Reynolds number of 3858. Consequently, the experimental results reveal that the best operating regime of all coiled wire inserts is detected at low Reynolds number, leading to more compact heat exchanger. 相似文献
102.
We study a selective and periodic inventory routing problem (SPIRP) and develop an Adaptive Large Neighborhood Search (ALNS) algorithm for its solution. The problem concerns a biodiesel production facility collecting used vegetable oil from sources, such as restaurants, catering companies and hotels that produce waste vegetable oil in considerable amounts. The facility reuses the collected waste oil as raw material to produce biodiesel. It has to meet certain raw material requirements either from daily collection, or from its inventory, or by purchasing virgin oil. SPIRP involves decisions about which of the present source nodes to include in the collection program, and which periodic (weekly) routing schedule to repeat over an infinite planning horizon. The objective is to minimize the total collection, inventory and purchasing costs while meeting the raw material requirements and operational constraints. A single-commodity flow-based mixed integer linear programming (MILP) model was proposed for this problem in an earlier study. The model was solved with 25 source nodes on a 7-day cyclic planning horizon. In order to tackle larger instances, we develop an ALNS algorithm that is based on a rich neighborhood structure with 11 distinct moves tailored to this problem. We demonstrate the performance of the ALNS, and compare it with the MILP model on test instances containing up to 100 source nodes. 相似文献
103.
Zarife Sibel ahin Hasan budak amil Ik 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(12):m463-m465
In the structure of the title compound, [Cd2(C4H4NO4S)2(C6H7N)2], the dinuclear CdII complex is located on a twofold axis with two Cd2+ ions bridged by two oxide O atoms. Each Cd2+ ion is additionally coordinated in an equatorial plane by two N and three O atoms of the acesulfamate ligands and axially by two N atoms of the 3‐methylpyridine ligands, resulting in a distorted pentagonal bipyramidal coordination. We present here an example of a supramolecular assembly based on hydrogen bonds in a mixed‐ligand metal complex; intermolecular C—H...O hydrogen bonds give rise to R44(40) rings, which lead to one‐dimensional chains. 相似文献
104.
Burcu Dogan‐Topal Burcin Bozal B. Tolga Demircigil Bengi Uslu Sibel A. Ozkan 《Electroanalysis》2009,21(22):2427-2439
The electrochemical behavior of atorvastatin and amlodipine at a glassy carbon electrode has been studied using different voltammetric techniques. First derivative of the ratio voltammetric methods for determination of amlodipine and atorvastatin in tablets in the presence of the other compound has been described. This technique depends on the measuring of first derivative of the ratio voltammograms of each concentration as a function of the increased concentrations. DP and SW voltammetric methods depend on first derivative of the ratio‐voltammetry by measurements of the selected potentials for amlodipine and atorvastatin. The linear response was within the range of 4×10?6–1×10?4 M for amlodipine and 2×10?6–1×10?4 M for atorvastatin. The proposed methods have been extensively validated. 相似文献
105.
Sibel Ozkan 《Discrete Mathematics》2009,309(14):4883-1973
A k-factor of a graph is a k-regular spanning subgraph. A Hamilton cycle is a connected 2-factor. A graph G is said to be primitive if it contains no k-factor with 1≤k<Δ(G). A Hamilton decomposition of a graph G is a partition of the edges of G into sets, each of which induces a Hamilton cycle. In this paper, by using the amalgamation technique, we find necessary and sufficient conditions for the existence of a 2x-regular graph G on n vertices which:
- 1.
- has a Hamilton decomposition, and
- 2.
- has a complement in Kn that is primitive.
106.
Fosamprenavir is a pro-drug of the antiretroviral protease inhibitor amprenavir and is oxidizable at solid electrodes. The
anodic oxidation behavior of fosamprenavir was investigated using cyclic and linear sweep voltammetry at boron-doped diamond
and glassy carbon electrodes. In cyclic voltammetry, depending on pH values, fosamprenavir showed one sharp irreversible oxidation
peak or wave depending on the working electrode. The mechanism of the oxidation process was discussed. The voltammetric study
of some model compounds allowed elucidation of the possible oxidation mechanism of fosamprenavir. The aim of this study was
to determine fosamprenavir levels in pharmaceutical formulations and biological samples by means of electrochemical methods.
Using the sharp oxidation response, two voltammetric methods were described for the determination of fosamprenavir by differential
pulse and square-wave voltammetry at the boron-doped diamond and glassy carbon electrodes. These two voltammetric techniques
are 0.1 M H2SO4 and phosphate buffer at pH 2.0 which allow quantitation over a 4 × 10−6 to 8 × 10−5 M range using boron-doped diamond and a 1 × 10−5 to 1 × 10−4 M range using glassy carbon electrodes, respectively, in supporting electrolyte. All necessary validation parameters were
investigated and calculated. These methods were successfully applied for the analysis of fosamprenavir pharmaceutical dosage
forms, human serum and urine samples. The standard addition method was used in biological media using boron-doped diamond
electrode. No electroactive interferences from the tablet excipients or endogenous substances from biological material were
found. The results were statistically compared with those obtained through an established HPLC-UV technique; no significant
differences were found between the voltammetric and HPLC methods. 相似文献
107.
Suzen S 《Combinatorial chemistry & high throughput screening》2006,9(6):409-419
Melatonin is known for its radical scavenger activity, which is related to its ability to protect cells from different kinds of oxidative stress. Oxidative stress has been implicated in the development of neurodegenerative diseases like Parkinson, Alzheimer's disease, Huntington's disease, epileptic seizures, stroke, and as a contributor to aging and some cancer types. The antioxidant properties of melatonin include scavenging free radicals and the regulation of the activity and expression of antioxidant and pro-oxidant enzymes. Due to its free radical scavenger and antioxidant properties, multiple melatonin-related compounds such as melatonin metabolites and synthetic analogues are under investigation to determine which exhibit the highest activity with the lowest side effects. This review addresses recent studies with melatonin and related compounds. 相似文献
108.
A Variational Monte Carlo (VMC) method is employed to investigate the properties of symmetric and asymmetric nuclear matter. The realistic Urbana V 14 twonucleon interaction potential of Lagaris and Pandharipande was used to describe the microscopic interactions. Also, many body interactions are included as a density dependent term in the potential. Total kinetic and potential energies per particle are calculated for asymmetric nuclear matter by VMC method at various densities and isospin asymmetry parameters. The results are compared with data found in literature, and it was observed that the results obtained in this study reasonably agree with the results found in the literature. Also, the symmetry energy and incompressibility factor of the nuclear matter were obtained. The results obtained are in good agreement with those obtained by various authors with different methods and techniques. 相似文献
109.
Cliff Konold Anthony Harradine Sibel Kazak 《International Journal of Computers for Mathematical Learning》2007,12(3):217-230
In current curriculum materials for middle school students in the US, data and chance are considered as separate topics. They
are then ideally brought together in the minds of high school or university students when they learn about statistical inference.
In recent studies we have been attempting to build connections between data and chance in the middle school by using a modeling
approach made possible by new software capabilities that will be part of TinkerPlots 2.0 (TinkerPlots is published by Key Curriculum Press and has been developed with grants from the National Science Foundation (ESI-9818946, REC-0337675, ESI-0454754). Opinions
expressed here are our own and not necessarily those of the Foundation.). Using a new Sampler object, students build “factories”
to model not only prototypical chance events, but also distributions of measurement errors and of heights of people. We provide
the rationale for having students model a wide range of phenomena using a single software tool and describe how we are using
this capability to help young students develop a robust, statistical perspective. 相似文献
110.
A series of novel N-, S-, and O-substituted p-chloranil derivatives were synthesized from the reactions of p-chloranil (1) and related nucleophiles in sodium carbonate (Na2CO3) solution of acetonitrile or in chloroform with Et3N. The structures of novel compounds were characterized by using microanalysis, Fourier transform–infrared, 1H NMR, 13C NMR, and mass spectrometry. 相似文献