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991.
《Particuology》2022
The utilization of hydrogen is gaining increasing attention due to its high heating value and environmentally friendly combustion product. The supercritical water circulating fluidized bed reactor is a promising and potentially clean technology that can generate hydrogen from coal gasification. Cyclone is a vital part of the reactor which can separate incomplete decomposition of pulverized coal particles from mixed working fluid. This paper aims to gain in-depth understanding of the cyclone separation mechanisms under supercritical fluid by computational fluid dynamics (CFD). Although the amount of supercritical carbon dioxide in mixed working fluid is minor, it obviously influences the flow fields and separation efficiency of a cyclone. The simulation results suggest that both the decreasing content of supercritical carbon dioxide and adding the extra dipleg cause the promoting performance of cyclones. Research findings could refine the design of supercritical fluid–solid cyclones. 相似文献
992.
《Particuology》2022
The three-dimensional computational fluid dynamics (3D-CFD) of a pulsating flow applied to the fluid catalytic cracking (FCC) reaction was investigated in the riser of a circulating fluidized bed reactor. The kinetic parameters of the FCC and coke burning reactions for predicting the reactant conversion and product yield percentages were applied. To increase the reactant conversion level and product yield, the effect of the pulsating flow operating parameters was considered using a 2k statistical experimental design with four factors (amplitude, frequency, types of the waveform, and amplitude ratio). The 3D-CFD simulation was successfully validated from the experimental literature data. The frequency and type of the waveform were found to be the significant operating parameters. The expression of the fitted regression model and response surface contour were derived and revealed that the pulsating flow provides a higher reactant conversion level and product yield percentages compared to a non-pulsating or steady flow. 相似文献
993.
《Particuology》2022
Fischer–Tropsch (F–T) synthesis is an important route to achieve the clean fuel production. The performance of gas–liquid separation equipment involving in the progressive condensation and separation of light and heavy hydrocarbons in the oil-gas products has become a bottleneck restricting the smooth operation of the F–T process. In order to remove the bottleneck, a gas–liquid vortex separator with simple structure, low pressure drop and big separation capacity was designed to achieve the efficient separation between gas and droplets for a long period. The RSM (Reynolds Stress Model) and DPM (Discrete Phase Method) are employed to simulate the flow characteristics and liquid distribution in the separator. The results show that the separation efficiency is influenced by the flow field and liquid phase concentration in the annular zone. The transverse vortex at the top of spiral arm entrains the droplets with small diameter into the upper annular zone. The entrained droplets rotate upward at an angle of about 37.4°. The screw pitch between neighbor liquid threads is about 0.3 m. There is a top liquid ring in the top of annular zone, where the higher is the liquid phase concentration, the lower is the separation efficiency. It is found that by changing the operating condition and the annular zone height the vortex can be strengthened but not enlarged by the inlet velocity. The screw pitch is not affected by both inlet velocity and annular zone height. The liquid phase concentration in the top liquid ring decreases with both the increases of inlet velocity and annular zone height. The total pressure drop is almost not affected by the annular zone height but is obviously affected by the inlet velocity. When the height of annular zone is more than 940 mm, the separation efficiency is not changed. Therefore, the annular zone height of 940 mm is thought to be the most economical design. 相似文献
994.
Jameel Ahmed Baig Abdul Qadir Shah Ghulam Abbas Kandhro Hassan Imran Afridi Sumaira Khan 《International journal of environmental analytical chemistry》2013,93(1):28-42
This study evaluated and interpreted complex data sets of water samples collected from different sampling origins of ground water (hand pump and tube well) and surface water (municipal, river and canal). The aim was to provide information concerning the apportionment of pollution sources to obtain better information about water quality and possible distribution of As with respect to its speciation. The As (III) formed complex with ammonium pyrrolidinedithiocarbamate (APDC) and extracted by surfactant-rich phases in the non-ionic surfactant Triton X-114, while total iAs in water samples was adsorbed on titanium dioxide (TiO2) and determined by electrothermal atomic absorption spectrometry. The accuracy of the proposed methodologies was confirmed by standard addition method. The recoveries of As (III) and total inorganic arsenic (iAs) were found to be >98%. The results revealed that the ground water of the area under study was more contaminated as compared to surface water samples. The mean concentration of As (III) and As (V) in the surface water samples was found to be 15.8 and 6.00?µg?L?1, respectively, whereas, in the case of ground water samples, the contents of As (III) and As (V) ranged from 6.20 to 51.0 and 6.40 to 53.0?µg?L?1, respectively. Principal component analysis performed on a combined (tube well and hand pump) samples data set extracted two significant factors explaining more than 60% of total variance, which suggested that the contamination sources might be natural or anthropogenic. 相似文献
995.
Ulrich Faigle Walter Kern Jeroen Kuipers 《Mathematical Methods of Operations Research》2006,63(3):427-433
The lexicographic kernel of a game lexicographically maximizes the surplusses s
ij
(rather than the excesses as would the nucleolus) and is contained in both the least core and the kernel. We show that an element in the lexicographic kernel can be computed efficiently, provided we can efficiently compute the surplusses s
ij
(x) corresponding to a given allocation x. This approach improves the results in Faigle et al. (in Int J Game Theory 30:79–98, 2001) and allows us to determine a kernel element without appealing to Maschler transfers in the execution of the algorithm.We thank the referees for clarifying the presentation of the proof of Proposition 2.1. 相似文献
996.
Jacek Krawczyk 《Computational Management Science》2007,4(2):183-204
This paper is about games where the agents face constraints in the combined strategy space (unlike in standard games where
the action sets are defined separately for each player) and about computational methods for solutions to such games. The motivation
examples for such games include electricity generation problems with transmission capacity constraints, environmental management
to control pollution and internet switching to comply to buffers of bounded capacity. In each such problem a regulator may
aim at compliance to standards or quotas through taxes or charges. The relevant solution concept for these games has been
known under several names like generalised Nash equilibrium, coupled constraint equilibrium and more. Existing numerical methods converging to such an equilibrium will be explained. Application examples of use of
NIRA, which is a suite of Matlab routines that implement one of the methods, will be provided.
相似文献
997.
The Vredefort Impact Structure in South Africa is the biggest and oldest remnant meteorite impact crater in the world where various ancient cultures thrived. In this paper some light will be shed on the Iron Age, iron smelting aspects of the people that inhabited the area and the results of a laboratory study of iron artefacts and a possible source of iron ore in the region is given. A sectional piece from a hoe manufactured in a small bloomery furnace was polished and etched and subsequently analyses with SEM and Mössbauer techniques were obtained. The hoe has a typical cast iron composition (2.9% C, 0.1% Mn, 0.4% Si, 0.4% P and 96.2% Fe, all wt.%) and contains many slag inclusions with wustite dendrites. The Mössbauer spectrum consisted of iron (86%), wustite (5%) and oxihydroxide (9%) and the thin (200 μm) corrosion layer consisted of hematite (55%) and oxihydroxides (45%). At a furnace site, various slag clumps (26.3% C, 24.8% SiO2, 11.3% Al2O3, 1.3% P2O5, 1.0% K2O, 0.4% CaO and 30.2 FeO, all wt.%, average of four samples) and iron nodules (7.6% C, 6.0% Mn, 4.3% Si, 1.4% Al, 80.7% Fe, all wt.%) were found. The Mössbauer spectrum of the slag consisted of iron (7%), magnetite (56%), fayalite (2%) and oxihydroxides (35%) and that of the iron nodules yielded iron (28%), wustite (12%), magnetite (20%) and oxihydroxides (40%). A possible ore source containing 84% FeO, 7% of Al2O3 and SiO2 (all in wt.%) and minor impurities is located a few kilometers from the furnace site, yielding a Mössbauer spectrum consisting of hematite (70%) and oxihydroxides (30%). 相似文献
998.
A new method for determining parameters of a relaxation spectrum of visco-elastic bodies is proposed. The basic idea of the
method consists of presenting measured frequency dependencies of the dynamic modules components by the power series. The coefficients
of these series are found by comparing varying values with experimental data by linear functional of errors. The parameters
of a spectrum are then calculated from the coefficients of the series. This procedure allows us to overcome the main problem
of finding relaxation times, i.e. to pass from non-linear to linear functional of errors. It gives us the unique possibility
of unambiguously estimating weights (partial moduli) of lines in a discrete relaxation spectrum and relaxation times because
there is only a single minimum in the functional of errors.
Received: 8 December 1999/Accepted: 10 December 1999 相似文献
999.
1000.
Interval analysis is a powerful tool which allows to design branch-and-bound algorithms able to solve many global optimization
problems. In this paper we present new adaptive multisection rules which enable the algorithm to choose the proper multisection
type depending on simple heuristic decision rules. Moreover, for the selection of the next box to be subdivided, we investigate
new criteria. Both the adaptive multisection and the subinterval selection rules seem to be specially suitable for being used
in inequality constrained global optimization problems. The usefulness of these new techniques is shown by computational studies. 相似文献