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151.
Luca Bergamaschi Giorgio Pini Flavio Sartoretto 《Numerical Linear Algebra with Applications》2000,7(3):99-116
A preconditioned scheme for solving sparse symmetric eigenproblems is proposed. The solution strategy relies upon the DACG algorithm, which is a Preconditioned Conjugate Gradient algorithm for minimizing the Rayleigh Quotient. A comparison with the well established ARPACK code shows that when a small number of the leftmost eigenpairs is to be computed, DACG is more efficient than ARPACK. Effective convergence acceleration of DACG is shown to be performed by a suitable approximate inverse preconditioner (AINV). The performance of such a preconditioner is shown to be safe, i.e. not highly dependent on a drop tolerance parameter. On sequential machines, AINV preconditioning proves a practicable alternative to the effective incomplete Cholesky factorization, and is more efficient than Block Jacobi. Owing to its parallelizability, the AINV preconditioner is exploited for a parallel implementation of the DACG algorithm. Numerical tests account for the high degree of parallelization attainable on a Cray T3E machine and confirm the satisfactory scalability properties of the algorithm. A final comparison with PARPACK shows the (relative) higher efficiency of AINV‐DACG. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
152.
Luca Garbuio Yongjun Li Sabrina Antonello José A. Gascón Ronald G. Lawler Xuegong Lei Yasujiro Murata Flavio Maran 《Photochemistry and photobiology》2014,90(2):439-447
We synthesized two molecular systems, in which an endofullerene C60, incarcerating one hydrogen molecule (H2@C60) and a nitroxide radical are connected by a folded 310‐helical peptide. The difference between the two molecules is the direction of the peptide orientation. The nuclear spin relaxation rates and the para → ortho conversion rate of the incarcerated hydrogen molecule were determined by 1H NMR spectroscopy. The experimental results were analyzed using DFT‐optimized molecular models. The relaxation rates and the conversion rates of the two peptides fall in the expected distance range. One of the two peptides is particularly rigid and thus ideal to keep the H2@C60/nitroxide separation, r, as large and controlled as possible, which results in particularly low relaxation and conversion rates. Despite the very similar optimized distance, however, the rates measured with the other peptide are considerably higher and thus are compatible with a shorter effective distance. The results strengthen the outcome of previous investigations that while the para → ortho conversion rates satisfactorily obey the Wigner's theory, the nuclear spin relaxation rates are in excellent agreement with the Solomon–Bloembergen equation predicting a 1/r6 dependence. 相似文献
153.
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155.
Laura Barp Giorgia Purcaro Flavio A. Franchina Mariosimone Zoccali Danilo Sciarrone Peter Q. Tranchida Luigi Mondello 《Analytica chimica acta》2015
Phthalates are a group of synthetic compounds mainly used as plasticizers, which have been classified as endocrine-disrupting chemicals and potential human-cancer causing agents. They can be found in high amounts in foods, deriving mainly from plastic packaging. The analytical determination of these compounds is very challenging since they are ubiquitous. Therefore, minimization of sample manipulation is highly desirable. 相似文献
156.
157.
The basics of active fiber technology and their application to optical amplifiers and lasers are reviewed, with particular reference to the activities of the Italian groups involved in this research. The main uses of optical amplifiers in telecommunications and the perspective of ultrafast soliton fiber lasers are presented and discussed. 相似文献
158.
We have studied the properties of an electron bubble close to the surface of liquid3
He, by using a Density Functional approach. We find that up to an electron-surface distanced
0 23 Åthe bubble is stable, while at smaller distances it becomes unstable and bursts. A potential energy barrier /K
B
38°K for the thermal emission of electrons is obtained from our results, in agreement with experiments. Even when the electron-surface distance is larger thand
0, however, tunneling through the surface layer dominates the electron escape probability. Large deviations of the electron potential energy from its ideal value are found close to the surface. These deviations have a profound effect on the calculated decay rates of the tunneling curent, which are much smaller than those obtained previously and in semi-quantitative agreement with experiments. 相似文献
159.
Applied Biochemistry and Biotechnology - The half-life of immobilized amyloglucosidase was determined in a fluidized-bed reactor operating continuously with a 30% w/v liquefied cassava starch... 相似文献
160.
Giovanni?Lugli Jacqueline?M?Krueger John?M?Davis Antonio?M?Persico Flavio?Keller Neil?R?SmalheiserEmail author 《BMC biochemistry》2003,4(1):9